During volume controlled ventilation with a circle system, the surgeon notes the patient making paradoxical chest movement. The inspiratory unidirectional valve of the circle system is found to be stuck in the closed position. The immediate consequence is:
- A Expired gas enters the inspiratory limb, producing rebreathing with an elevated capnograph baseline
- B All expired gas bypasses the absorber and accumulates in the expiratory limb
- C Gas cannot be drawn from the reservoir bag, so the patient generates marked negative pressure and the bag becomes distended ✓
- D Peak inspiratory pressure falls because the circuit opens to atmosphere
Correct answer: C. Gas cannot be drawn from the reservoir bag, so the patient generates marked negative pressure and the bag becomes distended
Explanation
In the circle layout the patient inhales gas that has passed from the absorber and reservoir bag through the inspiratory valve. If this valve is stuck closed, no gas reaches the patient despite vigorous effort, generating large negative pressures and a distended, immobile bag. A competent but leaking inspiratory valve would cause rebreathing of expiratory limb gas, and a stuck expiratory valve causes inability to exhale, both distinct scenarios.
Reference: Understanding Anesthesia Equipment (Dorsch and Dorsch), 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.