title: Diagnostic value of negative expiratory pressure for airway hyperreactivity.
abstract: OBJECTIVE
  To examine the value of negative expiratory pressure (NEP) in the assessment of methacholine bronchoprovocation testing (BPT).
  
  
  METHODS
  Prospective, observational study.
  
  
  METHODS
  Pulmonary function laboratory in a university hospital.
  
  
  METHODS
  Fifty-nine patients with chronic cough referred from outpatient clinics for methacholine BPT.
  
  
  METHODS
  Each subject inhaled successive doubling concentrations of methacholine (from 0.049 to 25 mg/mL) until the FEV(1) decreased for > 20% or the maximum concentration of methacholine was inhaled. NEP was measured in the sitting position during tidal breathing before and after methacholine BPT. The FEV(1) and forced oscillation airway resistance (Rrs) and interrupter airway resistance (Rint) were also obtained simultaneously. A positive BPT result was defined as a fall in FEV(1) > or = 20%.
  
  
  RESULTS
  At baseline, only five patients had expiratory flow limitation as demonstrated by NEP (EFL-N). There were 39 patients with positive BPT results, and the other 20 patients had negative results. Among the BPT-positive patients, only 13 patients (33.3%) had EFL-N after methacholine challenge. The sensitivity indexes (absolute change/SD) of FEV(1), NEP, Rrs, and Rint were 16.0 +/- 9.6%, 1.1 +/- 1.6%, 3.8 +/- 4.5%, and 5.89 +/- 4.4% (mean +/- SD), respectively. The percentage changes in FEV(1) in BPT-positive patients correlated with the percentage changes in Rrs (r = 0.419, p = 0.008) and only marginally with the percentage changes in Rint (r = 0.307, p = 0.058), but not with the changes in EFL-N (r = 0.048, p = 0.77).
  
  
  CONCLUSIONS
  These data suggest that NEP at sitting position is not sensitive in the assessment of methacholine bronchoprovocation as compared to FEV(1) and airway resistance measurements.
authors: Departments of Internal Medicine, Far Eastern Memorial Hospital, Taipei County, Taiwan.
authors: Ping-Huai
authors: PH
authors: Wang
authors: Ping-Hung
authors: PH
authors: Kuo
authors: Chia-Lin
authors: CL
authors: Hsu
authors: Huey-Dong
authors: HD
authors: Wu
authors: Yu-Shein
authors: YS
authors: Chang
authors: Sow-Hsong
authors: SH
authors: Kuo
authors: Pan-Chyr
authors: PC
authors: Yang
mesh_terms: D000328:Adult; D000403:Airway Resistance; D016535:Bronchial Hyperreactivity / Q000175:diagnosis*; D001985:Bronchial Provocation Tests; D005260:Female; D005540:Forced Expiratory Flow Rates; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D011446:Prospective Studies; D015656:Respiratory Mechanics; D012680:Sensitivity and Specificity; D014797:Vital Capacity
chemical_list: D016210:Methacholine Chloride