Blood volume changes in patients with cystic fibrosis.

Simultaneous red blood cell (RBC) and plasma volume determinations were obtained in 
16 patients with cystic fibrosis (CF) and moderately severe pulmonary involvement. 
Hypervolemia with an increase in both RBC and plasma volumes was 
observed. Changes in blood volume were marked when values were indexed 
by weight but less significant when indexed by height. Decreasing systemic 
arterial oxygen saturation was associated with a progressive increase in RBC 
mass, hematocrit value, and hemoglobin level and a decrease in mean 
corpuscular hemoglobin concentration. RBC and total blood volumes were highest in 
patients with cor pulmonale and congestive heart failure. However, the compensatory 
polycythemic response in patients with CF was inadequate when compared with 
the response to hypoxemia in patients with cyanotic congenital heart disease. 
The insufficient oxygen-carrying capacity may compromise tissue oxygen delivery and necessitate 
treatment. 