The thermal properties of a survival bag incorporating metallised plastic sheeting.

Five male subjects were exposed to a cooling environment equivalent to 1082 W/M2. The subjects wore a clothing assembly with insulation properties of 1.55 clo. A casualty bag in corporating metallised plastic sheeting was provided for additional insulation. Deep body temperature fell 1.2 degrees C. and mean skin temperature 2.6 degrees C. over the 2-h period. Metallised plastic sheeting did not prevent heat loss through the clothing assembly, as indicated by the falls in body and skin temperature and an increase in metabolic heat production. From measurements made during the exposure, the calculated insulation value of the complete assembly of 2.93 clo was close to the predicted value of 2.80 clo calculated from the thermal resistance of the assembly layers. It is concluded that the metallised plastic sheeting in this casualty bag did not provide significant additional thermal insulation.

Immersion suit insulation: the effect of dampening on survival estimates.

Immersion suit leakage values were obtained from realistic testing of helicopter passenger immersion suits using eight subjects. Simulated helicopter underwater escape resulted in mean leakages of 198 +/- 103, 283 +/- 127, 203 +/- 179, and 45.7 +/- 31.6 g (mean +/- S.D.) when wearing four different immersion suits. Suit leakages obtained from a 20-min swim test to simulate vital in-water survival actions produced leakages of 213 +/- 224, 1398 +/- 691, 145 +/- 96.5, and 177 +/- 139 g (mean +/- S.D.). Dampening of undergarments during simulated helicopter travel at an elevated cabin temperature of 30 degrees C was 115 +/- 47.3 (mean +/- S.D.; n = 4) when wearing an impermeable suit and 19 +/- 16.7 g (mean +/- S.D.; n = 4) when wearing a vapour-permeable suit. The commensurate loss of insulation with the impermeable suit at the upper level of temperature could reduce clothing insulation by 17%. A reduction of less than 5% may result under similar conditions when wearing the permeable suit. The combined dampening effect of sweating, helicopter underwater escape, and performance of vital survival actions could result in a total dampening of 247-1712 g, depending on the type of suit worn. The respective loss of insulation would be 15% and 50% respectively. This could reduce, for the 10th percentile thin man, his survival time in water at 5 degrees C from 3.5 h to between 2.4 h and 1.1 h, respectively.

The thermal protection offered by lightweight survival systems.

The thermal protection offered by lightweight survival systems was evaluated in a mountain environment. When subjects were exposed for 3 h in bags manufactured from polythene, in metallised plastic sheeting, and in a casualty bag incorporating MPS, no significant differences in thermal benefit were found. The protection offered by each system was comparable and the practical experience gained in the field would suggest that the simple polythene bag was superior to the MPS bag when one considers strength, durability, multiplicity of roles, and cheapness. Addition of a fibre pile liner equivalent to 1.5 clo units during exposure in the MPS-lined casualty bag effectively eliminated cold stress and metabolic compensation. Without this liner, the thermal performance of the casualty bag was very similar to the other two lightweight systems.

Seasickness in totally-enclosed motor-propelled survival craft: five offshore oil rig disasters.

Five mobile offshore drilling unit disasters--Alexander L. Kielland, Ocean Ranger, Vinland, Ocean Odyssey, and Rowan Gorilla I--were studied to assess the degree to which seasickness occurs and endangers the lives of occupants of totally-enclosed motor-propelled survival craft (TEMPSC). Thousands of other peacetime marine incidents were reviewed and a literature search was conducted to assess the same seasickness problem. The one reported death in the Vinland abandonment appears to be the only one that could be associated, even remotely, with seasickness. It cannot be established whether or not seasickness contributed to the cause of death in the case of the Ocean Ranger victims, but it did occur in 75% or more of TEMPSC occupants in the other four rig disasters. It has occurred both in relatively calm waters of 1-m wave height and in severe seas of 15-m heights. Evacuees in an intact TEMPSC are able to survive many hours of severe seas; consequently, they should not be rescued until the weather and sea conditions improve. Moreover, practical survival training and good leadership is a principal cornerstone in the amelioration of seasickness.

Application of weight-height relations for assessing adiposity in a United Kingdom offshore workforce.

Weight (W), height (H), and skinfold thicknesses at biceps, triceps, subscapular, and suprailiac sites were measured in a United Kingdom offshore workforce. Weight and height were used to calculate W/H relations. The percentage body fat was estimated from skinfold thicknesses and the correlations of adiposity with the various W/H relations were evaluated. The significant increase in percentage body fat (%BF) with increasing age resulted in the development of age group specific regression equations relating %BF to the indices of W/H1.5 and W/H2 (body mass index or Quetelet index). Little difference regarding the qualities of these two indices were detected in terms of poor correlation with height and strong correlation with weight. Thus either may be used with similar levels of confidence. Comparison with other studies, however, would be more easily accomplished if W/H2 were used. In the absence of skinfold thickness measurements the W/H2 could readily be implemented during a routine medical and applied for the estimation of %BF in the offshore population provided that the appropriate regression equation were used and that the limitations of the technique are recognised. Percentage values for W, H, W/H relations, and %BF by age group are provided for comparison with other population studies.

Percentage body fat and prevalence of obesity in a UK offshore population.

1. Body-weight, body height and skinfold measurements were taken in 419 adult males working in the UK offshore oil industry. Percentage body fat was estimated from skinfold thicknesses and the Quetelet index (weight:height) determined. 2. The prevalence of overweightness, assessed from the Quetelet index, in the age groups 20-29, 30-39 and 40-49 years was 31.6, 50.0 and 66.2% respectively. The Office of Population Census and Surveys (1981) showed that for age-matched groups, the incidence of overweightness in an onshore population was 26, 40 and 50% respectively. 3. The percentage body fat for each respective age group was greater than that reported for an age-matched onshore population. 4. The Quetelet index was significantly related to body fat (r 0.765, P less than 0.0001) and poorly correlated with height, thus this weight:height relation may be utilized in the assessment of overweightness in offshore personnel. 5. In conclusion it appears that the offshore population had a higher percentage body fat than their onshore peers and that the prevalence of overweightness was also greater.

Cooling responses in shivering and non-shivering dogs during induced hypothermia.

1. Hypothermia to a temperature of 30 degrees C was induced in both shivering and non-shivering groups of dogs. 2. There was a sustained increase in oxygen consumption in the dogs allowed to shiver and this was up to 300% greater than the oxygen consumption in the relaxed dogs. 3. The increased tissue requirement for oxygen was met both by increased cardiac output and increased oxygen extraction from haemoglobin. 4. Oxygen utilization remained adequate in hypothermia, as shown by the absence of hypoxic acidosis. 5. Heart rate fell during cooling and stroke volume increased to meet the increased oxygen demands associated with shivering during the induction of hypothermia.

Accidental hypothermia and rewarming in dogs.

1. Twenty lightly anaesthetized dogs were cooled to 29 degrees C by cold-water immersion. Ventilation was spontaneous and the animals were allowed to shiver freely. Metabolic heat production and respiratory heat exchange were measured during rewarming. 2. The animals were divided into four groups each of five dogs and each group was rewarmed by a different technique. The control group was allowed to rewarm spontaneously; a second group was given warm (45-50 degrees C) fully humidified air to breathe in addition; a third group was rewarmed in a hot-water bath (42-44 degrees C) and the remaining group was given in muscle relaxant to abolish shivering and rewarmed by warm inspired air only. 3. The group rewarmed in hot water achieved normal core temperature most rapidly but there was no difference in the rewarming rates of the group rewarmed spontaneously and of the group given warm air to breathe in addition. 4. The group given a muscle relaxant and rewarmed with warm inspired air required 12 h to achieve the same core temperature as the shivering groups achieved in 2 h. Compared with the heat produced by shivering the amount of heat which it was possible to transfer across the respiratory tract was so small that it did not materially influence the rate of rewarming.