Understanding, applying, and evaluating pressure modes of ventilation.

Volume ventilation has long been the preferred method of mechanical ventilation, especially in critically ill patients. Recently, pressure ventilation has been introduced as a potentially superior method of ventilating stable and unstable respiratory patients. The positive characteristics of pressure modes such as the associated decelerating flow pattern and the ability to limit pressure and thus prevent barotrauma have resulted in numerous clinical applications. Although promising, the applications require that clinicians understand the flow, volume, and pressure characteristics of the modes. To this end, two popular pressure modes, pressure support and pressure-controlled inverse ratio, are described. A new option (available on only a few ventilators) called volume-guaranteed pressure ventilation, also is introduced.