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ANZCA July 2007 Q64

Significant differences between the LMA-ProSeal™ and the standard laryngeal mask (LMA-Classic™) include all of the following EXCEPT

A. a built in bite-block

B. a double cuff arrangement

C. an improved seal pressure at a given cuff pressure

D. an independent oesophageal drain tube

E. improved aperture bars to prevent the epiglottis occluding the airway tube
ANSWER E

The LMA ProSeal™ achieves a high seal pressure, ranging from 30-35cm H2O with no increase in mucosal pressure, supporting good ventilation.

The double cuff design permits the walls of the cuff, when inflated, to match the contours of the pharyngeal and laryngeal surfaces, and improves the seal.

The cuff design, with its wider and deeper bowl, produces a better perilaryngeal fit and higher seal pressures without increasing pressure against the pharyngeal mucosa.

Mask Size Patient Size
1 Neonates up to 5kg
1.5 Infants 5-10kg
2 Infants/Children 10-20kg
2.5 10-20kg
3 30-50kg
4 50-70kg
5 70-100kg
EZ82 ANZCA Version [Jul06] Q108, [Apr07]

A 60-year-old man with BMI (body mass index) of 30 is having an inguinal hernia repair. He has a LMA-Proseal® in place and you plan positive pressure ventilation. If the device is properly seated the maximum pressure in cm of water before leaking during positive pressure ventilation should be

A. 15

B. 20

C. 30

D. 40

E. 50
ANSWER C

C. Classics are 20cmH2O.

BUT for proseal LMA it's about 30cmH2O!
EM40 ANZCA Version [Jul06] Q27

A Swan-Ganz catheter can be unreliable for measuring pulmonary artery systolic and diastolic pressures because the length and compliance of the tubing affects the measuring system by

A. reducing its resonant frequency

B. reducing its frequency response

C. reducing its damping coefficient

D. inducing a zero error

E. inducing baseline drift
ANSWER A and B

A. TRUE : Resonant frequency is decreased by long and compliant tubing

B: TRUE : frequency response is dependent on the resonant frequency,

C. FALSE : long compliant tubes have increased damping coefficients

D. FALSE : zero error is caused by incorrectly zeroing the system (not dependent on length and compliance)

E. FALSE : length and compliance is not related to baseline drift.

TWO forms of accuracy
*Static eg. MAP
*Dynamic eg BP

To accurately measure systolic and diastolic pressures with a catheter transducer system, the system needs to have an appropriate dynamic response. It is dependent on
*resonant frequency : inherent frequency of any oscillating system at which the system would tend to oscillate is disturbed
*damping coefficient : calculated from the ratio of the amplitude of 2 successive peaks
-optimal damping is D=0.64 allowing for minimal amplitude distortion, optimal frequency respsonse and minimal phase distortion
-critical dampening D=1, however if Fn is high (ei short), the dynamical accuracy will still be good
EM60 [Mar06] Q131, [Jul06] Q84

The PiCCO monitor (Pulsion Medical Systems) combines pulse contour analysis and transpulmonary thermodilution to provide a continuous measurement of:

A. cardiac output

B. cardiac output and intermittent assessment of intrathoracic blood volume

C. cardiac output and intermittent assessment of extravascular lung water

D. cardiac output and intermittent assessment of intrathoracic blood volume and extravascular lung water
ANSWER D

PiCCO : Pulse Contour Cardiac Output Monitoring

Uses CVC and femoral or axilliary IAL

Employs patented algorithms to combines real-time continuous monitoring through pulse contour analysis with intermittent thermodilution via the transpulmonary method.


PiCCO technology provides clinicians with the following clinical measurements, many of which can be displayed as absolute or indexed values:

via continuous pulse contour analysis

* Continuous pulse contour cardiac analysis (PCCO)
* Arterial blood pressure (AP)
* Heart rate (HR)
* Stroke volume (SV)
* Stroke volume variation (SVV)
* Systemic vascular resistance (SVR)
* Index of left ventricular contractility

via intermittent transpulmonary thermodilution

* Transpulmonary cardiac output (C.O.)
* Intrathoracic blood volume (ITBV)
* Extravascular lung water (EVLW) (Not Available in United States)
* Cardiac function index (CFI)
EZ62 ANZCA version [Mar06]

Precautions when providing anaesthesia for surgery using a Nd-YAG laser should include all of the following EXCEPT

A. avoidance of nitrous oxide

B. scavenging of smoke particles because they may contain viral DNA

C. awareness that gas embolism is possible from cooling gas down laser conduit

D. use of sunglasses to protect eyes

E. avoidance of an FiO2 above 0.4
ANSWER D : NdYAG requires special lens to protect retina from direct laser trauma.

LASER HAZARDS include
1. atmospheric contamination
2. perforation of vessel or structure
3. embolism
4. inappropriate energy

Atmospheric Contamination
-vaporization of tissue causes plume of smoke and fine particles (0.3um) which are efficiently transported to alveoli
-The laser plume may cause headache, tearing, nausesa, interstitial pneumonia, emphysema, mutogenic, teratogenic or a vector viral infection.
-Viral DNA has been detected in plume of warts and condylomas
-No HIV RNA has been detected, but HIV DNA (from host DNA) has been detected
-No cancer cells detected
-CO2 lasers produced more smoke than NdYAG

Tissue or vessel perforation
-misdirected laser may perforate any viscus or large blood vessel
-vessels>5mm are not coagulable by laser


Embolism
-NdYAG has been associated with venous gas embolism, as gas coolant is used to cool tip can enter through perforated vessels (similar to TURP syndrome),
-Reported in uterine, tracheal, laparoscopic and endoscopic procedures
-CO2 gas coolant is prefered

Inapproprate laser transfer
-eye protection
-ignition to tissue, endotracheal tube, drape

Eye protection
-requires special glasses/googles specific for the specific laser wavelength in use. Using the wrong filter provided no protection. Must wraparound to protect from reflected light.
-CO2 laser : any clear glass or plastic, they are opaque for infrared
-NdYAG laser : green-tinted lens
-Argon or kypton : amber-orange lens

Ignition
-avoid nitrous as it support combustion
-aim FiO2<0.4 as O2 supports combustion

Other strategies to avoid airway fire
1. reduction in flammability of ETT
2. removal of flammable materials using Metallic Jet Insufflation or intermittant extubation
3. reduction in FiO2

PVC ETT
-PVC is transparent and immune to NdYAG and laser light
-but thin coating of blood or mucus can absorb energy and cause ETT ignition

Flammablity
PVC>red rubber >silicon ETT
Describe your airway fire protocol
(Millrs)
If an airway fire or explosion occurs, the surgeon and the anesthesiologist must act quickly, decisively, and in a coordinated fashion.

1. Surgeon should remove source immediately
2. Anaesthetist should disconnect circuit and NOT ventilate
3. Extingiush flame with water
4. Ventilate with 100% O2 and maintain anaesthesia with MASK
5. Direct larngoscopy and rigid bronchoscopy to survey damage, if there is any damage patient should be re-intubated

CXR
High dose steroid
EZ78 ANZCA Version [Mar06] Q116, [Jul06] Q90

Regarding ball flowmeters the

A. flow control knob cannot stop gas leakage if the glass chamber is broken

B. flowmeter maintains accuracy when tilted

C. flowmeter will over estimate gas flow if connected to a high resistance device such as a nebuliser

D. gas flow rate is read at the centre of the ball

E. gas flow lifts the ball up in a parallel sided tube in the glass chamber
ANSWER D

A. FALSE : depends if flowmeter is pressurized with needle valve downstream

B. FALSE : important to keep vertical,
10 deg over reads 5%
25 deg over reads 10%
30 deg over reads 20%

C. FALSE - The chamber is pressurized by the inlet pressure and minor degrees of outlet occlusion do not alter the flow.

D. TRUE - middle of the ball

E. FALSE - The ball is lifted up a conical tube, meaning there is variable flow but constant pressure across the ball
EZ79 ANZCA Version [2006-Mar] Q115, [Jul06] Q59

An infant is anaesthetised and ventilated using an endotracheal tube and circle breathing system with CO2 absorber. The item which causes the most
resistance to breathing is the

A. airway pressure limiting (APL) valve

B. circuit hosing

C. endotracheal tube

D. heat and moisture exchange filter

E. inspiratory and expiratory valves
ANSWER C
What 11 components of an anesthesia machine are required?
The gas machine includes:
(1) gas inlets.
(2) pressure regulators.
(3) oxygen-pressure-failure devices.
(4) flow-control valves and flowmeters.
(5) vaporizers.
(6) fresh gas outlet.
(7) spirometers.
(8) breathing circuit pressure gauges.
(9) ventilators.
(10) waste-gas scavengers. and
(11) oxygen analyzers
List five components of the circle system.
The components of the circle system are:
(1) gas reservoir bag.
(2) two corrugated tubes,
(3) two unidirectional valves,
(4) a canister containing a CO2 absorbent, and
(5) an overflow valve to permit escape of excess gases
Describe five characteristics of the circle system.
(1) This is the most used semiclosed anesthetic breathing system.
(2) lt is a true breathing circuil.
(3) Anesthetic gases and O2 circulate in one direction entirely within the confines of the components of this system.
(4) Inspired concentrations change slowly unless the fresh gas inflow is increased.
(5) The inspired O2 concentration cannot be predicted when using low flows (fresh gas inflow below 1.2 L).
Identify five advantages of a circle system.
(1) Conservation of gases,
(2) conservation of body heat,
(3) conservation of moisture (H20),
(4) minimal operating room pollution, and
(5) relative constancy of inspired gas concentration
MC104 ANZCA Version [Apr 08]

It is MOST important to re-program a patient's implanted cardiac pacemaker prior to:

A. electroconvulsive therapy (ECT)

B. laser therapy to a laryngeal papilloma

C. lithotripsy of a renal calculus

D. magnetic resonance imaging of the thorax

E. percutaneous transhepatic cholangiography
ANSWER C?

From Millers

Situations Probably Requiring Pacemaker Reprogramming
Any rate-responsive device—see text (problems are well known[23,45] and have been misinterpreted with the
potential for patient injury; the Food and Drug Administration has issued an alert regarding devices
with minute ventilation
Special pacing indication (hypertrophic obstructive cardiomyopathy, dilated cardiomyopathy, pediatric
patients)
Pacemaker-dependent patients
Major procedure in the chest or abdomen
Rate enhancements present that should be disabled
Special procedures (see text)
Lithotripsy
Transurethral resection
Hysteroscopy
Electroconvulsive therapy
Succinylcholine use
Magnetic resonance imaging (generally contraindicated by device manufacturers)[51]
In some situations and for certain patients, a pacemaker should be reprogrammed either to avoid potential
patient injury or to prevent a pacemaker rhythm that could be confused with pacemaker malfunction

Lithotripsy pulse causes electromagnetic interference resulting in oversensing and inappropriate inhibition
EM EM69

BP measurement - overestimates with:

A. big (wide) cuff

B. skinny arm

C. severely peripherally vasoconstricted

D. atherosclerosis (it was arteriosclerosis)

E. slow cuff deflation
ANSWER D

Overestimates
1. calcified non compressible arteries
2. inappropriately small cuff
3. Peripheral oedema (sound travesl much better though water than tissue)
4. Cuff too loose

Underestimate
1. Vasoconstricted
2. Slow cuff INflation : venous congestion leading to low systolic and high diastolic (narrow pulse pressure)

Other conditions that will OFTEN render inaccurate measurements are;
-Certain heart diseases
-Cardiac arrhythmia
-Poor circulation
-Arterial sclerosis
-Preeclampsia
-Pulsus alternans
-Pulsus paradoxus
EM08 [Aug92] [Jul97] [Jul98]

The most sensitive monitor for air embolism is: (type A)

A. Respiratory pattern

B. Precordial /?oesophageal stethoscope

C. ECG

D. End-tidal pCO2 (“capnography”)

E. Precordial doppler device

F. SpO2 (“pulse oximeter”)

G. CXR
ANSWER D
TTE
-sensitivity 0.2ml/kg
-moderately specific
-non invasive
-not qualitative, difficult placement with high false negatives

But TOE is better
-Sensitivity of 0.02ml/kg
-able to see VAE, microembolii in pulmonary capillaries and PAE
-most sensitive and semi-quantitative
-requires continuous observation, potential glottic injury, expensive, operator dependent


Sensitivity
TOE > ETN2 >doppler > ETCO2

Specificity
ETN2 > TOE > Doppler >ETCO2 > PA

Quantitative
PA
EM08c ANZCA version [2004-Aug] Q142

Regarding venous air embolism (VAE) during posterior fossa neurosurgery

A. attempts to aspirate air from the caval-atrial junction are of little value

B. children are at greater risk than adults

C. Doppler ultrasonography is the most specific monitor available

D. end-tidal nitrogen monitoring is the most sensitive monitor available

E. positive end-expiratory pressure (PEEP) should be used in patients with intra-cardiac shunts
ANSWER A

A. TRUE : air has been successfuly aspirated form the right ventricle via central lines

B. FALSE : children are at no greater risk, however the effect will be much worse given their smaller size

C. FALSE : TOE is most sensitive and ETN2 is most specific

D. FALSE : ETN2 most specific

E. FALSE : PEEP will increase the right sided pressures, increasing the risk of R>L shunt and therefore PAE
EM08d ANZCA Version [Apr08]

The most sensitive monitor for detecting venous gas embolism during neurosurgery is a:

A. Capnograph

B. Praecordial Doppler transducer

C. Praecordial stethoscope

D. Pulmonary Artery Catheter

E. Transoesophageal echocardiograph
ANSWER E

Sensitive
TOE>ETN2>Precord doppler>ETCO2

Specific
ETN2>TOE>Precord doppler>PA>ETCO2

Quantitative : PA
Semiquantitative : ETCO2>PA
EM52b ANZCA version [2003-Apr] Q67, [2003-Aug] Q69, [Jul06] Q61

The following capnograph tracing is most likely to represent

A. partial obstruction of sampling tube

B. sticking ventilator bellows

C. incomplete neuromuscular blockade

D. air entrainment into sampling tube

E. partial obstruction of endotracheal tube
ANSWER D

Low plateau is caused by entrained air during respiration
Late peak results at end inspiration where there is a decrease in circuit pressure and briefly stop air entrainment.

Usually due to breach in the sampling tube of side-stream capnometer
EZ44 [1985] [Sep90] [Mar91] [Aug91] [Mar92] [Mar93] [Aug93]

If a tingling sensation is felt when touching an active electrical device the leakage current is approximately:

A. 80-120 micro Amp

B. 300-400 micro Amp

C. 1-2 milli Amp

D. 10-15 milli Amp

E. 100-200 milli Amp
ANSWER B

# Tingling 0.5 mA
# Pain at 1 mA
# 2-15 mA feel pain and muscles contract but can let go
# 100 – 200 mA will likely produce VF, but current density at heart depends on path of current. Also frequency important : 50 HZ is optimal (but very similar VF thresholds thru wide range 10 – 500 Hz)
EZ25 [1986] [Aug92] [Aug93] [Aug96] [Jul97]

The current required for microelectrocution with a connection onto the endocardium is:

A. 1-10 microamps

B. 10-100 microamps

C. 0.1-1.0 milliamps

D. 1-10 milliamps

E. 10-100 milliamps
ANSWER B

From Miller "10 microA is the max allowable leak, but usually needs to be ~ 50 microA to cause VF”

Cardiac-protected: must LEAK < 50 microamps through the cardiac catheter or wire EVEN with a SINGLE FAULT. Need 50 microamps THROUGH THE HEART to produce VF. TOTAL working current limited to <10 mAmp. [Ref for B] Parbrook p 218; RDM para 33615; Rosewarne p 136
EZ76 ANZCA version [2005-Apr]-Q115 | [2005-Sep]-Q64 | [Mar06]-Q19 | Aug10

Residual Current Devices (also known as Safety Switches)

A. detect differences in current between the active and neutral wires of a circuit

B. isolate the patient from earth

C. monitor the isolation of the power line

D. must be fitted to all Cardiac Protection areas

E. must be fitted to all operating theatres
ANSWER A
EZ88 [Aug10] [Mar10]

A device that detects a 10mA difference in active and neutral leads
and causes turning off of the circuit within 40 ms. This is a:

A. Class 1 device

B. Equipotential earthing

C. Line isolation monitor

D. Residual Current Device

E. Fuse
ANSWER D

A Class 1 device = equipment is fitted with a three core mains cable containing a protective earth wire. Exposed metal parts on class I equipment are connected to this earth wire.

Should a fault develop inside the equipment and the exposed metal comes into contact with the mains, the earthing conductor will conduct the fault current to ground. Regular testing procedures ensure that earthing conductors are intact, as the integrity of the earth wire is of vital importance.

B Equipotential earth is a mechanism where the casings of all the equipment in theatre are earthed to the same potential so there can't be a potential difference between two live casings which would be potential source for macro or microshock (green and yellow cabels)

C Line isolation monitor detects leakage currents >5mA and sounds an alarm, it does not automatically shut anything off

D = detects current leakages and then shuts off supply- not so good if there is life saving equipment being used, e.g. CPB
ANZCA Version [Jul07]

An anaesthetised patient is ventilated and has standard monitoring plus a central venous line. As the surgeon is commencing the case, the line isolation monitor (LIM) alarms indicating a potential leakage current of greater than 5 milliamps from one of the power circuits in use.
The most appropriate action is to

A.check the diathermy return plate

B.disconnect the central line to electrically isolate the patient till the fault is identified

C.make sure the patient is properly "earthed" or "grounded"

D.sequentially unplug non-vital equipment from the circuit until the fault is identified

E.suspend the operation and move the patient to a safe environment
ANSWER D

LIM alarm warns that there is a single fault with one device of >5mA. Two faults are required to complete the circuit and cause a shock.

The CVC transducer should be plugged into a type CF cardiac protected monitor. This means that even if the patient was to come into contact with a live source, less than 50microamps will flow through the CVL cable (due to either the module being isolated, or having very high internal resistance), hence preventing microshock. This means that theoretically, unplugging the CVL is not required, and may be actually harmful.
TMP-136 [Apr08] Q96

When obtaining an image using ultrasound, the most effective way to improve the
spatial resolution is to increase the:

A. 2D gain

B. frame rate

C. single scatter

D. time gain compensation

E. transducer frequency
ANSWER E

E - Increased frequency increases resolution (at the expense of decreased penetration).
What is the effect of 50 Hz electricity on muscle?
Effect of 50 Hz electricity on muscle

Microshock Fibrillation 0.1 mA

Threshold of sensation through skin 0.5 mA

Painful Sensation 1 mA

Muscle Spasm 10-20 mA

Ventricular Fibrillation >100 mA

Muscle Burns >1000 mA
What is microshock?
Microshock is a term describing the induction of ventricular fibrillation by small electrical currents (below the threshold of skin sensation) when applied to very small areas of ventricular muscle, usually by vascular catheters or wires. It requires a small area of contact with heart muscle so that the current density is high despite low current.

The myocardium is most sensitive to 30-100Hz electricity, so mains at 50Hz is ideal for inducing fibrillation.
What are the characteristics of a Class Z area?
Characteristics:

* Earthed Sockets with a Neutral Return Wire.
* Fuse Boxes which limit the maximum current through the active wire.
* 8 Amp fusewire for lighting circuits
* 15 Amp for power
* Standards limiting the amount of current through any set of power outlets.
What are the characteristics of a Class B area?
Characteristics:

1. As for Class Z Areas plus:
2. Earth-leakage detection devices must be used, ie Earth Leakage Core Balance Relays (RCD's) or Isolating transformers with Line Isolation Monitors.
3. The earth wiring must be tested regularly for low resistance.
4. All equipment having patient circuits must be class BF or CF.

Leakage of power through Earth Circuit but not enough to blow fuse, but lethal once patients protective skin resistance is reduced:
1. ECG machines
2. Diathermy Devices
What is an Earth Wire?
The earth wire allows a low-resistance pathway for electricity to drain should a leak occur.

-should always be in good contact with all metal parts of any appliance
-should the appliance come in contact with an active wire, the current will rush to earth and smoke will rise
-the active line fuse should then blow
-fault maybe due to
a. corrosion of sockets, leads or extension cables
b. bending of pines
c. corrosion or poor install of electrical supply

High resistance of normal DRY skin helps protect patients from eletrocution
What is a residual current device?
Also known as a surge protector.

Electromagnetic coupling of the active and neutral wire allows detection of any discrepancy in current between the two (they should be equal).

If the current in Active and Neutral wires are not equal, the RCD will be tripped : disconnecting both wires.

Responsive in 10-20 milliseconds
Leak of 5 to 10 mA
Protecting again macroshocks only
Cheap

Will not detect leak if it travels through patient and then through Neutral Wire

No protection again microshocks
What are Isolating Transformers and Line Isolation Monitors
Involved a large transformer mounted in the wall cavity, which compares two active wires :one to the appliance and another which is earthed (it indicates how much current could flow to earth if there were an earth connection).

If a potential earth current of more than 5mA is detected, an alarm will sound

More expensive than RCD
Will not alarm under 5mA, therefore microshocks can still occur
What is a Class A Area
Characteristics:

* As for Class B areas
* Equipotential Earthing.

Only these areas should be used when intracardiac conductors are present.

All potential sources of leak current must be equipotentially earthed by special low-impedance green cables.

This includes
1. anaesthetic machine
2. IV poles with IMEDs on them, etc.
AZ (Q26 Aug 2008) Patient burns during MRI can be associated with each of the following EXCEPT

A high intensity changing magnetic fields

B looped monitoring lines ...

C non ferromagnetic material in contact with the patient

D cosmetics worn by the patient (which do not contain metals)

E temperature monitoring with thermister probes
ANSWER D>C

Causes of contact burn with MRI due to induction of current by high intensity magnetic field.
-contact with monitoring cable, equipment
-ferromagnetic items : bracelets
-ferromagnetic containing : tattoos, fentanyl/nicotine patchs (aluminium)
-looping

Recommendations
1. Monitors and sensors for MRI use nonconducting paths (e.g., fiberoptic cable and plastic tubing) or high-resistance paths (e.g., carbon ECG leads) are preferred, provided that they meet monitoring needs.

2. Do not loop leads or cables.

3. Place the sensor well away from the RF coil, and run the cables away from the coil whenever possible.

4. Check all sensors and cables to ensure that the electrical insulation around them is intact. Be sure that no other bare metal surface is in contact with the patient.

5. Keep the cables off the patient and run them over blankets whenever possible.

6. Remove all unused sensors, cables, and surface coils from the MRI system.

7. Instruct conscious patients to call out if they experience uncomfortable levels of warming anywhere, especially at sites of sensor application. Heed such calls. Install intercom systems and check them regularly. Operators should periodically check the sites of sensor locations on unconscious patients.
TMP-136 [Apr08] Q96

When obtaining an image using ultrasound, the most effective way to improve the spatial resolution is to increase the:

A. 2D gain

B. frame rate

D. time gain compensation

E. transducer frequency
ANSWER E

E - Increased frequency increases resolution (at the expense of decreased penetration).

Resolution determines the degree of image clarity : the ability to distinguish between two structures.

It is influenced by :
1. Axial Resolution : ability to distinguish between two structures that are parallel, determined by frequency (wavelength), higher freq the higher the resolution

2. Lateral Resolution : resolution of 2 objects side by side (ei perpendicular to beam), determined by transducer beam width
-inversely proportional to frequency
-related to focal zone (depth) is best at narrowest part of beam
What are the types of Laser?
CO2 - long wavelength (10,600nm), absorbed by water, good for superficial lesions (for example glottic tumours) as shallow tissue penetration: 0.2 mm

Nd-YAG

Argon

Dye
Classification of Lasers
Class 1 : safe for eye exposure

Class 2 : visible laser beam (400-700nm), power to 1mW, eye protected by blink relfex

Class 3a : Class 2 to 5mW with widen band width so still portected by blink

Class 3b : Power to 0.5W, direct viewing is hazardous

Class 4 : Power over 0.5W, wavelength 180nm to 1mm, capable of ignition
AC. With regard to fire in OT

A. Mainly caused by laser surgery

B. Decreased incidence since cessation of use of cyclopropane and ether

C. Need fuel, ignition source and oxidizing agent

D. ?

E. ?
ANSWER C

A. FALSE

B. FALSE : drastic fall in explosion, but not fires

C. TRUE : fire triad : oxidizer, ignition, fuel


Diathermy 70% and Laser 10% of OT fires
EM 65 Features most suspicious for myocardial ischaemia

a. ST depression 2mm during fem pop bypass in 60 yo man under spinal

b. T wave inversion in fem pop bypass in 60yo under spinal

c. 0.7mm ST elevation in fem pop bypass in 60 yo man under spinal

d. SAH in young man

e. 32 yo woman during LSCS
ANSWER A
EZ73 ANZCA version [2004-Apr] Q149, [2004-Aug] Q52

The electrical requirement that distinguishes a "cardiac protected area" from a "body protected area" is the

A. equipotential earth

B. isolation transformer

C. line isolation monitor

D. maximum leakage current to patient limit of 500 microamperes

E. residual current device
ANSWER A

Need a class A area for a cardiac protected area.

Class Z
-Fuse Boxes which limit the maximum current through the active wire.
-8 Amp fusewire for lighting circuits
-15 Amp for power
-Standards limiting the amount of current through any set of power outlets.

Class B
-As for Class Z Areas plus:
-Earth-leakage detection devices must be used, ie Earth Leakage Core Balance Relays (RCD's) or Isolating transformers with Line Isolation Monitors.
-The earth wiring must be used and tested regularly for low resistance.
-All equipment having patient circuits must be class BF or CF.


Equipotential Earth = Class A
EZ91 Aug10 Which LMA has highest seal pressure?

A. Classic

B. Disposable supreme

C. Flexible

D. Intubating

E. Proseal
ANSWER B


LMA Classic - Seal pressure up to 20cm H20

LMA Supreme™ - measured oropharyngeal leak pressures up to 37 cm H2O

LMA Flexible™ - oropharyngeal
LMA Fastrach - Seal pressures up to 20 cm H2O

LMA ProSeal™ - leak pressures up to 32 cm H2O
EZ90 [Apr09] Which of the following is the most frequent complication after use of LMA?

A. dysphagia

B. dysarthria

C. sore throat

D. hoarse voice

E. dry mouth
ANSWER E

Mr "LMA" Brimacombe again, chapter 21, p554-555 specifically lists all the problems with LMA:


Dry mouth 62-64%

Sore throat 13%

Dysphagia 11.5%

Dysarthria 5.3%
EZ89 [Apr09]

Why does a proseal LMA provide a better airway seal?

A. More stable position due to oesophageal tube

B. Doral cuff pushes ventral cuff...?

C. Presence of oesophageal lumen

D. Higher cuff pressure

E. ?
ANSWER B

Proseal LMA has a 2nd dorsal cuff, which pushes the LMA anteriorly to provide a better seal at the glottic apeture. It also helps anchor the LMA in place, and the Ventral cuff is larger than the classic LMA to help improve the seal.
EZ87 ANZCA version [2005-Sep] Q142 With regard to accidental electrocution, which of the following statements is true?


A. all electrical equipment in the operating room should be earthed

B. risk of ventricular fibrillation increases with increasing current frequency

C. risk of ventricular fibrillation is greater with alternating current (cf. direct)

D. risk of electrocution is reduced by earthing the patient

E. use of battery operated equipment avoids the risk of ventricular fibrillation
ANSWER C

A. FALSE : electrical equipment in OR should have isolated circuit

B. FALSE : between 30-100Hz

C. TRUE

D. FALSE : patients should not be earthed

E. FALSE
EV08

A hypothetical volatile anaesthetic agent with a saturated vapour pressure of 380 mmHg at 20C is placed in a copper kettle vaporiser. The flow meters are set at oxygen 2 l/min & nitrous oxide 2 l/min. Flow into kettle 0.5 l/min. At 20C the concentration of the volatile anaesthetic agent delivered in the gas is:

A. 1%

B. 2%

C. 5%

D. 10%

E. 11%
ANSWER D

Cooper Kettle Vaporizer :dial up 2 separate flows
1. Vapor inlet flow : where vapor is added, where the concentration vapor =SVP/ATM x 100
2. Diluting fresh gas flow : mixes and dilutes.

Conc vapor = 380/760 x 100 = 50%
As Inlet flow =0.5L, therefore Outlet flow must be 1L
Diluting flow is 4L, therefore total flow is 5L
Therefore Volatile Concentration = 0.5 / 5 = 10%

This is different to a variable pass vaporizer, where FGF is diverted to vaporizer.
Conc vapor = 380/760 x 100 = 50%
As Inlet flow =0.5L, therefore Outlet flow must be 1L
FGF is 4L, but 0.5L used for vaporizer, therefore total flow is 4.5L

Volatile Concentration = 0.5 / 4.5 =11%
EZ84 [Apr07]

You are performing a Level 2 check on the anaesthetic machine. The suction bulb at the common gas outlet does not stay compressed after 10 seconds. The cause of this could be:

A. leak in CO2 absorber

B. loosely seated vaporiser

C. leak in pipeline O2

D. leak in cylinder attachment to anaesthetic machine

E. malfunction in one of the valves of the ventilator circuit
ANSWER B

This is a low pressure test :
-Bulb is connected to common gas outlet
-squeezed repeatedly
-must stay deflated > 10 seconds
-tests flow meter to common gas outlet

NOT the circle system (tubing, valves, CO2 absorber, reservior, vaporizer)
EM68 [Aug09]

In an arterial line system

A. Overdamping exaggerates mean

B. Underdamping increases mean

C. Underdamping underestimates systolic

D. ? multiple damping coefficients in an optimal system

E. Compliant tubing is good
ANSWER D?

Damping of the pressure waveform due to poor positioning of the cannula, or the use of overly compliant tubing, underestimates systolic pressure and overestimates diastolic pressure. The mean pressure is still reasonably accurate.
EM67 [Aug09]

The tapered connector between the ETT and machine is

A. 12-20mm

B. 15-22mm

C. 20-30mm

D. 22-30mm

E. 25-35mm
ANSWER B
[Mar10]

Desflurane TEC6 vaporiser, unable to turn dial on. This is NOT because

A. vapouriser is tilted

B. Hotter than 39C

C. On battery power

D. Interlock not engaged, or not seated properly (or something like that)

E. other vapouriser is already on
ANSWER B

The TEC 6 desflurane vaporizer needs to warm up and the "operational" LED light needs to be illuminated before you can turn the dial to the ON position. If you try to turn it on before the "operational" light is on it will not work.
According to Graham (BJA 1994; 72:470-73), causes of vaporizer shutdown include:
o a tilt of about 10 degrees or more - although extremely unlikely given the design
+ excessive tilting of the vaporizer activates auditory and visual alarms and causes cessation of desflurane output.
o it will not work on battery power
+ the 9-volt battery does not supply the heaters with power or maintain the vaporizer in an operational mode.
o the vaporizer will not work unless locked into the selectatec mount, and the selectatec mount wil not allow the use of multiple vaporizers simultaneously
EZ80 ANZCA Version [Mar06] Q150, [Jul06] Q56

Line isolation monitoring protects against microshock

A. in no circumstances

B. only when all equipment in the region is monitored

C. as long as the hazard current is set to 30 milliamps

D. as long as the hazard current is set to 10 milliamps

E. only if grounded equipment is used.
ANSWER A

* Isolating Transformers and Line Isolation Monitors.
* These are the more expensive alternative to RCD's and are widely used in operating theatres because they do not disconnect the power when a fault is detected, yet provide safety should such a fault exist.
* The first component is a large transformer (the Isolating Transformer) mounted in the wall cavity which converts the earth-referenced mains supply to a "floating" supply. The floating supply provides 240V between two active wires, but because the supply is not earth-referenced, the presence of an earth circuit through the patient or anyone else is perfectly safe and no current will flow. All the circuit to earth does is to reference the floating supply to earth; no current actually flows through the earth connection.

* The Line Isolation Monitor continually checks that the floating supply is not earth-referenced, and indicates on a dial how much current could flow to earth if there was an earth connection. If the potential earth current would be more than 5mA an alarm will sound, alerting the anaesthetist to the presence of a loss of the "floating" nature of the supply. It does this by intermittently connecting one of the two active wires to ground through a very large resistance. If the other wire is connected to ground a circuit will be formed and current will flow, and this indicates how much current would flow through the circuit if either of the two active wires are connected to ground.

* As with an RCD the device will not alarm under 5mA, so microshock may still occur unnoticed, however macroshock is very unlikely; only current flowing through the patient from between the active wires will no be detected. (Electricity and electrical hazards
EZ76 ANZCA version [2005-Apr]-Q115 | [2005-Sep]-Q64 | [Mar06]-Q19 | Aug10

Residual Current Devices (also known as Safety Switches)

A. detect differences in current between the active and neutral wires of a circuit

B. isolate the patient from earth

C. monitor the isolation of the power line

D. must be fitted to all Cardiac Protection areas

E. must be fitted to all operating theatres
ANSWER A

A is BEST answer

B False - Need to use RCD or line isolation

C False - RCD or line isolation

D False

E False - RCD or LIM (LIM for things that are unsafe to turn off - like ventilators...)
What is Class I equipment?
Class I equipment is fitted with a three core mains cable containing a protective earth wire. Exposed metal parts on class I equipment are connected to this earth wire.

Should a fault develop inside the equipment and the exposed metal comes into contact with the mains, the earthing conductor will conduct the fault current to ground. Regular testing procedures ensure that earthing conductors are intact, as the integrity of the earth wire is of vital importance.
What is Class II equipment?
Class II equipment is enclosed within a double insulated case and does not require earthing conductors. Class II equipment is usually fitted with a 2-pin mains plug. An internal electrical fault is unlikely to be hazardous as the double insulation prevents any external parts from becoming alive. Class II or double insulated equipment can be identified by the class II symbol on the cabinet.
What does Defibrillator Proof mean?
Some medical equipment within the hospital is classified as defibrillator proof. When a defibrillator is discharged through a patient connected to defibrillator proof equipment, the equipment will not be damaged by the defibrillator's energy. Defibrillator proof equipment can remain connected to the patient during defibrillation. It is identified by one of the following symbols.
What does Body-Protected Electrical Area mean?
*
These areas are designed for procedures in which patients are connected to equipment that lowers the natural resistance of the skin. Applied parts such as electrode gels, conductive fluids entering the patient, metal needles and catheters provide an easy pathway for current to flow.
*
The main occurrence of injury from Body-Type procedures is from high current levels causing electric shock. A direct connection to the patient's heart is not present so the risk of 'Microelectrocution' - fibrillation from minute current levels - is reduced.
*
Residual Current Devices (RCD) or Isolation Transformers and Line Isolation Monitors (LIMís), are used in Body Protected areas to provide protection against electrocution from high leakage currents. Body-Protected Areas are identified with this sign.
What does Cardiac Protected Area mean?
*
Where the procedure involves placing an electrical conductor within or near the heart, protection against fibrillation induced from small leakage currents is required. Electrical conductors used in these procedures include cardiac pacing electrodes, intracardiac ECG electrodes and intracardiac catheters.
*
Equipotential earthing in conjunction with RCD's or LIM's provides protection against microelectrocution in Cardiac-Type procedures.
*
Fault currents are reduced to magnitudes that are unlikely to induce fibrillation. Used in conjunction with RCD's or LIM's, the magnitude and duration of any fault currents sourced from equipment are limited.
*
Cardiac-Protected Areas are identified with this sign.
What is Equipotential Earthing?
Equipotential earthing is installed in rooms classified as 'Cardiac Protected' electrical areas. Equipotential earthing in treatment areas used for cardiac procedures is intended to minimise any voltage differences between earthed parts of equipment and any other exposed metal in the room.

This reduces the possibility of leakage currents that can cause microelectrocution when the patient comes into contact with multiple items of equipment, or if the patient happens to come into contact with metal items in the room while they are connected to a medical device.

All conductive metal in an equipotential area is connected to a common equipotential earth point with special heavy duty cable.
PV23 ANZCA version [2005-Sep] Q131, [Mar06] Q54

Prior to surgical stimulation, which of the following drugs, when added to propofol or volatile anaesthesia, will decrease the bispectral index (BIS)?

A. 70% nitrous oxide

B. ketamine (0.5mg. kg-1)

C. midazolam (0.2 mg.kg-1)

D. remifentanyl infusion (0.25 microg.kg-1.min-1)

E. all of the above
ANSWER C
EZ87 ANZCA version [2005-Sep] Q142 [2006-Mar] Q79

With regard to accidental electrocution, which of the following statements is true?

A. all electrical equipment in the operating room should be earthed

B. risk of ventricular fibrillation increases with increasing current frequency

C. risk of ventricular fibrillation is greater with alternating current (cf. direct)

D. risk of electrocution is reduced by earthing the patient

E. use of battery operated equipment avoids the risk of ventricular fibrillation
ANSWER C

A equipment supplied by an isolated circuit is not earthed

B diathermy does not cause electrocution because of its very high frequency

C AC is more arrhythmogenic than DC - so this is the answer

D Should not earth them

E probably not if you connect the equipment up to their pacing wires
SZ23 [Mar06] Q102

Regarding decontamination of anaesthetic equipment

A. alcohol is sporicidal

B. disinfection is sporicidal

C. phenol is sporicidal

D. sterilisation with ethylene oxide requires 5-12 hours to work

E. sterilisation with glutaraldehyde requires 5-8 exposure hours to work
ANSWER D

* A. alcohol is sporicidal - false: " A few disinfectants have sporicidal activity with prolonged exposure and are called high-level disinfectants. It is this level of disinfection that is commonly used for semi-critical anaesthetic and respiratory therapy equipment. High-level disinfectants include gluteraldehyde, stabilized hydrogen peroxide, peracetic acid, chlorine and chlorine-releasing compounds. Low-level disinfectants will kill most vegetative bacteria and some viruses and fungi. Examples include alcohols, sodium hypochlorite and iodophore solutions."

* B. disinfection is sporicidal - false: See above

* C. phenol is sporicidal - false: See Table 2

* D. sterilisation with ethylene oxide requires 5-12 hours to work - true: "In the US, ethylene oxide is used commonly for the sterilization of heat- and moisture-sensitive devices. It is a colourless gas and very flammable; risks of fire are reduced by dilution with inert gases such as carbon dioxide or hydroflurocarbons. Microbiocidal activity is thought to be the result of alkylation of protein, DNA and RNA. Temperatures of 29–65°C are employed and cycles are 5–12 h."

* E. sterilisation with glutaraldehyde requires 5-8 exposure hours to work - false: "Immersion in gluteraldehyde 2% is a form of sterilization and is used for optical instruments such as cytoscopes or bronchoscopes as it is non-corrosive and has no deleterious effects on lens cement. Immersion must be >10 h; less time will result in disinfection, not sterilization."
What is the Spaulding classifcation
The Spaulding classification divides all hospital equipment into 3 catgegories based upon the degree of risk of infection involved with their use.

1. Critical Items
-items which enter sterile tissue or vascular system
-high risk of infection if contaminated
-surgical equipment, cardiac and urinary catheters, implants and needles
-sterile at time of use

2. Semi critical items
-contact mucus membrane and non-intact skin but not not break the blood barrier
-intermediate risk of infection
-laryngoscopys, fibre-optic endoscopes and thermometeres
-intact membranes are resistent to infection by spores
-require at least high level disinfection

3. Non-critical items
-contact with healthy skin but no mucus membranes
-blood pressure cuffs and pulse oximeters
-low risk of transmitting infectious agents
What are the methods of disinfection?
Disinfection is a process that eliminate all microorganisms except bacterial spores.
(decontamination : removal of micro-organism and unwanted matter frm contaminated material or living tissue)
(sterilisation : complete destruction of all micro-organisms, including spores.)

1. Liquid chemicals
-convenient, rapid and cheap but can be toxic, flammable and corrosive
-chemical disinfectants include Glueraldehyde 2%, Peracetic acid, Alcohol 60-80%, Hydrogen peroxide, Chlorine-releasing agents and Phenolics 0.6-2%
-Alcohol, hydrogen peroxide and phenolics are NOT sporicidal
-Hydrogen peroxide is poor mycobacterial disinfection
-All good bacterial disinfection
-Phenolics poor viral disinfection
-Hydorgen peroxide and Chlorine-releasing agents can be damaging
-Gluteraldehyde, Chlorine-releasing and Phenolics are irritant

2. Pasteurization
-use of hot water at 77°C for 30 minutes
-achieves intermediate-level of disinfection
-bacterial spores are not killed
What are the methods of sterilization?
Sterilization is a process which there is complete destruction of all microbial life, including spores

Sterility Assurance Level (SAL) : measure of sterility, probability of an organism surviving on the device

Sterilization is achieved by steam, ethylene oxide, gluteraldehyde or gas plasma.

1. Steam Sterilization
-recommended method for devices that can withstand heat and moisture
-most effecient and safest method
-non toxic, non corrosive, rapid and fully automated
-organisms are destroyed by denaturation and coagulation of enzymes and structural proteins
-instruments cleaned to reduce bioburden, packaged and loaded into autoclave
-autoclave at temp > 100°C, air evacuated to allow 100% dry and saturated steam
-minimum holding time is 121°C for 15 min or 134°C for 3 min

2. Chemical Sterilization
*Ethylene Oxide
-used for heat and moisture sensitive devices
-colourless gas and very flammable
-alkylation of protein, DNA and RNA
-temp 29-65°C, cycled for 5-12 hours
-lengthy, expensive and potentially toxic
-not recommended for respiratory equipment
*Gluteraldehyde
-immersion must be >10hours
-less time will result in disinfection not sterilzation
-used for optical instruments such as cytoscopes or bronchoscopes
-no lens cement

3. Gas Plasma Sterilization
-new technique
-higly ionized gas containing ions and free radicals
-particles can diffuse through packing materials and sterilize their contents
-non-toxic, dry, low-temperature sterilization
-cycle of only 75 minutes
What are some of the infection control guidelines for anaesthetic equipments
AZ51 ANZCA version [2001-Apr] Q33, [2003-Apr] Q21, [2003-Aug] Q46 (A-type with only 4 options) [2006-Mar] Q110-similar question but with 5 options

During anaesthesia for Magnetic Resonance Imaging,

A. any ferromagnetic items outside the 30 Gauss line will not be strongly attracted to the magnetic core

B. any battery-powered monitor of non-ferromagnetic construction can be safely placed close to the magnetic core without risk of attraction to the magnet

C. the most commonly used MRI contrast medium, gadopentetate dimeglumide (Magnevist) induces a similar incidence of side effects as does the iodinated contrast media used in radiology

D. it is essential to limit the use of halogenated agents as halogen atoms exhibit the property of nuclear magnetic resonance and may interfere with image quality

E. permanent pacemakers can only be permitted if they have been completely disabled prior to the MRI (2006 March paper)
ANSWER A

A. TRUE :
* 5 Gauss line - safe magnetic exposure
* 30 gauss line - safe for ferromagnetic objects

B. FALSE : some batteries are ferromagnetic and will thus be attracted to the magnet. Watch out for ferromagnetic batteries in non-ferromagnetic laryngoscopes as well. How do you tell? Buggered if I know, you'll just have to use the test-magnet in the control room

C. FALSE : Side effects secondary to iodinated contrast media are very common with anaphylactoid reactions occurring disturbingly frequently and renal failure being a well known problem. Magnevist is very safe with serious allergic reactions occurring in about 1:100,000 people

D. FALSE

E. FALSE : doesnt matter if they are disabled, the leads and the unit itself are ferromagnetic.
EM61 ANZCA Version [Jul06] Q100

Which statement about the use of Entropy depth of anaesthetic monitoring is true?

A. artefacts caused by cardiac pacemakers produce a high RE (Response entropy) value

B. RE only assesses the EEG (electroencephalogram) range from 32-47Hz (high frequency)

C. SE (State Entropy) values range from 0 – 100

D. SE is a stable indicator of the effects of hypnotics on the cortex

E. the RE algorithm filters the EMG (electromyogram) component
ANSWER D

Entropy provides information on the depth of anaesthesia
-measures the irrgularity of EEG and FEMG signs
-EEG from irregular to more regular patterns as anaesthesia deepens

Response entropy : fast-reacting
-0 to 47Hz
-display 0-100
-EMG
-sensitive to the activation of facial muscles

State Entropy : more steady and robust
-0 to 32Hz
-display 0-91
-EEG
-NMBA are not known to affect EEG
-state of hypnosis

N2O does not affect BIS

Pacemakers and diathermy are filtered
EM65 ANZCA Version [Jul06] Q125 Apr07 Q4

Insertion of a pulmonary artery catheter is relatively contraindicated if the patient has an ECG (electrocardiogram) showing

A. anterior fascicular block

B. atrial fibrillation

C. left bundle branch block

D. posterior fascicular block

E. right bundle branch block
ANSWER C

Passing PAC through RV can cause RBBB in 5% of patients
-therefore patients with LBBB can result in complete heart block

PAC contraindicated
-TV OR PV mechanical prothesis
-right heart mass (thrombus or tumor)
-TV or PV endocarditis

Relative contraindications to PAC
-LBBB
-WPW
-Ebstein's malformation
EZ68 ANZCA version [2002-Mar] Q96, [2002-Aug] Q31

Carbon monoxide production by soda lime degradation of volatile anaesthetic agents, is LEAST likely to occur with

A. the first case of the day and the use of isoflurane

B. the first case of the day and the use of sevoflurane

C. the first case of the day and the use of desflurane

D. fresh soda lime and the use of desflurane

E. fresh soda lime and the use of sevoflurane
ANSWER E

The anesthetic used: for a given minimum alveolar anesthetic concentration (MAC)-multiple, the magnitude of CO production (greatest to least) is Desflurane > enflurane > isoflurane >> halothane = sevoflurane. (Ref: Anesth Analg 1995; 80:1187-93)


In summary regarding CO production:

* Baralyme > Sodalime;
* Dry > fresh
* D>E>I>S=H
EZ72 ANZCA version [2004-Apr] Q147, [Jul06] Q78, [Apr07]

The output of a diathermy machine does NOT cause patient electrocution because the

A. current is too low

B. current travels on the surface of the body

C. frequency is too high

D. return electrode is never placed between the heart and the operating site

E. voltage is too low
ANSWER C

Electrocution related to the voltage and the current density.

Patients are not electrocuted because
1. every attempt is made to make sure the return electrode does not 'cross' the heart,
2. low current as possible is used, combined with the lowest voltage to make the resistance work (ie humans are more sensitive to voltage as a sensation)
3. frequency is high, too high to cause VF, frequency>100kHz produce entirely heat
EZ85 ANZCA version [Apr07] [Jul07]

In a rotameter the:

A. Bobbin spins inside a tube that has parallel sides

B. Flow is laminar at high flow rates

C. Height of the bobbin is proportional to the pressure drop across the bobbin

D. Pressure drop across the bobbin is constant at varying flows

E. Resistance increases with increasing gas flow
ANSWER D

Rotameters are widely used in gas delivery systems for continuous flow measurement.
-vertical tapered tube containing a bobbin or ball which is supported by the gas flow as it passes upwards through the tube
-weight of the bobbin (and thus the pressure drop required to support it) is constant, but as the flow increases its position in the tube rises, lowering the resistance as a larger pathway is created alongside the bobbin.

-laminar flow but at the top of the tube produce turbulent flow.
-The physical characteristics of the gas that determine the resulting flow are therefore viscosity at the bottom and density at the top of the tube.
-calibration of rotameters is gas-specific and for accuracy its use must be restricted to that gas
-the flow rate from the top of a bobbin but the centre of a ball.

The range of gas flow measurements can be increased by using two tubes (one for low and one for high flow rates), or by varying the taper so that a greatly increased diameter results at the top of the tube.

Inaccuracy results from anything that causes the bobbin to stick in the tube, including dirt or static electricity. To prevent build-up of static, the inside walls of a rotameter and its mounting points are made of conductive material. To demonstrate that the bobbin is not stuck, it has angled flutes to produce rotation, which is made easier to see by appropriate colouring.

Back pressure caused by downstream resistance also leads to an inaccurately low reading on a rotameter, though the actual flow is the same as that shown before the resistance was applied.
EP05

Which physical law relates to the function of rotameters?

A. Avogadro's law

B. Henry's law

C. Poiseuille's law

D. Graham's law

E. Bernoulli's law
ANSWER E

A: Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules

B: At equilibrium, the amount of gas (the mass) dissolved in a liquid, is directly proportional to the partial pressure of that gas in contact with the liquid at a given temperature.

C: False - C isn't true for several reasons. Poiseuille's Law was based on straight, round, rigid tubes with laminar flow. Rotameters on the other hand:

* Are variable orifice devices (ie tapered rather than straight tubes)
* Flow is a combination of Turbulent and Laminar flow
* The bobbin cannot be factored into Poiseuille's equation

D: Graham's law; the rate of effusion of a gas is inversely proportional to the square root of the mass of its particles.

E: The correct answer is Bernoulli's principle.
EZ13

A mixture of 20% oxygen and 80% helium is passed through an oxygen rotameter:

A. Flow will be independent of the rotameter setting

B. At 1 l/m flow setting, the real flow is 500 mls/min

C. At 10 l/m flow setting, the real flow is 20 l/m

D. At 10 l/m flow setting, the real flow is 15 l/m

E. At 5 l/m flow setting, the real flow is 15 l/m
ANSWER D

Rotameters
* Rotameters have a mixture of laminar and turbulent flow
o Tend to be laminar with low flows, turbulent with high flow
o Tend to laminar at bottom of rotameter, turbulent at top
* Rotameters are constant pressure, variable orifice flowmeters

* Laminar flow
o Q = ΔPπr4 / 8nl

* Turbulent flow
o Q ∞ r2
o Q ∞ sqrt(ΔP)
o Q ∞ 1 / length
o Q ∞1/ sqrt(ρ) (density)

Calculations

The actual flow rate is obtained by multiplying the flow rate on the meter by the square root of the density ratios.

Density Helium = 0.164 kg/m3
Density Oxygen = 1.31 kg/m3

Heliox 70/30, multiply reading by 1.6 (oxygen-calibrated meter) and 1.5 (air-calibrated one).

For heliox 80/20, the multiplying factors are 1.8 and 1.7 for oxygen and air-calibrated devices respectively.
EZ14

If a 50% mixture of helium and oxygen is passed through an oxygen rotameter which of the following statements are most nearly true:

A. If rotameter reads 10 l/m, the actual flow is approximately 20 l/m.

B. If rotameter reads 2 l/m, actual flow is approximately 1 l/m

C. If rotameter reads 2 l/m, actual flow is approximately 0.5 l/m

D. A direct relationship exists between reading and actual flow

E. None of the above
ANSWER D

The actual flow rate is obtained by multiplying the flow rate on the meter by the square root of the density ratios.

Density Helium = 0.164 kg/m3
Density Oxygen = 1.31 kg/m3

Heliox 70/30, multiply reading by 1.6 (oxygen-calibrated meter) and 1.5 (air-calibrated one).

For heliox 80/20, the multiplying factors are 1.8 and 1.7 for oxygen and air-calibrated devices respectively.
ANZCA Version [Apr 07]

When a circle absorption system is in use with an intubated 70kg adult patient, rebreathing of expired gas becomes practically negligible if

A. a fresh gas flow rate of > 9L/min is used

B. intermittent PPV is used, rather than spontaneous ventilation

C. the carbon dioxide absorbent is fresh and has an intergranular space of at least one litre

D. the minute volume is > 9L

E. the FGF enters the circle circuit on the absorber side of the inspiratory valve
ANSWER D??
EZ69 ANZCA version [2001-Aug] Q110, [2002-Mar] Q116

When a circle absorption system and tracheal intubation are in use with an adult subject, rebreathing of expired gas becomes practically negligible if

1. spontaneous breathing is replaced by intermittent positive pressure breathing

2. the minute volume is 8 L.min-1or more

3. the carbon dioxide absorbent is fresh and has an intergranular space of at LEAST one litre

4. a fresh gas flow rate of at LEAST 8 L.min-1 is used
ANSWER 4
EM64 [Apr07] See also EC03 & EC04

Oxygen cannot be measured by:

A. fuel cell

B. mass spectrometry

C. infra-red spectrophotometry

D. Paramagnetic analysis

E. Raman scattering
ANSWER C

Gases that have 2 or more different atoms will absorb infra-red radiation.

Infrared spectrophotometry can't be used for O2, He, Xe, Argon
EZ86 ANZCA Version [Jul07]

An anaesthetised patient is ventilated and has standard monitoring plus a central venous line. As the surgeon is commencing the case, the line isolation
monitor (LIM) alarms indicating a potential leakage current of greater than 5 milliamps from one of the power circuits in use.
The most appropriate action is to

A.check the diathermy return plate

B.disconnect the central line to electrically isolate the patient till the fault is identified

C.make sure the patient is properly "earthed" or "grounded"

D.sequentially unplug non-vital equipment from the circuit until the fault is identified

E.suspend the operation and move the patient to a safe environment
ANSWER B

LIM alarms it warns of the existence of a single fault, but 2 faults are required for a shock to occur. The last piece of equipment that was plugged in is suspect and should be removed from service until it is repaired.
AC155 [Apr07]

A patient with severe COPD on home oxygen is having an excision of a submandibular tumour under local anaesthesia. The best way to prevent fire in the operating room is:

A. seal the surgical site from the patients airway with adhesive drapes

B. use bipolar instead of monopolar diathermy

C. decr FIO2 to maintain sats 97%

D. use alcoholic chlorhex instead of iodine

E. add nitrous oxide to the inhaled gases to reduce the FiO2 and provide sedation
ANSWER B

Preventing fires
1. Controlling heat sources
-Bipolar < monopolar
-Using wet, sterile towels and non flammable drapes
-Cleaning diathermy tip, adherant burn tissue can ignite

2. Managing fuels
-giving sufficient time to allow bapors and gases to dissapate
-avoid or minimise pooling of volatile liquids

3. Minimizing oxgen contration
-minimize oxygen concentration, tritrate FiO2 to Sat>90%
-dilute oxygen with an inert gas (N2 or He), gas scavenging or a circle breathing system
List some fuels commonly encountered in surgery.
In/On Patient
-Hair (face, scalp, body)
GI tract gases (mostly methane)

Prepping Agents
-Degreasers (ether, acetone)
-Aerosol adhesives
-Alcohol (also in suture packets)
-Tinctures (Hibitane [chlorhexidine digluconate], Merthiolate [thimerosal]), DuraPrep [idophor])

Linens
-Drapes (woven, nonwoven, adherent)
-Gowns (reusable, disposable)
-Masks
-Hoods and caps
-Shoe covers
-Instrument and equipment drapes and covers
-Egg-crate mattresses
-Mattresses and pillows
-Blankets

Dressings
-Gauze
-Sponges
-Adhesive tape (cloth, plastic, paper)
-Ace bandages
-Stockinettes
-Collodion (mixture of pyroxylin, ether, and alcohol)

Ointments
-Petrolatum (petroleum jelly)
-Tincture of Benzoin (74% to 80% alcohol)
-Aerosols (e.g., Aeroplast)
-Paraffin
-White wax

Equipment/Supplies
-Anesthesia components (breathing circuits, masks, airways, tracheal tubes, suction catheters, pledgets)
-Flexible endoscopes
-Coverings of fiberoptic cables and wires (e.g., ESU leads, ECG leads)
-Gloves
-Blood pressure and tourniquet cuffs
-Stethoscope tubing
-Disposable packaging materials (paper, plastic, cardboard)
-Smoke evacuator hoses
-Some instrument boxes and cabinets
SF53 ANZCA version [2001-Apr] Q6, [2001-Aug] Q4, [2003-Aug] Q66, [2004-Apr] Q55, [Mar 10],[Aug10]

Carbon dioxide is the most common gas used for insufflation for laparoscopy because it

A. is cheap and readily available

B. is slow to be absorbed from the peritoneum and thus safer

C. is not as dangerous as some other gases if inadvertently given intravenously

D. provides the best surgical conditions for vision and diathermy

E. will not produce any problems with gas emboli as it dissolves rapidly in blood
ANSWER C

Carbon dioxide is the most frequently used gas for insufflation of the abdomen as it is colourless, non-toxic, non-flammable and has the greatest margin of safety in the event of a venous embolus (highly soluble). It is absorbed readily from the peritoneum, causing an increase in PaCO2.
EM16 ANZCA version [2002-Mar] Q68, [2002-Aug] Q64, [2005-Apr] Q94, [2005-Sep] Q75

Circuit disconnection during spontaneous breathing anaesthesia


A. will be reliably detected by a fall in end-tidal carbon dioxide concentration

B. will be detected early by the low inspired oxygen alarm

C. will be most reliably detected by spirometry with minute volume alarms

D. may be detected by an unexpected drop in end-tidal volatile anaesthetic agent concentration

E. can be prevented by using new, single-use tubing
ANSWER D

Circuit disconnection during spontaneous breathing anaesthesia

* A. will be reliably detected by a fall in end-tidal carbon dioxide concentration - false: If circuit disconnect at the machine, ETCO2 will be normal.
* B. will be detected early by the low inspired oxygen alarm - false: Disconnection allows entrainment of room air which will not be detected by low inspired O2 alarm
* C. will be most reliably detected by spirometry with minute volume alarms - false: Depends where the spirometry is taken from, but some spirometry taken near the filter and so a disconnect at the machine will not be detected
* D. may be detected by an unexpected drop in end-tidal volatile anaesthetic agent concentration - true: Any disconnect will allow entrainment of room air into the circuit and allow escape of the volatiles, thus a drop in the ET-agent.
* E. can be prevented by using new, single-use tubing - false: Single use tubing will not prevent a disconnection.
EZ70 ANZCA version [2002-Aug] Q104, [2004-Apr] Q87, [2004-Aug] Q69

Significant differences between the LMA-ProSeal™ and the standard laryngeal mask (LMA-Classic™) include all of the following EXCEPT

A. a built in bite-block

B. a double cuff arrangement

C. an improved seal pressure at a given cuff pressure

D. an independent oesophageal drain tube

E. improved aperture bars to prevent the epiglottis occluding the airway tube
ANSWER E
EV02c ANZCA Version [Jul07]

Isoflurane is administered in a hyperbaric chamber at 3 atmospheres absolute pressure using a variable bypass vaporizer.
At a given dial setting and constant fresh gas flow, vapour will be produced at:

A. the indicated vapour concentration

B. three times the indicated vapour concentration

C. one third the partial pressure obtained at 1 atmosphere

D. the same partial pressure as is obtained at 1 atmosphere

E. three times the partial pressure obtained at 1 atmosphere
ANSWER D

vaporisers use saturated vapour pressure, which is a function of temperature and not ambient pressure. The concentration delivered is inversely proportional to the ambient pressure.

Concentration of agent = SVP/Atmospheric pressure. For example at altitude and ambient P of 380mmHg, a vaporiser calibrated to deliver 1% at sea level will therefore deliver 2% (or in the case of iso SVP becomes 2/3 of 1 atmosphere), which is still 7.6mmHg (2% of 380mmHg). Thus although the output of the vapouriser in volume percent increases, the partial pressure is unchanged and it is this that is responsible for the clinical effect. Thus clinically at altitude vaporisers can be used as normal.
AZ04 ANZCA Version[Jul07]

Which of the following statements regarding infection control is FALSE ?

A. devices to be used in the upper airway that may cause bleeding must remain sterile until used

B. provided there is an adequate filter between the patient and the breathing circuit, the circuit can be re-used for subsequent patients on an operating list

C. when performing central neural blockade, the anaesthetist must adopt a full aseptic technique

D. when performing central venous cannulation, the anaesthetist must adopt a full aseptic technique

E. when performing vascular cannulation, the anaesthetist must wash hands and should wear gloves
ANSWER ??
They all appear true.
EM69 ANZCA version [Apr08] Q104 [Mar 10]

The systolic blood pressure may be overestimated by the auscultatory method of blood pressure measurement if:

A. the cuff is deflated too slowly

B. the patient has severe arteriosclerosis

C. the patient's arm is very thin

D. there is severe peripheral vasoconstriction

E. too wide a cuff is used
ANSWER D

A. FALSE - Inappropriately small cuff leads to BP overestimation

B. ? FALSE - With an appropriately sized cuff shouldn't matter...

* The maximal pressure under the cuff is proportional to the inflation pressure and cuff width. A cuff that is too narrow generates lower tissue pressures than indicated and thus overestimates blood pressure. Conversely, a very wide cuff slightly underestimates blood pressure. A correctly fitted cuff should cover two-thirds of the upper arm or should be roughly 20% wider than the diameter of the limb. (AICM 2005 6 (12); 405-7)

C. FALSE - Intense vasoconstriction leads to BP underestimation

D. TRUE - Calcified, noncompressible arteries lead to BP overestimation

E. FALSE - Overly rapid cuff deflation leading to BP underestimation


OVERESTIMATE -non compliant vessels
-small cuff
-periperal oedma
-cuff to loose
-too distal
-too frequent
EZ88 [Aug10] [Mar10]

A device that detects a 10mA difference in active and neutral leads
and causes turning off of the circuit within 40 ms.
This is a:

A. Class 1 device

B. Equipotential earthing

C. Line isolation monitor

D. Residual Current Device

E. Fuse
ANSWER D

A Class 1 device = earthed, insulated wires, fuses within equipment B Equipotential earth is a mechanism where the casings of all the equipment in theatre are earthed to the same potential so there can't be a potential difference between two live casings which would be potential source for macro or microshock (green and yellow cabels) C Line isolation monitor detects leakage currents >5mA and sounds an alarm, it does not automatically shut anything off D = detects current leakages and then shuts off supply- not so good if there is life saving equipment being used, e.g. CPB
TMP-136 [Apr08] Q96

When obtaining an image using ultrasound, the most effective way to improve the spatial resolution is to increase the:

A. 2D gain

B. frame rate

C. single scatter

D. time gain compensation

E. transducer frequency
ANSWER E

A. FALSE amplify signal intensity, brighter with increased noise

B. FALSE : applies to color flow, increasing the frame rate will increase solution

C.

D. FALSE : selectively amplify weak signals from deeper structures

E. TRUE - increase resolution and depth
AZ52 [Aug96] [Apr98] [Jul98] [Jul00] (type A)

In MRI scan, which will NOT cause patient burns:

A. Thermistor temperature probe

B. Non-metallic face makeup

C. Coiled monitor leads on patient chest in magnetic core

D. Non-ferromagnetic equipment touching patient

E. Pulsating magnetic field
ANSWER B
EZ89 [Apr09]

Why does a proseal LMA provide a better airway seal?

A. More stable position due to oesophageal tube

B. Doral cuff pushes ventral cuff...?

C. Presence of oesophageal lumen

D. Higher cuff pressure

E. ?
ANSWER B

Proseal LMA has a 2nd dorsal cuff, which pushes the LMA anteriorly to provide a better seal at the glottic apeture. It also helps anchor the LMA in place, and the Ventral cuff is larger than the classic LMA to help improve the seal.
EZ90 [Apr09]

Which of the following is the most frequent complication after use of LMA?

A. dysphagia

B. dysarthria

C. sore throat

D. hoarse voice

E. dry mouth
ANSWER E

Mr "LMA" Brimacombe again, chapter 21, p554-555 specifically lists all the problems with LMA:

* Dry mouth 62-64%
* Sore throat 13%
* Dysphagia 11.5%
* Dysarthria 5.3%
EV08 [1986] [1987] [1988] [Mar93] [Aug93] [Aug95] [Apr96] [Aug96] [Apr99] [Aug99] [Aug09]

A hypothetical volatile anaesthetic agent with a saturated vapour pressure of 380 mmHg at 20C is placed in a copper kettle vaporiser. The flow meters are set at oxygen 2 l/min & nitrous oxide 2 l/min. Flow into kettle 0.5 l/min. At 20C the concentration of the volatile anaesthetic agent delivered in the gas is:

A. 1%

B. 2%

C. 5%

D. 10%

E. 11%
ANSWER C

Cooper Kettle - 2 flows
1. Vopor flow = 100% saturated
-concentration of volatile = SVP/ATM x100 = 50%
-if flow 0.5L flow in, therefore 0.5L of volatile is added
-meaning 1L volume exits with 50% concentration of anaesthetic vapor

2. Dilutant flow
-4L in total (2L O2 and 2L N2O)
-therefore 0.5/5 =10%
26. (NEW) Negative pressure leak test in a Boyles type machine. This means

a. Vaporiser leak

b. Circuit leak

c. Brain leaking out of my ears by now

d. Leak in non return valve
ANSWER A
32. (NEW) In body protected OR with a Line Isolation Monitor reading 0 mA. If you touch one active wire what will happen.

a. nothing, because no connection to earth is completed

b. you get shocked

c. nothing because the floor is insulated

d. nothing because your shoes are nonconductive

e. RCD trips
ANSWER E
46.Appropriate infection control measures when anaesthetising a patient with suspected variant-CJD, the airway equipment should be

a.thrown away

b.plastic sheath, reuse

c.sterilization with ethylene oxide

d. sterilization with heat at 134 degrees for 3 minutes

e. Autoclave
ANSWER A

Variant CJD - spongiform encephalopathy
-psychiatric disturbance
-failure of muscle conduction
-memory impairment

Prions are not autoclavable
EV18 [Mar10]

Desflurane TEC6 vaporiser, unable to turn dial on. This is NOT because

A. vapouriser is tilted

B. Hotter than 39C

C. On battery power

D. Interlock not engaged, or not seated properly (or something like that)

E. other vapouriser is already on
ANSWER B

The TEC 6 desflurane vaporizer needs to warm up and the "operational" LED light needs to be illuminated before you can turn the dial to the ON position. If you try to turn it on before the "operational" light is on it will not work. I assume that any of the alarms which cause the "operational" light to go off (and subsequently halt delivery of desflurane) mean that if you turn the dial to 0% (i.e. OFF) then you will not be able to turn it back on, but I have not read that anywhere. According to Graham (BJA 1994; 72:470-73), causes of vaporizer shutdown include:

* a tilt of about 10 degrees or more - although extremely unlikely given the design
o excessive tilting of the vaporizer activates auditory and visual alarms and causes cessation of desflurane output...Pharmacology of Inhaled Anaesthetics, p212
* it will not work on battery power
o the 9-volt battery does not supply the heaters with power or maintain the vaporizer in an operational mode...Pharmacology of Inhaled Anaesthetics, p212
* the vaporizer will not work unless locked into the selectatec mount, and the selectatec mount wil not allow the use of multiple vaporizers simultaneously
o nb. note the "Tec" refers to the use with the Select-a-Tec manifold
EV19 [Mar10]

Plenum Vaporiser
A. ? something with fresh gas flows

B. Relies on a constant flow of pressurised gas

C. ? can be used out of circle

D. Not temperature compensated

E. ? Volatile injected into fresh gas flow
ANSWER B

* A - ?
* B - TRUE - Upstream gas source required to push fresh gas through the vaporizer (opposite to Draw-Over vaporizer)
* C - ? FALSE - Don't exactly understand the question/stem. You can use a plenum vaporizer with OR without a circle (e.g. T-piece in paeds)
o Think they are referring to VOC or VIC configuration...kingfed
* D - FALSE - ARE temperature compensated
* E - FALSE - This is refering to the Tec-6 for Desflurane but that is NOT a plenum vaporizer
PI83 [Mar 10]

Desflurane vaporiser, heated because of

A. High SVP

B. High boiling point

C. Low SVP

D. High MAC

E. Low MAC
ANSWER A

Vaporizer heated because of the high SVP.

Desflurane's BP is so much LOWER than the other volatiles, at 23C, that ambient temperature may cause the liquid to boil, causing significant variation in the vapour concentration.

Heated to well above boiling point to ensure reliable concentration of desflurane gas mixture.
TMP-Jul10-028

Cell saver. Which does NOT get filtered ?

A. Foetal cells

B. Free Haemoglobin

C. Platelets

D. Clotting factors

E. Microaggregates of leukocytes
ANSWER A

Foetal cells (particularly fetal RBC's) are NOT filtered/removed, and are spun down with maternal RBC's (ie the process does not differentiate between maternal and fetal RBCs) and then reinfused into the mother.

However, the risk of alloimmunisation is thought to be no greater than that occurring during a normal vaginal delivery. The risk of amniotic fluid embolism is also thought to be very low - so much so that cell salvage in obstetrics has been endorsed by the Obstetric Anaesthetists Association, AAGBI, NICE and CEMACH in the UK, as well as the ASA in America.

Cell salvage filters the following substances:

* Free haemoglobin
* White blood cells
* Plasma
* Platelets
* Heparin
* Clotting factors
* Complement
EZ91 Aug10

Which LMA has highest seal pressure?

A. Classic

B. Disposable supreme

C. Flexible

D. Intubating

E. Proseal
ANSWER B

From the LMA website / product information:

* LMA Classic - Seal pressure up to 20cm H20
* LMA Supreme™ - measured oropharyngeal leak pressures up to 37 cm H2O
* LMA Flexible™ - oropharyngeal seal pressures up to 20 cm H2O
* LMA Fastrach - Seal pressures up to 20 cm H2O
* LMA ProSeal™ - leak pressures up to 32 cm H2O
TMP-Jul10-029

You are on a humanitarian aid mission in the developing world.
Drawover vaporiser apparatus described being used.
Given 400 mm tubing, OMV or diamedica vaporiser, 200mm tubing attached to self-inflating bag.

Which ONE other piece of equipment is ESSENTIAL to make this system functional?

A. Halothane

B. In-line Waters' Cannister

C. Non-rebreathing valve

D. Oxygen source

E. Ventilator
ANSWER C

A drawover system (figure 2) is designed to provide anaesthesia without requiring a supply of compressed gases. Atmospheric air is used as the main carrier gas and is drawn by the patient's inspiratory effort through the vaporizer, where the volatile agent, normally ether or halothane, is added. The mixture is then inhaled by the patient via a non-rebreathing valve.

Features of drawover apparatus:

1. Robust, compact and portable
2. Low purchase price and running costs
3. Straightforward maintenance
4. Not dependent on compressed gases
What is nitric oxide? How is it produced? What are it's effects?
Nitric oxide
-synthesized within cells by an enzyme NO synthase (NOS). -catalyses the oxidation of L-arginine to L-citrulline, producing NO
-diffuses into vascular smooth muscle, activating guanylate cyclase which in turn converts guanosine triphosphate into cyclic guanosine monophosphate (cGMP), causing vascular relaxation

NOS is present in two forms:
1. The constitutive form (eNOS)
-Present in vascular, neuronal, cardiac tissue, skeletal muscle and platelets, producing small quantities of NO continuously. Here NOS is Ca2+/calmodulin dependant and is stimulated by cGMP.

2. The inducible form (iNOS)
-Present in endothelium, myocytes, macrophages and neutrophils, which produces relatively large quatities of NO after exposure to endotoxins in sepsis. Following induction high levels of NO produced may form cytotoxic radicals and cause capillary leakage.

Nitric oxide acts as a biological mediator throughout the body but especially in:

• Vascular endothelium: responsible for vascular relaxation.
• Platelets: involved in aggregation and adhesion.
• Brain tissue: acts as a neurotransmitter.
• Macrophages: involved in the response to infection.
Effects

Cardiovascular
-Nitric oxide is a potent vasodilator. -Shear stresses in vessels increase NO production and may account for flow dependant vasodilatation. -Endothelial NO inhibits platelet aggregation. In septic shock the overproduction of NO results in hypotension and capillary leak. NOS inhibitors have been investigated experimentally in the treatment of sepsis.

Respiratory
-Important basal vasodilatation in pulmonary vessels is provided by endogenous NO and this may be reversed in hypoxia. Nitric oxide inhibits hypoxic pulmonary vasoconstriction and preferentially increases blood flow through well-ventilated areas of the lung, thereby improving ventilation: perfusion relationships.

Neuronal
-Nitric oxide appears to have a physiological role as a neurotransmitter within the autonomic and central nervous system. Proposed roles include modulation of the state of arousal, pain perception, apoptosis and long term neuronal depression and excitation whereby neurones may “remember” previous signals. Peripheral neurones containing NO control regional blood flow in the corpus cavernosum.

Gastrointestinal
-NO is a determinant of gastrointestinal motility and appears to modulate morphine-induced constipation.

Genitourinary
-Nitric oxide may play a role in sodium homeostasis in the kidney. It is the physiological mediator of penile erection.

Immune
-Macrophages and neutrophils synthesize NO which can be toxic to certain pathogens and may be important in host defence mechanisms.

Haematological
-Platelet aggregation is inhibited by NO

Uses
-In neonatal, paediatric or adult pulmonary hypertension, inhaled NO (1-150 ppm) has been used to produce selective pulmonary vasodilatation. Its use in ARDS is increasing although clear effects on outcome have not been conclusively demonstrated.

Storage
-NO is stored in aluminium or stainless steel cylinders which are typically 40 litres. These contain 100/1000/2000 p.p.m. nitric oxide in nitrogen. Pure NO is corrosive and toxic.

Administration
-The drug is injected via the patient limb of the inspiratory circuit of a ventilator. The delivery system is designed to minimise the oxidation of nitric oxide to nitrogen dioxide.

Metabolism
-Inhaled NO readily reacts with oxidised haemoglobin to yield methaemoglobin. NO has a half-life of less than 5 seconds.

Monitoring
-Chemiluminescence and electrochemical analysers should be used and are accurate to 1 ppm.

Toxicity
-Exposure to 500-2000 ppm of NO results in methaemoglobinaemia and pulmonary oedema. Methaemoglobinaemia is only rarely significant and is more common in paediatric patients or those with methaemoglobinaemia reductase deficiency. Contamination by nitrogen dioxide can similarly lead to pneumonitis and pulmonary oedema. Environmental levels should not exceed 25 ppm for 8 hours (time-weighted average).
30. NEW. Flow with the O2 flush button pressed and volatile agent turned on will give you:

A: 20-30l/min O2

B: 30-70l/min O2

C: volatile agent + 30l/m O2

D: volatile agent + 40l/m O2

E: volatile agent + 50l/min O2
ANSWER B

The oxygen flush valve allows direct communication between the oxygen high-pressure circuit and the low-pressure circuit.

Flow from the oxygen flush valve enters the low-pressure circuit downstream from the vaporizers and downstream from the Ohmeda machine outlet check valve.

Actuation of the valve delivers 35 to 75 L/min at a presusre of 50psi to the breathing circuit.
43. NEW. What is the most common way to measure end tidal gas concentrations on our anaesthetic machines?


A: mass spectometry

B: Raman scattering

C: ultrasonic

D: infrared

E: piezoelectric
ANSWER D
TMP-Jul10-036

Which is NOT a disadvantage of drawover vaporiser versus plenum vaporiser?

A. Temperature compensation

B. Cannot use sevoflurane

C. Small volume reservoir

D. Flow compensation

E.
ANSWER B

Drawover vaporisers are

* "simple to assemble and use, and can operate without fresh gas supplies. They are lightweight and portable"
* not well compensated for temperature
o "the OMV...suffers a reduction in vapour output at lower temperatures, with a maximum output varying from 2-4% with halothane between 0-30OC, and higher above this
* very difficult to use with sevoflurane"
o "Sevoflurane (Sevorane) has been used in draw-over, but its use is hampered by a need to deliver high percentages which are at the upper limits of simple vaporiser performance capabilities...using additional wicks to maximise output can be helpful, but latent heat of vaporisation rapidly cools the system and lowers performance...two OMV vaporisers are required to provide adequate concentrations for induction."
* equipped with a small volume reservoir
o the OMV...contains 50mls of volatile agent, empties quite rapidly when in use"
* variable with regards to flow compensation
o for instance..."the OMV...OMV is reasonably accurate over a wide range of flow rates and tidal volumes and, in particular it performs well at small tidal volumes, making it suitable for paediatric anaesthesia"
o but..."EMO only begins to perform reasonably accurately with flow rates around 10 l/min, and is therefore not ideal for paediatric use with a T piece, although circuit adaptations can be made. If used in “pushover’ fashion, with a ventilator or bellows placed upstream, the output can significantly exceed the dial setting."