Single-Breath Simultaneous Measurement of DLNO and DLCO as Predictor of the Emphysema Component in COPD - A Retrospective Observational Study.

Background: Chronic Obstructive Pulmonary Disease (COPD) is a respiratory condition characterized by heterogeneous abnormalities of the airways and lung parenchyma that cause different clinical presentations. The assessment of the prevailing pathogenetic components underlying COPD is not usually pursued in daily practice, also due to technological limitations and cost.

Aim: To assess non-invasively the lung emphysema component of COPD by the simultaneous measurement of DL_NO and DL_CO via a single-breath (sDL_NO and sDL_CO).

Methods: COPD patients aged ≥40 years of both genders were recruited consecutively and labelled by computed tomography as "with significant" emphysema (>10% of CT lung volume) or "with negligible" emphysema otherwise. Current lung function tests such as sDL_NO, sDL_CO and Vc (the lung capillary blood volume) were measured. All possible subsets of independent spirometric and diffusive parameters were tested as predictors of emphysema, and their predicted power compared to each parameter alone by ROC analysis and area under the curve (AUC).

Results: Thirty-one patients with "significant emphysema" were compared to thirty-one with "negligible emphysema". FEV₁ and FEV1/FVC seemed to be the best spirometric predictors (AUC 0.80 and 0.81, respectively), while sDL_CO and Vc had the highest predicted power among diffusive parameters (AUC 0.92 and 0.94, respectively). sDL_CO and Vc values were the parameters most correlated to the extent of CT emphysema. Six subsets of independent predictors were identified and included at least one spirometric and one diffusive parameter. According to goodness-to-fit scores (AIC, BIC, log-likelihood and pseudo R²), RV coupled with sDL_CO or Vc proved the best predictors of emphysema.

Conclusion: When investigating the parenchymal destructive component due to emphysema occurring in COPD, sDL_NO, sDL_CO and Vc do enhance the predictive power of current spirometric measures substantially. sDL_NO, sDL_CO and Vc contribute to phenotype of the main pathogenetic components of COPD easily and with high sensitivity. Organizational problems, radiation exposure, time and costs could be reduced, while personalized and precision medicine could be noticeably implemented.