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101 Cards in this Set
- Front
- Back
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Where must the capnography be to measure both inspired and exhaled gases?
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between the patient and the breathing system
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What does the CO2 waveform show? Numerical value produced?
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*CO2 concentration during the respiratory cycle
*ETCO2 |
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What information does capnography provide?
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CO2 production, pulmonary perfusion, alveolar ventilation, respiratory patterns, and elimination of CO2 from the anesthesia circuit and ventilator
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What events can capnography detect early?
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respiratory events such as malpositioned ETT, circulatory failure, and defective breathing circuits
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According to the ASA closed claim study, how many deaths could have been prevented w/ pulse oximetry and capnography together?
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93%
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Per the ASA, capnography is a standard of care for whom?
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Pt undergoing GA
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Best method to confirm correct ETT placement?
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ETCO2
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What gases does capnography measure?
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CO2, N2O, des, sevo, forane
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How does capnography work?
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Concentration of gas directly proportional to the amount of infrared (IR) light it absorbs
*O2 does not absorb IR light |
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How much IR light does CO2 absorb?
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4.3 milli microns
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How does the capnography monitor identify the gases in use?
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by their absorbance pattern
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Why are both inspired and expired gases monitored?
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Tells us that pt is getting the concentration of anesthetic that was dialed in.
*with CO2 tells us whether they are rebreathing or now |
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Where is the sampling tube located? What is its flow? Where does the gas go after sampled?
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*b/w the ETT and breathing system
*50-200 ml/min *returned to breathing system |
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Advantages to side stream sampling
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*used on non-intubated pt
*several gases can be measured *easy connection *used in many positions *light weight *minimal added dead space |
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Diadvantages to side stream sampling
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*mechanical problems
*tubing obstruction (secretions, blood) *delayed response time *failure of aspiration pump |
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Why is the water trap or filter important?
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Water increases CO2 and volatile agent readings
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Issues causing falsely low CO2?
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poor mask fit, uncuffed ETT, lose connection/crack in tube, dilution of exhaled gas if sampling site far from pt
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Issue causing falsely absent CO2?
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sampling line blockage
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Factors increasing ETCO2
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increased CO, fever, MH, sodium bicarb, venous CO2 emboli, hypoventilation, tournique release, CO2 absorption in peritoneal cavity, faulty valves, inadequate fresh gas flow (bain), exhausted CO2 absorber, rebreathing, PARTIAL airway obstruction
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Factors decreasing ETCO2
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TOTAL airway obstruction, reduced CO, hyperventilation, air/pulmonary emboli, internal calibration cycle, tracheal extubation (lose waveform), cardiac arrest, HoTN
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Correlation b/w PaCO2 and ETCO2 is estimated to be what? Which one should be higher?
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5-10 mmHg
*PaCO2 should always be higher b/c ETCO2 is diluted w/ alveolar dead space gas from underperfused alveoli |
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Highest waveform point tells us what? Frequency of waveform tells us what? What should baseline always be?
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*ETCO2
*RR *Zero |
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Phases of expiratory segment?
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I: anatomic dead space
II: alveolar and anatomic dead space III: alveolar dead space |
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What is Phase O of the cycle
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Inspiration
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If the capnography waveform does not return to baseline (zero), what does this mean?
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rebreathing of CO2
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What can cause inspiratory and expiratory valves to fail? What does this result in?
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*may stick d/t water vapor condensation
*enormous dead space increase, elevated CO2 above baseline |
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What does the shark fin CO2 waveform signify?
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COPD, bronchospasm or upper airway obstruction
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When are cardiac oscillations seen? Are they normal?
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Normal, seen when pt is awakening from anesthesia
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What does the curare cleft signify?
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Pt is initiating their own breath
*or surgeon may be pushing on diaphragm |
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What should you do when a curare cleft is seen?
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*Give more paralytic
*Hyperventilate pt to decrease their drive to breathe *Give more agent |
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What could cause a CO2 waveform w/ an esophageal intubation?
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*Cola drinks
*positive pressure mask ventilation *waveform will decrease in step-wise fashion |
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Purposes of anesthesia breathing systems?
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*deliver anesthetic gases and O2
*deliver anesthesia w/out significant increase in airway pressure *convenient/safe method to deliver inhaled gases |
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2 fundamental purposes of breathing systems?
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*Deliver O2 & anesthetic gases
*Eliminate CO2 **all create some resistance to flow |
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What does APL valve stand for?
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adjustable pressure limiting value
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Types of anesthesia breathing systems?
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open, semiopen, closed, semiclosed
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Describe an open system and give an example?
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no rebreathing, no reservoir bag, no CO2 neutralization, no unidirectional valves
*N/C, open drop ethers *Exhaled gases released into atm |
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Describe a semiopen system and give an example?
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*presence of gas reservoir bag
*no rebreathing *no CO2 neutralization *no unidirectional valves *Mapleson A,B,C,D; Bain, Jackson Rees |
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What is the minimum FGF rate with semiopen systems? Why is there a minimum?
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5 L/min
*FGF must exceed minute ventilation (2-3X) to prevent rebreathing |
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What do NRB circuits lack? amount of rebreathing is dependent on what?
Is WOB increased or decreased? |
*unidirectional valves and soda lime CO2 absorption
*FGF *decreased b/t no valves or CO2 absorbent to create resistance |
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Classification of the Mapleson breathing system is based on what?
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location of the fresh gas inlet and the APL valve; presence or absence of a reservoir bag
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Required fresh gas flow for Mapleson A & E? Mapleson B, C, D, F? Bain
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*3 X minute ventilation
*2 X minute ventilation *Spontaneous: 200-300 cc/kg/min (2 X minute ventilation); Controlled: 70 cc/kg/min |
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How is the Bain system set up?
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*Coaxial (tube w/in a tube)
*Fresh gas enters through narrow inner tube *Exhaled gas exits through corrugated outer tube |
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Advantages of Bain system
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*warming of FGiF by surrounding exhaled gases
*improved humidification w/ partial rebreathing *ease of scavenging waste gases *APL valve *disposable/sterile |
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Disadvantages of bain system?
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*unrecognized disconnection
*kinking of inner FGF tubing *requires high flows |
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Describe a closed circle system?
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*always has gas reservoir bag
*allows for total rebreathing of exhaled gases *always provides for chemical neutralization of CO2 *always contains unidirectional valves |
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How can we create a closed circle system w/ our semi-closed system at DMH?
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Keep FGF to metabolic requirements (250 ml/min) in a 70 kg pt & close APL valve w/ spontaneous ventilation
*no scavenging needed d/t total rebreathing |
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Describe the semi-closed system used at DMH?
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*type of circle system
*always has gas reservoir bag *allows for PARTIAL rebreathing *always has 2 unidirectional valves (I & E) *always has an APL valve *FGF is < minute ventilation |
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7 components of a semi-closed circle system
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FGF source, I & E unidirectional valves, I & E corrugated tubing, y piece connector, APL valve, reservoir bag, & CO2 absorbent
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Advantages of the semi-closed system?
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constancy of inspired concentration, conserves resp. heat and moisture, minimal OR polln.
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Disadvantages of the semi-closed system?
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complex design, multiple connections that can disconnect or leak, malfunctioning valves
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What happens if unidirectional valves are stuck open? Closed?
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*Open: rebreathing CO2
*Closed: total occlusion of circuit |
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Other names for unidirectional valves?
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flutter valves, one way valves, check valves, directional valves, dome valves
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Purpose of the APL valve? When is it completely open? Isolated?
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limits the amount of pressure build up that can occur during manual ventilation
*completely open during spont ventilation *isolated during mechanical ventilation |
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If your CO2 absorbent becomes exhaused during your case what should you do?
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Increase your FGF
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Two types of CO2 absorbents? What do both contain?
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soda lime and barium lime
*hydroxid salts (OH) that neutralizes carbonic acid |
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Reaction in CO2 absorbent and end products
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*base neutralizing an acid
*water, heat, and carbonate |
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Components of soda lime
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4% NaOH, 1% KOH, 14-19% H2O, 100% CaOH, silica for hardening
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Components of barium lime
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*20% barium OH
*80% CaOh *NO silica |
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What color does CO2 absorbent turn when exhaused? What color is it when fresh?
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*Violent w/ CO2 (ethyl violet dye)
*White when fresh |
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Cominbation of small and large granules in CO2 absorbent provides what purpose?
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*Small: increase surface area
*Large: lower resistance to air flow |
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What size are the granules? What is the max volume of CO2 that can be absorbed?
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*4-8 mesh (higher # = smaller particles
*26 L CO2/100 gm of granules |
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What toxic compounds can be produced when anes agents interact w/ CO2 absorbent?
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* CO & Compound A
*Sevo: compound A whether moist or dessicated *Des: dessicated baralyme produces CO |
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APSF recommendations to reduce dessication and production of toxic compounds?
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*turn off all gas flow when machine not in use
*use low fresh gas flow when possible *change absorbent regularly *change absorbent whenever the color change indicates exhaustion *change all absorbents in system (both cannisters) |
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The inside of the bellow is connected to what?
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the breathing system
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What is the power source for the ventilator bellows?
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compressed gas (driving gas) and electricity
*piston vent does not require driving gas |
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What is the drive mechanism for the bellows?
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*Pneumatically driven double circuit
*pneumatic force compresses a bellow which empties fresh gas content into pt |
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What is the driving gas for the Ohmeda system? Drager?
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*Ohmeda: 100% O2 (good b/c if there is a leak, inspired O2 concen. will increase
*Drager: venturi mix of O2 and RA |
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Types of Bellow systems?
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*Ascending: (standing/upright)rise during expiration, safer b/c will not fill is a disconnection occurs
*Descending (hanging/inverted): continues its up and down movement with disconnection |
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Ventilator Hazards (3)
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*disconnection (most commonly at Y-site
*failure to initiate ventilation or resume after pause *Never take for granted that flipping the switch will result in ventilation: ALWAYS OBSERVE AND LISTEN |
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What is the CMV ventilator mode?
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Volume control mode
*Set volume delivered despite pressure; delivered @ constant flow and rate; volume adjusted for ETCO2 |
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What is the PVC mode? When is it used?
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pressure control mode
*controls inspir pressure resulting in increased Vt at lower PIP *lap sx and w/ obesity |
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What is the SIMV mode?
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Synchronized Intermittent Mandatory Ventilation
*useful during emergence |
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What factors can decrease the reliability of the pulse oximeter?
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low flow states, hypothermia, methemoglobinemia, shivering/movement, IV dyes (methylene blue, indigo), electrocautery, anemia (Hgb < 5), ambient light
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What is the purpose of a scavenging system?
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*disposal of gases from the ventilator circuit
*avoids polluting the OR |
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NIOSH recommended safe levels of exposure to N2O and volatile/halogenated anesthetics?
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*N2O 25 ppm
*N2O w/ volatile agents <.5 ppm *Volatile agents alone <2 ppm |
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What is the purpose of the negative and positive pressure relief valve in the scavening system?
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*Neg: protects the pt from the vacuum system
*Pos: protects the pt from the increased pressures secondary to the obstructed circuit |
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Where is the scavenger vacuum located?
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connected to the scavenger's DISS inlet
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What type of scavenger interface does the Ohmeda have?
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*Closed
*communicates to the atm only through valves *used w/ active system (+ and - pressure relief valves) *5 L bag attached/mounted at the bottom |
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What type of scavenger interface does the Drager have?
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*Open
*no valves, open to atm, negative and positive pressure relief built in *use only w/ active system |
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What does a low pressure alarm detect?
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disconnects, major air leaks, leaking tracheal cuff, failure of ventilator to cycle
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What does a high pressure alarm detect?
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*airway obstructions-laryngospasms
*decreased lung compliance-bronchoconstriction *kinked/occluded ETT *pt coughing against ETT *occlusion of expiratory limb |
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What does a sub-ambient pressure alarm detect?
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*pt attempting to inhale against empty reservoir bag
*blocked inspiratory limb *malfunctioning of an active scavenging system *NG tube in trachea |
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What should the pressure threshold limit alarm be set to?
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as close as possible to the pt's PIP w/out exceeding it
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Best way to pre-oxygenate pt?
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8-10 L FGF, APL valve open, tight mask fit (observe a good CO2 waveform), 3-5 minutes of Vt
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Which devices do not require wall outlet electric power?
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*manual assisted ventilation
*mechanical flowmeters *scavenging *variable bypass vaporizers |
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Which devices require wall outlet electrical power?
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*mechanical ventilator
*electronic monitors *digital flowmeters *gas/vapor blender vaporizer (des) |
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Minimum machine check requirements in emergency situations?
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*High pressure test of breathing circuit
*check sxn *observe/palpate breathing bag during pre-oxygenation |
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How do you perform a high pressure test on the breathing circuit?
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*close the APL
*occlude circuit *increase pressure w/ O2 flush *IF PRESSURE DECREASES, THEN THERE IS A LEAK |
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Regulatory agencies for medical gas cylinders
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*FDA
*Director of Transportation (DOT) *OSHA *Nat'l Fire Protection Assoc. (NFPA) |
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How often must E-cylinders be inspected? What must they be stamped with?
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*q 5 years
*stamped w/ month/year |
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How are e-cylinders tested?
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*external/internal visual check for corrosion, impact, or distortion
*leak tested by increasing their service pressure by 1.66X |
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What is the service pressure?
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max pressure at which the cylinder may be filled (70 F, 21 C)
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What types of gases are allowed to be filled at 10% beyond their service pressure?
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non-liquefied, nonflammable gases
*O2, He, CO2/O2 mixtures, He/O2 mixtures |
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For gases other than N2O and CO2, the pressure at 130F (55C) may not exceed what?
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1.25X service pressure
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Tank color coding should be found where?
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top & shoulder of tank
*DO NOT use as primary means of identification |
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Who requires specific markings permanently stamped on should of tank?
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DOT and TC
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What markings are found on cylinders?
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*tank material
*service pressure (PSI) *serial # and purchaser symbol *initial qualifying test date and retest date *+ sign=can add 10% to service pressure |
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What does the diamond shape figure denote? What does yellow, green, and red mean on them?
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*Hazard class
*yellow: oxidizer *green: non-flammable *red: flammable |
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What are tags used for?
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denoting the amount of cylinder contents, NOT and identification device
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What are most cylinders made of? MRI cylinder?
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*Steel
*MRI: aluminum (can have explosion/fires w/ aluminum O2 regulators) |
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If a cylinder is unsecured, how should it be placed?
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on its side
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