Negative expiratory pressure test: A new method to detect upper airway flow limitation - a review

The negative expiratory pressure (NEP) technique is used to assess upper airway collapsibility in patients with obstructive sleep apnea (OSA). Expiratory flow limitation (EFL) has been described as a transient or sustained decrease in expiratory flow during the application of the NEP test. The aim of this article was to describe the application of a new NEP method for assessing EFL during spontaneous breathing to identify patients at risk for OSA. Upper airway collapsibility was evaluated by measuring decreases in flow and expired volume during the first 0.2 s after the application of NEP at 10 cmH2O. The NEP test was easily applied to evaluate EFL caused by upper airway obstruction in patients with OSA. The NEP is a method for detecting upper airway flow limitation and has been used worldwide over the past 2 decades. Authors have applied the NEP in a number of different subjects including healthy individuals, patients with chronic obstructive pulmonary disease, obese individuals, and those with sleep disorders such as OSA, to detect airflow limitation. A number of studies have been performed in different populations and have shown that NEP is a reliable method for detecting upper airway collapsibility and can be used as a screening method for diagnosing OSA.