Biomedical subjects

J A Porlier

Publications and source records attributed to J A Porlier.

5 recordsLinked to original sources

PubMed1991

Oxyhemoglobin saturation following rapid decompression to 18,288 m preceded by diluted oxygen breathing.

This investigation studied oxyhemoglobin saturation (SaO2) and cardiovascular indices after rapid decompression (RD). Before RD, fractional inspired O2 concentration (FIO2) simulated the range of product gas from molecular sieve O2 generating systems (MSOGS). Four subjects breathed 1.0-0.80 FIO2 at 6,858 m. After decompression to 18,288 m, the subject received 1.0 FIO2 at a positive pressure of 70 mm Hg for 3 min. There were no incidents of severe hypoxia. The mean SaO2 was 98.0% before RD. After RD, SaO2 was maintained at the pre-RD level for 8 s, decreased rapidly over the next 10 s, and over the rest of the 1st min decreased more gradually to reach approximately 82%. Varying FIO2 before RD had no effect on the alteration in SaO2, heart rate, stroke index, and blood pressure after RD. The MSOGS O2 product range offers adequate protection against hypoxia during RD to 18,288 m.

Adult↗

PubMed1987

Decrement in postural control during mild hypobaric hypoxia.

The effects of mild hypoxia on the postural control system of 39 naive subjects were examined by measuring the postural sway with a Kistler force platform, at ground level and at one of four simulated altitudes: 1,521 m (5,000 ft), 2,438 m (8,000 ft), 3,048 m (10,000 ft), or 3,658 m (12,000 ft). The total sway increased above the ground level controls for the 1,521 m, 2,438 m, and 3,048 m exposures (p less than or equal to 0.005) as did the sway at the lowest measurable frequency (p less than or equal to 0.002), but no change in sway was seen in those subjects exposed to 3,658 m as compared to ground level values. Significant interaction between altitude and exposure was observed at p less than or equal to 0.04, reflecting the definite effect at the lower altitudes and the lack of an effect at the higher altitude. The multiple comparison test indicated no difference between the responses at 1,524 m, 2,438 m, and 3,048 m. Both arterial oxygen saturation, SaO2, and the end-tidal oxygen partial pressure, PetO2, decreased in relation to the test altitudes with a statistically significant interaction between altitude and PetO2 (p less than or equal to 0.02), and SaO2 (p less than or equal to 0.005). There was no significant interaction between altitude and end-tidal carbon dioxide partial pressure (p = 0.4853). The postural control mechanisms, as an intergrative functional unit, are very sensitive to acute mild hypoxia. Arguments are advanced to indicate that intervention of compensatory mechanisms at higher altitudes may explain the recovery of postural stability at 3,658 m.

Adult↗

PubMed1982

Postural stability during slow-onset and rapid-onset hypoxia.

The standing steadiness and postural tremor of seven male volunteers were examined during slow and rapid induction of hypoxia. Spectrum analysis of position coordinates and tremor data generated from a quartz multicomponent force measuring platform and a tremor transducer showed that postural tremor (pt) and anteroposterior sway (ay) increased significantly during hypoxia. Rate of onset of hypoxia, however, did not affect the development of the increased tremor, whereas rapid-onset hypoxia consistently induced a greater anteroposterior sway than slow-onset hypoxia. Lateral sway (ax) was not affected by either slow- or rapid-onset hypoxia; however, it was significantly greater when eyes were closed compared to when they were opened. Anteroposterior sway (ay) was also significantly greater when visual cues were eliminated during both slow- and rapid-onset hypoxia. Heart rate (HR) and cardiac index (CI) of subjects increased significantly during both conditions of hypoxia.

Adult↗

PubMed1980

Respiratory gas exchange during positive pressure breathing and rapid decompression to simulated altitudes of 18.3 and 24.4 km.

Respiratory gas exchange was studied, using the technique of mass spectrometry, during events of slow and rapid decompression of human subjects to simulated altitudes of 60,000 and 80,000 ft (18.3 and 24.4 km, respectively). Positive breathing pressures and G-suit counterpressures were employed in three series of decompression experiment. Low levels of inspired carbon dioxide and nitrogen reflected the rebreathing of gases throughout the experiments. Application of a positive breathing pressure of 70 torr, accompanied by a jerkin pressure equal to breathing pressure and a G-suit counterpressure of four times the breathing pressure on the trunk and limbs, respectively, maintained alveolar oxygen at physiologically safe levels during decompression to 60,000 ft (18.3 km) altitude. Similarly, 80 torr positive breathing pressure, in combination with four times the breathing pressure in the G suit, adequately satisfied the requirements for oxygen during rapid decompression to 80,000 ft (24.4 km) simulated altitude.

Aerospace Medicine↗

PubMed1978

Protection against the physiological effects of positive pressure breathing.

The degree of protection afforded by three jerkin G-suit systems (British, Canadian and Swedish) using different pressures against the adverse physiological effects produced by high levels (50 mm Hg and 70 mm Hg) of positive pressure breathing (PPB) was investigated at ground level in 10 male subjects. The British and Canadian systems were evaluated with G-suit pressure equal to breathing pressure and 3.2 times breathing pressure, whereas the Swedish system was studied only with 3.2 times breathing pressure in the G suit. The experimental design was a 10 X 10 Latin swuare. PPB produced significant increases in heart rate, peripheral resistance, and systolic, diastolic and mean arterial blood pressures, and significant decreases in stroke volume and cardiac output. These effects were directly related to the level of PPB. Our results show that the British system provides the highestdegree of protection against PPB, followed by the Swedish and the Canadian systems. It was also found that a G-suit pressure of 3.2 times breathing pressure significantly increases the degree of protection afforded by the British and Canadian systems.

Adult↗