Making a virtue out of an evil: Are red blood cells from chronic mountain sickness patients eligible for transfusions?

We investigated highlanders, permanently living at an altitude of 5100 m and compared Chronic Mountain Sickness (CMS) patients with control volunteers. While we found differences in systemic parameters such as blood oxygen content, hematocrit, hemoglobin concentration, and blood viscosity, the mechanical and rheological properties of single red blood cells did not differ between the two investigated groups.

Effects of acute and chronic hematocrit modulations on blood viscosity in endurance athletes.

The aim of the present study was to investigate the effects of manipulating hematocrit by different methods (acute exercise, training or isovolumic hemodilution) on blood viscosity in high-level aerobic endurance athletes. We hypothesized than increasing hematocrit does not always cause a rise in blood viscosity.Sixteen endurance athletes underwent maximal exercise before and after 4 weeks of training with (LHTL; n = 10) or without (placebo; n = 6) Live High-Train Low modalities. Total hemoglobin mass was measured before and after training by a carbon monoxide rebreathing technique. After training, subjects performed two maximal exercise bouts separated by isovolumic hemodilution (phlebotomy and/or plasma volume expander) to readjust red blood cell volume and plasma volume to baseline values. Blood samples were obtained before and after exercise to assess hematocrit and blood and plasma viscosity.Training session (LHTL and placebo) increased hematocrit (Hct) in all subjects but without any significant change in blood viscosity. The decrease in plasma viscosity in all groups may explain this result. Isovolumic hemodilution caused a drop of Hct without any significant change in blood viscosity at rest. Maximal exercise increased Hct, blood and plasma viscosities in both groups, regardless of isovolumic hemodilution. However, peak hemorheological values after exercise were lower after isovolumic hemodilution.In conclusion, while acute increase in Hct during exercise caused an increase of blood viscosity, the chronic increase of Hct induced by training session did not result in a rise in blood viscosity. The lowering of plasma viscosity during training may compensate for the increase of Hct, hence limiting its impact on blood viscosity.

Role of glutamate and serotonin on the hypoxic ventilatory response in high-altitude-adapted plateau Pika.

The highland "plateau Pika" is considered to be adapted to chronic hypoxia. We hypothesized that glutamate N-methyl-D-aspartate (NMDA) and non-NMDA receptors, nitric oxide (NO) synthase, and serotonin are involved in hypoxic ventilatory response (HVR) in Pikas. We tested the effects of NMDA (memantine) and non-NMDA receptors (DNQX) antagonists, NO synthase inhibitor (L-NAME), and selective serotonin reuptake inhibitors (fluoxetine) on ventilation and HVR in Pikas. Ventilatory parameters were measured before and after drug (or vehicle) injections in conscious Pikas at their natural living altitude (PIO2 86 mmHg) and after a hypoxic challenge (PIO2 57 mmHg, 3 min) to assess the influence of peripheral chemoreceptor on HVR. Minute ventilation (VI) and tidal volume (Vt) increased during hypoxic challenge after vehicle injection, whereas the Ti/Ttot ratio remained unchanged. The increase in VI and Vt observed with vehicle at PIO2-57, when compared with PIO2-86, was inhibited after memantine and fluoxetine injection, whereas the DNQX injection increased HVR. At PIO2-57, L-NAME induced an increase in the Ti/Ttot ratio when compared with vehicle. Therefore, the glutamate through NMDA-R/AMPA receptor bindings and serotonin pathway are implicated at the peripheral chemoreceptor level in HVR in Pikas. However, NO influences the ventilatory pattern of Pikas at their habitual living altitude.

Relationship between acute chest syndrome and the sympatho-vagal balance in adults with hemoglobin SS disease; a case control study.

The present study evaluated the relationship between acute chest syndrome (ACS) and autonomic nervous system (ANS) activity in patients with hemoglobin SS disease (Hb SS). Nine patients had suffered ACS were matched by age and gender to patients who had not suffered ACS and ANS activity, pulmonary function and history of painful crisis were compared. Correlations between number of episodes of ACS suffered and these variables were determined. The results demonstrated that 1) patients with a history of ACS ever had lower parasympathetic nervous system (PNS) activity and lower global ANS activity than patients with no ACS ever (p < 0.05), 2) the number of ACS episodes ever negatively correlated (p < 0.05) with PNS activity and global ANS activity and 3) There were no significant associations between lung function or a history of painful crisis in these patients. In conclusion, a history of ACS was associated with ANS dysfunction in adults with Hb SS disease.

Spectral analysis of heart rate variability during exercise in trained subjects.

PURPOSE: To investigate the effects of strenuous exercise on heart rate variability (HRV). METHODS: We evaluated the effects of exercise intensity and duration on HRV indices in 14 healthy trained subjects. Each subject exercised for 3, 6, and 9 min at 60 and 70% of the power achieved at maximal oxygen consumption (PVO2(max)) and for 3 and 6 min (or 3 min twice) at 80% of PVO2(max). The electrocardiogram RR intervals were recorded then processed by fast(FFT) and short-time (STFT) Fourier transform for determination of low-frequency (LF, 0.045-0.15 Hz) and high-frequency (HF, 0.15-1.0 Hz) components. RESULTS: The LF and HF components expressed as absolute power (ms2) decreased significantly at the onset of exercise (P < 0.05). However, with increasing exercise intensity, the HF component expressed as normalized units (n.u.) (reflecting parasympathetic modulation) increased significantly, whereas the LF component (n.u.) and LF/HF ratio (both reflecting sympathetic modulation) decreased significantly (P < 0.05). STFT showed that increasing exercise intensity was associated with a shift in HF peak frequency related to an increase in respiratory rate and a marked decrease in LF power (ms2). Moreover, HFn.u. rose (r = 0.918, P < 0.01) and LFms2 fell as minute ventilation increased (r = 0.906, P < 0.01). CONCLUSIONS: Parasympathetic respiratory control and nonautonomic mechanisms may influence the HF-peak shift during strenuous exercise. HRV and the usual indexes of sympathetic activity do not accurately reflect changes in autonomic modulation during exhaustive exercise.