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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of adaptation to cold, hypoxia, or exercise on hyperbaric decompression tolerance were investigated in two factorial experiments. For either 14 or 28 days, groups of mice were handled (control); exposed discontinuously for 4 h to cold (4 degrees C) or hypoxia (P approximately 379 or 320 Torr); or exercised by swimming (15 min at 31 degrees C) or treadmill excursion (8.1 m/min for 1 or 1.5 h). The animals were divided into subgroups, exposed to one of three hydrostatic pressures (7.6--11.1 ATA) for 30 min, decompressed, and observed to determine survival rate or bends incidence (type II decompression sickness). Decompression sickness was significantly reduced (P less than 0.05) in the treadmill-trained animals, was unchanged in cold-exposed and swim-exercised mice, and tended to increase in animals adapted to hypoxia. Enhanced tolerance by treadmill training is presumably due to lean body conformation, which could reduce nitrogen saturation of tissues, and greater muscle capillarization and cardiovascular fitness, which may improve nitrogen elimination. Reduced tolerance with adaptation to hypoxia may be attributed to rheological changes associated with polycythemia, which facilitate bubble production.
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PMID:Cross-adaptive effects of cold, hypoxia, or physical training on decompression sickness in mice. 46 99

Twenty-four oxygen exposures lasting 80 to 271 min were performed by six immersed exercising subjects at 25 fsw (1.76 ATA) in both warm and cold water. Two types of exercise were performed, moderate work (50 watts) for long periods of time, and graded exercise (25-150 watts) lasting 85 min. In 21 degrees C water, moderate exercise lasted 228 +/- 39 min, with a mean VO2 of 1.72 +/- 0.11 liter/min. In 4 degree C water, the duration was 163 +/- 22 min, with a mean VO2 of 1.83 +/- 0.16 liter/min. The differences in duration of oxygen exposure in warm and cold water reflect termination at an inspired PCO2 of 7.6 mmHg, a level reached earlier in cold water because of CO2 absorbent exhaustion. In 21 degrees C water, the VO2 for graded exercise ranged from 1.51 to 3.00 liter/min and in 4 degrees C water, from 2.00 to 3.16 liter/min. Central nervous system oxygen toxicity was not observed during these exposures, although two divers had clinical and spirometric evidence of early pulmonary oxygen toxicity. The absence of CNS oxygen toxicity is attributed to low resistance and minimization of dead space, which caused a low inspired PCO2, although the divers' experience with oxygen diving and their excellent physical condition may have contributed as well.
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PMID:Prolonged oxygen exposures in immersed exercising divers at 25 fsw (1.76 ATA). 53 63

Cardiorespiratory, thermal, and renal responses to a 30-min head-out immersion in 15 degree C water were studied at 1-ATA air and 11-ATA helium-oxygne environments in four male subjects wearing dry suits. Cardiorespiratory responses to immersion (reductions in heart rate, expiratory reserve volume, vital capacity, and thoracic impedance; and increases in stroke volume, cardiac output, and inspiratory capacity) were comparable at both pressures. However, thermal responses to immersion (a reduction in mean skin temperature and increases in skin heat flux and suit conductance) were significantly greater at 11 ATA compared to those at 1 ATA. The rate of urinary excretion of norepinephrine increased significantly during and after immersion at 11 ATA but not at 1 ATA. In contrast, the urinary excretion of epinephrine was not altered by pressure or immersion. The immersion diuresis was greater and lasted longer at 11 ATA than at 1 ATA although there was no difference in the endogenous creatinine excretion . This diuresis was accompanied by a significant natriuresis which was more marked at 1 ATA than at 11 ATA. At 1 ATA, the urinary excretion of both aldosterone and antidiuretic hormone (ADH) decreased during immersion. At 11 ATA, the rate of excretion of these hormones before immersion was lower compared to that at 1 ATA and did not change significantly during immersion. These results indicate that immersion in a hyperbaric helium-oxygen environment presents a greater cold stress than at 1-ATA air, and also that immersion diuresis and natriuresis at high pressure may be induced by a factor other than inhibition of aldosterone and ADH.
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PMID:Physiological responses to head-out immersion in water at 11 ATA. 63 73

The heart rate (HR) responses to breath-holding (BH) with the without face immersion (FI) in 31 or 27 degrees C water was studied in 1 ATA air and hyperbaric He-O2 environments in 4 male subjects during a dry saturation dive to simulated depth of 580 ft (18.6 ATA). When a 60 sec BH or FI was performed while leaning forward, there was a significant linear correlation between the maximal bradycardial response (delta HRmax) and ambient pressure for simple BH (r-0.08, P less than 0.05) and 31 degrees C FI (r = 0.91, P less than 0.01), but not for 27 degrees C FI. A similar trend was seen during 30 sec BH's while seated erect. The facial cold-dependent component of the FI bradycardia was not significantly altered by pressure. In general, there were significant correlations between the initial HR and the initial thoracic conductive volume (TCV; measured by the four-electrode Minnesota impedance cardiograph), and between the initial TCV and delta HRmax observed during seated erect BH's. Since the TCV was generally higher at depth, it is suggested that a mechanical effect due to increased TCV at depth, possibly related to increased gas density, is at least partly responsible for the pressure dependence of BH bradycardia.
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PMID:Heart rate response to breath holding at 18.6 ATA. 87 51

The dive (Hana Kai II) described in these papers was designed to determine the effects on man of a prolonged exposure to a dry helium-oxygen hyperbaric environment. Comprehensive studies on energy balance, body fluid balance, cardiorespiratory functions, maximal oxygen uptake, psychological performance, and physiological responses to cold were performed at a simulated depth of 580 ft (18.6 ATA) over a 30-day period in March-April 1975. Following a 3-day predive control period at 1 ATA air (period 1), 5 male divers spent 17 days at 18.6 ATA in a helium-oxygen environment (periods 2-6), and returned to 1 ATA air after 7 days of decompression (periods 7-8). They stayed an additional 3 days inside the chamber for postdive control measurements (period 9). The chamber temperature was maintained at 25-27 degrees C during periods 1 and 9, 30-31 degrees C during periods 2-5, and 27-28 degrees C during period 6. At 18.6 ATA, the PO2 and PCO2 of the chamber gas were maintained at approximately 225 and 2 mmHg, respectively. In this introductory paper, physical and physiological characteristics of individual subjects, the major daily activity schedule, and the scope of investigation are presented.
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PMID:Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. I. Objectives, design, and scope. 91 Mar 14

Impedance plethysmography was used to measure resting cardiac stroke volume (SV) and thoracic conductive volume (TCV) in four divers at intervals during a prolonged dry saturation dive (17 days at 18.6 ATA and 7 days' decompression). Resting heart rate (HR), blood pressure (BP), and pulmonary minute ventilation (VE) were measured 4 times per day for the duration of the 30-day experiment. The vital capacity (VC) and its subdivisions IC and ERV were measured by spirometry every 3 days. In nonsmokers, VC fell significantly with time (r = 0.64), while VC in smokers increased nearly 400 ml during the first week at pressure before tending to fall with time. Compared to predive, the mean ERV was increased 629 ml at pressure, while VE and respiratory rate were not changed. The increased ERV did not persist postdive and was probably the result of the increased work of breathing a dense gas (4.1 g/liters). Residual volume (RV) measured by nitrogen dilution before and after the dive increased 38% and remained significantly increased (22%) even after one year in 4 divers. It is suggested that hyperoxia (0.3 ATA PO2) combined with increased gas flow resistance caused the VC to fall and RV to increase. The major cardiovascular findings were a transient bradycardia associated with increased stroke volume leading to a significant increase in resting cardiac output associated with an increased rate of rapid ventricular filling, TCV, and BP at depth. Lowering the ambient temperature for 3 days did not re-establish the bradycardia, suggesting that hyperbaric bradycardia is not due to a subtle cold stress.
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PMID:Hana Kai II: a 17-day dry saturation dive at 18.6 ATA. IV. Cardiopulmonary functions. 91 Mar 17

Measures of spatial orientation, associative memory, general intelligence, arithmetic ability, reaction time, and personal/social perceptions were administered to five subjects during a 31-day saturation exercise. Performance decrements were noted during 17 days of exposure to hyperbaric Hi-O2 at 18.6 ATA. Significant losses in general intellectual ability were noted, as well as trends toward significant losses in other cognitive tests. Reaction time and arithmetic errors increased significantly during the early testing sessions. Performance during a 3-day cold period was equivocal; arithmetic errors increased, but other measures improved or remained constant. Environmental stressors such as fatigue, anxiety, health problems, personal and social adjustment, and aspects of perceptual deprivation were considered to be influential in reducing performance effectiveness.
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PMID:Hana kai ii: a 17-day dry saturation dive at 18.6 ATA. VI: Cognitive performance, reaction time, and personality changes. 91 Mar 19

Rectal temperatures of salicylate-treated and untreated rats were observed in 21-23 degrees C air at 1, 3, 6, and 8 ATA, in 21-23 degrees C helium at 1 and 6 ATA, and in 1 ATA thermal neutral air (28 degrees C). Significant dose-related temperature decreases occurred in 21-23 degrees C 1 ATA air with 180 and 300 mg/kg of salicylate; 60 mg/kg had no effect. However, in thermal neutral air, 300 mg/kg significantly elevated temperatures. Hyperbaric air and helium had temperature-lowering effects which were correlated with thermal properties of these environments, and in them the hypothermic effects of salicylate were similar to those in 1 ATA air, the total temperature decreases being the sum of the salicylate hypothermia and that caused by the hyperbaric air or helium. These additive temperature effects are unlike previously reported results in which the temperature lowering effects of 5 degrees C cold exposure and salicylate together were greater than the sum of the two individual effects.
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PMID:Salicylate hypothermia in rats exposed to hyperbaric air and helium. 119 49

Changes in total lung resistance (RL) during inhalation of cold gas mixtures were measured in 4 human volunteers during an experimental dive at 46 ATA. The subjects breathed helium-nitrogen-oxygen mixtures during the decompression schedule, and measurements were performed at 46, 36, 21, 12.5, 6 and 2 ATA (1 ATA = 100 kPa). RL was measured during eupneic ventilation when individuals inhaled either ambient gas at +30 to +33 degrees C (control condition), or cooled gas at +7 to +18 degrees C. RL values measured in control conditions increased with gas density. Thus, the changes in RL induced by cold gas breathing were expressed in percent of the corresponding control values. No cold-induced bronchospasm occurred at low ambient pressure, even at the lowest inspired temperature, +7 degrees C. However, the airway response was present at pressure up to 21 ATA and then occurred at higher level of inspired gas temperature. The convective respiratory heat loss (Cr), calculated at each pressure level and experimental condition, was linearly related to cold-induced changes in RL; the value of Cr inducing 20% increase in RL was around 1.4 kcal.min-1. The bronchomotor response was related to the increase in respiratory heat loss induced by the high thermal capacity of the gas mixture used in hyperbaric environment. The present observations confirm previous data obtained under hyperbaric conditions (25 ATA) as well some experiments performed at sea level in normal individuals breathing very cold air.
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PMID:Respiratory effects of cold-gas breathing in humans under hyperbaric environment. 225 97

Effects of inhalation of cold air or helium-oxygen mixture on lung resistance (RL) were studied in anesthetized and tracheotomized rabbits under normal ambient pressure and in human volunteers under normo- and hyperbaric conditions. In artificially ventilated rabbits, an increase in RL occurred when the tracheal temperature fell to 10 degrees C. This effect was more than double with helium breathing compared to air, despite a lower respiratory heat loss by convection (Hc) with helium. In 3 normal humans, inhalation of cold air (mouth temperature = 8 degrees C) at sea level had no effect on RL value. However, with a helium-nitrogen-oxygen mixture, a weak but significant increase in RL due to cold gas breathing was measured in 1 subject at 2 ATA and in 2 individuals at 3.5 ATA. The density of inhaled gas mixture (air or He-N2-O2) was near the same in the three circumstances (1, 2, and 3.5 ATA) but Hc value increased with helium. At 8 ATA a 30-55% increase in RL occurred in the 3 divers during inhalation of cold gas (Hc was multiplied by 6 compared to air at sea level) and at 25 ATA the cold-induced bronchospasm ranged between 38 and 95% (Hc multiplied by 27). Thus, in rabbits and humans helium breathing enhanced the cold-induced increase in RL at normal or elevated ambient pressure, and this effect was interpreted as resulting from different mechanisms in the two circumstances.
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PMID:Bronchomotor response to cold air or helium-oxygen at normal and high ambient pressures. 338 28


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