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Spleen contraction during 20 min normobaric hypoxia and 2 min apnea in humans.
Aviat Space Environ Med. 2010 Jun;81(6):545-9
Authors: Lodin-Sundström A, Schagatay E
INTRODUCTION: Spleen contraction occurs in humans during exercise, apnea, and simulated altitude, resulting in ejection of stored red blood cells into circulation. The mechanisms responsible for initiating the contraction are not fully known: hypoxia is likely involved, but other, unknown factors may also contribute. To reveal the initiating factors, we studied its occurrence in two different situations involving similar reductions in arterial oxygen saturation (SaO2). We hypothesized that similar spleen responses would result if the level of hypoxia is the main factor involved. METHODS: Five female and four male healthy volunteers performed two different trials on separate days: (1) 20 min of normobaric hypoxic breathing (14.2% oxygen); and II) 2 min of apnea after a deep inspiration of air. Both trials started and en…

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
nd 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

In phocid seals, an increase in hematocrit (Hct) accompanies diving and periods of apnea. The variability of phocid Hct suggests that the total red cell mass is not always in circulation, leading researchers to speculate on the means of blood volume partitioning. The histology and disproportionate size of the phocid spleen implicates it as the likely site for RBC storage. We used magnetic resonance imaging on Northern elephant seals to demonstrate a rapid contraction of the spleen and a simultaneous filling of the hepatic sinus during forced dives (P 0.0001, R(2) = 0.97). The resulting images are clear evidence demonstrating a functional relationship between the spleen and hepatic sinus. The transfer of blood from the spleen to the sinus provides an explanation for the disparity between the timing of diving-induced splenic contraction ( approximately 1-3 min) and the occurrence of peak Hct (15-25 min). Facial immersion was accompanied by an immediate and profound splenic contraction, with

In diving mammals splenic contraction increases circulating red cell volume, whereas in humans increased haemoglobin concentrations have been reported. It is unknown, however, whether repetitive apnea diving also comprises an adaptive increase in total red cell volume as reported in endurance athletes. The first aim of the study therefore was to investigate the effect of repeated apnea dives on splenic size and putative red cell release in trained apnea divers (n = 10) and control subjects (SCUBA divers performing apneas without long-term apnea training, n = 7). Long-term effects of repetitive apnea diving may elevate the oxygen transport capacity by an adaptive increase in total haemoglobin mass as reported in endurance athletes. The second goal, therefore, was to compare the trained apnea divers' and the control divers' total haemoglobin mass (tHb-mass) with that of endurance-trained (n = 9) and untrained (n = 10) non-divers. Before and immediately after a series of five dives to a depth of 4

We investigated the spleen volume changes as related to the cardiovascular responses during short-duration apneas at rest. We used dynamic ultrasound splenic imaging and noninvasive photoplethysmographic cardiovascular measurements before, during, and af

Related Items

• document: Speed of spleen volume changes evoked by serial apneas
• document: Spleen volume and blood flow response to repeated breath-hold apneas
• document: The human spleen
• document: Effect of Human Splenic Contraction on Variation in Circulating Blood Cell Counts

Diving mammals may enhance dive duration by injecting extra erythrocytes into the circulation by spleen contraction. This mechanism may also be important for apneic duration in humans. We studied the speed and magnitude of spleen volume changes evoked by serial apneas, and the associated changes in hematocrit (Hct) and hemoglobin (Hb) concentration, diving response and apneic duration. Three maximal apneas separated by 2 min rest elicited spleen contraction in all ten subjects, by a mean of 49 (27) ml (18%; P<0.001). During the same period, Hct and Hb rose by 2.2 and 2.4% respectively (P<0.01 and P<0.001), and apneic duration rose by 20 s (22% P<0.05). The mean heart rate reduction of the diving response was 15%, which remained the same throughout the apnea series. While the diving response was completely reversed between the apneas, spleen size was not recovered until 8–9 min after the final apnea corresponding with recovery of Hct and Hb. Thus, although the spleen contraction may be associated with the cardiovascular diving response, it is likely to be triggered by different mechanisms, and it may remain activated between dives spaced by short pauses. The two adjustments may provide a fast, quickly reversed, and a slow, but long-lasting, way of shifting to a diving mode in humans.

Related Items

• document: Sylvain: Apnée - le rôle de la rate...
• document: Spleen volume and blood flow response to repeated breath-hold apneas
• document: The human spleen
• document: Effect of Human Splenic Contraction on Variation in Circulating Blood Cell Counts

Abstract from jap.physiology.org

The purpose of this study was 1) to answer whether the reduction in spleen size in breath-hold apnea is an active contraction or a passive collapse secondary to reduced splenic arterial blood flow and 2) to monitor the spleen response to repeated breath-hold apneas. Ten trained apnea divers and 10 intact and 7 splenectomized untrained persons repeated five maximal apneas (A1-A5) with face immersion in cold water, with 2 min 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 min 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 s in apnea divers, intact, and splenectomized persons, respectively). A rapid decrease in spleen volume (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 min after A5. The well-known physiological responses to apnea diving, i.e., 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.

Related Items

• document: Sylvain: Apnée - le rôle de la rate...
• document: Speed of spleen volume changes evoked by serial apneas
• document: The human spleen
• document: Effect of Human Splenic Contraction on Variation in Circulating Blood Cell Counts

Abstract from jap.physiology.org

Twelve subjects without and ten subjects with diving experience performed short diving-related interventions. After labeling of erythrocytes, scintigraphic measurements were continuously performed during these interventions. All interventions elicited a graduated and reproducible splenic contraction, depending on the type, severity, and duration of the interventions. The splenic contraction varied between ~10% for 'apnea' (breath holding for 30 s) and 'cold clothes' (cold and wet clothes applied on the face with no breath holding for 30 s) and ~30-40% for 'simulated diving' (simulated breath-hold diving for 30 s), 'maximal apnea' (breath holding for maximal duration), and 'maximal simulated diving' (simulated breath-hold diving for maximal duration). The strongest interventions (simulated diving, maximal apnea, and maximal simulated diving) elicited modest but significant increases in hemoglobin concentration (0.1-0.3 mmol/l) and hematocrit (0.3-1%). By an indirect method, the splenic venous hematocrit was calculated to 79%. No major differences were observed between the two groups. The splenic contraction should, therefore, be included in the diving response on equal terms with bradycardia, decreased peripheral blood flow, and increased blood pressure.

Related Items

• document: Sylvain: Apnée - le rôle de la rate...
• document: Speed of spleen volume changes evoked by serial apneas
• document: Spleen volume and blood flow response to repeated breath-hold apneas
• document: Effect of Human Splenic Contraction on Variation in Circulating Blood Cell Counts

Abstract from blackwell-synergy.com

1. The human spleen sequesters 200–250 mL densely packed red blood cells. Up to 50% of this viscous blood is actively expelled into the systemic circulation during strenuous exercise or simulated apnoea (breath-hold) diving. The contribution of splenic contraction to changes in the circulating volume of red blood cells (RBCV), as well as the venous concentration of white blood cells (WBC) and platelets (PLT), was investigated following repeated breath-hold apnoeas.


2. Eighteen trained apnoea divers and 18 intact and six splenectomized subjects without diving experience repeated five maximal apnoeas with face immersion in cold water, with 2 min intervals between successive attempts. Venous blood samples were taken before and between consecutive apnoeas, as well as at 0, 10 and 20 min after the last breath hold. Arterial pressure, heart rate and transcutaneous partial pressure of oxygen and carbon dioxide were monitored continuously.


3. Plasma protein concentration decreased by 5.8, 2.2 and 9% in apnoea divers, untrained and splenectomized subjects, respectively, indicating an expansion of plasma volume. The RBCV and venous concentration of WBC, corrected for changes in plasma volume, increased in both trained apnoea divers (4.9 ± 1.0 and 14.9 ± 3.1%, respectively) and intact subjects (1.7 ± 0.8 and 7.2 ± 1.8%, respectively), whereas in splenectomized subjects there was no change in RBCV and a delayed increase in WBC concentration. Furthermore, an initial lymphocytosis detected during repeated breath holds in divers and intact subjects was completely absent in splenectomized subjects. None of the groups showed significant changes in PLT concentrations. The well-recognized diving response to apnoea (bradycardia and increased blood pressure) was seen during all breath-hold attempts in all subjects.


4. Repeated breath-holds (apnoeas) contribute to increased RBCV and venous blood concentrations of WBC through splenic contraction.

Related Items

• document: Sylvain: Apnée - le rôle de la rate...
• document: Speed of spleen volume changes evoked by serial apneas
• document: Spleen volume and blood flow response to repeated breath-hold apneas
• document: The human spleen

Twelve subjects without and ten subjects with diving experience performed short diving-related interventions. After labeling of erythrocytes, scintigraphic measurements were continuously performed during these interventions. All interventions elicited a

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 fiv

Spleen emptying and venous hematocrit in humans during exercise