Is Hemoglobin Desaturation Related to Blood Viscosity in Athletes During Exercise?

Abstract

Several studies have suggested that athletes with low hemoglobin saturation during exercise may experience impaired pulmonary blood gas exchange during maximal exercise. Blood viscosity may be implicated in exercise-induced pulmonary hemorrhage in race horses. We hypothesized that blood rheology may contribute to impaired gas exchange and reduced hemoglobin saturation during exercise in humans. A group of 20 highly trained endurance athletes participated in this study, 9 with low hemoglobin saturation during exercise (Low-SpO (2) group) and 11 with normal hemoglobin saturation (High-SpO (2) group). All subjects performed a progressive exercise test conducted to V.O (2max). Venous blood was sampled at rest, 50 % V.O (2max) and maximal exercise. Blood viscosity (etab) was measured at very high shear rate (1000 s (-1)) and 37 degrees C with a falling ball viscometer. The erythrocyte rigidity coefficient, "Tk", was calculated using the Dintenfass equation. At rest, no significant difference in etab was observed between the two groups (3.00 +/- 0.08 mPa . s vs. 3.01 +/- 0.04 mPa . s for the Low-SpO (2) and High-SpO (2) group, respectively). At 50 % V.O (2max) and maximal exercise, etab was higher in Low-SpO (2) (p < 0.01). Tk decreased in High-SpO (2) (p < 0.01) but remained unchanged in the other group during testing. The greater increase in etab in the Low-SpO (2) group during exercise may therefore have been due to the lack of reduction in Tk. As suggested by previous studies, the greater increase in blood viscosity in athletes with low hemoglobin saturation may lead to vascular shear stress. Whether this could impair the blood gas barrier and result in exercise-induced hypoxemia requires further study.

Hematologic and hemorheological determinants of resting and exercise-induced hemoglobin oxygen desaturation in children with sickle cell disease

“…45 In a non-SCD context, blood rheological alterations have been suspected to participate to the occurrence of EIHOD. 27,28 The independent association between the elevated RBC disaggregation threshold and EIHOD in SS children reported in the present study also supports a role for blood rheology in EIHOD. A high RBC disaggregation threshold means that RBC aggregates are tightly bound.…”

“…27,28 A similar observation has been documented in exercising horses, with hypoxemic horses exhibiting decreased RBC deformability and increased RBC aggregation. 27,29 These RBC rheological abnormalities may affect the recruitment of pulmonary capillaries, hence increasing ventilation-perfusion mismatching and leading to a reduction in oxygen saturation.…”

Effects of short supramaximal exercise on hemorheology in sickle cell trait carriers

“…Surprisingly, we observed an increase in RBC deformability in the subjects with normal Hb during exercise, as already reported (Hardeman et al 1995;Connes et al 2004a), but also in the SCT group. Twenty-four hours after this exercise, however, we observed a great increase in RBC rigidity above baseline value in the SCT carriers, which suggested an increased risk for microcirculatory disorders during the post-exercise period in this population.…”

Optimal hematocrit for maximal exercise performance in acute and chronic erythropoietin-treated mice

“…It should be noted, however, that this may vary under different circumstances because of the blood's non-Newtonian behavior (13). Factors affecting this variation include the species, the organs involved, and whether the organism is in resting or exercising conditions (11,12,(14)(15)(16). Thus, the above mentioned observations do not always reflect the general situation in exercising mammals and humans.…”