Pulmonary artery pressure and PaO2 in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common cause of pre-capillary pulmonary hypertension (PH). This complication may be overlooked in patients with COPD, as symptoms frequently are attributed to ventilatory limitation. Predictors of PH may identify patients with increased risk of morbidity and mortality.

The aims of this COPD study were to (i) evaluate the relationship between mean pulmonary artery pressure (mPAP) and PaO2, (ii) identify significant predictors of mPAP and PaO2 and (iii) use PaO2 as a marker of PH.

Altogether 95 COPD patients with mild to very severe airway obstruction and without left ventricular (LV) dysfunction were included. Pulmonary function tests, right heart catheterizations and exercise tests with blood gases were performed.

Multivariate regression analyses showed that only PaO2 was a significant predictor of mPAP. FEV1 and mPAP were significant predictors of PaO2 both at rest and at peak exercise. PaO2 at peak exercise was better to identify pulmonary hypertension than PaO2 at rest. By combining PaO2 at rest and peak exercise, it was possible to predict PH with a detection rate of 76% and a false-positive rate of 24%.

In an outpatient COPD population where LV disease was thoroughly excluded, we observed that only PaO2 was a significant predictor of mPAP. PaO2 at rest and peak exercise below 9.5 kPa (71 mmHg) and 8.5 kPa (64 mmHg), respectively, indicates the need for further evaluation of coexisting PH.