Comparison of various methods for reading maximal expiratory flow-volume curves

Area of Science:

• Pulmonary Physiology
• Respiratory Mechanics

Background:

• Maximal expiratory flow-volume (MEFV) curves are essential for assessing lung function.
• Standardized methods for analyzing MEFV curves are needed to ensure accurate and reproducible results.

Purpose of the Study:

• To evaluate and compare different digital processing methods for analyzing MEFV curves.
• To identify the most reliable procedure for obtaining maximal expiratory flow indices.

Main Methods:

• Eighty-nine subjects performed MEFV maneuvers, generating two sets of five curves each.
• Eight distinct digital processing methods were applied to analyze the curves.
• Key indices analyzed included forced expiratory flows at 25%, 50%, and 75% of forced vital capacity (FVC), and maximal mid-expiratory flow (MMEF).

Main Results:

• Methods selecting the highest FVC or FVC + FEV1 yielded significantly lower and less reproducible flow values.
• Averaging indices from the two largest FVC curves produced lower values with improved reproducibility.
• Maximal flows were overestimated when using highest values based on FVC or superimposing breaths at residual volume.

Conclusions:

• Composite curves created by superimposing breaths at total lung capacity or on the descending limb offer more reproducible and unbiased data.
• These methods are recommended for accurate analysis of MEFV curves.
• Proper selection of MEFV curve analysis technique is critical for reliable pulmonary function testing.