Effects of breathing air containing 3% carbon dioxide, 35% oxygen or a mixture of 3% carbon dioxide/35% oxygen on cerebral and peripheral oxygenation at 150 m and 3459 m

Abstract

The effects of gas mixtures comprising supplementary 3% carbon dioxide, 35% oxygen or a combination of 3% CO(2) plus 35% O(2) in ambient air have been compared on arterial blood gases, peripheral and cerebral oxygenation and middle cerebral artery velocity (MCAV) at 150 m and on acute exposure to 3459 m in 12 healthy subjects. Breathing 3% CO(2) or 35% O(2) increased arterial blood oxygen at both altitudes, and the CO(2)/O(2) combination resulted in the most marked rise. MCAV increased on ascent to 3459 m, increasing further with 3% CO(2) and decreasing with 35% O(2) at both altitudes. The CO(2)/O(2) combination resulted in an increase in MCAV at 150 m, but not at 3549 m. Cerebral regional oxygenation fell on ascent to 3459 m. Breathing 3% CO(2) or 35% O(2) increased cerebral oxygenation at both altitudes, and the CO(2)/O(2) combination resulted in the greatest rise at both altitudes. The combination also resulted in significant rises in cutaneous and muscle oxygenation at 3459 m. The key role of carbon dioxide in oxygenation at altitude is confirmed, and the importance of this gas for tissue oxygenation is demonstrated.

Cerebral Blood Flow During Treadmill Exercise Is a Marker of Physiological Postconcussion Syndrome in Female Athletes

“…21 Breathing 7% CO 2 can increase CBF approximately 2-fold in both men 19 and women, 50 which is similar to what we observed in this study during exercise. CO 2 sensitivity is a measure of the level of ventilation for a given arterial CO 2 tension (PaCO 2 ).…”

“…Depressed PaCO 2 reduces CBF and increased PaCO 2 increases CBF. 19 For a given carbon dioxide production (VCO 2 ), the PaCO 2 is inversely proportional to the pulmonary ventilation (V E ): asV E increases PaCO 2 decreases and vice versa. Normally, as oxygen consumption (VO 2 ) andVCO 2 increase with exercise intensity, PaCO 2 increases until the onset of excess blood lactic acid accumulation, at which point there is a hyperventilation, that is, a respiratory compensation for the metabolic acidosis that reduces PaCO 2 and CBF.…”

Problems with capnography at high altitude*

“…The study showed that the reduced air density at altitude has effects upon the pump, causing difficulty in entraining gas, and that high altitude has additional effects upon calibration of the instruments. There is ongoing interest in the effects of carbon dioxide (CO 2 ) on acclimatisation and mountain sickness at high altitude [1][2][3]. Experiments involving the measurement of CO 2 with capnography, however, have frequently been hampered by instrument malfunction.…”

“…There is ongoing interest in the effects of carbon dioxide (CO 2 ) on acclimatisation and mountain sickness at high altitude [1][2][3]. Experiments involving the measurement of CO 2 with capnography, however, have frequently been hampered by instrument malfunction.…”

Effect of magnesium, high altitude and acute mountain sickness on blood flow velocity in the middle cerebral artery

“…Again, the available data are conflicting. In field studies, exposure to high altitude led to a significant increase in both CBF and MCAv [7,[10][11][12]. In an experimental study in a hypobaric chamber, however, an increase in MCAv could not be confirmed [9].…”