Selected Contribution: Role of spleen emptying in prolonging apneas in humans

Abstract

This study addressed the interaction between short-term adaptation to apneas with face immersion and erythrocyte release from the spleen. Twenty healthy volunteers, including ten splenectomized subjects, participated. After prone rest, they performed five maximal-duration apneas with face immersion in 10 degrees C water, with 2-min intervals. Cardiorespiratory parameters and venous blood samples were collected. In subjects with spleens, hematocrit and hemoglobin concentration increased by 6.4% and 3.3%, respectively, over the serial apneas and returned to baseline 10 min after the series. A delay of the physiological breaking point of apnea, by 30.5% (17 s), was seen only in this group. These parameters did not change in the splenectomized group. Plasma protein concentration, preapneic alveolar PCO2, inspired lung volume, and diving bradycardia remained unchanged throughout the series in both groups. Serial apneas thus triggered the hematological changes that have been previously observed after long apneic diving shifts; they were rapidly reversed and did not occur in splenectomized subjects. This suggests that splenic contraction occurs in humans as a part of the diving response and may prolong repeated apneas.

Exercise induced hemoconcentration following spleen contraction in subjects with COPD

“…The latter finding suggests that this spleen function may be essential for these individuals during hypoxic challenges similar to that found in healthy subjects during maximal exercise [23], high altitude simulation [13,14] or apnea [4,5,7]. In …”

“…2 Mean (IQR) hemoglobin concentration (Hb) after 10 min rest, after 6 min walking and after 10 min recovery in 24 subjects. P < 0.001 is indicated with *** and P < 0.01 with ** compared with values obtained after 10 min rest apneic diving, these responses have been shown to be protective against acute hypoxia [5,18], and we suggest this may be the case also in COPD.…”

“…diving seals, spleen contraction may prolong aerobic dive duration [2,3]. In healthy human subjects, spleen contraction and circulating hemoglobin (Hb) increase have also been observed during apnea [4][5][6][7]. Interestingly, apnea in splenectomized subjects was found not to induce a Hb increase [5], and neonates with asplenia showed impaired transient elevation of blood Hb in response to acute hypoxia [8].…”

“…In healthy human subjects, spleen contraction and circulating hemoglobin (Hb) increase have also been observed during apnea [4][5][6][7]. Interestingly, apnea in splenectomized subjects was found not to induce a Hb increase [5], and neonates with asplenia showed impaired transient elevation of blood Hb in response to acute hypoxia [8]. Bakovic and associates concluded that the contraction is an active process, as no differences in blood flow in the splenic artery or vein occurred [9], and total plasma protein levels remained unchanged across apnea series ruling out extravasation of plasma [5].…”

Comparison of heart rate in the aquatic environment and on the land

“…Tento fakt by potvrzoval, že diving reflex se neprojevuje po celou dobu ponoření organismu pod vodní hladinu. Po určité době (zhruba 30 sekund) dochází k ustálení kardiovaskulárních parametrů srdečního rytmu a jeho hodnota se výrazněji nemění do konce ponoření (Schagatay, Andersson, Hallén, & Pålsson, 2001). Tepová frekvence byla z důvodu maximálního eliminování případného projevu diving reflexu zaznamenávána až po setrvání pěti minut v klidu v poloze určené pro měření.…”