Repetitive hemodilution in chronic obstructive pulmonary disease and pulmonary hypertension: Effects on pulmonary hemodynamics, gas exchange, and exercise capacity

Background: In cor pulmonale associated with severe chronic obstructive pul monary disease (COPD), disturbances of pulmonary microcirculation may contr ibute significantly to hypoxemia, pulmonary hypertension, and exercise into lerance. Objective: It was tested whether reduction of brood viscosity indu ced by repetitive hemodilution might improve pulmonary hemodynamics and oxy gen uptake. Methods: Seven patients with stable COPD (forced expiratory vol ume in 1 s 33 +/- 3 % of predicted, means +/- SE) and pulmonary hypertensio n were phlebotomized 5-6 times over a period of 3 months with substitution of 6% hydroxyethyl starch (molecular weight 40,000). This resulted in a ste pwise reduction of the hematocrit from 53.3 +/- 2.6 to 45.8 +/- 3.1% and a reduction of whole blood viscosity from 9.8 +/- 0.6 to 8.8 +/- 0.7 mPa x s at a shear rate of 2.0 s(-1). Before and after the treatment period, patien ts underwent cardiopulmonary exercise testing and right heart catheterizati on. Results: Mean pulmonary artery pressure (PA,) decreased from 30 +/- 3 t o 22 +/- 2 mm Hg and arterial oxygen partial pressure (Pa-O2) increased fro m 63.2 +/- 2.2 to 71.8 +/- 3.7 mm Hg at rest. During peak exercise, PA, dec reased from 59 +/- 7 to 53 +/- 7 mm Hg and Pao, increased from 54.0 +/- 5.7 to 63.2 +/- 2.4 mm Hg after hemodilution. Peak oxygen consumption rose fro m 573 +/- 84 to 750 +/- 59 mi x min(-1), corresponding to an increase in ca rdiac index from 4.25 +/- 0.5 to 5.88 +/- 0.76 liters x min(-1) x m(-2) Pul monary vascular resistance fell from 345 +/- 53 to 194 +/- 32 dyn x s x cm( -5). The patients' peak exercise capacity increased from 9.2 +/- 2.0 before to 13.5 +/- 3.2 kJ at the end of the study (p < 0.05 for all differences, pal red t test). Conclusion: The findings suggest that a prolonged improvem ent of pulmonary microcirculation by reducing blood viscosity may improve p ulmonary gas exchange, central hemodynamics, and exercise tolerance in pati ents with severe COPD and pulmonary hypertension.