Final answer:
Pressure support is the ventilator mode that requires patients to start each respiratory cycle. It aids patient's spontaneous breaths with a preset level of pressure and is used during the weaning process.
Step-by-step explanation:
The ventilator mode that requires patients to initiate a respiratory cycle is B) Pressure support. In this mode, the patient must exert effort to begin inspiration, at which point the ventilator delivers a preset level of pressure to aid the patient's breathing. This contrasts with other modes where the ventilator might fully control the timing and volume of breaths or maintain a constant airway pressure. Pressure support encourages spontaneous breathing efforts and is often used during the weaning process from mechanical ventilation.
Modes like volume control and pressure control are typically initiated by the ventilator according to a preset rate or in response to patient attempts that don't meet set criteria. Likewise, PEEP (positive end-expiratory pressure) mode is not a ventilation mode per se, but an adjunct setting that helps prevent alveolar collapse at the end of expiration.