Spleen volume and blood flow response to repeated breath-hold apneas

The purpose of this study was (i) to answer whether the reduction in the spleen size in breath-hold apnea is an active contraction or a passive collapse secondary to reduced splenic arterial blood flow and (ii) to monitor the spleen response to repeated breath-hold apneas. Ten trained apnea divers, 10 intact and 7 splenectomized untrained persons repeated five maximal apneas (A1-A5) with face immersion in cold water, with two minutes interposed between successive attempts. Ultrasonic monitoring of the spleen and noninvasive cardiopulmonary measurements were performed before, between apneas and at times 0, 10, 20, 40, and 60 minutes after the last apnea. Blood flows in splenic artery and splenic vein were not significantly affected by breath-hold apnea. The duration of apneas peaked after A3 (143, 127, and 74 seconds in apnea divers, intact and splenectomized persons, respectively). A rapid decrease in spleen volume (about 20% in both apnea divers and intact persons) was mainly completed throughout the first apnea. The spleen did not recover in size between apneas and only partly recovered 60 minutes after A5. The well-known physiological responses to apnea diving: bradycardia and increased blood pressure were observed in A1 and remained unchanged throughout the following apneas. These results show rapid, probably active contraction of the spleen in response to breath-hold apnea in humans. Rapid spleen contraction and its slow recovery may contribute to prolongation of successive, briefly repeated apnea attempts.