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PubMed1997

Inactivation of food microorganisms by high-pressure carbon dioxide treatment with or without explosive decompression.

In order to elucidate the sterilization mechanism underlying the explosive decompression system, baker's yeast was pressurized with CO2, N2O, N2, or Ar gas at 40 atm and 40 degrees C for 4h, and then explosively discharged. The survival ratio was markedly decreased only by the treatments with CO2 and N2O, which are relatively soluble gases in water, suggesting that the microorganisms' death may be highly correlated with gas absorption by the cells. Lower decompression rates to atmospheric pressure, however, led to neither any lower reduction of remaining cells nor any smaller release of total cellular proteins. Furthermore, operating with a longer treatment time and smaller number of repetitions was usually more lethal than with a shorter time and more frequent repetition. From these results, most of the yeast cells appear to have been sterilized during the pressurization process. The spore cells of B. megaterium are considered to have been killed in a somewhat different manner, because of their distinct sensitivity to the applied gases.

Argon↗
PubMed1978

Explosive decompression of subjects up to a 20,000-m altitude using a two-pressure flying suit.

The RSAF two-pressure flying suit system to protect the pilot at high altitude has been tested from different medical safety aspects. To secure adequate alveolar oxygen pressure, the suit admits up to 70 mm Hg (9.3 kPa) positive pressure breathing by counter-pressure against the thorax and by a 3.2 times higher pressure in the anti-G suit. After 1 h of oxygen breathing, subjects were exposed to explosive decompression from an altitude of 9,000 m to 17,500 or 20,000 m in 0.5 s in a hypobaric chamber. No symptoms of decompression sickness or of alveolar rupture with gas embolism to the central nervous system were seen. Pulmonary X-rays after the test did not reveal any signs of lung rupture with extrapulmonary gas leakage. With the precordial Doppler ultrasound technique, intracardial gas bubbles (silent bubbles) could be detected only in one subject after explosive decompression to a 20,000-m altitude in the 10 experiments.

Adult↗
PubMed1976

Mechanism of lung damage in explosive decompression.

It is known that pressure equalization via the trachea may diminish or prevent lung damage in explosive decompression. In this report, evidence is presented which demonstrates that closure of the trachea does not affect lethality in mice exposed to maximally rapid decompression. This observation suggests that in maximally rapid decompression the lungs and thorax may be treated as a closed system to which Boyle's Law might be applicable.

Animals↗
PubMed1997

The Peak Flow Working Group: test of portable peak flow meters by explosive decompression.

In 1991, 50 new Vitalograph peak flow meters and 27 previously used mini-Wright peak flow meters were tested at three peak flows by use of a calibrator applying explosive decompression. The mini-Wright peak flow meters were also compared with eight new meters. For both makes of meter there was an excellent within-meter and between-meter variation. The accuracy, however, was poor, with a maximal overestimation of true flows of 50 and 70 L.min-1 in the interval from 200 to 400 L.min-1 for the Vitalograph and mini-Wright meters, respectively. The deviation is explained by the physical characteristics of the variable orifice peak flow meters. They have been supplied with equidistant scales, which give non-linear readings.

Calibration↗
PubMed1980

Calibration of time derivatives of forced vital capacity by explosive decompression.

A simple, portable, inexpensive device is described that simulates expiratory flow curves for calibration of spirometers. A 4-L metal cylinder filled with copper mesh is fitted with a precision manometer. The pressure is increased to twice atmospheric and released by explosive decompression through 4 easily interchangeable resistors. The ratio of forced expiratory volume in one second to forced vital capacity ranged from 0.80 to 0.25, thus encompassing the range from normal to severe obstruction. Accuracy was defined by 25 measurements of forced vital capacity that differed by no more than 0.5% from the actual cylinder volume. Repeatability was reflected by a standard deviation of at most 0.04 L/s for one-second forced expiratory volume, mid-expiratory flow, and instantaneous flows at 50 and 25% of the forced vital capacity. Peak flow was less reproducible. Calibrations of a water spirometer at increased altitude and at temperatures from 4 degrees to 37 degrees C revealed no significant changes in volume or flow rates. Standard values have remained unchanged for 2.5 yr. Three volume spirometers and 2 primary flow devices were tested extensively.

Altitude↗