Survival of the fittest? The scientific basis for the Royal Navy pre-joining fitness test.

The Royal Navy introduced a pre-joining fitness test to the selection procedures for RN Ratings from Summer 2003. The scientific basis for the test came from the present study to investigate if anthropometric and physical fitness measures predicted training failure. Fitness and anthropometric data from 1641 trainees were collected, together with their training outcome (i.e. pass or fail), during the period from September 2001 to March 2002. In addition, a retrospective interrogation of medical records identified those who reported any lower limb injuries. The overall rate of training attrition was 22%. Success in training was associated with: gender; age; physical fitness; and, in the case of females, Body Mass Index (BMI). The reported incidence of lower limb injury (LLI) was associated with: gender; physical fitness; and, for female trainees, BMI. The reported incidence of LLI was approximately 50% in the 'least-fit' female group compared to 10% in the 'most-fit' male group. 16% of females and 2% of males were considered 'unfit' (i.e. did not attain the prescribed run standards of 13 min 15 s and 11 min 13 s respectively). 3% of trainees were considered 'obese' (a BMI > 30 kg.m-2) whereas more than 25% were overweight (BMI > 25 kg.m-2). As a result of this work, selection candidates must now demonstrate a minimum standard of aerobic fitness prior to arrival at HMS Raleigh. The future impact of this selection measure on the reported incidence of lower limb injury and financial costs of training requires further investigation.

Task and postural factors are related to back pain in helicopter pilots.

BACKGROUND: A previous survey by Shear et al. revealed a high prevalence of back pain in Royal Navy helicopter aircrew, compared with controls. It was recommended that a second survey be undertaken, taking account of flying tasks and cockpit ergonomics. This was the purpose of the present investigation. METHOD: A questionnaire containing items on back pain and posture was circulated to all 246 acting pilots, with returns of 75%. The questionnaire sought information on pain in both the flying pilot and co-pilot/instructor roles. RESULTS: The 12-mo prevalence of back pain was 80%. Task-related back pain was greatest in instrument flying (72%) and least in the co-pilot and instructor roles (24%). Self-ratings of posture indicated that forward flexed trunk postures predominated in the flying roles and were most extreme in instrument flying. In non-flying roles, symmetrical, reclining postures were more often reported. No demographic or psychosocial variables were significantly related to back pain prevalence or disability. CONCLUSIONS: Much of the back pain experienced by helicopter pilots appears to be due to the posture needed to operate the cyclic and collective controls. In instrument flying, it is suggested that the visual demands of scanning the displays may exacerbate the pain by causing the pilot to lean further forward.

Spirometric indices and the risk of pulmonary barotrauma in submarine escape training.

Between 1975 and 1997, a total of 115,090 ascents, from depths of between 9 and 28 m, have been made by trainees at the submarine escape training tank HMS Dolphin. During this 22-yr period, 53 incidents have occurred in which, after an ascent, the trainee required hospital or recompression therapy or both. Scrutiny of the incident records revealed unequivocal evidence of pulmonary barotrauma in six incidents with an additional four in which, despite a negligible gas burden, a confident diagnosis of acute neurologic decompression illness with short latency could be made. No causative mechanism other than arterial gas embolism following pulmonary barotrauma can be implicated in these four cases despite the absence of clinical or radiographic evidence of lung injury. In all 10 cases the forced vital capacity (FVC) of the trainees was less than the predicted value for their age and height, revealing a statistically significant (P< 0.01) association between values of FVC below predicted and pulmonary barotrauma. The median FEV1 for the 10 cases was also significantly (P < 0.05) less than the predicted value after allowing for age and height. No such association was found for the FEV1:FVC ratio. FVC would thus seem to be the measure of lung function most closely associated with increased risk of pulmonary barotrauma. Possible reasons for this finding are discussed. It is concluded that although the association between low FVC and pulmonary barotrauma is statistically significant, it is insufficiently specific for low FVC to serve as an exclusion criterion for submarine escape training.

Prognosis in malignant mesothelioma related to MIB 1 proliferation index and histological subtype.

The aims of this study were to evaluate the use of the proliferation marker MIB 1 and histological subtype as indicators of prognosis in malignant mesothelioma. Sections from 41 cases of malignant mesothelioma were histologically subtyped on hematoxylin and eosin sections and stained immunohistochemically for the proliferation marker MIB 1. A proliferation index was derived and the results compared with patient survival data. A statistically significant difference was found between the survival of patients having a low and high MIB 1 index (P < .001). Patients with tumors having a low MIB 1 index lived significantly longer than those with a high MIB 1 index. Patients with the spindle cell histological subtype of malignant mesothelioma had significantly shorter survival times than those with the epithelioid or mixed tumors (P < .01). The MIB 1 proliferation index and histological tumor subtype are useful markers of prognosis in malignant mesothelioma.

Is testicular cancer an occupational disease? A case-control study of Royal Naval personnel.

Testicular cancer is the commonest malignancy arising in men actively serving in the Royal Navy. This study, which includes a literature review of the aetiology of the disease, is designed to determine the relative risk of developing testicular cancer in various occupational groups within the Service by means of a Case-Control study. All cases of testicular cancer occurring in serving personnel between 1976 and June 1994, inclusive, were identified. One hundred and ten cases were found. Four randomly selected controls were matched on the basis of date of birth and length of service to each case. Results reveal statistically significant increased Odds Ratios for members of the Fleet Air Arm (OR = 1.90 95% CI: 1.04-3.48). Air Engineers (OR = 2.32 95% CI: 1.20-4.48) and the Aircraft Handling sub-specialty (OR = 7.31 95% CI: 1.81-29.53). It is speculated that exposure to glycol ethers in aviation fuel may be the causative mechanism. No associations were found in relation to ionising radiation exposures or length of time served in nuclear submarines.

Outcome of neurological decompression illness: development of a manifestation-based model.

A significant proportion neurological decompression illness cases remain symptomatic after the first recompression treatment. Currently, the factors that predict an incomplete resolution are poorly defined. In this study, 214 cases of neurological decompression illness were reviewed and classified according to the presenting manifestations and outcome after a standard therapeutic regimen. The neurological manifestations were classified by type (loss of sensory or motor function, or loss of consciousness) and then by either the number of sites involved or the location of each manifestation. Cases with both sensory and motor manifestations were less likely to have complete resolution than those with sensory or motor manifestations alone. Cases with manifestations involving the legs were less likely resolve completely than those with manifestations in the arms, especially if both sensory and motor manifestations were reported. Based on these data, a linear logistic model was developed to predict the probability of incomplete resolution after the first recompression treatment depending on the type and location of the manifestations.

Retinal angiography in divers.

OBJECTIVE: In the light of previous reports, to examine the possibility that professional diving might cause abnormalities of the retina and choroid. METHODS: The retinal fluorescein angiograms of 55 Royal Naval divers and 24 non-diver servicemen were compared. RESULTS: No differences were found between divers and non-divers and the prevalence of abnormalities was not correlated with diving experience. CONCLUSION: In contrast to previous reports, there seem, at least in naval personnel, to be no ocular consequences of diving.

Back pain in aircrew--an initial survey.

BACKGROUND: In the early 1990's staff at a Royal Naval Air Station formed the view that pilots and observers of the Navy Lynx helicopter fleet appeared to have a higher incidence of back pain, to be seeking medical assistance more frequently and to be spending more time medically "unfit to fly" when compared to their counterparts in other helicopters. HYPOTHESIS: To quantify the incidence of low back pain in helicopter aircrew by use of a questionnaire. METHODS: A questionnaire was used to establish the prevalence and nature of back pain in Naval aircrew (161) compared to a control group of randomly selected non-flying military personnel (310). RESULTS: Results show that aircrew (82%) experience significantly more back pain than controls (52%) (p < 0.01) though the nature of pain was similar in both groups. Significantly more aircrew (73%) than controls (49%) (p < 0.01) reported a previous history of back pain and report pain in shoulders (19%), midback (42%), lower back (72%) and across the buttocks (12%). Ergonomic factors were thought to be causative. Of aircrew surveyed, 11 (8%) had been issued with personal lumbar supports which resulted in major subjective improvements in flight-related symptoms. CONCLUSIONS: Helicopter aircrew have a higher incidence of back pain. Crew station design was identified as a major contributor to the prevalence of back pain while personal supports reduced the levels of discomfort. While these findings are not new, no significant steps have been taken to redesign the crew station. It is recommended that personal supports are provided to all aircrew and that a more detailed study of crew station ergonomics is indicated following a more comprehensive study of prevalence of back pain in Royal Navy aircrew.

Cerebral perfusion and psychometric testing in military amateur boxers and controls.

The objective was to compare two neurophysiological variables in active amateur boxers with non-boxing sportsmen. 41 boxers and 27 controls were given psychometric tests: 34 boxers and 34 controls underwent technetium-99m hexamethylpropyleneamineoxime single photon emission computerised tomography (Tc-99m HMPAO SPECT) cerebral perfusion scans. The controls performed better at most aspects of the psychometric tests. Boxers who had fought fewer bouts had a tendency to perform better at psychometric tests than those boxers who had fought more bouts. Tc-99m HMPAO SPECT cerebral perfusion scanning showed that controls had less aberrations in cerebral perfusion than the boxers. In conclusion, significant differences were shown in two neurophysiological variables between young amateur sportsmen who box and those who do not. The long term effects of these findings remain unknown.

Electroencephalographic study of divers with histories of neurological decompression illness.

OBJECTIVE: To determine whether divers with histories of neurological decompression illness are electroencephalographically distinguishable from non-divers. METHODS: The electroencephalograms (EEGs) from 68 divers with histories of neurological decompression illness and 45 non-diver controls were examined independently by two clinical neurophysiologists. RESULTS: The diver and non-diver groups were electroencephalographically indistinguishable. CONCLUSION: There is no electroencephalographic evidence for the existence of cerebral dysfunction in divers with histories of decompression illness.

Neurophysiological assessment of divers with medical histories of neurological decompression illness.

OBJECTIVE: To examine the possibility that subclinical damage may persist after clinical recovery from neurological decompression illness. METHODS: The neuraxes of 71 divers with medical histories of neurological decompression illness and 37 non-diver controls were examined by recording the somatosensory evoked potentials produced on stimulation of the posterior tibial and median nerves. RESULTS: Although the tests gave some objective support for the presence of "soft" residual neurological symptoms and signs, no evidence was given for the presence of subclinical damage. CONCLUSIONS: The contention that neurological damage persists after full clinical recovery from the neurological decompression illness was not supported.

A comparison of the efficacy of cinnarizine with scopolamine in the treatment of seasickness.

Scopolamine was compared with cinnarizine in a double-blind sea trial involving 179 subjects from the crews of 2 warships. Medication was initiated prophylactically when weather information indicated the approach of nauseogenic conditions. Ship motion was measured during drug treatment periods. In one ship, moderate to severe nauseogenic conditions were encountered; a parallel group comparison was achieved in this. In the other ship, the motion experienced was of a mild nature; a crossover comparison was achieved. Scopolamine was shown to be more effective than cinnarizine in protecting against the symptoms of seasickness. In mild motion, cinnarizine was better tolerated than scopolamine in having less marked side effects. As motion severity increased, the comparative tolerability of scopolamine improved.

A comparison of the forces required to produce tooth movement in vitro using two self-ligating brackets and a pre-adjusted bracket employing two types of ligation.

Friction in fixed appliance systems has received considerable attention in the recent literature, although that attributable to the type of ligation used has not been fully investigated. This in vitro study of 0.022 x 0.028 inch slot Minitwin, Activa ('A' Company, San Diego, California, USA), and SPEED brackets (Strite Industries Ltd., Cambridge, Ontario, Canada), investigates friction in two forms of self-ligating brackets and in two methods of ligating Minitwin straight wire brackets with polyurethane elastomeric ligatures. The resistance to sliding of rectangular archwires through the ligated brackets was measured on a vertically mounted Instron testing machine. The stainless steel archwires used were straight lengths of 0.016" x 0.022", 0.017" x 0.025", 0.018" x 0.025", and 0.019" x 0.025" Nubryte Gold (GAC International Inc., Central Islip, New York, USA). The results showed a significant reduction (P < 0.01) in frictional resistance in the Activa brackets compared with SPEED brackets by a factor of approximately 15. When the SPEED brackets were compared to Minitwin brackets, the reduction in friction was by 50-70 per cent (P < 0.01). The placing of 'figure-of-eight' elastomeric ties increased friction by a factor of 70-220 per cent compared to conventional elastomeric ties (P < 0.01) except for 0.016" x 0.022" archwires. The results indicate that self-ligating brackets require less force to produce tooth movement because they apply less frictional contact to the archwire than conventionally tied siamese brackets.

A clinical trial to compare plaque removing efficiency of a prototype toothbrush with alternative toothbrushes.

Three alternative toothbrushes were investigated in a double blind Latin Square repeated measures design study for their relative efficiency at removing plaque 'in vivo'. A prototype filament suspension design toothbrush was tested, with the suspension mechanism both active and inactive, against a conventional toothbrush. Following an initial control plaque score, subjects were ordered by oral hygiene levels and randomly allocated to each of the three test groups. The trial was made up of three periods of 14 days consisting of four days of no brushing followed by 10 days of brushing with each of the three toothbrushes. All plaque scores were recorded using the Greene and Vermillion Index of Oral Hygiene and plaque scores were recorded for each patient at the start, four days later and at the end of each 14-day period. There were no significant differences in the quantity of plaque remaining after brushing with any of the brushes tested in this study. Ignoring the toothbrush used, the end brushing average plaque scores for period 1 were found to be higher than the control plaque scores. It is suggested that this resulted from the patients finding new toothbrushes less comfortable to use initially but following a period of accommodation and adjustment, end brushing plaque levels in subsequent periods returned to near the same level as the control plaque score.

Acclimatization to altitude: effects on arterial oxygen saturation and pulse rate during prolonged exercise at altitude.

Changes in the arterial haemoglobin-oxygen saturation (SaO2) of the blood, in the blood pressure and in the heart rate, were monitored in subjects performing static exercise at an altitude of 3,600 metres before and after an acclimatization period of 28 days during an expedition to the Bolivian Andes. It was found that acclimatised subjects could maintain their SaO2 during prolonged exercise better than non-acclimatised subjects. The pulse rate of acclimatised subjects was consistently lower at the same work level than that of non-acclimatised subjects. Acclimatised subjects were able to reach higher levels of exercise than when they had first arrived at altitude. These data imply that acclimatization to altitude improves the delivery of oxygen to the tissues. The mechanism of this is not certain, but it may be concerned with a reduction in the degree of ventilation-perfusion inequality of the lung which occurs on exposure to high altitude.

DERMIS: a computer system for assisting primary-care physicians with dermatological diagnosis.

DERMIS is a computerized skin disease diagnostic prompting system which has been derived from the prospective study of 5203 cases. It has been designed for use by non-dermatologists such as general practitioners. The program produces a list of reasonable diagnoses based on probabilities calculated using Bayes' theorem. Out of 221 precise diagnoses made by the dermatologist in the clinic, 42 groupings were created to encompass the most common or important diseases encountered in general practice. Four 'remainder' or 'send to specialist' groups were included for the 13% of uncommon conditions. The program, when tested by 'one out' analysis on the original cases, placed the correct diagnosis first on 76% of occasions, and within the first three on 95% of occasions. In 76 of 125 cases randomly selected from the data base, a request for diagnostic assistance had been made by the referring general practitioner. It has been estimated that in 54 of these 76 cases the DERMIS system could have provided differential advice with the correct diagnosis appearing at the top of the list. The system has been written in MUMPS and runs on an IBM-compatible desk-top computer. The software allows real time data entry. Arrangements are in hand for performing clinical trials of the system in general practice. If current performance is maintained, and the response to the system's output is favourable, then DERMIS might well enhance performance in medical decision making for the benefit of patients, medical services and budget holders.

An audit of resuscitation and anaesthesia during Operation 'Safe Haven'.

The Royal Navy combined Surgical Support Team deployed for six weeks to Northern Iraq. Eighteen casualties of civilian and military trauma required active resuscitation, 10 of whom were under the age of 16. Three died. Triage of multiple casualties was necessary on three occasions. The principles of Advanced Trauma Life Support (ATLS) were adopted and the experience is described under the ABCDE headings of the primary survey. Deficiencies of training and equipment are identified. Seventy one anaesthetics, administered to 52 patients, were audited prospectively in detail. Systolic blood pressure was significantly higher with isoflurane and controlled ventilation (ICV), compared with halothane and trichloroethylene (HTCV) (P < 0.05). ICV patients recovered more quickly than with HTCV (P < 0.05), but were significantly older and heavier (P < 0.05). Isoflurane should replace the standard halothane/trichloroethylene combination. Controlled ventilation or ketamine anaesthesia allowed satisfactory SpO2 on air alone. With controlled ventilation, anaesthesia was entirely satisfactory for children down to 6.5 kg. Local anaesthetic procedures were useful. The entire anaesthetic drug cost was only 127 pounds. Three patients received a degree of intensive care. Recommendations are made to improve future outcome, but sophisticated resuscitation, anaesthesia and monitoring is now possible in the front line.

Ventilation with isoflurane in the Triservice anaesthetic apparatus: a comparison with halothane and trichlorethylene.

Recovery from anaesthesia using the Triservice anaesthetic apparatus with either isoflurane alone or halothane and trichlorethylene, was assessed by measurement of reaction time. There was no statistically significant improvement in recovery between patients who received low concentrations of isoflurane and those who received halothane and trichlorethylene. The mean profiles of systolic pressure and heart rate were significantly greater in the isoflurane group (P less than 0.05) than in the halothane/trichlorethylene group. Cardiovascular stability was maintained into the recovery period. The benefits of low concentrations of isoflurane as sole agent in the Triservice anaesthetic apparatus and their extrapolation to a shocked casualty in a military setting are discussed.

Minimum oxygen requirements during anaesthesia with the Triservice anaesthetic apparatus. A study of drawover anaesthesia in the young adult.

Thirty-six servicemen were anaesthetised using the Triservice anaesthetic apparatus. They were allocated randomly into one of two groups, to breathe spontaneously or to receive artificial ventilation, and into subgroups who were given air alone, or air supplemented with 1 or 4 litres/minute of oxygen. A further 12 subjects were studied subsequently using 0.5 litres/minute of added oxygen. Intra-operative blood gases were compared with those of awake premedicated controls. Artificial ventilation was associated with an unchanged arterial oxygen tension with air alone; in the other subgroups arterial oxygen tension was higher than with spontaneous respiration when related to inspired oxygen fraction (p less than 0.05). Air anaesthesia caused significant hypoxaemia with spontaneous ventilation (p less than 0.05), and 50% of the subjects required assisted ventilation. There was also a significant respiratory acidosis (p less than 0.05). Intermittent positive pressure ventilation is the method of choice for field anaesthesia when oxygen is unavailable. Spontaneous respiration must be supplemented with at least 0.5 litres minute of oxygen.

Excretion of a toxic dose of thallium.

We report a successfully treated case of severe thallium intoxication that required 95 days of assisted ventilation and 224 days of hospitalization. Monitoring of the patient for 500 days by measuring thallium in whole blood, serum, and urine is documented, and the role of the laboratory and utility of the measurements are considered.