Determination of esophageal probe insertion length based on standing and sitting height.

The present study derives simple formulas for the prediction of optimal insertion length of an esophageal temperature-sensitive probe from the measurements of either standing or sitting height. The formulas assume that the optimal site for an esophageal temperature probe is in the region of the esophagus bounded by the left ventricle and aorta, corresponding to the level of the eighth and ninth thoracic vertebrae (T8 and T9, respectively). An esophageal probe was constructed of polyethylene tubing containing 1-cm segments of alternating radiopaque and nonradiopaque tubing in the distal 20 cm of the probe.

Effect of peripheral temperature on the formation of venous gas bubbles.

Temperature of the tissue affects the many components involved in the formation of tissue gas phase formation: diffusion, perfusion, and inert gas solubility. Since the effects of perfusion and inert gas solubility may be counteracting in terms of enhancing growth of gas bubbles, the optimal thermal status of divers throughout a dive remains unresolved. To elucidate the role of peripheral body temperature on gas phase formation, four subjects were exposed to a 10 degree and 40 degree C environment for 3 h on two separate occasions, after a no-stop decompression from a 12-h dive to 9.

Core threshold temperatures for sweating.

To detect shifts in the threshold core temperature (Tc) for sweating caused by particular nonthermal stresses, it is necessary to stabilize or standardize all other environmental and physiological variables which cause such shifts. It is, however, difficult to cause progressive changes in Tc without also causing changes in skin temperature (Tsk). This study compares the technique of body warming by immersion in water at 40 degrees C, and subsequent body cooling in water at 28 degrees C, to determine the core threshold for sweating, with one by which Tc was raised by cycling exercise in air at 20 degrees C, and then lowered by immersion in water at 28 degrees C.

The increased oxygen uptake upon immersion. The raised external pressure could be a causative factor.

The principal cause of the immediate transient elevation in ventilation (VE, L.min-1) and oxygen uptake (VO2, L.min-1), when a human subject is immersed in cold water is considered to be the stimulation of cutaneous cold receptors.

Effect of occluded venous return on core temperature during cold water immersion.

Recent studies using inanimate and animal models suggest that the afterdrop observed upon rewarming from hypothermia is based entirely on physical laws of heat flow without involvement of the returning cooled blood from the limbs. During the investigation of thermoregulatory responses to cold water immersion (15 degrees C), blood flow to the limbs (minimized by the effects of hydrostatic pressure and vasoconstriction) was occluded in 17 male subjects (age, 29.0 +/- 3.

Dynamic moisture permeation through clothing.

Dynamic moisture permeation through clothing often occurs during thermal transience, causing an imbalance between evaporative heat loss from the skin (Esk) and that from the clothing surface (Ecl). A device was designed to observe Esk and Ecl simultaneously. It consists of two relative humidity sensors coupled with thermistors so that densities of water vapor at two points within the boundary layer can be calculated.

Respiratory drive during sudden cold water immersion.

Sudden decreases in cutaneous temperature induce an immediate ventilatory response, which has been termed the inspiratory or 'gasp' reflex. This respiratory response has been implicated as a contributing factor to cold water immersion drowning. In the present study, five subjects wearing either shorts or a variety of thermal protective apparel were immersed on separate occasions in 10 degrees C water.

Helicopter pilot suits for offshore application. A survey of thermal comfort and ergonomic design.

The objective of this study was to determine the existing problems associated with helicopter pilot survival suits currently in use. A survey was conducted of helicopter pilots from both Canadian commercial and military disciplines. Pilots commented on eight different types of survival suits.

Clothing surface area as related to body volume and clothing microenvironment volume.

The evaluation of clothing surface area becomes important in analyses of heat exchange between the clothed body and its environment. The evidence accumulated in the studies of radiation area has led to the conclusion that the ratio of clothing surface area to body surface area (fcl) may be defined as a function of clothing insulation. However, the effects of clothing fit have been disregarded.

Determining the rate of body heat storage by incorporating body composition.

The rate of body heat storage (S) is often used as an index of thermal stress. The traditional approach for determining S assumes that the specific heat (Cp) of all body tissues may be averaged to 0.83 kcal X kg-1 X degrees C-1, irrespective of the actual proportion of different tissues in the body.

The pattern of breathing during hypoxic exercise.

Breathing pattern was studied in six subjects in normoxia (FIO2 = 0.21) and hypoxia (FIO2 = 0.12) at rest and during incremental work-rate exercise.

Evaluation of predictive formulae for determining metabolic rate during cold water immersion.

Five models predicting shivering thermogenesis on the basis of steady state skin and core temperature were evaluated: Hayward et al., Stolwijk and Hardy,; Nadel et al.,; Timbal et al.

Inhibition of shivering in man by thermal stimulation of the facial area.

The contribution of the facial thermoreceptors to thermoregulatory shivering was studied. Seven subjects were exposed to -3 degrees C ambient air for 1 h. Radiant heat was applied to the facial area during 30 s periods at 10 min intervals and the effects on the integrated electromyographic activity (IEMG) in the brachial biceps, trapezius and femoral rectus muscles, and on the heart rate (HR) were studied.

Effect of reduced atmospheric pressure on patients with fluctuating hearing loss due to Ménière's disease.

Subjective symptomatic and objective audiologic effects of reduced atmospheric pressure on patients with confirmed fluctuating hearing loss due to Ménière's disease were statistically assessed on a prospective basis. The effect of hypobaric environments on absolute hearing thresholds was investigated in 10 normal subjects at 6,500 ft. Absolute hearing threshold levels obtained at altitude, after one hour altitude exposure, and on descent to normobaric conditions were compared with levels obtained prior to the hypobaric exposure.

Effect of core cooling on short and long latency reflex responses.

Subjects were immersed in 10 degrees C water until the rectal temperature dropped to 35 degrees C. Reflexes of wrist flexors were tested before and after cooling with tendon taps and torque motor produced perturbations. Comparison of pre- and post-cooling reflex responses showed that the longer latency reflex (LLR) was delayed in onset more than the short latency monosynaptic reflex (SLR) response.