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Total lung capacity by plethysmography and high-resolution computed tomography in COPD
Jamie L Garfield1, Nathaniel Marchetti, John P Gaughan
1Department of Pulmonary and Critical Care Medicine and Department of Radiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA. jamie.garfield@tuhs.temple.edu
Summary
Total lung capacity (TLC) measured by plethysmography is often higher than by high-resolution computed tomography (HRCT) in COPD patients. Gas trapping significantly predicts these differences, aiding in accurate lung volume assessment.
Area of Science:
- Pulmonary Medicine
- Radiology
- Medical Imaging
Background:
- Accurate measurement of total lung capacity (TLC) is crucial for diagnosing and managing chronic obstructive pulmonary disease (COPD).
- Plethysmography and high-resolution computed tomography (HRCT) are common methods for assessing lung volumes, but discrepancies exist.
- Understanding factors influencing these discrepancies is essential for clinical interpretation.
Purpose of the Study:
- To compare TLC measurements obtained via plethysmography and inspiratory HRCT in COPD patients.
- To identify predictors of the differences observed between these two TLC measurement modalities.
Main Methods:
- Retrospective review of 59 COPD patients who underwent pulmonary function testing and HRCT.
- TLC measured by plethysmography according to ATS/ERS standards.
- TLC measured by HRCT using custom software on contiguous slices at full inspiration.
Main Results:
- A strong correlation (r=0.92) was found between TLC by plethysmography and HRCT.
- Plethysmography yielded higher TLC values (mean difference of ~1.12 L) compared to HRCT (P < 0.05).
- Gas trapping (RV%, FRC%) independently predicted the magnitude of difference between plethysmography and HRCT TLC measurements.
Conclusions:
- Plethysmography can overestimate TLC by up to 2 L compared to inspiratory HRCT in COPD.
- Gas trapping is a key factor explaining significant variations in TLC measurements between plethysmography and HRCT.
- These findings have implications for the interpretation of lung volumes in COPD assessment.
Keywords:
gas trappinghigh-resolution computed tomographylung capacitylung volume measurement errorsplethysmographyMore Related Videos
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