What is a disadvantage of assist control ventilation regarding patient comfort?

• A. Higher risk of hypoventilation
• B. Can be poorly tolerated in awake or non-sedated patients
• C. Requires full sedation for effectiveness
• D. Reduces patient autonomy in breathing

Answer: (B)

Assist control ventilation (ACV) is a mode of mechanical ventilation where the ventilator delivers a set tidal volume for each assisted breath triggered by the patient, as well as providing the same tidal volume for any mandatory breaths initiated by the ventilator.

In cases where patients are awake or minimally sedated, they may find assist control ventilation uncomfortable due to the fixed tidal volume delivered by the ventilator. The mode can lead to a sensation of being "over-ventilated," where each breath is mechanically supported rather than initiated naturally by the patient. This can result in anxiety or discomfort, particularly if the patient feels unable to control their own breathing effectively.

The other options mention aspects that do not directly address the patient comfort issue as effectively. The risk of hypoventilation relates more to the ventilatory setting and patient condition than comfort. While sedation can improve tolerance to mechanical ventilation, it is not universally required for ACV's effectiveness, and the mode does not inherently reduce patient autonomy in breathing, as patients still have the ability to trigger breaths themselves. Overall, the discomfort associated with assist control in awake patients stems from the nature of the interaction between the mechanical support and the patient's own respiratory efforts.