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Biomedical subjects

C Higenbottam

Publications and source records attributed to C Higenbottam.

8 recordsLinked to original sources
PubMed1998

Temperature dependence of habituation of the initial responses to cold-water immersion.

The initial responses to cold-water immersion, evoked by stimulation of peripheral cold receptors, include tachycardia, a reflex inspiratory gasp and uncontrollable hyperventilation. When immersed naked, the maximum responses are initiated in water at 10 degrees C, with smaller responses being observed following immersion in water at 15 degrees C. Habituation of the initial responses can be achieved following repeated immersions, but the specificity of this response with regard to water temperature is not known. Thirteen healthy male volunteers were divided into a control (C) group (n = 5) and a habituation (H) group (n = 8). Each subject undertook two 3-min head-out immersions in water at 10 degrees C wearing swimming trunks. These immersions took place at a corresponding time of day with 4 days separating the two immersions. In the intervening period the C group were not exposed to cold water, while the H group undertook another six, 3-min, head-out immersions in water at 15 degrees C. Respiratory rate (fR), inspiratory minute volume (VI) and heart rate (fH) were measured continuously throughout each immersion. Following repeated immersions in water at 15 degrees C, the fR, VI and fH responses of the H group over the first 30 s of immersion were reduced (P < 0.01) from 33.3 breaths x min(-1), 50.5 l x min(-1) and 114 beats x min(-1) respectively, to 19.8 breaths x min(-1) 26.41 x min(-1) and 98 beats x min(-1), respectively. In water at 10 degrees C these responses were reduced (P < 0.01) from 47.3 breaths x min(-1), 67.61 x min(-1) and 128 beats x min(-1) to 24.0 breaths x min(-1), 29.5 l x min(-1) and 109 beats x min(-1), respectively over a corresponding period of immersion. Similar reductions were observed during the last 2.5 min of immersions. The initial responses of the C group were unchanged. It is concluded that habituation of the cold shock response can be achieved by immersion in warmer water than that for which protection is required. This suggests that repeated submaximal stimulation of the cutaneous cold receptors is sufficient to attenuate the responses to more maximal stimulation.

Adaptation, Physiological↗
PubMed1985

The effect of leakage on the insulation provided by immersion-protection clothing.

The effect of controlled, incremental water leakage on the thermal insulation provided by three immersion-protection assemblies has been measured using a thermal manikin. The results show an average loss of 30% of the initial insulation for a leak of 500 g, 40% for a leak of 1000 g, and nearly 60% for a leak of 3000 g. The assemblies differed only in the thermal insulation layer which consisted of: A. A single thickness of wool (initial immersed insulation 0.63 clo) B. A double thickness of wool (initial immersed insulation 0.79 clo) and C. A layer of polypropylene batting between nylon covers (initial immersed insulation 0.76 clo). Differences between the assemblies in loss of insulation with leakage were small and no evidence was found to support claims that the insulating properties of polypropylene are more resistant to wetting than those of wool. It is considered that the substantial loss of insulation even with small leaks makes it essential that tests of the water-excluding performance of immersion suits are undertaken in realistic conditions rather than in calm water.

Body Temperature Regulation↗
PubMed1984

The energy expenditure of helicopter pilots.

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.

Adult↗
PubMed1979

Effect of cockpit temperature gradients on the validity of single-point measurements.

Dry bulb temperature was measured at six sites throughout seven sorties in F4E aircraft in a study of vertical and lateral cockpit temperature gradients designed to determine the validity of single-point measurements. The results show that both vertical and lateral gradients exist in F4E aircraft and that single-point measurements of Tdb close to the right shoulder show a bias of up to 4 degrees C in relation to mean cockpit dry bulb temperature derived from measurements at five sites. This bias may be removed by using the predictive relationships developed in this study. The relationship between black globe and dry bulb temperatures is also given for F4E aircraft flown in warm, sunny conditions.

Aerospace Medicine↗
PubMed1978

Relationships between ambient, cockpit, and pilot temperatures during routine air operations.

Thermal data obtained from aircraft flying routine sorties from RAF Germany in summer have been reduced to a form suitable for statistical analysis by describing thermal stress in terms of a modified wet bulb globe temperature (WBGT) index, and thermal strain in terms of mean body temperature (Tb). Ambient temperature could be related to cockpit temperature, and cockpit temperature to pilot Tb, by linear equations of positive slope. Relationships between Tb and sortie time could be represented by exponential equations. The relationships between cockpit temperature and sortie time could also, in fixed-wing aircraft, be described by exponential equations, although in helicopters the relationships were better described by linear equations of negative slope. Models capable of predicting cockpit thermal stress and aircrew thermal strain given ambient temperature and sortie time have been constructed. These provide a description of the temperature relationships within aircraft during flight.

Aerospace Medicine↗
PubMed1977

Heat stress in an aircraft cockpit during ground standby.

Measurements have been made of cockpit temperatures in a Buccaneer aircraft exposed to high air temperatures and radiation loads. With the canopy open 8 cm, and with the wind direction unfavourable for convective cooling, air temperatures inside the cockpit exceeded those outside by approximately 20 degrees C. This reduced to 10 degrees C with a favourable wind direction. An assessment of the likely heating effect of cockpit avionic equipment indicated that the addition of 1 kW and 2 kW of heat would raise cockpit temperatures by 20 degrees C and 30 degrees C respectively. Prediction of the combined effect of solar and avionic heat suggests that, in hot weather conditions, cockpit temperatures will be considerably in excess of the upper limit for effective physiological temperature regulation. Therefore, if aircrews are to be required to remain on ground standby within their aircraft under such conditions, maximum use must be made of convective cooling of the cockpit by the prevailing wind, and of sun shades to eliminate the greenhouse effect completely.

Aerospace Medicine↗
PubMed1977

Thermal data from helicopters operating in a sub-arctic environment.

Using automatic and observer-operated equipment for monitoring thermal data, observations have been made during Royal Navy Wessex 5 helicopter operations in a sub-Arctic climate. Measurements were taken in flight of front and rear cabin temperatures and aircrew deep body and skin temperatures. The results indicate that the "arcticised" aircraft used had more than enough cabin heating to alleviate cold stress on the aircrew.

Aerospace Medicine↗