Tissue Oxygen Partial Pressure Distribution within the Human Skeletal Muscle during Hypercapnia
The effects of arterial hypercapnia on the cardiovascular system have been extensively investigated. However, few data exist on the effects of hypercapnia on the peripheral circulation in man. In animal experiments the increase of the systemic sympathetic tone due to hypercapnia (Loeschke 1982, Pelletier 1972, Rose et al. 1983, Soladoye et al. 1985, Suutarinen 1966) elicited an increase in total peripheral resistance (Rose et al. 1983, Rothe et al. 1985). Stimulation of sympathetic nerves resulted in vasoconstriction of vascular beds which were constantly perfused with blood kept at a constant and physiological paO2, pCO2, and pH (Lioy et al. 1978, Pelletier 1972, Soladoye et al. 1985). However, vasodilation and an increase of blood flow occurred, if denervated vascular beds were perfused with hypercapnic blood (Daugherty et al. 1967). It is unknown, whether one of these apparently antasonistic effects of hypercapnia on vascular tone changes the peripheral blood flow to an extent that the oxygen delivery to the tissue could be impaired. In order to study the effects of hypercapnia on the oxygen offer to peripheral tissue in man, the distribution of local oxygen partial pressure (pO2-histogram) within the skeletal muscle was measured in healthy human volunteers during inhalation of a 6.5% carbon dioxide containing air mixture. In order to distinguish between effects on the pO2-histograms due to hypercapnia and the effects on the pO2-histograms due to a change of blood pH, the present study was performed with and without buffering the blood pH during carbon dioxide inhalation.
KeywordsOxygen Partial Pressure Base Excess Total Peripheral Resistance Carbon Dioxide Tension Healthy Human Volunteer
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