Effects of a Maximal Exercise Followed by a Submaximal Exercise Performed in Normobaric Hypoxia (2500 m), on Blood Rheology, Red Blood Cell Senescence, and Coagulation in Well-Trained Cyclists

Acute normoxic exercise impacts the rheological properties of red blood cells (RBC) and their senescence state; however, there is a lack of data on the effects of exercise performed in hypoxia on RBC properties. This crossover study compared the effects of acute hypoxia vs. normoxia on blood rheology, RBC senescence, and coagulation during exercise. Nine trained male cyclists completed both a session in normoxia (FiO2 = 21%) and hypoxia (FiO2 = 15.3% ≈ 2500 m). The two sessions were randomly performed, separated by one week, and consisted of an incremental and maximal exercise followed by a 20 min exercise at the first ventilatory threshold (VT1) on a home-trainer. Blood samples were taken before and after exercise to analyze hematological parameters, blood rheology (hematocrit, blood viscosity, RBC deformability and aggregation), RBC senescence markers (phosphatidylserine (PS) and CD47 exposure, intraerythrocyte reactive oxygen species (ROS), and calcium content), and blood clot viscoelastic properties. Hemoglobin oxygen saturation (SpO2) and blood lactate were also measured. In both conditions, exercise induced an increase in blood viscosity, hematocrit, intraerythrocyte calcium and ROS content, and blood lactate concentration. We also observed an increase in blood clot amplitude, and a significant drop in SpO2 during exercise in the two conditions. RBC aggregation and CD47 exposure were not modified. Exercise in hypoxia induced a slight decrease in RBC deformability which could be related to the slight increase in mean corpuscular hemoglobin concentration (MCHC). However, the values of RBC deformability and MCHC after the exercise performed in hypoxia remained in the normal range of values. In conclusion, acute hypoxia does not amplify the RBC and coagulation changes induced by an exercise bout

Impaired microvascular function in patients with sickle cell anemia and leg ulcers improved with healing

International audienceSummary Leg Ulcer (LU) pathophysiology is still not well understood in sickle cell anaemia (SCA). We hypothesised that SCA patients with LU would be characterised by lower microvascular reactivity. The aim of the present study was to compare the microcirculatory function (transcutaneous oxygen pressure (TcPO 2 ) on the foot and laser Doppler flowmetry on the arm) and several blood biological parameters between nine SCA patients with active LU (LU+) and 56 SCA patients with no positive history of LU (LU−). We also tested the effects of plasma from LU+ and LU− patients on endothelial cell activation. We observed a reduction of the TcPO 2 in LU+ compared to LU− patients. In addition, LU+ patients exhibited lower cutaneous microvascular vasodilatory capacity in response to acetylcholine, current and local heating compared to LU− patients. Inflammation and endothelial cell activation in response to plasma did not differ between the two groups. Among the nine patients from the LU+ group, eight were followed and six achieved healing in 4.4 ± 2.5 months. Among thus achieving healing, microvascular vasodilatory capacity in response to acetylcholine, current and local heating and TcPO 2 improved after healing. In conclusion, microcirculatory function is impaired in patients with LU, and improves with healing