Abstract

Continuous flying operations, in which crews sleep aboard the aircraft instead of sleeping at route stations, provide an operational capability independent of positioned crews. Such missions may lead to sleep difficulties and it is concluded from two missions operated by Royal Air Force Air Support Command that the optimum duration is 48 hours. In the case of a fast strategic transport aircraft this provides a world-wide capability.

Abstract

Recent data from manned space flights has shown a marked demineralization of bone. Such data could be expected as a result of Wolff’s Law which correlates bone structure and imposed strain. Presented is a mechanism of bone maintenance as a feedback control system which, when operating under reduced gravity conditions, would predict the observed skeletal atrophy–and furthermore, a plateau would be reached after which no further skeletal loss would occur.

Abstract

This study established blood alcohol levels in man at 12,000 ft. with and without supplemental oxygen and at 20,000 ft. with supplemental oxygen. At 2.50 ml of 100 proof bourbon/kg body weight, subjects exhibited a lower blood alcohol level at 12,000 ft. without supplemental oxygen than at 20,000 ft. with supplemental oxygen. A difference in blood alcohol levels was not seen with 1.25 ml of 100 proof bourbon/kg body weight. It was established that dehydration effects alone could not account for these findings. The effect of breathing a normal oxygen mixture could not be ascertained with the data collected. An increased motility of the gastrointestinal tract caused by the high alcohol concentration and the increased motility attributable to the lowered barometric pressure could increase the absorption rate of the alcohol at 20,000 ft. with the high dose, thereby contributing to higher blood alcohol levels.

Abstract

The high density in hyperbaric environments increases the work of breathing thus limiting the ventilatory reserve for strenuous exercise. An attempt was made to assess the handicap imposed by this factor on work capacity unmodified by concurrent hyperoxia usually present when breathing air at high pressures. Eight men worked on a treadmill with increasing grades to exhaustion at 2 ATA and 3 ATA whereby the inspired O₂ tension was maintained equivalent to that in the control tests breathing air at 0.83 ATA (Albuquerque). At 2 ATA max. ventilation, work time and V_O2 max. were reduced to 63, 83 and 95% respectively of controls. At 3 ATA the results were 38, 58 and 68% respectively. Mixed expired CO₂ tensions rose markedly indicating relative ventilatory insufficiency at the end of exercise under hyperbaric conditions.

Abstract

Eight basic airmen and 17 experienced jet pilots were exposed to five different levels of centripetal acceleration under two separate conditions. Trials were given with and without illumination and while the subject was facing toward or away from the center of rotation. Subjects were required to position themselves to the subjective horizontal plane under each of these conditions. The illusion of pitch developed rapidly and showed little change or adaptation over a 4-minute time interval. Both the inexperienced basic airmen and the experienced jet pilots were equally susceptible to the illusion of pitch induced by the acceleration; there were no significant differences between the two groups. Primary sensory input appeared to be from the otoliths and the subjects’ responses appeared to be linearly related to the resultant force for the five levels tested.

Abstract

Sudden and complete incapacitation of 45 captains or first officers was simulated in the DC-8 and B-737 aircraft simulators. Three-man crews were utilized in the DC-8, two-man crews in the B-737. The remaining crew was instructed to perform as if they were flying regular line trips. No instructions were given to the crews regarding their activity following the “incapacitation,” such as decision to land, restraint of the affected pilot, or first aid measures. Cockpit activity was recorded on sound movie film. The basic aircraft instruments were photographed separately in the radio-aids room. The synchronized films were then spliced together for simultaneous viewing.

The paper discusses the results of the “incapacitations” as evaluated by flight instructors, flight surgeon, and aviation psychologist.

The need of an educational program for airline pilots is discussed.

Abstract

Five young men who had previously fainted in an orthostatic heat-test (40°C, 26% relative humidity), and one subject who had shown acute orthostatic weakness in the same test, were given two additional 20-minute tilt table tests in the same climatic conditions. Pneumatic cuffs inflated to 62 mm. Hg were applied to the legs and to the lower abdomen in each test respectively.

In three subjects both methods prevented syncope and in a fourth subject only cuff application to the legs prevented it. In the other two subjects syncope occurred earlier in the abdominal cuff tests.

These results suggest that heat syncope is caused by blood pooling in the vascular beds of the legs and the splanchnic areas, and that in prevention of heat syncope cuff application to the legs is somewhat more effective than cuff inflation applied to the lower abdomen.

Abstract

The influence of photoperiod on food and water intake was investigated in male, Sprague-Dawley rats exposed to two types of artificial days–LD 12:12 and LD 2:2. Food and water intake were measured for each animal for each day and at various times during the day. The methods for measuring food and water intake gave highly reproducible results. These results indicate that there is an endogenous circadian food and water intake rhythm under periods of LD 12:12 which persists during LD 2:2. Moreover, there appears to be a transient exogenous photoperiodic influence and phase shift for food intake following a change to LD 2:2. This shift appears to involve a slow and fast stage. Thus, the endogenous but not the exogenous feeding rhythm of rats seems to be correlated with their activity patterns.

Abstract

Eight instrument rated pilots with flying experience ranging from 600 to 12,271 hours each flew ten simulated ILS instrument approaches in a single engine, general aviation aircraft equipped with a primary flight display arranged in a conventional “T” configuration. Continuous heart rate data were recorded during each approach. Approaches were flown consecutively at approximate ten-minute intervals, with a one-minute in-flight rest period prior to each approach. Principal findings were: heart rate increased significantly during each approach; mean increase in heart rate during the approaches was 5.2 beats per minute (BPM) and was of a relatively constant magnitude for each of the ten approaches. The overall mean heart rate level decreased on successive approaches for a total of 11.0 BPM for the ten approaches. Results are discussed in terms of response to stress introduced by the demands of the task.

Abstract

The disappearance rates and volumes of distribution of infused cortisol were obtained from analyses based on an open two-com-partmental model in acutely prepared hypercalcemic (calcium gluconate infusion), hypocalcemic (ethylenediamenetetraacetate infusion), and normocalcemic dogs. No significant differences in volumes of distribution, rate constants to and from the two compartments and metabolic clearance rates were observed among the groups. There were some indications that hypercalcemia altered the half-life and secretory rate of cortisol.

Abstract

The indirect measurement of systolic and diastolic blood pressure in active subjects usually results in grossly inaccurate values due to the fact that most arm and body movements generate such broad noise and pressure fluctuation spectra that the signal processing electronics circuits erroneously interpret these random signals as true arterial pulse wave phenomena.

The incidence of false triggering of the blood pressure readout circuits can be reduced considerably by making use of the fact that each true Korotkow-sound is always preceded by its causative sequence of electrical cardiac events. The authors’ circuit utilizes the differentiated R-wave of a reference ECG to open an adjustable-delay, variable-width gate, shortly before the corresponding K-sound is expected. During the interval between gate closure and the next gate opening, the system is immune to random triggering. A pressure level sensing switch, connected to the cuff pressure programmer output, further prevents the last stage of the circuit, a multiple-input AND gate, from passing any output signal when the pressure inside the sphygmomanometer cuff is below a preset level, for instance, 35 mmHg. The circuit eliminates false triggering of the systolic and diastolic blood pressure readout circuits during approximately 90% of each cardiac cycle when measurements are being taken on highly active subjects, and prevents random triggering completely when the blood pressure cuff is deflated. The artifact suppression characteristics of the circuit are such that it would allow the indirect measurement of arterial blood pressure from highly active experimental subjects, or from an astronaut working in a full pressure suit on the lunar surface without the necessity of interrupting his activities.

Abstract

Observations were made as to the possible influence of simulated Apollo flight and lunar surface explorations on incidence of decompression sickness. Briefly stated, the various exposures of 19 men started with 3 hours of “shirtsleeve” exposure to O₂ at “ground level.” Next, this was rapidly changed to either 60:40::O₂:N₂ or 80:20::O₂:N₂ at 5 psia (lbs sq in-1, absolute). Four hours later the next decompression was to 3.5 psia O₂ for 2 hours during which there were 4 bouts of “rowing” for 4 min interspersed with 3 intervals of mark time. The measured rate of oxygen utilization during rowing ranged from 1.2 to 1.8 liter min-1 STPD depending on lean body mass. “Bends” did not occur after decompression from 14.5 to 5 psia. There was a lesser incidence of bends after decompression to 3.5 psia O₂ from 5 psia 80:20 than from 60:40::O₂:N₂. There was no correlation between the grade of bends and peak levels of energy expenditure resulting from rowing at 12 strokes per min against an identical tension.

Abstract

Parenteral administration of fluids as the sole source of hydration was found to be well-tolerated in adult domestic fowl for a period of at least thirty days. Animals hydrated in this manner exhibited no significant deviations in body mass or relative lymphocyte counts. The approximate fluid dose and concentration (as % NaCl) required to maintain an adult male Single Comb White Leghorn chicken was determined. The combination of restraint with parenteral hydration was well-tolerated. The birds appeared quite normal on a clinical basis. Restrained birds did, however, exhibit modest reductions in body mass and relative lymphocyte counts accompanied by statistically significant increases in adrenal organ weights when compared with non-re-strained controls. Thus, the combination of restraint and parenteral hydration would appear to produce a mild stress response though this was not clinically obvious.

Abstract

Sixteen day old female CFW mice were inoculated intraperitoneally with either 0.25 ml of saline, uninfected HEp-2 supernatant or similar supernatant containing about 1.5 × 10⁶ TCD₅₀/ml of Coxsackievirus B-1. Some mice received these inoculations prior to exposure to 100% oxygen at 3 atmospheres absolute for 15 minutes following hyperbaric exposure. Other infected mice were kept at a normal atmosphere. Appropriate uninfected hyperbaric and normal pressure controls were included. By 72 hours twice as many hyperbaric and infected mice died than with infection alone. Virus assay of heart and brown fat also disclosed significantly (P = 0.02) greater amounts of virus with hyperbarism provided that infection followed oxygenation. Exposure of the host to hyperbaric oxygen before infection not only exacerbates virus induced host pathology but also enhances virus synthesis.

Abstract

A population of 4,400 flight personnel was exposed to reduced atmospheric pressure employing a low pressure chamber training flight profile. Subjects ranged in age from 18 to 45 years and were categorized as designated aviators, advanced jet flight students, and passengers. Without lengthy denitrogenation, and following exposure to the stress of hypoxia followed by exposure to 3.46 psia at simulated 35,000 feet concomitant with positive pressure breathing equivalent to 10″-12″ H₂O, incidence of bends rated no more severe than Grade I was less than 0.5% among the population of 4,400 subjects. It is concluded on the basis of the reported work that lengthy time-and-money consuming denitrogenation may not be required to preclude incidence of bends among subjects exposed to simulated altitudes no higher than 35,000 feet for brief periods. Further, the practice of exposing subjects to the stress of hypoxia prior to ascents to higher simulated altitudes for brief periods may not be as hazardous as originally thought.

Abstract

Hyperbaric oxygen (OHP) has been shown to cause RBC damage and lysis. In the present studies we examined the effect OHP on the WBC. Adult male Sprague-Dawley chow-fed rats were exposed to 100% O₂ (OHP) or room air (AHP) at 4 atm. pressure for 90 min. Rats exposed to OHP showed a significant decrease in total WBC count from 13,520/mm³ to 9,180/mm³. In contrast rats exposed to AHP had no significant change (13,040 to 11,360). The absolute granulocyte count showed no significant change, but the absolute lymphocyte count declined significantly in rats exposed to OHP (11,900 to 6,600) in contrast to those exposed to AHP (11,000 to 9,500). Neither OHP or AHP resulted in hemolysis. Splenectomy and/or administration of vinblastine sulfate had no influence on these changes. Rats given hydrocortisone showed a lymphocyte decrease of similar magnitude to those exposed to OHP. Adrenalectomy abolished the decrease in lymphocyte count caused by OHP. These data demonstrate that rats exposed to hyperoxia (and not 4 atm. pressure alone) show a decrease in the total WBC count. This decrease is a selective effect on the absolute number of lymphocytes. The results are consistent with the hypothesis that OHP causes a reduction in lymphocyte count by a stress response mediated by adrenocorticosteroids and not by a direct toxic effect on the cell.

Abstract

To measure the stressor stimulus effect of rotational velocity in terms of the number of the standardized head tilt movements required to evoke a common severity level of symptoms characterizing motion sickness, sixteen young healthy subjects were rotated in a laboratory (Stille) rotational chair at various velocities within a range suitable for each subject and the limits of 1.0 to 30.0 rpm. Standardized 90° head movements were executed at each test velocity until the preselected and quantitatively determined motion sickness endpoint of moderate (M IIA) or severe (M III) malaise was reached. When individual ability to make head movements without evoking symptoms was exceeded, the derived average stressor effect (E factor) of each head movement varied directly and, in log-log terms, linearly with rotational velocity. These data provide the basis for grading individual susceptibility to Coriolis (motion) sickness with a single numerical score as well as define the high rate of change of Coriolis stressor effect as a function of rotational velocity, which may find practical application for specifying rotational rates of space stations.

Abstract

Newly hatched chicks exhibit a selective hypertrophy of extensor muscles involved in locomotion and postural maintenance. The effect is of short duration, being complete in three days of terrestrial existence. It is considered that these changes represent an adaptation to Earth gravity in an organism which had developed in a buoyant state.

Abstract

A photographic film dosimetry technique is presented which can be used to determine the power density distribution of a continuous wave laser beam operating in the visible or near visible wavelengths. This technique was developed at the United States Air Force School of Aerospace Medicine to provide the medical service with a means with which to survey operational laser systems.

In use, a white target is placed so as to intercept the beam, and a sequence of photographs is taken at constant shutter speed and decreasing f/stops (increasing aperture). Plots of the locus of any selected transmission ratio in successive images of the beam are the iso-intensity contours for the beam power density distribution. The usefulness of the technique can be extended by placing a spike filter over the camera lens to prevent broad spectrum ambient illumination from exposing the film while allowing narrow spectrum laser energy through.

Abstract

Migraine presenting as pain in the occipital region can be a difficult diagnostic problem. Three illustrative cases evaluated at the USAF School of Aerospace Medicine are reviewed. In two, subarachnoid hemorrhage was initially suspected. In the third, symptoms had been attributed to labile hypertension or spasm of cervical musculature. Factors supporting the diagnosis of migraine and influencing the disposition regarding flying status are discussed.

Abstract

Alcohol most severely disrupts short-term memory in man; this is briefly presented in terms of social drinking, state-dependent learning, alcohol amnesia, the Wernicke-Korsakoff syndrome, and pathological alcoholic intoxication. The implications of the latter are discussed in terms of flying safety.

Abstract

MoIIuscum Contagiosum infections of the lower abdomen and pubic areas have been noted in returnees from Southeast Asia. Transmission of this viral disease appears to be by venereal contact.

Abstract

Trauma is widely accepted as an etiologic factor in venous thrombosis and thrombophlebitis of the lower extremities. Because of the frequent participation of military pilots and test pilots in athletic activities, the incidence of venous thrombosis of the extremities may be expected to be significant in this population. This group is likely to fly high performance vehicles and, therefore, likely to use the g-suit. On theoretical grounds, use of the g-suit in the face of recent venous thrombosis in the lower extremities should be hazardous. This problem is considered in this paper.

Abstract

This report describes progress in the development of the Vietnamese Air Force and its Medical Service for the year 1969. Support of the VNAF expansion program required the careful selection of medically qualified personnel for pilot training. Improvements in medical facilities, training programs, and activities in flight and preventive medicine are noted.

Abstract

Apparatus is described for kinetic studies of the pertinent air revitalization reactions of “active chemicals” used for air regeneration in closed environments. This apparatus has been employed to confirm reaction stoichiometries, to elucidate reaction mechanisms, to determine the extent of conversion of the air revitalization chemicals, and to relate the observed respiratory quotient to that required for man in a closed environment. The apparatus was designed to simulate the conditions of a closed environment such as a space cabin.