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A normal FEV1/VC ratio does not exclude airway obstruction
1Pulmonary Laboratory and Division, Cliniques Universitaires Saint-Luc, Brussels, Belgium.
Respiration; International Review of Thoracic Diseases
|August 19, 2004
Summary
Small airways syndrome (SAOS) may indicate airway obstruction even with a normal FEV1/VC ratio. Reduced FEV1 with normal TLC suggests small airway obstruction in SAOS patients.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- Airway obstruction is typically defined by a decreased forced expiratory volume in 1 second/vital capacity (FEV1/VC) ratio.
- Small airways syndrome (SAOS) is a proposed pattern of lung function with normal FEV1/VC and total lung capacity (TLC), suggesting small airway obstruction.
Purpose of the Study:
- To validate the hypothesis that SAOS reflects small airway obstruction.
- To compare lung function tests, particularly maximal expiratory flow rates (MEFR), in SAOS subjects versus matched controls.
Main Methods:
- 12 SAOS subjects and 36 age-matched controls without chronic lung/heart disease were studied.
- Lung volumes, MEFR, and diffusing capacity (DLCO) were measured.
- Comparison of lung function parameters between SAOS and control groups.
Main Results:
- SAOS subjects had higher smoking history and lower BMI than controls.
- FEV1/VC ratio and TLC were similar between groups.
- SAOS group showed lower FEV1, VC, DLCO, MEFR, and higher residual volume (RV) and RV/TLC ratio.
- MEFR curves in SAOS suggested premature airway closure.
Conclusions:
- A normal FEV1/VC ratio does not rule out airway obstruction.
- Decreased FEV1 with normal TLC can indicate small airway obstruction.
- SAOS represents a distinct pattern of small airway disease.