Diffusing capacity in normal-for-age spirometry and spirometric impairments, using reference equations from the...

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Diagnostic Imaging

Background:

• Global Lung Function Initiative (GLI) reference equations are available for spirometry and diffusion.
• Respiratory phenotypes based on GLI diffusion measures require evaluation within GLI spirometry categories.

Purpose of the Study:

• To assess respiratory phenotypes using GLI-based diffusion measures in individuals with normal-for-age spirometry and spirometric impairments.
• To determine the prevalence of abnormal diffusion parameters (DLCO, VA, KCO) in different spirometric categories.

Main Methods:

• Cross-sectional analysis of 2100 Caucasian adults (40-85 years).
• Categorization of spirometry: normal-for-age, restrictive-pattern, and three-level airflow obstruction (mild, moderate, severe).
• Evaluation of GLI-based diffusion measures: DLCO, VA, and KCO, comparing values below the lower limit of normal (LLN) across spirometric groups using multivariable regression.

Main Results:

• Restrictive spirometry significantly increased odds of low DLCO and VA, but not KCO.
• Airflow obstruction, from mild to severe, elevated odds for low DLCO, VA, and KCO.
• Notably, 34.5% with normal spirometry had low DLCO, 19.7% had low VA, and 25.3% had low KCO.

Conclusions:

• Abnormal lung diffusion is prevalent in spirometric impairments.
• Abnormal diffusion also occurs in individuals with normal-for-age spirometry.
• Findings refine understanding of respiratory phenotypes for GLI spirometric categories and aid in respiratory disease evaluation.