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["Mixed" changes in spirometry--verification of the pattern of lung function impairment]
Piotr Boros1, Monika Franczuk, Stefan Wesołowski
1Zaklad Fiziopatologii Oddychania Instytut Gruźlicy i Chorób Płuc w Warszawie.
Pneumonologia I Alergologia Polska
|August 13, 2004
Summary
Many patients with reduced FEV1/FVC and FVC ratios actually have airway obstruction and lung hyperinflation, not a true mixed ventilatory defect. Further tests like plethysmography are needed to determine the cause of reduced vital capacity.
Area of Science:
- Pulmonary Medicine
- Respiratory Physiology
Background:
- Reduced FEV1/FVC ratio and FVC are often termed "mixed" ventilatory disturbances.
- This study investigates the actual prevalence of combined obstructive and restrictive lung disease patterns.
Purpose of the Study:
- To determine the frequency of overlapping obstructive and restrictive lung impairments.
- To evaluate patients with FEV1/FVC < 0.7 and FVC < 80% predicted.
Main Methods:
- Retrospective analysis of 748 patient pulmonary function tests meeting inclusion criteria.
- Included spirometry and body plethysmography performed per ERS standards.
- Utilized ERS guidelines for reference values.
Main Results:
- Only 17% of patients exhibited volume restriction (TLC below normal limits).
- An inverse correlation was found between FEV1% predicted and RV%TLC% predicted.
- Increased residual volume (RV) is the primary cause of reduced vital capacity (VC) and FVC in patients with normal total lung capacity (TLC).
Conclusions:
- "Mixed" ventilatory impairment often signifies airway obstruction with lung hyperinflation.
- Reduced FVC and FEV1/FVC ratio necessitate further investigation, such as plethysmography, to identify the cause of diminished vital capacity.