Triggering and cycling off during pressure support ventilation: simplicity or sophistication?

Excerpt

The vast majority of patients receiving invasive mechanical ventilation in the intensive care unit (ICU) are put on assisted modes, with pressure support ventilation (PSV) being the most commonly used mode during weaning off the machine [1]. The primary objectives of PSV are usually to unload the respiratory muscles and to improve coordination between respiratory muscle contraction and machine breaths [2, 3]. How can this be achieved? First, as with all assisted modes, the ventilator initiates the delivery of positive pressure at airway opening after sensing the triggering signal. Each PSV cycle of flow delivery is triggered by the patient, and the physician simply sets the airflow or airway pressure threshold, or “sensitivity,” which triggers the ventilator. Second, the PSV level determines the degree of respiratory muscle unloading. Third, during PSV, airflow is the signal that causes the ventilator to cycle off, i.e., to stop generating a flow of gas. …