The oxygen uptake and pulmonary blood flow during resuscitation from asphyxia in foetal and adult sheep

1. The foetuses of twenty-seven Welsh ewes and eight Clun Forest ewes were delivered by Caesarian section at an approximate gestational age of 140 days, maintaining the umbilical circulation. They were asphyxiated by clamping the umbilical cord, and resuscitated with IPPV. Oxygen consumption, heart rate, and blood pressures were recorded, and in one series of eight, blood flow through the left lung was recorded whilst IPPV was applied to this lung only.2. The hypothesis that oxygen consumption is abnormally low during resuscitation of the new-born from extreme asphyxia because of limited blood flow, was supported.3. Adult ewes were also asphyxiated and in a series of eight a quite different pattern of behaviour was observed, due to very rapid and complete recovery of the circulation.4. Observations on the pulmonary vascular resistance suggest that complete vasomotor paralysis occurs during extreme asphyxia, so that resistance falls to a near-minimum level for unexpanded lung. Expansion of the lung produced a large fall in resistance which appeared to be due to the introduction of gas into the alveolar spaces, lessening the resistance to flow of the capillaries.

The Hill reaction of chloroplasts isolated from glutaraldehyde-fixed spinach leaves

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Effect of oxygen upon pulmonary circulation in acclimatized man at high altitude

The response to breathing 100% oxygen was studied in 26 acclimatized residents of the Peruvian Andes at altitudes of 12,300 and 14,200 ft. Arterial oxygen saturation increased from 86% to 96%. Mean pulmonary artery pressure decreased by 5 mm Hg and cardiac output did not change. Calculated pulmonary arteriolar resistance was lowered. Pulmonary artery pressure during oxygen breathing was not decreased to normal values observed at sea level. The data suggest the presence of two factors responsible for the increase in pulmonary arteriolar resistance at high altitude: 1) hypoxic vasoconstriction which is reversed by oxygen breathing and 2) anatomic alterations which are not affected by oxygen breathing. Oxygen breathing at high altitude also produced a slowing of the heart rate and increased the relative height of the secondary or tidal wave of the brachial arterial pressure pulse.

pulmonary arteriolar resistance and 100% oxygen; arterial pulse contour–effect of 100% oxygen at high altitude; pulmonary arteriolar resistance–nature of in high altitude; hypoxic vasoconstriction at high altitude–reversal by 100% oxygen breathing; oxygen breathing–comparison of effect on pulmonary circulation at high altitude and sea level

Submitted on May 8, 1964

Pulmonary circulation in acclimatized man at high altitude

Cardiac catheterization studies have been carried out in 30 acclimatized adults at an altitude of 12,3000 ft in the Peruvian Andes. Mean pulmonary artery pressure was 22 mm. Hg (range 14-31 mm Hg) compared to 15 mm Hg (range 11-17 mm Hg) observed in sea-level subjects. The pulmonary artery wedge pressure was normal and calculated pulmonary arteriolar resistance was increased by 180% over sea-level values. The arteriovenous oxygen content difference and oxygen consumption were slightly greater at high altitude, but the cardiac output was normal. There was no relationship between hematocrit and pulmonary artery pressure or resistance, suggesting that in the high-altitude resident, blood viscosity in a hematocrit range of 40-78% does not significantly affect resistance to blood flow. Nine subjects studied at 14,200 ft had the same mean pulmonary artery pressure (22 mm Hg, range 17-32 mm Hg) as the larger group at 12,300 ft.

pulmonary artery pressure

Submitted on May 8, 1964

INTERDIFFUSION OF POLYISOBUTYLENE AND CYCLOHEXANE

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