Pulmonary embolism in patients with chronic obstructive pulmonary disease exacerbations of unknown origin: clinical characteristics and risk factors

Abstract

To evaluate the prevalence of pulmonary embolism(PE) in patients with chronic obstructive pulmonary disease (COPD) exacerbations of unknown origin and to explore the risk factors associated with PE. A total of 208 consecutive patients with COPD were referred to this hospital for severe exacerbations of unknown origin. Their age was 50 - 82 years, with a mean of (62 ± 12) years. All patients were examined within 48 h of admission by CT pulmonary angiography (CTPA) and lower extremity ultrasonography. The patients were classified as PE positive (positive results on CTPA) or PE negative (negative results on CTPA). Arterial blood gas, the levels of D-dimer and ET-1 were measured in all the patients. Differences between groups were analyzed using a two-tailed unpaired t test for normally distributed variables and a Mann-Whitney u test for non-normally distributed variables. Qualitative data were assessed using chi-square test, and risk factors were analyzed using logistic regression analysis. The frequency of PE was 33% in this series of 208 consecutive patients with COPD referred for exacerbations of unknown origin. There were differences between PE positive and PE negative groups in the following factors (χ(2) = 4.32 - 6.79, mean P < 0.05): immobilization ≥ 7 days 21.7% (15/208) vs 13.7% (19/208); difference in circumference of lower limbs ≥ 1 cm 34.8% (24/208) vs 15.1% (21/208); deep venous thrombosis (DVT) 37.7% (26/208) vs 12.2% (17/208); syncope 11.6% (8/208) vs 0.06% (9/208); S(I)Q(III)T(III) syndrome 11.6% (8/208) vs 0.04% (5/208); decrease in PaCO2 ≥ 5 mm Hg (1 mm Hg = 0.133 kPa) 27.5% (19/208) vs 9.3% (13/208). Plasma D-dimer and ET-1 levels were significantly higher in patients with PE as compared to patients without PE. D-dimer levels were (760 ± 152) µg/L and (253 ± 56) µg/L (Z = -2.946, P < 0.01); ET-1 levels were 5.4 ng/L (1.6 - 6.9 ng/L) and 1.8 ng/L (1.3 - 4.8 ng/L), Z = -2.532, P < 0.01. Risk factors identified by logistic regression analysis included immobilization ≥ 7 days (P < 0.05, OR = 3.24, 95%CI = 1.56 - 4.98), difference in circumference of lower limbs ≥ 1 cm (P < 0.05, OR = 2.56, 95%CI = 1.48 - 3.93), and deep venous thrombosis (DVT) (P < 0.05, OR = 2.31, 95%CI = 1.23 - 3.58). This study showed a 33% prevalence of PE in patients with COPD who were hospitalized for severe exacerbations of unknown origin. Immobilization ≥ 7 days, difference in circumference of lower limbs ≥ 1 cm, and DVT were risk factors for PE in this group of patients.