Methods

We identified COPD patients with proven PE between October, 2005 and October, 2015. Patients in risk classes III–V on the basis of the PESI score were excluded. We extracted demographic, clinical and laboratory information at the time of admission from medical records. All subjects were followed until hospital discharge to identify all-cause mortality.

Results

We enrolled 629 consecutive patients with COPD and PE at low risk: 132 of them (21.0%) with and 497 (79.0%) without secondary polycythemia. Compared with those without polycythemia, the polycythemia group had significantly lower forced expiratory volume in one second (FEV 1) level (0.9±0.3 vs. 1.4±0.5, P= 0.000), lower PaO 2 and SpO 2 as well as higher PaCO 2 (P= 0.03, P= 0.03 and P= 0.000, respectively). COPD patients with polycythemia had a higher proportion of arrhythmia in electrocardiogram (ECG)(49.5% vs. 35.7%, P= 0.02), a longer hospital duration time (15.3±10.1 vs. 9.7±9.1, P= 0.001), a higher mechanical ventilation rate (noninvasive and invasive, 51.7% vs. 30.3%, P= 0.04 and 31.0% vs. 7.9%, P= 0.04, respectively), and a higher in-hospital mortality (12.1% vs. 6.6%, P= 0.04). Multivariate logistic regression analysis revealed that polycythemia was associated with mortality in COPD patients with low-risk PE (adjusted OR 1.11; 95% CI, 1.04–1.66).

Conclusions

Polycythemia is an independent risk factor for all-cause in-hospital mortality in COPD patients with PE at low risk.