Assist Control can cause hyperventilation in awake patients because spontaneous breaths that occur are:

• A. assisted by the ventilator and count toward the total respiratory rate
• B. assisted by the ventilator but do not count toward the total respiratory rate
• C. unassisted and do not count toward total rate
• D. unassisted but count toward total rate

Answer: (B)

In assist-control mode, the ventilator provides breaths at a set rate and tidal volume, but patient efforts can trigger additional breaths that are supported by the machine. These spontaneous, patient-triggered breaths are assisted by the ventilator, delivering the full tidal volume, yet they do not change the ventilator’s programmed respiratory rate display. Because the patient can generate extra breaths without the rate reflecting them, minute ventilation can be higher than the set rate, leading to hyperventilation.