Escalated functional debility in chronic obstructive pulmonary disease linked to concomitant interstitial affection

Abstract

Background
Chronic obstructive pulmonary disease (COPD) is often complicated by interstitial lung abnormalities (ILAs). Existing literature lacked robust studies directly assessing the relationship between visual CT scoring of interstitial lung abnormalities in patients with COPD and both gas exchange impairment and exertional oxygen desaturation during the six-minute walk test (6MWT).


Patients and methods
In this observational analytic cross-sectional study, 138 patients with COPD and CT-confirmed ILAs completed assessments, comprising 69 patients with fibrotic ILA and 69 patients with non-fibrotic ILA. Visual CT scoring was used to quantify the total extent of ILA and specific fibrotic features. Outcomes included DLCO and exertional desaturation. Multivariable linear regression models were adjusted for physiological and clinical covariates.


Results

Patients with fibrotic ILA demonstrated significantly lower basal SpO₂ (95% vs. 97%;
p
 = 0.002) and a tenfold higher proportion of severe DLCO reduction (23.3% vs. 2%). Multivariable analysis confirmed reticulation with architectural distortion (
p =
 0.002) and fibrotic ILA extent (
p =
 0.021) as independent predictors of lower DLCO. Conversely, exertional desaturation was independently predicted by basal SpO₂ (
p
 < 0.001) and residual volume (
p
 < 0.001), but measures of ILA extent lost independent significance in this model. An ILA extent > 14% marked the onset of functional decline (AUC = 0.89 for DLCO decline).



Conclusion
Visual quantification of fibrotic ILA extent was a precise, independent predictor of gas exchange failure in COPD. The progression to exertional desaturation was a complex process mediated by coupled physiological determinants of resting oxygen status and mechanical constraints of hyperinflation, which should inform targeted management.