Abstract

Using the spinal cord decompression sickness model described in Part I, we explored the effects of delay to treatment on the recovery of spinal evoked potentials (SEP). The primary treatments of oxygen at 60 fsw (2.8 bar) and air at 165 fsw (6.0 bar) were studied. In this exploratory study the results were surprisingly poor in oil treatments applied. There is evidence that in this model a delay of 15–18 min between diagnosis and start of therapy would generally allow some recovery of SEP, which would rarely be complete. Supporting experiments involving cord ischemia are described. The results from this study enabled us to design o set of practicable experimental criteria for the purpose of discovering the optimal combinations of oxygen and pressure for the treatment of spinal cord decompression sickness.

Abstract

Rat experiments on the Cosmos blosotellites demonstrated that the percentage of renal excretion of consumed water after flight was lower than after synchronous experiment. This can be attributed not only to water retention but also to a different level of extrorenal losses postflight. Weightless rats showed increased sodium excretion after water load tests and increased potassium excretion after potassium load tests. The sodium, potassium, and calcium balance was positive after weightlessness. Analysis of the electrolyte composition of different kidney zones revealed a decreased potassium content in the medulla, which is considered to be one of the causes of changed renal iono- and osmoregulotory function in weightlessness. The normalizing effect of artificial gravity on the natri- and kaliuretic renal function was demonstrated.

Abstract

The space adaptation syndrome is one of the more vexing problems confronted by our nation's astronauts during their journeys. This syndrome may be a variant of motion sickness, although this possibility has been questioned. Physostigmine, a centrally active cholinesterase inhibitor which increases brain acetylcholine, was found to cause a motion sickness-like syndrome—in psychiatric patients and normals—including nausea, emesis, malaise, dysphoria, increases in serum ACTH, beta-endorphin, certisol, and prolactin. Neostigmine, a non-centrally acting cholinesterase inhibitor, and saline placebo caused no such effects. The above effects closely parallel those of motion sickness. Thus, the effects of physostigmine may be a convenient model for screening for treatments for motion sickness or space adaptation syndrome, or for predicting who will develop these syndromes.

Abstract

The +Gz acceleration tolerance in a homogeneous group of 21 male clinically healthy pilots or candidates to airservice was evaluated. The +Gz acceleration tolerance was compared with the Wenchebach point, i.e., the lowest rate of atrial stimulation needed to produce constant Wenckebach or Mobitz II atrio-ventricular (AV) block. The Wenckebach point was used as an autonomic nervous system activity index, it was demonstrated that the degree of +Gz acceleration tolerance depends greatly upon autonomic nervous system activity, and is lower in people with enhanced parasympathetic tone. The possibility of pharmacological correction of +Gz acceleration tolerance was discussed.

Abstract

Cardiovascular responses to orthostasls were assessed in eight men (18–29 years old) before and after an 8-d cycle ergometer exercise training (E) regimen far 2 h·d⁻¹ at 65% maximal O₂ uptake (V̇o₂ mux). Each subject underwent 60° head-up tilt (60 rain max) before (T1) and after (T2) E. Heart rate (HR), systolic (SBP), and diastolic (DBP) pressures were measured each rain before, during, and after tilt; pulse pressure (PP), mean arterial pressure (MAP), and rate-pressure-product (RPP) were calculated. Changes in plasma renin activity (PRA), vasopressin (pVP), hematocrit, hemoglobin, and plasma volume (PV, T-1824) were measured from venous blood samples taken pre- and immediately post-tilt. Following IE, Vo= mux increased by 8.3% (p<0.05), resting HR decreased by 8.1% (p<0.05), and PV increased by 430 ml (12.2%, p<0.05). Mean (±S.E.) tilt duration went from 40.0±5.1 rain during T1 to 46.7±3.4 rain during T2 (NS); mean tilt HR decreased from 86±4 bpm to 77±3 bpm (p<0.05), RPP decreased from 10,320±390 to 9,317±310 mm Hg·bpm (p<0.05), while mean SBP, DBP, PP, and MAP were unchanged. Plasma volume decreased during tilt by 479 in T1 compared to 544 ml in T2 (p<0.05), while % ΔPV were similar: −13.6% and −13.9%, respectively. Peak fluid-accumulation in the calf and total leg during tilt increased (p<0.05) following E. Mean changes in PRA and pVP during tilt were similar between T1 and T2. The magnitude of PV expansion correlated with tilt HR: r= −0.68 (p<0.05); and with tilt duration; r= +0.82 (p<0.05). Heart rate and blood pressure responses were dependent upon the rate of PV loss and pooling. In contrast to the hypothesis that endurance training per se reduces the effectiveness of the blood pressure control during orthostasis, these data suggest that short duration E with associated increase in V̇o₂ max enhances cardiovascular adjustments during tilt.

Abstract

Rats pretreated with 500 μg·kg⁻¹ endotoxin are resistant to the pulmonary toxic effects of normobaric hyperoxia (>95% O₂). After endotoxin-pretreatment and exposure to 1.0 ATA O₂ for 72 h, such rats are found to have elevated total superoxide dismutase, glutathione peroxidase, and catalose activities in homogenates of whole lungs. Despite increases in these protective antioxidant enzymes which persist in 2.0 ATA 02 (4 h) and 4.0 ATA O₂ (1.0 h), such rats do not have improved survival in hyperbaric hyperoxia. Likewise, endotoxin-pretreatrnent im-mediately prior to 2.0 or 4.0 ATA O₂ exposure does not prolong survival compared to controls. It is likely that lung injury during the normobaric oxygen preexposure and the central nervous system toxicity of hyperbaric oxygen interact to limit survival.

Abstract

The purpose of this study was to determine if the changes in selected blood hormones and substrates, metabolic rate, and rectal temperature (T_re) in nine males after immersion in 10°C water, while clad in standard flight suits, were related to the level of aerobic fitness. Fitness was evaluated by the blood lactate response to submaximal exercise. Immersion time (IT) was defined as the time required for a 1°C decrease in T_re and averaged 38.5 (range: 21–62) min. Metabolic rate increased 3.4 times the resting rate. Lactate, free fatty acids, triiodothyronine and thyroxine increased by 81%, 38%, 11%, and 8%, respectively, in contrast to insulin which decreased by 32%, with all changes being statistically significant (p<0.05). Glucagon increased slightly but not significantly (p=0.11) while glucose levels did not change. The IT was correlated directly with a measure of aerobic fitness, with relative body fat, and with the T₃ levels postimmersion (p<0.05). The results suggest that the aerobic fitness level can significantly influence the cooling rate during water immersion.

Abstract

The distributions of fatal diving accidents in commercial diver populations were examined in the Gulf of Mexico from 1968 to 1975 and in the British sector of the North Sea from 1971 to 1978. Influences and causes of death were analyzed by examining the interaction between host, environmental and agent factors. The interaction of host and environrnentai factors appeared to be the greatest contributing factor to diving fatalities among the estimated 900 commercial divers in the Gulf of Mexico and the 700 in the North Sea. The most significant host factors were level of experience and behavioral dysfunction. They are also the host characteristics most amenable to change through improved and more thorough training. The most significant environmental factors were equipment failure and supervisor/ tender errors. These factors would be minimized by iraproved selection, maintenance and operation of equipment, together with improved operating and emergency diving procedures. In recent years there has been a significant downward trend in mortality rates in the commercial diver populations of this study due to improved diving techniques and operations. Further research is needed, however, on the cause(s) of diver unconsciousness and inexplicable actions that occur at depths below 91.44m (300 ft.).

Abstract

Variations in the growth of animals from exposure to a magnetic field have been reported by several authors. In this study, young rats and mice were exposed daily to constant uniform magnetic fields. The strength of the field was 400, 600 or 800 roT. Rats were exposed for 4 weeks and mice for 250 d or more. Some mice were exposed in a permanent way to a non-uniform magnetic field of 4.6 roT. No significant effect on the growth was observed.

Abstract

Beneficial effects of exposure to negative air ions have been suggested, to include improved performance, mood, attention, and physiological condition. Existing support is clouded by methodological problems of control and standardization in treatment and equipment. This study investigated effects of negative ions produced by a commercially marketed air purification device on grip magnitude, coding, motor dexterity, reaction time, tracking, pulse, blood pressure, and temperature. Two groups of 12 males were exposed to 6 continuous h of either negative or “normal” ion environments under a double blind condition. Repeated measures (0,3,6 h) on each variable were obtained. MANOVA applied to change scores revealed no differences between groups, and 0 vs. 3 and 0 vs. 6-h group differences showed no significant alteration in any measure. Negative ions generated by an air purification device were concluded to produce no general or specific alteration of cognitive or psychomotor performance or physiological condition.

Abstract

The eye movements elicited by auditory stlmuli—the audioocular response (AOR)—differ from those made in response to a visual target. The movements consist of both rnonosaccadic and multiple saccadic refixations (MSR). In visual refixation, monosaccadic refixations are always accurate; in AOR, they rarely are. In MSR, many strategies were used in the attempt to find the target but they wore not always successful. However, final amplitudes of the total refixation were quite accurate in both MSR and monosaccadic refixations. Velocity profiles of the AOR showed such anomalies as discrete decelerations and multiple, closely-spaced saccades. These data suggest that, without visual feedback, the location of acoustic targets is difficult. In the absence of visual afference, when vigilance may be decreased by the lack of arousal, the velocity profiles also became abnormal, even at small amplitudes. Thus, for cockpit warning devices, a combination of auditory and visual indicators should be used.

Abstract

Experiments were conducted to quantify the cardiovascular response (blood pressure and heart rate) elicited by sustained isometric contractions of the neck muscles. The response was secondary to dynamic exercise with various headgear loading combinations. The neck muscles were loaded by the head itself (CON), the standard U.S. Army SPH-4 helmet (HEL), and a combination of the SPH-4 helmet with Night Vision Goggles (H/NVG). During two exercise periods of 5 rain and 35 min, each of the five subjects would rotate the head from side-to-side in the CON, HEL, or H/NVG configuration. Immediately thereafter, the subject would position his head in an isometric head dynamometer and exert a sustained right lateral (LAT) neck contraction or forward (FOR) neck contraction at 70% of a maximal voluntary contraction (MVC). During this isometric neck muscle contraction, the subject's endurance time to fatigue was recorded, the blood pressure was manually recorded, and the heart rate was continuously recorded. Characteristic increases in the systolic and diastolic blood pressure and heart rate occurred with sustained isometric neck muscle contractions. There was an average 40% increase in the systolic blood pressure, an average 50% increase in the diastolic blood pressure, and an average 45% increase in the heart rate from resting to the end of a fatiguing 70% MVC (p<0.05). These responses appear to be relatively independent of the duration of the exercise period, the loading during the exercise period, and the specific muscle mass involved. The mechanisms for the pressor response and the heart rate response are reviewed.

Abstract

The energy expenditure of Army Air Corps and Royal Air Force pilots has been measured during flight in Gazelle and Puma helicopters respectively. Heart rates were also recorded.

The results were compared with resting values obtained in the crewroom before flight, and confirmed the findings of other authors that the energy cost of flying helicopters in level flight is about 50% higher than that of sitting at rest.

Abstract

Refractive error distribution of active duty U.S, Air Force pilots and navigators required to wear corrective lenses is presented in sphere and cylinder components. Data were retrieved from a random sample survey.

Abstract

Professional responsibilities, tradition, and personal conscience along with legal, philosophical, and religious convictions dictate nursing interventions. Inevitably, these factors embrace life-sustaining therapies; however, in view of complications, prognosis, pain and suffering, and their own views of quality of life, some patients express wishes inconsistent with life-sustaining measures. In other situations, the health care provider as well as the patient may view heroic efforts as more debilitating than resortative. Resolving the conflict while preserving the patient's best interests requires a confrontation with the status of “do-not resuscitate” policies within the nurse's institution. A nurse-attorney presents definitions of death, resuscitation, informed consent, refusal, and competency as the necessary underpinnings for the development of an ethical and legal posture within the profession, with which to approach significant decisions regarding life-sustaining therapies. Literally every hour of every day nurses are immediately and directly involved with resolving ethical dilemnas based upon judgements and interpretations of oral or written orders, patient and family wishes, professional training, and an infinite number of other factors. When clear policies or orders are lacking, the nurse is left with the burden of making a life or death decision. It is imperative that professional nurses assess the administrative, legal, and ethical ramifications of their actions in terms of ethical codes of practice, patients' rights, institutional and personal liability, civil and criminal laws, and private conscience. An understanding of these issues, passive and active euthansia, state and national trends, and uniform legislation can assist in resolutions of the no-code dilemna. Nursing as a profession must strive to develop sound and consistent guidelines and rationale for the scope of practice in ethical dilemnas.