Pima - Mechanical Ventilation

Front 1

What is acute respiratory failure?

Back 1

PAO2<60 and / Or PaCO2 >50 with pH < 7.25

Front 2

What are the two types of respiratory failure?

Back 2

Type 1: Acute Hypoxic Respiratory Failure (Low O2)

Type 2: Acute Hypercapnic Respiratory Failure (High CO2)

Front 3

Primary causes of Acute Hypoxic RF

Back 3

V/Q mismatch
Shunt
alveolar hypoventilation
diffusion impairment
decreased inspired O2

Front 4

V/Q Mismatch

Back 4

Normally lungs have more perfusion at the basis than at the apices because of gravity. Mismatches occur when normally perfused areas become unventilated due to such things as bronchospasm, mucus plugging, airway inflammation, etc.
V/Q mismatches will respond to supplemental O2
V/Q mismatch VS Shunt - Shunts don’t contact the capillary beds

Front 5

V/Q Mismatch: Clinical Presentation

Back 5

Hypoxemia
dypsnea
tachycardia
tachypnea
use of accessory muscles
nasal flaring
cyanosis
abnormal BS - wheezing, diminished, unilateral abnormalities
whiteout or blackout of CXR

Front 6

Alveolar hypoventilation

Back 6

This form of hypoxemia exists when a patient goes into resp failure and the PCO2 rises significantly enough to displace the alveolar PAO2, thereby causing hypoxemia.

Front 7

Diffusion Impairment

Back 7

Most common causes with patients with interstitial lung diseases (Fibrosis, Asbestosis, Silicosis) where the interstitial wall is abnormally thickened which increases the time needed for gas to diffuse.
also caused by the alveolar destruction common to emphysema, and patients with abnormal pulm vasculature, or anemia, pulm hypertension and PE.
Clinical Presentation: No real clinical presentation for diffusion impairment itself-usually patient will show symptoms of the underlying causative disease. Silicosis, anemia, emphysema, etc.
Also the CXR will reflect the disease that is the cause of the impairment.

Front 8

Decreased inspired Oxygen

Back 8

May occur at high altitudes (mountain climbing, airplane)
Pb decreases which lowers the PaO2
-O2 becoming disconnected - cylinder empties, etc

Front 9

What is the primary purpose of PEEP?

Back 9

It increases FRC

(NBRC question)

Front 10

Acute Hypercapnic R.F.

Back 10

Also called ventilatory failure.
Elevated CO2=uncompensated respiratory acidosis
pH<7.25 PCO2>50 HCO3 wnl
Because elevated CO2 levels eventually displace alveolar O2-Hypoxemia will usually accompany ventilatory failure.

Front 11

3 Major disorders responsible for hypercapnic resp. failure:

Back 11

Decreased ventilatory drive
respiratory muscle fatigue or failure
increased WOB

Front 12

Decreased Ventilatory Drive

Back 12

Anything that interferes or disrupts the CNS breathing mechanisms such as the spinal cord, phrenic nerves, and central and peripheral chemoreceptors
Drugs
Brainstem lesions
hypothyroidism
morbid obesity
sleep apnea
most causes are reversible

Front 13

Clinical Presentation of Decreased Ventilatory Drive

Back 13

Bradypnea
Apnea
Adult RR < 12 bpm is ABNORMAL
May be obtunded, comatose
Obese may have sleep apnea

Front 14

Respiratory Muscle Fatigue / Failure

Back 14

Caused by neuromuscular disease such as ALS, Myasthenia gravis, Guillain barre syndrome, polio, and Muscular Dystrophy
May be irreversible and terminal (ALS) or reversible and self limiting (GB-MG)

Front 15

Respiratory Muscle Fatigue / Failure: Presentation

Back 15

Drooling, weakness, respiratory fatigue

Front 16

Increased WOB

Back 16

May be caused by COPD, asthma exacerbations, pneumothorax, rib fxs, pleural effusions, extensive burns

Front 17

Acute Hypercapnic RF

Back 17

Hypercapnic respiratory failure occurs when ventilation is impaired due to
decreased ventilatory drive,
muscle fatigue, or
increased WOB

Front 18

Complications of Acute Respiratory Failure

Back 18

Psychosis
GI complications
Multi Organ Failure
Renal Failure
Cardiac Failure
Death

Front 19

Standard Criteria for Mechanical Ventilation

Back 19

Apnea
Acute RF
Impending RF
Hypoxemic RF with increased WOB

Front 20

In order to assess a patient's need for vent support we have to evaluate 3 main factors:

Back 20

Ventilatory mechanics - Is he strong enough to breathe?
Ventilation - Can his body eliminate CO2? ABG?
Oxygenation - Can his lungs deliver O2 to the tissues?

Front 21

Tests to determine if patient is strong enough to breath:

Back 21

Some tests to determine:
MIF/NIF = (>-20)
VC = > 15 ml/kg
VT = >5 ml/lg
RR = <30
VE = <10 lpm

Front 22

Evaluate Oxygenation - Are tissues being oxygenated?

Back 22

PaO2 - from ABG
PaO2/FIO2 ratio

Front 23

PaO2

Back 23

measured off the ABG. Reflects the pressure of oxygen in the arterial blood (plasma)
Normal = 80 to 100 MMHG (varies with age)
critical < 60

Front 24

PaO2/FIO2 ratio

Back 24

calculate normal range on RA
100 mmhg/.21 = 476
critical values are
<300 (ALI)
<200 (ARDS)

Front 25

Indications for mechanical ventilation

Back 25

Apnea - absence of breathing
acute respiratory failure
impending respiratory failure
Hypoxemic respiratory failure with increased WOB or ineffective breathing pattern

Front 26

Mechanical ventilation - Definition

Back 26

Using a machine to effectively protect the airway and manage ventilation and or oxygenation for patients unable to do so normally.

Front 27

Philip Drinker

Back 27

The first modern and practical respirator nicknamed the “iron lung: was invented by Harvard medical researchers Philip Drinker and Louis Agassiz Shaw in 1927.

Front 28

Control Ventilation

Back 28

The ventilator delivers a pre-determined Vt (volume or pressure targeted) at a preset frequency (patient controls nothing)
Advantages - Guaranteed minute ventilation or peak pressure
Disadvantages - No patient interaction. The patient cannot initiate a breath

Front 29

Maximum plateau pressure

Back 29

plateau pressure should not be allowed to exceed 30/CMH20

Front 30

Barotrauma

Back 30

PEEP > 10 cmH20
MAP> 30 cmH20
PIP >50 cmH20
Plat > 20

Front 31

Assist/Control Ventilation (AC)

Back 31

The ventilator delivers a pre-determined VT with each inspiratory effort generated by the patient. A back-up frequency is set to insure a minimum VE
Advantages - Patient can increase VE by increasing respiratory rate
Disadvantages -
Dys-synchrony
Respiratory alkalosis
Dynamic hyperinflation (auto peep / intrinsic peep)

Front 32

Synchronized Intermittent Mandatory Ventilation (SIMV)

Back 32

The ventilator delivers a pre-determined VT at a preset frequency and allows the patient to take spontaneous breaths between ventilator breaths. Spontaneous breaths may be augmented with pressure support
Advantages
Decreased mean airway pressure
Improved venous return
Disadvantages
increased oxygen consumption
increased work of breathing

Front 33

Pressure Control Ventilation (PCV)

Back 33

The practitioner sets the maximal pressure obtained by the ventilator (preset pressure), frequency and time the pressure is sustained (inspiratory time). Inspiratory time is set as a percent of the total cycle or absolute time in seconds.
Advantages
Tidal volume variable with constant peak airway pressure
Full ventilatory support
Decreased mean airway pressure
Control frequency
Disadvantages
Ventilation does not change in response to clinical changing needs.

http://www.ccmtutorials.com/rs/mv/page10.htm

Front 34

Pressure Support Ventilation (PSV)

Back 34

The ventilator delivers a predetermined level of positive pressure each time the patient initiates a breath. A plateau pressure is maintained until inspiratory flow rate decreases to a specified level (e.g. 25% of the peak flow value).
Advantages
The flow rate, inspiratory time, and frequency are variable and determined by the patient
Decreased inspiratory work
enhanced muscle reconditioning
Disadvantages
Requires spontaneous respiratory effort
Delivered volumes affected by changes in compliance

http://www.ccmtutorials.com/rs/mv/psv.htm

Front 35

PEEP

Back 35

PEEP is “Positive End Expiratory Pressure”
PEEP is not really a mode of its own, but is used in conjunction with other modes as a tool to improve oxygenation.
PEEP is the application of positive pressure to change baseline variable during CMV, SIMV, IMV and PCV. PEEP is primarily used to improve oxygenation in patients with severe hypoxemia.

Front 36

Advantages of PEEP

Back 36

Improves oxygenation by increasing FRC
Decreases physiological shunting
Improved oxygenation will allow the FIO2 to be lowered
(FIO2s of 60% and greater run risk of oxygen toxicity)
Increased lung compliance

Front 37

Disadvantages of PEEP

Back 37

Increased incidence of pulmonary barotrauma
Potential decrease in venous return
Increased work of breathing (particularly auto peep)
increased intracranial pressure

Front 38

Indications for PEEP

Back 38

Refractory hypoxemia and intrapulmonary shunt
Decreased FRC and Lung compliance

Front 39

Complications of PEEP Therapy

Back 39

Decreased venous return and cardiac output
Barotrauma
Increased ICP
Impaired renal function

because of the decreased pressure gradient, the amount of blood delivered to the RA is decreased which in turn results in a decreased cardiac output and hypotension - That’s why any vented patient with a dangerously low BP Should have any PEEP DC’d ASAP.

Front 40

Plateau Pressure (Pplat)

Back 40

To measure the Pplat on a Ventilated patient, you must perform an “Inspiratory hold” maneuver-usually 1-2 seconds.
Once you determine the Plateau pressure you can use it to calculate the patient’s static lung compliance.
Pplat represents the actual pressure in the lungs minus Raw

Front 41

Compliance Calculation

Back 41

Compliance = Vte/Plat (static) press - PEEP
500/15-5 = 50 ml/cmH20

Front 42

Airway Resistance Calculation

Back 42

Raw = (PIP- Plateau (static))/peak flow
Raw = (20-15)/1L/sec = 5cmH20/L/sec

Front 43

decreasing lung compliance

Back 43

indicated by increasing plateau pressures as well as increasing peak pressures.

Front 44

What Respiratory Rate?

Back 44

Normal adult 8-12 bpm
COPD 8-12 bpm
Asthma 12-24
Closed head injury (CHI)15-20
ARDS 15-25

Front 45

What Tidal volume?

Back 45

First find IBW
Formula to find IBW
Males IBW in lbs = 106+[6x(height in inches - 60)]
Females IBS in lbs = 105+[5 x (height in inches -60)]
convert lbs to kgs by dividing lbs by 2.2
Normal lungs - 6-12 ml/kg
COPD 8-10
Asthma 6-10
CHI 8-12
ARDS 4-8

Front 46

What FIO2 to start?

Back 46

start at 100% and titrate lower watching SATs or ABGs

weaned down to <60% ASAP as long as Sats allow to avoid O2 toxicity

Front 47

Initial PEEP Settings

Back 47

Probably 95% of docs will order 5 CM PEEP initially. It is though 3-5cm PEEP is low enough to be safe and yet may help oxygenation.

PEEP may be titrated upwards if patient is still hypoxemic on FIO2’s greater than 40-50%

Front 48

I Time or I:E Ratio

Back 48

Normal IE ratio is 1:2 - 1:3. In some cases it may be desirable to manipulate the IE ratio on Patients with air trapping or auto peep. They may benefit from a longer expiration than normal
COPD 1:3 or even 1:4
ARDS - inverse ratio - 2:1, 3:1....10:1

Front 49

Peak Flow

Back 49

Most adults require a peak flow of at least 40Lpm

increasing Peak flow will shorten I time

Front 50

square wave

Back 50

Provides even, constant peak flow during insp. phase.
Usually results in higher peak pressures

Front 51

Accelerating Flow

Back 51

Accelerating - increases flow throughout resp cycle, may improve distribution of ventilation in patients with partial airway obstruction

Front 52

Decelerating flow / tapered flow

Back 52

Produces high initial inspiratory pressure and then decelerates. Helps reduce peak pressure in COPD patients.

Front 53

What flow pattern to use?

Back 53

Most RTs set a tapered or decelerating flow pattern. Most of the newer vents calculate which flow pattern is most beneficial for that patient and will automatically use it.

Front 54

2 types of sensitivity

Back 54

pressure triggering
flow triggering

Pressure set @ -1 to -2 cmH2O
Flow set @ 1-10LPM below baseline
Use flow triggering if given the choice

Front 55

Ventilator alarm settings:

Low exhaled VT

Back 55

Set about 100 MLS lower than your set tidal volume. If volumes drop that low alarm will sound to warn of possible leak or circuit disconnect.

Front 56

Low Minute Volume Alarm

Back 56

Best to set at 1 liter below the current exhaled minute volume

Front 57

Low Inspiratory Pressure

Back 57

Set 10-15 below the PIP. (Not usually done in real life. Usually set much lower to avoid nuisance alarms)

Front 58

High Inspiratory Pressure Alarm

Back 58

Set 10-15 above PIP. (Once again usually set at 50-60) if alarms, might need Sxing, sedation, etc.

Front 59

Apnea alarm

Back 59

Apnea interval - usually set at 20”. If no breath occurs after 20” period, vent will alarm and go into backup anea mode. Set VT, RR, etc to match set parameters.

Front 60

High Respiratory Rate

Back 60

Set 10-15 above total RR.

Important if patient on CPAP. Shows if patient is tiring

Front 61

High / Low FIO2

Back 61

Set 5-10% above the analyzed FIO2 and 5 to 10% below

Front 62

Pressure control Ventilation - PCV

Back 62

A preset pressure is set in the ventilator. Once it it reached, inspiration ends.
The delivered VT is unknown but varies with Raw and Cstat.
pressure is constant-volume is variable
when lung compliance decreases, delivered VT decreases. In other words, as the lungs become stiffer and harder to ventilate, the VT becomes smaller
The pressure control can be used like the VT control. When Inspiratory pressure is increased, the VT will increase

Front 63

Why use PCV instead of Volume control?

Back 63

In patients with ARDS that have lungs so stiff that conventional VCV is now ineffective.
Usually they will be on FIO2 of 1.0, PEEP 15, and have PIPs > 50cmH20

Front 64

PCV - Initial Settings

Back 64

Usually are close to these:
PIP set to about 50% of what it was on VCV (or may use Pplat from VCV)
FIO2 100% to start
Target VT 4-8ml/kg
PEEP 50% of previous
I/E 1:2 or 2:1 * with APRV mode
Important to closely monitor exh VT

Front 65

Reported benefits of PCV

Back 65

Improved gas exchange
increased PaO2
Lower PIP
Lower PEEP
Less CV effects
Less Barotrauma

Front 66

Volume Ventilation

Back 66

Volume delivery constant
inspiratory pressure varies
inspiratory flow is constant
Inspiratory time determined by set flow, Vt and rate

Front 67

Pressure Ventilation

Back 67

Volume varies
inspiratory pressure is constant
inspiratory flow varies
Inspiratory time set by clinician

Front 68

Pressure Control Ventilation - PCV

Back 68

The ventilator delivers a set pressure limit over a set inspiratory time
Classification: Pressure controlled, machine triggered, pressure limited and machine cycled.

Front 69

Figure a required FIO2:

Back 69

[PaO2 (desired) * FIO2 (current)] / PaO2 (current)

Front 70

Figure a required RR

Back 70

[RR (current) * PCO2 (current)] / PCO2 (desired)

Front 71

Find a required VT

Back 71

[Vt (current) * PCO2 (current)] / PCO2 (desired)

Front 72

Advantages of Noninvasive ventilation

Back 72

Avoids complications related to artificial airway
Easier to start and stop ventilation
Less sedation required
Preserves airway defense, speech and swallowing
No need for invasive monitoring

Front 73

Disadvantages of Noninvasive ventilation

Back 73

Not for patients at risk of aspiration (mask)
Excess secretions
May not be effective in patients with severe hypoxemia
May irritate eyes, cause gastric distention, skin pressure lesions, dry nose, claustrophobia

Front 74

CPAP

Back 74

Continuous Positive Airway Pressure
Improves oxygenation by opening and recruiting the airways and allowing more time for alveoli to exchange gases
Increases FRC
Usually set at low levels (2-10 cm). Pressures Higher than 10 will probably be ineffective as it will be too uncomfortable for the patient to tolerate.
CPAP helps Oxygenation only
(+PaO2)
It has NO effect on Ventilation (PCO2)

Front 75

When to initiate weaning

Back 75

When there is:
Adequate Oxygenation
PaO2/FIO2> 250
Vent setting: Peep < 8 and FIO2 , 0.5
PH > 7.25
Hemodynamic stability
Ability to initiate an Inspiratory effort
Sedation (especially with resp-depressing drugs) has itself been weaned

Front 76

Weaning Failure

Back 76

HR > 140 bpm or a sustained increase of > 20%
RR > 35 breaths/min for > 5 mins
O2 Sats < 90% for >30 seconds
HR with a sustained decrease of > 20%
SBP > 180 for > 5 mins
SBP < 90 for > 5 min
Clinical features: Anxiety, agitation, diaphoresis