Mechanical Ventilation

Question 1

Resistance

Answer 1

• How hard is it to get air in?
• The difficulty of a tube to carry gas
• opposition to airflow
• “airway resistance”

Difference between PIP and Plateau. The closer the plateau to PIP the lower the pressure loss

Question 2

Compliance

Answer 2

• How difficult is it to inflate?
• Characteristics of the lung to make it strechy
• “static compliance”
• Balloon

Question 3

Mandatory breath

Answer 3

• the start or end (or both) of the breath is determined by the ventilator, independent of the pt

Question 4

Plateau pressure

Answer 4

• end inspiratory alveolar pressure attained during mechanical ventilation
• <30

Question 5

Adaptive pressure control

Answer 5

A volume feedback mechanism for pressure-controlled or pressure supported breaths, the desired tidal volume is set and the vent adjusts the inspiratory pressure to deliver the minimal tidal volume

Question 6

Flow triggering

Answer 6

A alternate to pressure triggering in mechanical vent, in which the vent responds to a change in flow rather than pressure drop

Question 7

Mean airway pressure (MAP)

Answer 7

• Average airway pressure during a breathing cycle.
• directly related to insp time, RR and peak insp pressure and end- exp pressure
• <12
• associated with oxygenation

Question 8

Positive end-expiratory pressure

PEEP

Answer 8

• Baseline pressure applied during exhalation with mech vent
• reestablished FRC and makes it easier for the pt to breath

Question 9

Volume control

Answer 9

Vent controls the inspiratory flow and tidal volume;

tidal volume in this mode is delivered regardless of resistance or compliance

Question 10

Pressure control

Answer 10

Airway pressure set and remains constant regardless of resistance or compliance

Question 11

Auto-PEEP

Answer 11

End expiratory alveolar pressure that is greater than the pressure at the proximal airway, which results from high airway resistance and a short expiratory time

AKA air trapping

Breath stacking

Question 12

Indications for mechanical ventilation

Answer 12

apnea

Acute ventilatory failure

Impending ventilatory failure

OD

Question 13

Goals of mechanical ventilation

Answer 13

Provide adequate oxygenation

Provide adequate alveolar oxygenation

Avoid autoPEEP

Question 14

Pulmonary barotrauma

Answer 14

Excessive pressure and volume delivery to the lung and is a consequence of alveolar overdistention to the point of rupture

Question 15

Lung protective ventilator strategy

Answer 15

Vent technique where the target tidal volume is 6mL/kg of predicted body weight, the plateau pressure is kept below 30 cm H2O and PEEP is applied to maintain alveolar recruitment

Question 16

Phases of a breath

Answer 16

• Initiation of inspiration
• Inspiration
• End of inspiration
• Expiration

Question 17

assisted breath

Answer 17

A breath during which all or part of inspiratory (or expiratory) flow is generated by the ventilator doing work for the patient

Question 18

What is the cycle?

Answer 18

The signal that ends the inspiratory phase of breathing

Question 19

elastic load

Answer 19

a component of the patient-ventilator interaction, describing the elastance of the respiratory system (lungs and chest wall) and the volume of flow as a function of time

Question 20

Equation of motion

Answer 20

Pvent(t) = EV(t) + R

Question 21

What factors increase resistance?

Answer 21

• Bronchospasm
• Mucous
• Airway inflammation
• tumor

Any factors that decrease airway radius increase the resistance

associated with size and patency of airways as well as turbulence of airflow

Question 22

what is normal resistance

Answer 22

• spontaneously breathing adult 1-3 cmH2O/LPM
• Intubated adult ( increase resistance due to tube): 4-7 cm of H2O/LPM

Question 23

Peak Inspiratory Pressure

P_Max, PIP, P_AW

Answer 23

• highest pressure produced during the inspiratory phase

Question 24

Volume control pros and cons

Answer 24

Cons

• risk of barotrauma
• machine controls flow (more asynchrony)
• pressure changes with changes in Raw and Cst

Pro

• Min vent guaranteed

Question 25

Pressure control pros and cons

Answer 25

Pro: * less risk for barotrauma * patient controls flow Con * volume changes with changes in Raw and Cst * minute vol not guaranteed

Question 26

What is the P/F ratio?

Answer 26

* PaO2/FiO2 ratio quantifies ventilator-induced lung injury * normal P/F is \> 300

Question 27

What is the P/F for ALI?

Answer 27

200-300

Question 28

What is the P/F for ARDS?

Answer 28

Less than 200

Question 29

What causes Ventilator-associated pneumonia?

Answer 29

A result of the aspiration of contaminated oral and gastric secrections

Question 30

What are factors that help prevent VAP?

Answer 30

* 30^o head up * good airway cuff seal, subglottic ET * good oral hygiene * maintain gastric acidity

Question 31

What are the potential adverse effects of mechanical ventilation?

Answer 31

* increased intrathoracic pressure * decreased CO * Decreased urine output * Gastrointestinal ischemia * increased intracranial pressure (ICP) * Increased Deadspace * increased shunt * ventilator-induced lung injury * VAP * Psychological stress/sleep disturbances

Question 32

What can cause increased airway resistance?

Answer 32

* Bronchospasm * aspiration * secretions * obstruction * small ETT

Question 33

What can cause a decreased compliance?

Answer 33

* atelectasis * Auto-PEEP * pneumothorax * pulmonary edema

Question 34

what are the advantages of volume control? Disadvantages?

Answer 34

Advantages: guaranteed minute volume Disadvantages: * risk of barotrauma * machine controls the inspiratory flow * pressure change with changes in compliance and resistance

Question 35

What are the advantages of pressure control? Disadvantages?

Answer 35

Advantages: * Less risk of barotrauma * patient can control flow (and so can we) * improved synchrony Disadvantages * Minute volume changes with changes in compliance and resistance * minute volume is not guaranteed