Area under the forced expiratory flow-volume loop in spirometry indicates severe hyperinflation in COPD patients

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology

Background:

• Severe hyperinflation in COPD leads to dyspnea, reduced exercise capacity, and increased mortality.
• Diagnosing severe hyperinflation typically requires static lung volumes, often inaccessible in primary care.
• The area under the forced expiratory flow-volume loop (AreaFE) correlates with air trapping indices like RV/TLC.

Purpose of the Study:

• To investigate the utility of AreaFE% and conventional spirometry in indicating severe hyperinflation in COPD patients.
• To compare the diagnostic performance of AreaFE% against established criteria for severe hyperinflation.

Main Methods:

• A cohort of 215 COPD individuals was analyzed.
• Severe hyperinflation was defined by elevated air trapping (RV/TLC >60%) or reduced inspiratory capacity (IC/TLC <25%).
• AreaFE% was calculated and analyzed using ROC curve analysis to determine cut-offs, subsequently validated in a separate group of 104 COPD subjects.

Main Results:

• ROC analysis established cut-offs of 15% for RV/TLC >60% and 20% for IC/TLC <25% for AreaFE% (N=215).
• Validation (N=104) showed these AreaFE% cut-offs achieved 80% accuracy, with high sensitivity and specificity.
• AreaFE% outperformed conventional spirometry parameters in identifying severe hyperinflation.

Conclusions:

• AreaFE% offers a superior and convenient estimation of severe hyperinflation in COPD.
• This parameter can facilitate timely referrals for body plethysmography to assess static lung volumes.