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Improvement in spirometry following lung volume reduction surgery: application of a physiologic model
Henry E Fessler1, Steven M Scharf, Solbert Permutt
1Divisions of Pulmonary and Critical Care Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA. hfessler@welch.jhu.edu
American Journal of Respiratory and Critical Care Medicine
|January 10, 2002
Summary
The ratio of residual volume to total lung capacity (RV/TLC) predicts forced vital capacity (FVC) improvement after lung volume reduction surgery (LVRS). Increased FVC largely determines improved forced expiratory volume in one second (FEV1).
Area of Science:
- Pulmonary Medicine
- Thoracic Surgery
- Respiratory Physiology
Background:
- Emphysema is characterized by hyperinflated lungs.
- A theoretical model links residual volume to total lung capacity ratio (RV/TLC) with lung-chest mismatch in emphysema.
- This model predicts RV/TLC as a key indicator for FVC improvement post-LVRS.
Purpose of the Study:
- To test the theoretical model's predictions regarding RV/TLC and its relationship with FVC and FEV1 changes after LVRS.
- To identify preoperative predictors of functional improvement following LVRS.
Main Methods:
- Studied 13 patients undergoing LVRS with detailed lung mechanics measurements.
- Utilized stepwise regression to identify independent predictors of FVC increase.
- Assessed a separate cohort of 78 LVRS patients using standard pulmonary function tests.
Main Results:
- In the initial group, RV/TLC was the sole preoperative predictor of FVC increase.
- Seventy percent of FEV1 increase was attributed to FVC improvement post-LVRS.
- In the larger group, RV/TLC correlated with FVC increase, but not consistently with FEV1 increase due to variable FEV1/FVC changes.
Conclusions:
- Findings support the model's proposed mechanism for FVC enhancement after LVRS.
- The study highlights limitations of the RV/TLC model in predicting FEV1 directly.
- Suggests further hypotheses for optimizing patient selection for LVRS.