Differential splenic responses to hyperoxic breathing at high altitude in Sherpa and lowlanders

Abstract The human spleen contracts in response to stress‐induced catecholamine secretion, resulting in a temporary rise in haemoglobin concentration ([Hb]). Recent findings highlighted enhanced splenic response to exercise at high altitude in Sherpa, possibly due to a blunted splenic response to hypoxia. To explore the potential blunted splenic contraction in Sherpas at high altitude, we examined changes in spleen volume during hyperoxic breathing, comparing acclimatized Sherpa with acclimatized individuals of lowland ancestry. Our study included 14 non‐Sherpa (7 female) residing at altitude for a mean continuous duration of 3 months and 46 Sherpa (24 female) with an average of 4 years altitude exposure. Participants underwent a hyperoxic breathing test at altitude (4300 m; barrometric pressure = ∼430 torr; PO2 = ∼90 torr). Throughout the test, we measured spleen volume using ultrasonography and monitored oxygen saturation (SpO2). During rest, Sherpa exhibited larger spleens (226 ± 70 mL) compared to non‐Sherpa (165 ± 34 mL; P