Measurement of pulmonary artery to aorta ratio in computed tomography is correlated with pulmonary artery pressure in critically ill chronic obstructive pulmonary disease patients

Chronic obstructive pulmonary disease (COPD) is one of the leading chronic diseases and a common cause of death. Identification of COPD patients at high risk for complications and mortality is of utmost importance. Computed tomography (CT) can be used to measure the ratio of the diameter of the pulmonary artery (PA) to the diameter of the aorta (A), and PA/A ratio was shown to be correlated with PA pressure (PAP). However, the prognostic value of PA size remains unclear in patients with COPD. We hypothesized that PA enlargement, as shown by a PA/A ratio greater than 1, could be associated with a higher risk of mortality in COPD patients admitted to the intensive care unit. Data of patients admitted to a medical intensive care unit of a university hospital were retrospectively reviewed between January 2008 and December 2012. Patients who were identified to have a diagnosis of acute exacerbation of COPD and who had an echocardiogram and CT scan were included. Pulmonary artery to aorta ratio was calculated and patients were grouped as PA/A ≤ 1 and PA/A > 1. Comparisons were made between the groups and between patients who died and survived. Correlation analysis, survival analysis, and logistic regression analysis were done, where appropriate. One hundred six COPD patients were enrolled. There were 40 (37.4%) patients who had a PA/A > 1. Echocardiography measured PAP was higher in the group with PA/A > 1 than in those with PA/A ≤ 1 (62.1 ± 23.2 mm Hg vs 45.3 ± 17.9 mm Hg, P = .002). Mortality rate of patients with PA/A > 1 was higher (50%) than of those patients with PA/A ≤ 1 (36.4%), although the difference did not reach a statistical significance (P = .17). Correlation was found between vmeasured PA diameter and PAP (r = 0.51, P = .001) as well as between the Acute Physiology and Chronic Health Evaluation II values and PAP (r = 0.25, P = .025). The PA/A ratio is an easily measured method that can be performed on thorax CT scans. Although, we failed to demonstrate a statistically significant association between higher PA/A and increased mortality, PA/A can be used as a surrogate marker to predict the pulmonary hypertension.