An ascending (standing) bellows ventilator is in use. Compared with a descending (hanging) bellows design, the principal disadvantage cited for descending bellows is:
- A A circuit disconnection may go undetected because the bellows continue to fall as they entrain room air ✓
- B They cannot be used with pressure controlled ventilation
- C They require a higher driving gas pressure
- D They cannot accommodate fresh gas flow contributions to tidal volume
Correct answer: A. A circuit disconnection may go undetected because the bellows continue to fall as they entrain room air
Explanation
With descending bellows, gravity pulls the bellows down during inspiration even if the patient circuit is disconnected, so the bellows keep moving and the disconnection is masked. Room air may be drawn through the leak into the circuit, delivering a hypoxic mixture. With ascending bellows, loss of circuit volume causes the bellows to fall and stay down at end exhalation, making disconnection visually obvious. Both designs can provide pressure controlled ventilation.
Reference: Miller's Anesthesia, 9th ed.
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Written and medically reviewed by the StethoPrep medical team.