Patient-ventilator interactions: optimizing conventional ventilation modes.

Assisted (interactive) breathing is generally preferred to controlled breaths in patients on mechanical ventilators. Assisted breaths allow the patient's respiratory muscles to be used, and ventilatory muscle atrophy can be prevented. Moreover, the respiratory drive of the patient does not have to be aggressively blunted. However, interactive breaths need to be synchronized with the patient's efforts during the trigger, the flow delivery, and the cycling phases. Asynchrony during any of these can put an intolerable load on the respiratory muscles, leading to fatigue and the need for a high level of sedation or even paralysis. Current ventilation modes have a number of features that can monitor and enhance synchrony, including adjustment of the trigger variable, the use of pressure-targeted versus fixed-flow-targeted breaths, and manipulations of the cycle variable. Clinicians need to know how to use these ventilation mode and monitor them properly, especially understanding the airway pressure and flow graphics. The clinical challenge is synchronizing ventilator gas delivery with patient effort.