Exercise induced hemoconcentration following spleen contraction in subjects with COPD

Abstract

Background: The blood-boosting spleen contraction represents a potential protective response to hypoxia by raising the blood gas storage capacity. Human spleen contraction has been observed during exercise, apnea and simulated altitude resulting in ejection of stored red blood cells into circulation. High-altitude exposure has been shown to increase spleen contraction suggesting that long-term hypoxia may improve the response in humans. Subjects with COPD are often exposed to hypoxia, which limits their physical performance. However, it is not known if spleen contraction occurs in subjects with COPD. Our aim was to reveal whether subjects with COPD recruit the spleen erythrocyte reserve during mild exercise. Methods: SpO 2 , spleen volume and Hb were measured before and after 6 min walking test (6MWT) in 24 subjects with COPD. Results were analyzed for all subjects pooled and for subject groups with resting SpO 2 above and below 90 % separated and expressed as mean. Results: 6MWT reduced SpO 2 from 91 to 83 % and spleen volume from 254 to 181 mL, while Hb increased from 150 to 154 g/L (p = 0.001 for all). Compared to subjects with SpO 2 > 90 %, the group with SpO 2 < 90 % displayed the largest resting spleen volume (339 vs 202 mL; p = 0.001) and the most pronounced spleen volume reduction (139 vs 40 mL; p = 0.007). Conclusion: Exercise with hypoxia evokes spleen contraction in subjects with COPD and may represent a protective response during periods of hypoxia. The larger spleen volume and more pronounced contraction in the most hypoxic subjects may suggest long-term adaptation to hypoxia.

The Magnitude of Diving Bradycardia During Apnea at Low-Altitude Reveals Tolerance to High Altitude Hypoxia

“…Also, native Bajau divers, who are continuously exposed to hypoxia, were recently reported to have larger spleens compared to a native population within close proximity but not exposed to hypoxia associated with apneic diving (Ilardo et al, 2018). We also reported larger spleens in the most hypoxic COPD patients, compared to less hypoxic patients (Schagatay et al, 2015). Furthermore, we found that spleen contraction was enhanced after a HA expedition to the summit of mount Everest (Engan et al, 2014).…”

Spleen Size and Function in Sherpa Living High, Sherpa Living Low and Nepalese Lowlanders

“…It would have been valuable to do repeated blood sampling for Hb, in parallel with spleen measurements, but such sampling and analysis was not possible for logistical reasons. We believe, however, that other studies conducted in permanent research laboratories have reliably confirmed that transient spleen contraction is closely associated with transiently elevated Hb (Schagatay et al, 2005(Schagatay et al, , 2015. We also did not take any biological samples to study genetics in this initial study, and our results may therefore be regarded as indirect evidence of genetic predisposition in the Sherpa.…”

“…A possible long-term acclimatization of the spleen has also been observed in patients with chronic obstructive pulmonary disease (COPD), whereby patients with SaO 2 < 90% had larger spleens and also a more pronounced contraction after exercise compared to patients with >90% SaO 2 (Schagatay et al, 2015). Greater resting spleen volume was recently also found following 8 weeks of long-term apnea training (Bouten et al, 2019), while no effect was found after 2 weeks of apnea training (Engan et al, 2013), suggesting that a fairly strong exposure/training dose is required to induce changes.…”

Spleen contraction elevates hemoglobin concentration at high altitude during rest and exercise

“…The decrease in spleen volume typically increases the total amount of circulating erythrocytes by 3-6% with individuals responding with up to 10% increases (Richardson et al 2008). This natural blood-boosting was also found to be active during exercise in chronically hypoxic patients with chronic obstructive pulmonary disease (COPD), where the most hypoxic patients were found to have the largest spleens and the most pronounced spleen contractions with exercise (Schagatay et al 2015).…”

“…After maximal spleen contraction, it takes approximately 10 min before the spleen red cell supply is re-stored and the spleen has expanded to the resting volume (Schagatay et al 2005). The spleen function as a dynamic red cell reservoir will not only transiently increase oxygen storage and delivery during exercise or hypoxic exposure, but lower blood viscosity between bouts of exercise or severe hypoxia and thereby reduce the sheer stress and thereby the work of the cardiovascular system (Schagatay et al 2015).…”