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Biomedical subjects

A Lockhart

Publications and source records attributed to A Lockhart.

At least 145 records · Page 8Linked to original sources
PubMed1977

Splanchnic blood flow, O2 consumption, removal of lactate, and output of glucose in highlanders.

An impairment of gluconeogenesis has been proposed to explain the low arterial blood glucose of highlanders. Therefore, we studied splanchnic blood flow, splanchnic uptake of oxygen and lactate, and output of glucose in nine normal and six anemic highlanders at an altitude of 3,750 m. Splanchnic blood flow, arteriovenous difference for oxygen, and oxygen consumption were comparable at rest in both groups and in lowlanders from the literature, whereas splanchnic output of glucose, and uptake of lactate were approximately twice those in lowlanders. After 10 min of mild exercise in 12 subjects (7 normals, 5 anemic), no significant changes in splanchnic hemodynamics and metabolism were found. During 29% oxygen breathing in 8 subjects (5 normals, 3 anemics), arterial lactate, splanchnic uptake of lactate and output of glucose fell to normal sea-level values. We concluded that splanchnic hemodynamics are similar in adapted highlanders and in lowlanders, and that there is no evidence of an impaired gluconeogenesis at the altitude of the present study.

Adaptation, Physiological↗
PubMed1976

Pressure-flow-volume relationships in pulmonary circulation of normal highlanders.

Pulmonary vascular pressures and blood flow were measured with and without unilateral pulmonary arterial occlusion (UPAO) at rest and during exercise in 10 normal highlanders at La Paz, Bolivia (altitude, 3,750 m). In 6 other highlanders at rest and during exercise, pulmonary pressures, flow, and blood volume were measured during air breathing (PIO2 congruent to 100 Torr) and 29-30% oxygen (PIO2 congruent to 150 Torr). During air breathing, pulmonary vascular resistance was elevated at rest and did not change with exercise. Pulmonary arterial pressure rose less at rest with UPAO than during exercise without UPAO, and pulmonary vascular resistance was less in the former. Raising PaO2 to normal sea-level values had no effects on the pulmonary circulation at rest but prevented to a large extent the rise in pulmonary arterial pressure during exercise. Hence pulmonary vascular resistance during exercise was lower with oxygen than without. Thus, hypoxic vasoconstriction contributed to the pulmonary hypertension during exercise in normal highlanders. Circumstantial evidence suggests that this is related to the profound mixed venous hypoxemia caused by exercise in a hypoxic environment.

Adolescent↗
PubMed1975

[Pulmonary blood volume. Definition, measurement, normal values].

We propose a simplification of the double-injection method whereby left atrial catheterization is made unnecessary by use of injection of indicator in the pulmonary wedge position instead of into the left atrium. Normal values of PBV range between 204 +/- 51 ml. m-2 and 326 +/- 51 ml. M-2. Such a large scatter is due in all likelihood partly to techniques themselves, partly to the small number of studied subjects, which precludes standardization of normal values according to age, sex and body build. Determination of PBV may help in assessing the overall distensibility of the pulmonary vascular bed, but is of no avail to assess separately the distensibility of arteries, microcirculation, and veins whose respective volumes cannot be measured in vivo for lack of undisputable methods. Morphometric and physiological observations suggest that the measurement of PBV is no avail to estimate changes in caliber of pulmonary arterioles caused by vasoactive stimuli.

Blood Volume↗