Sources of variation in FEV1

Area of Science:

• Pulmonary Physiology
• Respiratory Medicine
• Clinical Diagnostics

Background:

• American Thoracic Society (ATS) guidelines ensure forced expiratory volume in one second (FEV1) reproducibility using specific criteria for forced vital capacity (FVC) maneuvers.
• Previous research suggested effort-dependent variations and FVC magnitude influencing FEV1, necessitating further investigation.

Purpose of the Study:

• To investigate the relationship between effort (work) and FEV1 reproducibility.
• To determine if FVC magnitude influences FEV1, independent of effort.

Main Methods:

• Examined the correlation between FEV1 and work (area under the alveolar pressure-volume curve) in 13 normal individuals and 17 patients with cystic fibrosis or asthma.
• Compared maneuvers with maximal vs. minimal work, ensuring FVCs were within 5% of each other.
• Assessed the relationship between changes in FEV1 (delta FEV1) and changes in FVC, work, FRC, and initial FEV1.

Main Results:

• No correlation was found between changes in work and changes in FEV1 when FVCs were similar.
• A significant positive correlation (r = 0.49, p < 0.01) existed between delta FEV1 and changes in FVC.
• Delta FEV1 did not correlate with hyperinflation (FRC) or airflow limitation (initial FEV1).

Conclusions:

• FVC magnitude, rather than direct effort (work), significantly impacts FEV1 reproducibility.
• Emphasizes the critical importance of a maximal inspiration at the beginning of spirometry testing for accurate FEV1 assessment.
• The observed FEV1 variations were generally small and within acceptable reproducibility limits.