Pulmonary hemorrhage of the toad produced by explosive decompression to an ambient pressure of 30 mm. Hg.
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Aerospace Medicine↗
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The appearance of pulmonary hemorrhage following explosive decompression in rabbits.
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Animals↗
Calibration of forced expiration curves by explosive decompression.
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Calibration↗
Development of serial bio-shock tubes and their application.
OBJECTIVE: To design and produce serial shock tubes and further examine their application to experimental studies on blast injury. METHODS: Bio-medical engineering technique was used for the design and development of the serial shock tubes. One thousand four hundred and fifty nine animals (757 rats, 105 guinea pigs, 335 rabbits, 240 dogs and 22 sheep) were then used to test the wounding effects of the shock tubes. RESULTS: Three types of bio-shock tubes, that is, large-, medium- and small-scale shock tubes were made in our laboratory. The large-scale shock tube is 39 meters long; the inner diameter of the test section is 1 meter; and the maximum overpressure in the driving section is 10.3 MPa. A negative pressure could be formed by means of the reflected rarefactive wave produced by the end plate. The medium-scale shock tube is 34.5 meters long; the maximum overpressure in the driving section is 22 MPa; the test section is designed to be a knockdown, showing 5 basic types with inner diameter of 77 to 600 millimeters, which could be used for researches on overpressure, explosive decompression, underwater explosion, and so on. The small-scale shock tube is 0.5 meter long with the maximum endured overpressure of 68.6 MPa. Results from animal experiments showed that this set of shock tubes could induce various degrees of systemic or local blast injury in large or small animals. CONCLUSIONS: This set of bio-shock tubes can approximately simulate typical explosive wave produced by nuclear or charge explosion, and inflict various degrees of blast injury characterized by stability and reproducibility. Therefore, they can meet the needs of blast research on large and small animals.
Animals↗
Skeletal response of rats to repeated short-term hyperbaric helium-oxygen exposures.
Young male rats were exposed to repeated heliox dives and analyzed for skeletal alterations. Animals were exposed 1, 3, 5, or 7 times to either 1 ATA He-O2 for 12.5 h, or to 5 ATA He-O2 for 4 h and a 8.5 h decompression, or to 5 ATA He-O2 for 4 h and a 1.5 h decompression. In a separate study, 30 rats were exposed 6 times to 5 ATA He-O2 and explosively decompressed. Animals were sacrificed 20 d after the last dive. There were no significant changes in femur wet weight, density, ash weight, length, or mineral content. Plasma calcium, phosphorus, and alkaline phosphatase remained normal. Eighteen of 30 animals survived the six explosive decompressions; however, there were no significant changes in bone. These results indicate that the number and rate of decompressions used in this study have no lasting effect on bone growth and mineral composition in the rat.
Alkaline Phosphatase↗
Hyperbaric oxygen may reduce gas bubbles in decompressed prawns by eliminating gas nuclei.
It is accepted that gas bubbles grow from preexisting gas nuclei in tissue. The possibility of eliminating gas nuclei may be of benefit in preventing decompression sickness. In the present study, we examined the hypothesis that hyperbaric oxygen may replace the resident gas in the nuclei with oxygen and, because of its metabolic role, eliminate the nuclei themselves. After pretreatment with oxygen, prawns were 98% saturated with nitrogen before explosive decompression at 30 m/min. Ten transparent prawns were exposed to four experimental profiles in a crossover design: 1) 10-min compression to 203 kPa with air; 2) 10-min compression with oxygen; 3) 10-min compression with oxygen to 203 kPa followed by 12 min air at 203 kPa; and 4) 10 min in normobaric oxygen followed by compression to 203 kPa with air. Bubbles were measured after explosive decompression. We found that pretreatment with hyperbaric oxygen (profile C) significantly reduces the number of bubbles and bubble volume. We suggest that hyperbaric oxygen eliminates bubble nuclei in the prawn.
Animals↗
[Explosive high-pressure decompression].
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Decompression↗
Scanning and transmission electron microscopy of the blood-bubble interface in decompressed rats.
Scanning and transmission electron-microscopy have been applied for study of the ultrastructural features of the blood-bubble interface in the vasculature of explosively-decompressed rats. In scanning electron-microscopy, the surface facing the bubble appeared smooth, with slight undulation and frequent roundish protrusions. In cross sections of the material between the bubbles, there could be observed a continuous surface layer facing the bubble, a loosely-bound meshwork of fibrous material, and extreme congestion of erythrocytes. In transmission electron-microscopy there were found alignment of platelets along the interface, and a thin (10-20 nm) layer of osmiophilic material, in accordance with earlier ultrastructural studies. The platelets were often rounded. It is concluded that the initial phase of the blood-bubble interaction is the deposition of a plasma protein coat, followed by the attachment platelets, possibly related to activation of the coagulation system.
Animals↗
Decompression scenarios in a new underground transportation system.
BACKGROUND: The risks of a public exposure to a sudden decompression, until now, have been related to civil aviation and, at a lesser extent, to diving activities. However, engineers are currently planning the use of low pressure environments for underground transportation. This method has been proposed for the future Swissmetro, a high-speed underground train designed for inter-urban linking in Switzerland. HYPOTHESIS: The use of a low pressure environment in an underground public transportation system must be considered carefully regarding the decompression risks. Indeed, due to the enclosed environment, both decompression kinetics and safety measures may differ from aviation decompression cases. METHOD: A theoretical study of decompression risks has been conducted at an early stage of the Swissmetro project. A three-compartment theoretical model, based on the physics of fluids, has been implemented with flow processing software (Ithink 5.0). Simulations have been conducted in order to analyze "decompression scenarios" for a wide range of parameters, relevant in the context of the Swissmetro main study. RESULTS: Simulation results cover a wide range from slow to explosive decompression, depending on the simulation parameters. Not surprisingly, the leaking orifice area has a tremendous impact on barotraumatic effects, while the tunnel pressure may significantly affect both hypoxic and barotraumatic effects. Calculations have also shown that reducing the free space around the vehicle may mitigate significantly an accidental decompression. CONCLUSION: Numeric simulations are relevant to assess decompression risks in the future Swissmetro system. The decompression model has proven to be useful in assisting both design choices and safety management.
Accidents↗
Decompression incidence in air- and liquid-breathing hamsters.
The effects of hyperbaric compression on heart rate, rectal temperature, respiratory rate, bubble formation, and survival were studied in three groups of anesthetized golden hamsters (Mesocricetus auratus). Group I (15 animals) breathed air while exposed to 7 ATA of pressure for 1 h in a hyperbaric chamber; Group II (13 animals), at the same pressure level (7 ATA) and for the same time period (1 h), breathed an oxygenated fluorocarbon liquid (temperature 27 degrees C) that was open to the chamber atmosphere; Group III (10 animals), at the same pressure and time period as the other groups, were sealed in a flexible plastic bag filled with oxygenated fluorocarbon as a breathing mixture. A fourth, Group IV (12 animals), breathed oxygenated fluorocarbon for 1 h at 1 ATA. Survival after rapid decompression in each group varied, 9 animals died in Group I, 12 animals in Group II, whereas none of the animals died in either Groups III or IV. Thirty minutes after decompression postmortem examinations of all the animals demonstrated the presence of large amounts of gas bubbles in the right ventricle and some gas bubbles in the left ventricle of all the hamsters in Groups I and II. No gas bubbles were found in the hearts of the Group III animals. Group III animals, breathing a liquid unsaturated by an inert gas, survived rapid explosive decompression without the signs and symptoms of decompression sickness. Immersion in the liquid fluorocarbon produced a profound decrease in heart rate, rectal temperature, and respiration in Groups II, III, and IV.
Air↗
Optimal oxygen pressure and time for reduced bubble formation in the N2-saturated decompressed prawn.
Bubbles that grow during decompression are believed to originate from preexisting gas micronuclei. We showed that pretreatment of prawns with 203 kPa oxygen before nitrogen loading reduced the number of bubbles that evolved on decompression, presumably owing to the alteration or elimination of gas micronuclei (Arieli Y, Arieli R, and Marx A. J Appl Physiol 92: 2596-2599, 2002). The present study examines the optimal pretreatment for this assumed crushing of gas micronuclei. Transparent prawns were subjected to various exposure times (0, 5, 10, 15, and 20 min) at an oxygen pressure of 203 kPa and to 5 min at different oxygen pressures (PO2 values of 101, 151, 203, 405, 608, and 810 kPa), before nitrogen loading at 203 kPa followed by explosive decompression. After the decompression, bubble density and total gas volume were measured with a light microscope equipped with a video camera. Five minutes at a PO2 of 405 kPa yielded maximal reduction of bubble density and total gas volume by 52 and 71%, respectively. It has been reported that 2-3 h of hyperbaric oxygen at bottom pressure was required to protect saturation divers decompressed on oxygen against decompression sickness. If there is a shorter pretreatment that is applicable to humans, this will be of great advantage in diving and escape from submarines.
Animals↗
[Spirometry: quality in the respiratory medicine clinics of a public health care area].
BACKGROUND: Spirometry can be considered a routine way to evaluate patients with respiratory complaints, both inside and outside the hospital setting. OBJECTIVE: To assess the quality of spirometry in a public health care area with respect to two factors: the technicians' performance and the calibration of spirometers. MATERIAL AND METHOD: Four health care clinics were studied. Four technicians participated and the four spirometers were tested at different volumes (calibration syringes 1L and 3L) and different flows (explosive decompression). Eight patients with COPD participated in the study of inter-technician variability. RESULTS: Agreement among the technicians was very high: 0.98-0.99 for FEV1 and 0.91-0.98 for FVC. The mean results obtained by the technicians were: FEV1 = 2.15 0.03, range 2.20-2.14; FVC = 3.25 0.05, range 3.30-3.21 (ns). Volumetric readings from the spirometers were correct for the 1I calibration syringe, but 2 out of 4 spirometers lost linearity with the 3I calibration syringe. One spirometer gave readings out of range for all flow levels, and 2 out of 4 spirometers were out of range at low flows. CONCLUSIONS: 1. Results obtained by different technicians were not significantly different and there was high agreement among them, confirming that performance of spirometry was good. 2. The spirometers showed poor linearity at low flows.
Aged↗
A general purpose microprocessor for spirometry.
A portable, inexpensive microprocessor is described for on-line spirographic analysis of FVC and its time derivatives and MVV, using a primary flow or volume signal. Resolution is +/- 0.02 L and maximal collection time 66 seconds. Algorithms according to the Snowbird Conference recommendations include back extrapolation, "end of test" determination and the selection criteria for satisfactory tests, and best FVC, FEV1 and other flow rates. Differentiation is digital and flow-volume outputs are available. Actual, predicted and percent predicted values for children or adults are displayed, or can be printed together with an interpretation and a flow-volume loop. Four hundred tests with a Stead-Wells spirometer, a pneumotachograph and a turbinometer using an explosive decompression FVC simulator showed standard deviations of +/- 0.04 L or L/sec or less, except for peak flow. Differences between microprocessor values and tracing analyses were less than 0.04 L. MVV with a reciprocating pump equalled exactly the MVV calculated from stroke volume and frequency (r = .999) from 8 to 325 L/min. Tests of 168 patients were comparable to the calibration devices.
Computers↗
Laboratory and clinical evaluation of a portable computerized peak flow meter.
A mini-Wright based peak flow meter (VMX Mini-Log), which stores the readings together with the time and date of each measurement, has recently been marketed but has not yet been evaluated. The accuracy, reproducibility, and interdevice variability of this instrument were investigated using a pneumotachograph connected in series as a standard. Flows from 100 to 700 L/min were generated by an explosive decompression chamber. The performance of this instrument was also tested in 20 normal subjects and in 20 patients with airflow obstruction. The accuracy of the instrument was expressed as the percentage of error, and reproducibility and interdevice variability were assessed using the coefficient of variation. In the laboratory evaluation, all devices recorded flow rates that were within +/-10% of the pneumotachograph readings at flows between 200 and 600 L/min. At the extreme flow rates of 100 and 700 L/min, the mean error was higher than 10%. The reproducibility of the VMX was within +/-5% at all the flows tested. The interdevice variability was less than 5% at flow rates between 200 and 700 L/min. When tested on normal subjects with PEF between 400 and 700 L/min, the VMX performed well. In patients with airflow obstruction, four devices had greater than 10% error. The largest error was observed in those patients with PEF below 200 L/min. The VMX Mini-Log peak flow meter is accurate and precise in the flow range between 200 and 600 L/min. Its performance, however, may be affected in subjects with airflow obstruction and PEF below 200 L/min.
Adolescent↗
An evaluation of the Breath-Taker peak flow meter.
This study was designed to evaluate the Breath-Taker peak flow meter, recently released by the Asthma Foundation of Victoria. The performance characteristics of five Breath-Taker units were compared with those of five Wright and five mini-Wright peak flow meters. The between-unit reproducibility of each type of peak flow meter was measured using an explosive decompression device with a peak flow reproducibility of better than 1%. Each individual meter was used to measure the peak flow delivered by the decompression device three times for each of six flow rates (97-622 L/min). The coefficient of variation (CV) was lowest for the Wright meters (mean CV, 4.8%) and, similarly to the Breath-Taker units (mean CV, 8.4%), this decreased with increasing flow. The CV of the mini-Wright meters, however, increased as flow increased (mean CV, 7.5%). The Breath-Taker meter had less inter-unit variability than the mini-Wright meter at peak flows above 200 L/min. The accuracy of the three meter types was assessed by comparing measurements of peak expiratory flow rate (PEFR) made with each type and also with a computerized pneumotachograph system in 30 subjects with various degrees of irreversible airflow obstruction. Each subject performed at least three reproducible PEFR manoeuvres on the pneumotachograph and on each type of meter, in randomized order. The results showed that in comparison with the pneumotachograph system the Breath-Taker meter underestimated PEFRs by a mean of 27 L/min and the mini-Wright meter overestimated PEFRs by a mean of 45 L/min, whereas the Wright meter was not significantly different. Since the differences between the Breath-Taker meter and the pneumotachograph were independent of flow rate, a scale offset would suffice to "correct" the Breath-Taker readings.
Adolescent↗
The war years at the Aeromedical Lab: Wright Field (1941-46).
The author narrates his experiences at the Aeromedical Laboratory (AML) from his first visit in Spring 1941, when Maj. Otis O. Benson was its Chief, to the end of 1945, when its wartime Chief, Col. William Randolph Lovelace, returned to the Mayo Foundation and when Col. Lloyd E. Griffis arrived as the interim Chief. The rapid growth of the Laboratory is described--from a small unit in Bldg. 16 in 1941 to its new Bldg. 29 in Spring 1942--to its emergence as a fully active, working laboratory. The highlights of AML major wartime projects are presented: development and production of breathing oxygen equipment, including pressure breathing for use above 50,000 ft; evaluation of insulative and electrically heated flying clothing, useful for confined cockpit space and for use at first in B-17 gun turrets; development and evaluation of anti-G suits for the new, high-performance, fighter aircraft; the role of anthropometry in design of aircraft cockpits and personal flying equipment; Laboratory tests of human tolerance to explosive decompression in new Air Force pressurized bombers (B-29) and future fighters (P-80 series), and actual flight tests in the Lockheed Constellation and Boeing C-97. Individual contributions of many distinguished physiologists, physicians, biophysicists, and engineers then on duty at Wright Field are mentioned whenever possible.
Aerospace Medicine↗
Frequency response of variable orifice type peak flow meters: requirements and testing.
Little is known about the response of variable orifice peak flow meters to high frequency flow input. The purpose of this study was to define and test dynamic requirements for such peak flow meters. In a population sample we measured peak expiratory flow (PEF), rise time (tr), from 10-90% PEF and the duration of the flow in excess of 97.5, 95 and 90% of PEF, by use of a carefully calibrated Fleisch pneumotachograph with known and adequate frequency response. Three peak flow meters (Mini Wright, Vitalograph and Ferraris) were tested with an explosive decompression calibrator adjusted to values for PEF and tr as close as possible to the 95th and 5th percentile values, respectively, both for males and females, and with peak durations between 5 and more than 100 ms. The 95th percentile values of PEF were 597 L.min-1 for females and 894 L.min-1 for males. The 5th percentile values of tr were, respectively 55 and 45 ms. The duration of flow in excess of 95% PEF was longer than 10 ms in 99% of the subjects. For all meters, the deviation of PEF corrected for alinearity were less than 5% at a peak duration of 10 ms. We conclude that PEF, rise time, and peak duration can be used for description of dynamic properties of variable orifice meters, and that the tested meters had a satisfactory frequency response for recording PEF in mostly normal subjects.
Adult↗
[A proposal for spirometry standardization in the city of Buenos Aires].
This paper refers to a Multicentric Quality Control Program on spirometry performed in Buenos Aires city. Seventeen spirometers (9 water seal, dry rolling seal or bellows, 5 flow detection type and 3 peak-flow meters) owned by 8 different Hospitals were tested. Reference values were obtained by means of an Explosive Decompression Simulator calibrated against a Stead-Wells bell spirometer, which meets ATS recommendations. Only 42% (6/14) of the tested spirometers agreed with the ATS minimal requirements with regard to FVC and FEV1; volumetric spirometers performed better than flow detectors. The maximal error was 11% when measuring a FVC of 3.41 L. Peak flow showed a very high inter-instrument coefficient of variation. The need of frequent quality control checks is stressed.
Argentina↗