Autotriggering during pressure support ventilation due to cardiogenic oscillations.

Newer generation anesthesia machines are equipped with a pressure support mode of ventilation, which can be used to support spontaneous ventilation in anesthetized patients. The Drager Apollo anesthesia machine uses an inspiratory limb hot-wire flow sensor to measure inspiratory flow rates. Detected flow rates that exceed the pressure support flow trigger will trigger pressure support breaths (Internal communication document. Drager Medical, 2007). In the case we are presenting, cardiac oscillations produced inspiratory flow rates that exceeded the flow trigger and autotriggered pressure support breaths. Autotriggering could be suppressed by increasing the trigger threshold or the positive end-expiratory pressure setting.