Is the pulmonary artery to aorta ratio a prognostic indicator in acute exacerbation of COPD?

To evaluate whether the pulmonary artery to ascending aorta diameter ratio (PA/A ratio), measured via thoracic computed tomography (CT), is associated with poor clinical outcomes and mortality in patients hospitalized for acute exacerbation of chronic obstructive pulmonary disease (COPD).

This retrospective study included 486 COPD patients admitted between 2017 and 2023 with available thoracic CT or CT angiography at admission. PA and aortic diameters were measured by radiologists, and PA/A ratios were calculated. Clinical parameters including blood gas values, need for non-invasive (NIMV) or invasive mechanical ventilation (IMV), and mortality data were collected. Statistical analyses included Mann-Whitney U, Chi-square, Spearman correlation, and ROC curve analysis.

Among the 486 patients, 451 had a PA/A ratio ≤ 1, and 35 had a PA/A ratio > 1. The median PA/A ratio was 0.80 [IQR: 0.72-0.88]. Higher PA/A ratios were significantly associated with female gender, acidosis, hypercapnia, and increased need for both NIMV and IMV (p < 0.05). ROC analysis identified a PA/A cut-off of > 0.80 for predicting IMV need (sensitivity 71.43%, specificity 46.02%). No significant difference was found in early or late mortality between PA/A groups. RDW and PCO₂ levels were higher in patients with PA/A > 1, while MCV was lower.

One of the most striking findings of this study is that the PA/A ratio was not directly correlated with early or late mortality; however, it showed a significant positive correlation with the need for both non-invasive and invasive mechanical ventilation as well as presence of hypercapnia. This suggests that the PA/A ratio may be a valuable marker for predicting clinical deterioration and the need for ventilatory support rather than mortality itself.The PA/A ratio may serve as a valuable non-invasive marker in the prognostic assessment of COPD exacerbations, especially when the ratio exceeds 0.8.