Characterizing functional lung heterogeneity in COPD using reference equations for CT scan-measured lobar volumes

Area of Science:

• Pulmonary Medicine
• Radiology
• Medical Imaging

Background:

• Computed tomography (CT) scanning is vital for characterizing Chronic Obstructive Pulmonary Disease (COPD).
• Accurate normal ranges for CT-measured lung lobar volumes at maximal inflation (total lung capacity [TLC]) and relaxed exhalation (functional residual capacity [FRC]) were previously unknown.
• This study aimed to establish these crucial reference ranges using COPDGene data.

Purpose of the Study:

• To develop and validate race-specific reference equations for lobar volumes at TLC and FRC.
• To provide a tool for assessing regional lung volumes in individuals with and without COPD.
• To aid in understanding disease progression and treatment response.

Main Methods:

• Linear regression models were employed to create race-specific (non-Hispanic white, African American) lobar volume equations.
• Models incorporated height and sex as covariates, using derivation and validation cohorts totaling 1015 subjects with normal pulmonary function.
• Final equations were applied to 2,191 subjects with GOLD stage II-IV COPD.

Main Results:

• Women exhibited smaller lobar volumes than men; height positively correlated with lobar volumes.
• Non-Hispanic whites generally had larger lobar volumes than African Americans at TLC, with differences noted in lower lobes at FRC.
• In COPD patients, upper lobes exceeded predicted volumes in GOLD II, while lower lobes showed significant inflation only in GOLD IV; gas trapping was severe and uniform at FRC.

Conclusions:

• Developed reference equations for lobar volumes can effectively assess regional lung dysfunction.
• These equations may help monitor therapeutic responses to pharmacologic treatments.
• The findings support the use of lobar volume assessment in guiding lung volume reduction strategies.