Mechanisms of the haematological changes induced by hyperventilation

During voluntary hyperventilation an increase in the lymphocyte and thrombocyte counts occurs, paralleled by an increase in plasma epinephrine and norepinephrine. All these changes are rapidly reversible after hyperventilation and are followed by an increase in the neutrophil granulocyte count. The pathophysiological mechanisms of these changes were investigated by comparison of the hyperventilation-induced changes of the blood picture in 11 normal, 9 splenectomized and 12 β-blocked volunteers. Splenectomy did not affect the hyperventilation-induced mobilization of lymphocytes and neutrophils but totally suppressed the change in the thrombocyte count, β-blockade by 80 mg propranolol did not suppress the hyperventilation-induced increase in neutrophils. It reduced the absolute increase of lymphocytes and thrombocytes by half, but it also increased the baseline counts of these cells. The study shows that hyperventilation mobilizes thrombocytes from the spleen but not from extralienal pools, and that lymphocytes and neutrophils are mobilized from extralienal pools. Whereas neutrophil mobilization is not suppressed by β-blockade, the reduction of hyperventilation-induced mobilization of lymphocytes and thrombocytes may be due to a reduction in the size of the mobilizable cell pools, and therefore cannot be interpreted as a sure indication that adrenergic mechanisms are involved in their hyperventilation-induced mobilization.