The plateau pressure reflects the pressure the alveoli and small airways of the lung are exposed to during mechanical ventilation. This is sometimes referred to as the transpulmonary pressure.
Excessively high plateau pressures may put the patient at risk for barotrauma and atelectotrauma during mechanical ventilation.
The plateau pressure is measured during peak inspiration and while there is no air movement inside the lungs. To accomplish this an inspiratory pause maneuver is performed for 0.5 to 1 second at peak inspiration.
The peak inspiratory pressure (PIP) records the highest pressure that occurs inside the lungs at peak inspiration. The PIP should always be higher than the plateau pressure because of the effect airway resistance has on the PIP as air flows through the lungs.
Airway secretions, inflammation, bronchoconstriction, and even a kinked endotracheal tube can all increase airway resistance and increase the PIP as a result.
Unlike the PIP, the plateau pressure records the pressure inside the lungs when no air is moving by performing an inspiratory pause at peak inspiration. As a result, the plateau pressure does not factor in airway resistance. The plateau simply reflects the pressure it takes to hold a given volume inside the lungs. This is the pressure the small airways and alveoli are subjected to, also known as the trans pulmonary pressure.
External chest wall pressure may give false high results. For example, the lungs of obese patients or those in the advanced stages of pregnancy may have elevated plateau pressures that do not reflect the trans pulmonary pressure (the pressure alveoli and small airways are subjected to), but rather external pressures
Other limitations may occur if the patient forcibly exhales during the inspiratory pause maneuver which may cause false high readings.
The ARDSnet.org protocol recommends a goal of keeping the plateau pressure less than or equal to 30 cm H2O.
Lung conditions that stiffen the lungs, such as ARDS or pulmonary fibrosis may cause high plateau pressures during mechanical ventilation.
Inappropriate ventilator settings, particularly excessively large tidal volumes used during volume control ventilation can also increase the plateau pressure.