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.

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.

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.

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.

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.

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.

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.

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.

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.

[Follow-up after infraligamental PTA treatment]. / Followup efter infraligamentaer PTA-behandling.

A total of 48 percutaneous transluminal angioplasties (PTAs) of the superficial femoral and popliteal artery performed between 1993 and 1998 were evaluated with ultrasound duplex scanning and ankle-arm pressure. Twenty-seven (60%) patients presented with claudication and 18 (40%) had limb-threatening ischaemia. Three patients had bilateral PTA. The PTAs were initially successful, corresponding to an early patency rate of 87.5% within the first four weeks. The 12 month patency rate, calculated by life table method, was 68% and 72%, respectively (non-significant). The mortality was 4% and 33% respectively during the first year (p < 0.05). In spite of the size of the material, PTA of the femoropopliteal arterial segment is considered as a valid alternative treatment to vascular surgery in patients presenting with claudication and in patients presenting limb-threatening ischemia.

[Glycosylated hemoglobin (HbA1c) and acute hemolytic anemia]. / Glykosyleret haemoglobin (HbA1c) og akut haemolytisk anaemi.

The concentrations of glycosylated haemoglobin (HbA1c) were determined in eight patients with acute haemolytic anaemia and were found to be significantly lower than in a control group of 16 patients. A case history is presented in which HbA1c was employed as longitudinal parameter of haemolysis. It is concluded that in haemolytic anaemia in non-diabetic patients, HbA1c is a specific parameter of haemolysis which may be employed as a supplement to the traditional parameters of haemolysis.

[The chronic Philadelphia chromosome-negative myeloproliferative syndrome I. Pathogenesis and pathophysiology]. / Det kroniske Philadelphia-kromosom-negative myeloproliferative syndrom I. Patogenese og patofysiologi.

In polycythaemia vera (PV) the erythroid progenitors proliferate autonomously independently of the circulating erythropoietin. The progenitors are hypersensitive to various growth factors, including insulin-like growth factor 1, which inhibits apoptosis in erythroid and myeloid progenitor cells. No change has been found in the erythropoietin (EPO) receptor. Thrombopoietin (Tpo) regulates the production of haematopoietic progenitor cells, particularly of platelets. By inhibiting apoptosis, this growth factor may be responsible for the autonomous proliferation of the megakaryocyte cell lineage in PV and idiopathic myelofibrosis (IMF), which are featured by highly elevated circulating Tpo levels. Thrombopoietin may also be involved in the pathogenesis of myelofibrosis and development of extramedullary haematopoiesis. Both fibrogenesis and angiogenesis in the bone marrow, spleen, and liver develop secondary to the release of various growth-promoting factors from the megakaryocyte cell lineage. The lesion of the pluripotent stem cell in PV and IMF seems to imply several defects, including lack of or decreased expression of the Tpo receptor, alterations in the sensitivity of progenitor cells to various growth factors, and alterations in important gene systems (Bcl-2), which govern cell survival. Essential thrombocytosis seems to be a heterogeneous disease entity, as about 50% of the patients have polyclonal haematopoiesis.

[The chronic Philadelphia chromosome-negative myeloproliferative syndrome II. Clinical findings, diagnostics and treatment]. / Det kroniske Philadelphia-kromosom-negative myeloproliferative syndrom II. Klinik, diagnostik og behandling.

Polycythaemia vera (PV) and essential thrombocytosis (ET) are clinically characterised by non-specific neurologic symptoms, peripheral circulatory disturbances (acrocyanosis, wounds, erythromelalgia) or abdominal symptoms. The treatment of PV includes phlebotomy, antiaggregation and cytoreduction. In ET, the primary treatment is also low-dose aspirin except for patients presenting with a haemorrhagic diathesis. Hydroxyurea may be associated with an increased risk of acute leukaemia or myelodysplasia. Therefore alpha-interferon and anagrelide should be considered in younger patients. Early cytoreductive therapy is advocated in patients with idiopathic myelofibrosis (IMF) to inhibit further progression of bone marrow fibrosis and further expansion of myeloid metaplasia in the spleen and liver. Treatment with androgens (danazol) and glucocorticoids may improve severe anaemia and thrombocytopenia. In younger patients, allogeneic bone marrow transplantation should be considered.

[Acute thrombotic complication at the debute of the Philadelphia chromosome-negative myeloproliferative syndrome]. / Akut trombotisk komplikation ved debut af det Philadelphia-kromosom-negative myeloproliferative syndrom.

METHODS: We describe eight patients with a diagnosis of a chronic myeloproliferative disorder, characterised in most patients by severe thrombotic complications at the debut of the disease. RESULTS: The symptoms were life-threatening in seven patients: acute upper gastrointestinal haemorrhage from oesophageal varices in four, an acute abdominal catastrophy owing to mesenteric vein thrombosis with intestinal gangrene in two, and a large cerebral infarction, which was lethal, in one. The same patient also suffered a thrombosis of the axillary and subclavian veins. Neurological symptoms, with headache, visual disturbances, dizziness, and impaired memory, were initial cardinal symptoms. In two patients, explorative laparotomy was performed with intestinal resection owing to gangrene. One patient had a toe amputation. DISCUSSION: The above symptoms are explained by thrombosis in the microcirculation because of thrombocytosis and circulating platelet aggregates. In patients with polycythaemia vera, the elevated haematocrit contributes significantly to the impaired microcirculation. Early diagnosis and management of these disorders are of utmost importance to prevent the potentially life-threatening complications described above.

[Reproducibility of a rapid test for HIV antibody]. / Reproducerbarheden af hurtigtest for HIV-antistoffer.

This study evaluated three rapid test kits for HIV antibody detection. Thirty consecutive blood specimens from the infectious diseases outpatient clinic were examined by three house officers who tested each specimen twice in a blind and randomized experiment. HIV-Chek (Du Pont) and HIV-1/HIV-2 TestPack (Abbott) were easy to handle and gave good intra- and interobserver agreement and good agreement with routine ELISA. Recombigen (BioScience) was difficult to interpret and gave poorer intra- and inter-observer variation. We suggest that HIV-Chek and TestPack can be used for assessment of patients' HIV antibody status in emergency circumstances with only minimal instruction of the staff.