[Salt and hypertension. The most current research on molecular biology increases the knowledge of the connection].
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Diet, Sodium-Restricted↗
Biomedical subjects
H T Andersen
Publications and source records attributed to H T Andersen.
[Physicians on vacation].
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Aerospace Medicine↗
[Is there a physician on board?].
Physicians responding to emergency calls on board airliners in intercontinental traffic may not be aware of certain legal complications which may arise. For instance, the medical practitioner may hold a license valid in one country, the air carrier may be registered in another, and the patient may be a third state national. Legislation varies between nations, as do courts decisions. Physicians may not be aware of the laws and regulations which apply or of the subtle differences between terms and interpretations used in formal language. This article contains a scenario description from a commercial air liner in intercontinental transit carrying a patient unknown to the physician who responds to a call for medical assistance. The main considerations to be made, the more likely diagnoses and various strategies for immediate interventions are reviewed. Likewise, appraisal and use of medical equipment on board are discussed, as are issues concerning responsibility and liability when equipment is used in supposedly "trained hands". Main themes in the current international medico-legal debate are considered with emphasis on the "Good Samaritan Principle", the responsibility of commercial air carriers, and telemedicine with insurance against law suits. The article concludes with some practical advice to the travelling medical community.
Aerospace Medicine↗
Effects of active noise reduction on noise levels at the tympanic membrane.
BACKGROUND: Active noise reduction (ANR) is an electronic system that works by continuous sampling of noise inside the earshell of the headset with a small microphone. This signal is inverted in phase through the headset speaker, thus reducing noise levels by destructive interference of the acoustic field. The system provides good low-frequency noise attenuation, but aircrew differ in their subjective opinion of ANR. The present study is an attempt to provide an objective assessment of the effect of ANR on noise levels at the tympanic membrane. METHODS: There were 7 subjects with normal ears who were placed in an environment of recorded noise from a BO-105 helicopter. A microphone probe was inserted to within 5 mm of the tympanic membrane of each subject's right ear. Noise levels in the ear were measured without a headset and with two different ANR headsets. Measurements were performed with and without the ANR system on, and with and without white noise through the headset communication system. The white noise was used to simulate aircraft communication noise. RESULTS: The two headsets tested had differing levels of passive and active attenuation. The ANR system produced a substantial low-frequency attenuation. However, noise levels in the mid frequencies increased somewhat when the ANR system was switched on. This effect was augmented when white noise in the communications system was introduced, particularly for one of the two headsets. Low-frequency noise attenuation of ANR systems is substantial, but an increased mid- and high-frequency noise level caused by the ANR may affect both communication and overall noise levels. Our data provide advice on what factors should be taken into account when ANR is evaluated for use in an aviation operational environment.
Aerospace Medicine↗
[Is there a physician on board?].
Physicians responding to emergency calls on board airliners in intercontinental traffic may not be aware of certain legal complications which may arise. For instance, the medical practitioner may hold a license valid in one country, the air carrier may be registered in another, and the patient may be a third state national. Legislation varies between nations, as do court decisions. Physicians may be aware neither of the laws and regulations which apply nor the subtle differences between terms and interpretations used in formal language. This article contains a scenario description from a commercial air liner in intercontinental transit carrying a patient unknown to the physician who responds to a call for medical assistance. The main considerations to be made, the more likely diagnoses and various strategies for immediate interventions are reviewed. Likewise, appraisal and use of medical equipment on board are discussed, as are issues concerning responsibility and liability when equipment is used in supposedly "trained hands". Main themes in the current international medico-legal debate are considered with emphasis on the "Good Samaritan Principle", the responsibility of commercial air carriers, and telemedicine with insurance against law suits. The article concludes with some practical advice to the travelling medical community.
Aircraft↗
Spinal X-ray screening of high performance fighter pilots.
Neck pain and neck injury are common complaints among military aviators flying high performance (HPF) aircraft. Since all candidates for military flying training with the Royal Norwegian Air Force have to meet HPF medical standards, medical selection procedures include a radiological examination of the spine. Nine films of the vertebral column are made with emphasis put on cervical structures. Among 232 applicants, 527 deviations from normal conditions were described--anomalies, degenerative changes and deviations of posture--which average 2.27 diagnoses per spine X-rayed. Of the candidates, 80 were considered entirely within normal limits; 20 were rejected due to the roentgen findings; and five candidates were excluded on final evaluation, their radiological diagnoses contributing to the decision. Although most changes are slight, many significant conditions are demonstrated among young healthy individuals. Since the population is highly selected, the figures we present may be minimum numbers in a western industralized society.
Adult↗
[The back and neck in healthy young Norwegians. A radiologic examination of the spine of 232 applicants for air force pilot education].
Neck pain and neck injuries are common complaints among aviators flying modern fighter aircraft. For this reason all candidates for military flying training in the Air Force have to undergo a radiological examination of the spine as part of the selection procedure. Nine films are produced, with particular emphasis on cervical structures. Altogether 527 positive findings were made among 232 applicants, an average of 2.27 diagnoses per x-rayed spine. Since the candidates had been medically screened prior to the radiological examination, it is not unlikely that the results reported in this highly selected group represent minimum figures for young adult Norwegians.
Adult↗
Impairment of rat polymorphonuclear neutrophilic granulocyte phagocytosis following repeated hypobaric hypoxia.
Exposure of rats to repeated hypobaric hypoxia (17 h at 0.5 atm for 0-7 d) induced significant reduction of the phagocytic capacity of peripheral blood polymorphonuclear neutrophilic granulocytes (PMNL). In addition, the hypoxia induced a significant increase of the hematocrit, hemoglobin, thrombocyte, and total leukocyte concentrations. Differential counting of peripheral blood revealed significant granulocytosis. An increase of the concentration of corticosterone was demonstrated following 2 d of hypobaric hypoxia, whereas 5 d later the corticosterone concentrations were similar to that of the controls. The reduced PMNL phagocytic capacity observed following repeated hypobaric hypoxia may have consequences for host defence in situations of hypoxia exposure.
Aerospace Medicine↗
Adjustment of sleep and the circadian temperature rhythm after flights across nine time zones.
The adjustment of sleep-wake patterns and the circadian temperature rhythm was monitored in nine Royal Norwegian Air-force volunteers operating P-3 aircraft during a westward training deployment across nine time zones. Subjects recorded all sleep and nap times, rated nightly sleep quality, and completed personality inventories. Rectal temperature, heart rate, and wrist activity were continuously monitored. Adjustment was slower after the return eastward flight than after the outbound westward flight. The eastward flight produced slower readjustment of sleep timing to local time and greater interindividual variability in the patterns of adjustment of sleep and temperature. One subject apparently exhibited resynchronization by partition, with the temperature rhythm undergoing the reciprocal 15-h delay. In contrast, average heart rates during sleep were significantly elevated only after westward flight. Interindividual differences in adjustment of the temperature rhythm were correlated with some of the personality measures. Larger phase delays in the overall temperature waveform (as measured on the 5th day after westward flight) were exhibited by extraverts, and less consistently by evening types.
Aerospace Medicine↗
Neck injury sustained during exposure to high-G forces in the F16B.
Neck pain is a frequent complaint among aviators flying high performance fighter (HPF) aircraft. However, very few--if any--cases of subjective symptoms have been confirmed by objective methods and reported in the literature. The present paper relates an incident of documented injury of the cervical spine which occurred during an abrupt and violent maneouver in the F16B. The rear seat occupant, a flight surgeon, who had just handed over controls to the instructor flying from the front seat, was caught unaware. He suffered a ligament injury C5-6 and a sliding of the C6 relative to the C5. It is concluded: 1) The accelerative forces in HPF aircraft can cause serious injury to the cervical spine and its supporting structures in the neck. 2) Aircrew not engaged in the flying task may be at risk if left ignorant of pilots' intentions. 3) Lightweight helmets reduce the medical hazards imposed upon aviators in the high-G environment. 4) Specific exercises aimed at strengthening the neck muscles are encouraged.
Aerospace Medicine↗
Lack of bubble formation in hypobarically decompressed cells.
Suspensions of human erythrocytes or of unicellular microorganisms (Tetrahymena pyriformis, Euglena gracilis, Escherichia coli, and Microcyclus aquaticus) were equilibrated with nitrogen gas pressures up to 200 atm and rapidly decompressed to hypobaric pressures below the vapor point of water. The intracellular environments proved to be very tolerant to the gas supersaturations induced. None or only a few cells were damaged in each case, and bubbles were never observed intracellularly after decompression. In view of such extreme tolerances, it is doubtful that bubbles originate intracellularly during decompression of multicellular organisms, in which bubbles occur with far lower gas supersaturations, unless the tolerances are greatly affected by extensive mechanical deformations of the cells or by the presence of internalized particles with bubble-promoting properties.
Animals↗
Proteinuria in fighter pilots after high +Gz exposure.
Exposure to high gravitational forces acting along the body axis towards the feet (+Gz) causes considerable strain on several organ systems, including the kidneys. During +Gz tolerance studies without anti-G suits, significant amounts of protein and hyaline casts were found in 17 of 20 fighter pilots after centrifugation. The G load alternated between 3.5 and 5.5 G. Mean time in the centrifuge was 15 min. For comparison we examined another group of 19 fighter pilots after air combat maneuver training with anti-G suits. None showed proteinuria. The proteinuria most likely indicates a severely depressed renal blood flow during centrifugation.
Adult↗
Isometric abdominal muscle training and G tolerance.
Methods to increase G tolerance of pilots flying high-performance aircraft are of vital importance. Straining maneuvers to increase G tolerance involve abdominal muscles, and high intra-abdominal pressures (IAP) are recorded during G exposure. This study was carried out to examine the effects of an 11-week abdominal muscle training program on maximal IAP, G tolerance and muscle strength/endurance in 10 fighter pilots. G tolerance was measured in a human centrifuge using simulated aerial combat maneuvers (ACM). The pilots had a higher maximal IAP before training than a control group. G tolerance, maximal IAP, and maximal peak torque of knee extensors were not changed by the training. In contrast, leg muscle endurance increased (p less than 0.01) and ratings of local perceived exertion decreased (p less than 0.01). Static endurance of the knee extensors was positively correlated (p less than 0.05) with G tolerance. It is concluded that the present abdominal training program, employed in experienced fighter pilots, is not sufficient to increase IAP or G tolerance.
Abdomen↗
Analyses of maximum cardiopulmonary performance during exposure to acute hypoxia at simulated altitude--sea level to 5000 meters (760-404 mm Hg).
The maximum cardiopulmonary performance of seven healthy male subjects was studied repeatedly in graded hypoxia at ambient pressures ranging from 760 to 404 mm Hg (sea level to 5000 m of simulated altitude). Using this approach it has been possible to not only establish a reproducible value for VO2max, but to determine an equation which may be used to predict the VO2 at altitude for healthy, unacclimatized males exercising to exhaustion. Moreover, we have attempted to explain the limits to pulmonary ventilation at decreasing levels of PO2 by comparing a given VO2max (STPD) to the corresponding VEmax (BTPS), showing that any further increase in the latter is impossible when a certain level of altitude has been reached. Finally, our series of experiments indicates that the HRmax falls at altitude. Although statistically significant, this decrement is not conspicuous. Thus, when used with the VO2max to calculate the number of ml of O2 consumed per beat of the heart, the "oxygen pulse" turns out to be more sensitive to the fall in VO2max at altitude than to the corresponding decrease in the HRmax.
Adult↗
Modification of the 'dividing bradycardia' by hypoxia or exercise.
The oxygen-conserving efficiency of the physiological adjustments to diving depends on two factors: (1) the rate of onset of reflex action, and (2) the extent to which circulating blood is withdrawn from the organs which are not irreparably damaged by transient hypoxia. We report a study in which either hypoxia or exercise has been imposed as an additional stress on human subjects performing apneic face immersion in order to determine any early changes in the reflex rate of onset and/or the final level of cardiovascular adjustment. It is concluded that the rate of onset of the diving reflex varies with the stresses imposed whereas the final level of adjustment does not.
Adult↗
[Evaluation of patients for transport by scheduled airlines].
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Aerospace Medicine↗
Epidural anesthesia in obstetrics.
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Anesthesia, Epidural↗
Obstetrical analgesia assessed by free fatty acid mobilisation.
Two groups of six parturients each have been compared. One group received centrally acting analgesics, sedatives and intermittent nitrous oxide and the other group was given epidural anaesthesia. The serum free fatty acid (FFA) concentrations of the parturients in the former group increased steadily during labour, attaining peak values between 1050 and 1750 mumol/l at delivery. In parturients belonging to the epidural group, the serum FFA concentrations remained level or even fell towards the time of delivery. It is suggested that the increase in serum FFA reflects a stress induced adrenergic lipolysis which may be used to assiss the various methods for obstetrical analgesia. It is concluded that epidural anaesthesia is superior to the conventional methods of pain relief. Analyses of blood sampled from the unbilical veins show that the concentrations of FFA in the blood of the newborns do not reflect the corresponding maternal values. Thus, epidural anaesthesia does not seem to deprive the fetus of FFA during labour since the factor limiting its transfer appears to be independent of the concentration gradient over the placental membrane.
Adult↗