[Critical Closing Pressure (Pcrit) and Negative (Subatmospheric) Expiratory Pressure (NEP) for Diagnosis of...

The determination of critical closing pressure (Pcrit) is the diagnostic gold standard for assessing the severity of pharyngeal instability. Pcrit measurements are typically performed during natural nocturnal sleep (NREM Stage 2) in combination with polysomnography. However, determining Pcrit during sleep is time-consuming and impractical for routine use. Alternatively, Pcrit measurements can also be done during drug-induced sleep. A disadvantage of this method is the varying doses of propofol needed to induce sleep, which can affect muscle tone differently. As an alternative to these methods, the application of negative pressure during wakefulness (NEP test) has proven effective. In this test, the patient is administered a subatmospheric pressure of -5 or -10 cmH₂O via mask at the beginning of expiration, and the change in expiratory airflow in the pharynx is measured. NEP test can be performed in both sitting and lying position. According to current knowledge, the NEP test appears to be a diagnostic procedure comparable to critical closing pressure (Pcrit) for assessing upper airway collapsibility.