NBRC Mechanical Ventilation 1 — Questions and Answers
Question 1: Which ventilator mode delivers a set tidal volume regardless of airway resistance or compliance changes?
- Pressure control ventilation (PCV)
- Volume control ventilation (VCV) (Correct answer)
- Pressure support ventilation (PSV)
- CPAP
Correct answer: Volume control ventilation (VCV)
Volume control ventilation guarantees delivery of a preset tidal volume by adjusting peak inspiratory pressure as lung mechanics change.
Question 2: Plateau pressure should ideally be kept below which threshold to reduce ventilator-induced lung injury (VILI)?
- 20 cmH2O
- 25 cmH2O
- 30 cmH2O (Correct answer)
- 40 cmH2O
Correct answer: 30 cmH2O
Current lung-protective ventilation guidelines recommend keeping plateau pressure below 30 cmH2O to minimize barotrauma and VILI.
Question 3: PEEP (positive end-expiratory pressure) is used primarily to:
- Decrease mean airway pressure
- Prevent alveolar collapse and improve oxygenation (Correct answer)
- Reduce the work of breathing by eliminating auto-PEEP
- Decrease functional residual capacity
Correct answer: Prevent alveolar collapse and improve oxygenation
PEEP maintains alveolar patency at end-expiration, recruits collapsed lung units, and improves V/Q matching and oxygenation.
Question 4: Auto-PEEP (intrinsic PEEP) occurs when:
- Set PEEP exceeds 10 cmH2O
- Insufficient expiratory time prevents full exhalation before the next breath (Correct answer)
- Inspiratory time is too short
- Tidal volume is set below 6 mL/kg IBW
Correct answer: Insufficient expiratory time prevents full exhalation before the next breath
Auto-PEEP develops when air trapping occurs because the next breath is delivered before the previous breath is fully exhaled, leading to gas stacking.
Question 5: In pressure support ventilation (PSV), the ventilator:
- Controls both rate and tidal volume
- Provides a fixed pressure boost to patient-initiated breaths (Correct answer)
- Delivers mandatory breaths independent of patient effort
- Cycles based on a set inspiratory time
Correct answer: Provides a fixed pressure boost to patient-initiated breaths
PSV augments each spontaneous patient-initiated breath with a clinician-set pressure boost, reducing work of breathing while maintaining patient control of rate and timing.
Question 6: Which parameter is used to calculate static compliance on a mechanically ventilated patient?
- Peak pressure minus PEEP divided by tidal volume
- Plateau pressure minus PEEP divided by tidal volume (Correct answer)
- Mean airway pressure divided by respiratory rate
- Tidal volume divided by peak inspiratory flow
Correct answer: Plateau pressure minus PEEP divided by tidal volume
Static compliance = Tidal Volume / (Plateau Pressure – PEEP), reflecting the compliance of the respiratory system without the influence of airway resistance.
NBRC Mechanical Ventilation 1
Which ventilator mode delivers a set tidal volume regardless of airway resistance or compliance changes?