Browsing by Autor "Durand, Jacques"

Now showing 1 - 2 of 2

Cerebral blood flow, brain metabolism and CSF acid-base balance in highlanders
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1977) Durand, Jacques
SUMMARY. Cerebral blood flow (Qc), local arterio-venous oxygen difference (0₂ AVD); and pH, O₂ and CO₂ partial pressures in arterial and jugular blood and in lumbar and cisternal cerebrospinal fluids (CSF) were measured in subjects born and residing at high altitude (3,800 - 4,800 m). Qc, was determined by 85Kr wash-out. Studies were made while subjects were breathing room air as control, while breathing gas mixtures or while voluntarily hyperventilating to alter Pao₂ and/or Paco₂. (1) Qc control values are lower than at sea level, 0₂ AVD larger and cerebral oxygen consumptions identical; cerebral respiratory quotient is close to 1.0, lactic acid production is negligible and glucose uptake fits with the local O₂ consumption. (2) Qc as function of Paco₂ describes a curve similar to that obtained at sea level but with a higher setting: therefore, for a given Paco₂. Qc is higher in highlanders than in lowlanders Correction of altitude hypoxia reduces highlanders' Qc to a lower value. Conversely, when deeper hypoxia is induced, Qc rises above control values. This influence of Pao₂, on Qc contrasts with what is observed at sea level. (3) A curvilinear relationship is found between cerebral mean circulatory transit time and hematocrits ranging from .35 to .84: sea level values fall on the same curve. Cerebral red cell flow is comparable at sea level and at altitude. (4) A consistent difference is found between cisternal and lumbar CSF : pH, and Po₂ are lower in lumbar CSF and Pco₂, higher than in cisternal fluid, whereas [HC03-] is not significantly different at the two sites: CSF heterogeneity is larger in highlanders than in lowlanders. Cisternal pH was not signilicantly different from sea level values.
Influence of altitude on the cutaneous circulation of residents and newcomers
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1969) Durand, Jacques
SUMMARY. Blood flow, pressure, and volume have been measured in the right hand considered as representative of a cutaneous vascular bed. Measurements have been made comparatively at sea level and at high altitude (3.750 and 4,800 m) on residents and newcomers. The results show an increase of the tone of both resistance and capacitance vessels at high altitude. The changes are more marked when the skin temperature is higher, that is, when the cutaneous circulation is increased. Extrapolating these results to the whole skin area, one can conclude that the cutaneous circulation acts as a blood reservoir during the circulatory adjustments caused by high-altitude hypoxia.