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Biomedical subjects

A Cymerman

Publications and source records attributed to A Cymerman.

131 records · Page 8Linked to original sources
PubMedDate not supplied

The effect of elevated intracranial pressure on the vibrational response of the ovine head.

Although potentially fatal increases in intracranial pressure (ICP) can occur in a number of pathological conditions, there is no reliable and noninvasive procedure to detect ICP elevation and quantitatively monitor changes over time. In this experimental study, the relationships between ICP elevation and the vibrational response of the head were determined. An ovine animal model was employed in which incremental increases in ICP were elicited and directly measured through intraventricular cannulae. At each ICP increment, a vibration source elicited a flexural response of the animal's head that was measured at four locations on the skull using accelerometers. Spectral analysis of the responses showed changes in proportion to ICP change up to roughly 20 cm H2O (15 mm Hg) above normal; a clinically significant range. Both magnitude and phase changes at frequencies between 4 and 7 kHz correlated well (gamma > 0.92) with ICP across the study group. These findings suggest that the vibrational response of the head can be used to monitor changes in ICP noninvasively.

Animals↗
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Operation Everest II: cardiac filling pressures during cycle exercise at sea level.

To examine the relationship between cardiac filling pressures during exercise in man and oxygen transport, we examined sea level data from Operation Everest II. The results showed that, (1) both right atrial and wedge pressures rose with heavy exercise in normal man, (2) the magnitude of the rise in these filling pressures related both to stroke volume and maximum exercise capacity, (3) wedge pressure was tightly coupled to right atrial pressure, with each mm Hg increase in right atrial pressure resulting in a 1.4 mm Hg increase in wedge pressure, and (4) very high wedge pressures occurred (in some subjects greater than 30 mm Hg), which contributed to an elevation of pulmonary arterial pressure. Thus direct measurements indicate right heart filling pressure increases with exertion in normal man, probably providing the necessary right heart output to fill the left heart. We speculated that the high cardiac filling pressures might be needed to maintain oxygen transport during heavy exercise, and that such pressures could contribute both to elevated pulmonary arterial pressure and to increased filtration of water into the lung.

Adult↗
PubMedDate not supplied

Influence of altitude and caffeine during rest and exercise on plasma levels of proenkephalin peptide F.

The purpose of this study was to examine the resting and exercise response patterns of plasma Peptide F immunoreactivity (ir) to altitude exposure (4300 m) and caffeine ingestion (4 mg.kg b.w.-1). Nine healthy male subjects performed exercise tests to exhaustion (80-85% VO2max) at sea level (50 m), during an acute altitude exposure (1 hr, hypobaric chamber, 4300 m) and after a chronic (17-day sojourn, 4300 m) altitude exposure. Using a randomized, double-blind/placebo experimental design, a placebo or caffeine drink was ingested 1 hour prior to exercise. Exercise (without caffeine) significantly (p less than 0.05) increased plasma Peptide F ir values during exercise at chronic altitude only. Caffeine ingestion significantly increased plasma Peptide F ir concentrations during exercise and in the postexercise period at sea level. Conversely caffeine ingestion at altitude resulted in significant reductions in the postexercise plasma Peptide F ir values. The results of this study demonstrate that the exercise and recovery response patterns of plasma Peptide F ir may be significantly altered by altitude exposure and caffeine ingestion. These data support further study examining relationships between Peptide F (and other enkephalin-containing polypeptides) and epinephrine release in response to these types of physiological stresses.

Adult↗