title: A negative expiratory pressure test during wakefulness for evaluating the risk of obstructive sleep apnea in patients referred for sleep studies.
abstract: OBJECTIVE
  Obstructive sleep apnea is characterized by increased upper airway collapsibility during sleep. The present study investigated the use of the negative expiratory pressure test as a method to rule out obstructive sleep apnea.
  
  
  METHODS
  Flow limitation was evaluated in 155 subjects. All subjects underwent a diurnal negative expiratory pressure test and a nocturnal sleep study. The severity of sleep apnea was determined based on the apnea-hypopnea index. Flow limitation was assessed by computing the exhaled volume at 0.2, 0.5, and 1.0 s (V0.2, V0.5, and V1.0, respectively) during the application of a negative expiratory pressure and expressed as a percentage of the previous exhaled volume. Receiver-operating characteristic curves were constructed to identify the optimal threshold volume at 0.2, 0.5, and 1.0 s for obstructive sleep apnea detection.
  
  
  RESULTS
  Mean expiratory volumes at 0.2 and 0.5 s were statistically higher (p <0.01) in healthy subjects than in all obstructive sleep apneic groups. Increasing disease severity was associated with lower expiratory volumes. The V0.2 (%) predictive parameters for the detection of sleep apnea were sensitivity (81.1%), specificity (93.1%), PPV (98.1%), and NPV (52.9%). Sensitivity and NPV were 96.9% and 93.2%, respectively, for moderate-to-severe obstructive sleep apnea, and both were 100% for severe obstructive sleep apnea.
  
  
  CONCLUSIONS
  Flow limitation measurement by V 0.2 (%) during wakefulness may be a very reliable method to identify obstructive sleep apnea when the test is positive and could reliably exclude moderate and severe obstructive sleep apnea when the test is negative. The negative expiratory pressure test appears to be a useful screening test for suspected obstructive sleep apnea.
authors.affiliation: Institute of Biomedicine and Molecular Immunology A. Monroy, National Research Council of Italy, Palermo, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Romano
authors.forename: Adriana
authors.initials: A
authors.lastname: Salvaggio
authors.forename: Anna
authors.initials: A
authors.lastname: Lo Bue
authors.forename: Oreste
authors.initials: O
authors.lastname: Marrone
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Insalaco
mesh_terms: D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography / Q000009:adverse effects* / Q000379:methods; D012123:Pulmonary Ventilation / Q000502:physiology; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000209:etiology; D013990:Tidal Volume / Q000502:physiology; D014851:Wakefulness / Q000502:physiology*
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