Defining obstructive ventilatory defect in 2015

Abstract

Introduction: There is no clear consensus as to what constitutes an obstructive ventilatory defect (OVD): Is it FEV1/FVC<lower limit of normal (LLN) or<0.70 (respectively, physiological and operational definitions)? Aim: To determine, according to the two definitions, the percentage of subjects having an OVD among them explored in a lung function exploration laboratory. Population and methods: This is a retrospective study including 4,730 subjects aged 17–85 years. Subjects were divided according to the presence [physio (+) or operat (+)] or absence [physio (−) or operat (−)] of an OVD, and into younger (<45 years, n=2,076), older (≥45 years, n=2,654), smokers (n=1,208), and non-smokers (n=3,522) groups. Results: For the total sample, the younger and older groups [mean±SD of age (years), respectively, 46.7±14.1; 33.9±7.4, and 56.8±9.1], the ‘physiological definition’ detected, respectively, 13.46, 43.22, and 5.09% more OVD than the ‘operational one’ (p<0.05). In addition, the operational definition, compared with the physiological one, overdiagnosed OVD in 2.33 and 0.44% of smokers and non-smokers, respectively, and underdiagnosed it in 4.46% and 29.72% of smokers and non-smokers, respectively (p<0.05). Compared with the group ‘physio (−), operat (+)’, the ‘physio (+), operat (−)’ one was younger (74.2±4.7 years vs. 40.9±10.3 years) and had significantly higher FEV1 (62±13% vs. 78±17%) and FVC (71±15% vs. 93±19%). Conclusion: The frequency of OVD much depends on the criteria used for its definition.

Keywords

• obstructive ventilatory defect
• FEV1/FVC
• fixed threshold
• lower limit of normal
• spirometry
• guideline