Effects of hemoglobin on pulmonary arterial pressure and pulmonary vascular resistance in patients with chronic emphysema

Background: The increase in viscosity caused by secondary polycythemia is t hought to be one of the major causes of pulmonary hypertension secondary to chronic emphysema. However, very few clinical studies considered the relat ion between pulmonary hypertension and polycythemia in the case of chronic obstructive pulmonary disease. Objective: The purpose of this study is to e lucidate the relative contribution of an increase in hemoglobin level (Hb)t o mean pulmonary arterial pressure (mPAP) and pulmonary vascular resistance (PVR). Methods: We retrospectively investigated 41 patients with chronic e mphysema who had undergone a right heart catheterization. Multiple-regressi on analysis and F test were performed to investigate both direct effects of Hb and PaO2 as independent variables on mPAP and PVR as dependent variable s. Results: Significant correlations were found between PaO2 and mPAP (or P VR), or Hb and mPAP (or PVR), indicating that both Hb and PaO2 are contribu tory to mPAP and PVR. The F test demonstrated that Hb and PaO2 could direct ly affect the level of either mPAP or PVR, Conclusions: It was concluded th at Hb had a direct effect on mPAP and PVR, independently of hypoxia in pati ents with chronic emphysema, Copyright (C) 2000 S. Karger AG, Basel.