The Circulatory and Ventilatory Effects of Normovolemic Polycythemia †

The effects of primary and secondary polycythemia on circulatory and ventilatory events have been the center of much investigation. There has, however, been sharp disagreement about the clinical merit of phlebotomy in cases of secondary polycythemia. Howarth, et al.' and Lewis, et al.,' among others, have concluded, although for somewhat different reasons, that therapeutic phlebotomy is detrimental in patients with polycythemia and lung disease. Cournand,3 on the other hand, has stated that polycythemia is responsible for some of the pulmonary hypertension and phlebotomy constitutes an important aspect of treatment. In attempting to explain the physiological effects of disease states such as polycythemia vera or secondary erythrocytosis, it would be of considerable value to know the response of normal subjects to an increase in hematocrit without associated changes of blood volume or pulmonary disease. With this objective in mind several cardiorespiratory parameters have been monitored in dogs rendered acutely polycythemic but whose blood volumes remained normal.