title: A new method of negative expiratory pressure test analysis detecting upper airway flow limitation to reveal obstructive sleep apnea.
abstract: BACKGROUND
  Expiratory flow limitation (EFL) by negative expiratory pressure (NEP) testing, quantified as the expiratory flow-limited part of the flow-volume curve, may be influenced by airway obstruction of intrathoracic and extrathoracic origins. NEP application during tidal expiration immediately determines a rise in expiratory flow (V) followed by a short-lasting V drop (deltaV), reflecting upper airway collapsibility.
  
  
  OBJECTIVE
  This study investigated if a new NEP test analysis on the transient expiratory DeltaV after NEP application for detection of upper airway V limitation is able to identify obstructive sleep apnea (OSA) subjects and its severity.
  
  
  METHODS
  Thirty-seven male subjects (mean +/- SD age, 46 +/- 11 years; mean body mass index [BMI], 34 +/- 7 kg/m2) with suspected OSA and with normal spirometric values underwent nocturnal polysomnography and diurnal NEP testing at - 5 cm H2O and - 10 cm H2O in sitting and supine positions.
  
  
  RESULTS
  deltaV (percentage of the peak V [%Vpeak]) was better correlated to apnea-hypopnea index (AHI) than the EFL measured as V, during NEP application, equal or inferior to the corresponding V during control (EFL), and expressed as percentage of control tidal volume (%Vt). AHI values were always high (> 44 events/h) in subjects with BMI > 35 kg/m2, while they were very scattered (range, 0.5 to 103.5 events/h) in subjects with BMI < 35 kg/m2. In these subjects, AHI still correlated to deltaV (%Vpeak) in both sitting and supine positions at both NEP pressures.
  
  
  CONCLUSIONS
  OSA severity is better related to deltaV (%Vpeak) than EFL (%Vt) in subjects referred to sleep centers. DeltaV (%Vpeak) can be a marker of OSA, and it is particularly useful in nonseverely obese subjects.
authors.affiliation: Italian National Research Council, Institute of Biomedicine and Molecular Immunology A. Monroy, Section of Respiratory Pathophysiology, Via Ugo La Malfa, 153-90146 Palermo, Italy. insalaco@ibim.cnr.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Insalaco
authors.forename: Salvatore
authors.initials: S
authors.lastname: Romano
authors.forename: Oreste
authors.initials: O
authors.lastname: Marrone
authors.forename: Adriana
authors.initials: A
authors.lastname: Salvaggio
authors.forename: Giovanni
authors.initials: G
authors.lastname: Bonsignore
mesh_terms: D000328:Adult; D015992:Body Mass Index; D006801:Humans; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D011175:Positive-Pressure Respiration / Q000379:methods*; D015203:Reproducibility of Results; D012129:Respiratory Function Tests; D012891:Sleep Apnea Syndromes / Q000503:physiopathology* / Q000628:therapy*; D013147:Spirometry