title: Importance of slow vital capacity in the detection of airway obstruction.
abstract: OBJECTIVE
  To investigate the presence of airway obstruction by determining the FEV1/FVC and FEV1/slow vital capacity (SVC) ratios.
  
  
  METHODS
  This was a quantitative, retrospective cross-sectional study. The sample comprised 1,084 individuals who underwent spirometry and plethysmography in a central hospital in Lisbon, Portugal. The study sample was stratified into six groups, by pulmonary function.
  
  
  RESULTS
  The analysis of the FEV1/FVC ratio revealed the presence of airway obstruction in 476 individuals (43.9%), compared with 566 individuals (52.2%) for the analysis of the FEV1/SVC ratio. In the airway obstruction, airway obstruction plus lung hyperinflation, and mixed pattern groups, the difference between SVC and FVC (SVC - FVC) was statistically superior to that in the normal pulmonary function, reduced FEF, and restrictive lung disease groups. The SVC - FVC parameter showed a significant negative correlation with FEV1 (in % of the predicted value) only in the airway obstruction plus lung hyperinflation group.
  
  
  CONCLUSIONS
  The FEV1/SVC ratio detected the presence of airway obstruction in more individuals than did the FEV1/FVC ratio; that is, the FEV1/SVC ratio is more reliable than is the FEV1/FVC ratio in the detection of obstructive pulmonary disease.
authors.affiliation: Portuguese Red Cross, School of Health, Lisbon, Portugal. raquel.barros@cardiocvp.net
authors.forename: Ana Raquel Gonçalves de
authors.initials: AR
authors.lastname: Barros
authors.forename: Margarida Batista
authors.initials: MB
authors.lastname: Pires
authors.forename: Nuno Miguel Ferreira
authors.initials: NM
authors.lastname: Raposo
mesh_terms: D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000175:diagnosis*; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010991:Plethysmography; D011174:Portugal; D018467:Positive-Pressure Respiration, Intrinsic / Q000503:physiopathology; D012189:Retrospective Studies; D012720:Severity of Illness Index; D013147:Spirometry; D018709:Statistics, Nonparametric; D014797:Vital Capacity / Q000502:physiology*