In mech ventilation, what triggers the transition from exhalation to inspiration for flow, pressure, or volume?

• A. Patient
• B. Ventilator
• C. Time
• D. Lung Pressure

Answer: (A)

Breaths start when the patient’s own inspiratory effort is detected by the ventilator as a trigger. Whether the trigger is a slight drop in airway pressure (pressure trigger), a small change in flow (flow trigger), or a tiny sensed change in volume (volume trigger), crossing that threshold signals the ventilator to begin the inspiratory phase. In other words, the transition from exhalation to inspiration is driven by the patient’s effort, not by the ventilator alone; without patient trigger, breaths can be delivered at a set rate by the machine.