Pressure support ventilation

Changes in airway pressure, flow, and volume as measured in the distal endotracheal tube during unsupported and pressure-supported spontaneous breaths in intubated patients. The unsupported patient (blue lines) must first generate an initial negative pressure "spike" to open the ventilator demand valves and then must maintain a small amount of negative pressure during inspiration to produce flow through the ventilator circuitry. The addition of increasing levels of pressure support (green lines) provides plateaus of positive pressure that augment the spontaneous tidal volume in accordance with the patient's spontaneous respiratory flow demand and inspiratory time pattern.