Acute mountain sickness and sleep disturbances differentially influence cognition and mood during rapid ascent to 3000 and 4050 m.

The impact of acute mountain sickness (AMS) and sleep disturbances on mood and cognition at two altitudes relevant to the working and tourist population is unknown. Twenty unacclimatized lowlanders were exposed to either 3000 m (n = 10; 526 mmHg) or 4050 m (n = 10; 460 mmHg) for 20 h in a hypobaric chamber. AMS prevalence and severity was assessed using the Environmental Symptoms Questionnaire (ESQ) and an AMS-C score ≥ 0.

Acute Mountain Sickness is Reduced Following 2 Days of Staging During Subsequent Ascent to 4300 m.

Objective: To determine whether 2 days of staging at 2500-3500 m, combined with either high or low physical activity, reduces acute mountain sickness (AMS) during subsequent ascent to 4300 m.

Methods: Three independent groups of unacclimatized men and women were staged for 2 days at either 2500 m (n = 18), 3000 m (n = 16), or 3500 m (n = 15) before ascending and living for 2 days at 4300 m and compared with a control group that directly ascended to 4300 m (n = 12). All individuals departed to the staging altitudes or 4300 m after spending one night at 2000 m during which they breathed supplemental oxygen to simulate sea level conditions.

Is normobaric hypoxia an effective treatment for sustaining previously acquired altitude acclimatization?

This study examined whether normobaric hypoxia (NH) treatment is more efficacious for sustaining high-altitude (HA) acclimatization-induced improvements in ventilatory and hematologic responses, acute mountain sickness (AMS), and cognitive function during reintroduction to altitude (RA) than no treatment at all. Seventeen sea-level (SL) residents (age = 23 ± 6 yr; means ± SE) completed in the following order: ) 4 days of SL testing; ) 12 days of HA acclimatization at 4,300 m; ) 12 days at SL post-HA acclimatization (Post) where each received either NH ( = 9, [Formula: see text] = 0.122) or Sham ( = 8; [Formula: see text] = 0.

Effect of hypohydration and altitude exposure on aerobic exercise performance and acute mountain sickness.

Hypoxia often causes body water deficits (hypohydration, HYPO); however, the effects of HYPO on aerobic exercise performance and prevalence of acute mountain sickness (AMS) at high altitude (ALT) have not been reported. We hypothesized that 1) HYPO and ALT would each degrade aerobic performance relative to sea level (SL)-euhydrated (EUH) conditions, and combining HYPO and ALT would further degrade performance more than one stressor alone; and 2) HYPO would increase the prevalence and severity of AMS symptoms. Seven lowlander men (25 ± 7 yr old; 82 ± 11 kg; mean ± SD) completed four separate experimental trials.

Evaluation of two cold thermoregulatory models for prediction of core temperature during exercise in cold water.

Cold thermoregulatory models (CTM) have primarily been developed to predict core temperature (T(core)) responses during sedentary immersion. Few studies have examined their efficacy to predict T(core) during exercise cold exposure. The purpose of this study was to compare observed T(core) responses during exercise in cold water with the predicted T(core) from a three-cylinder (3-CTM) and a six-cylinder (6-CTM) model, adjusted to include heat production from exercise.

Cognitive, psychomotor, and physical performance in cold air after cooling by exercise in cold water.

Introduction: This study evaluated performance after lowering core temperature at different rates while local tissues were either cooled (lower body) or not cooled (upper body).

Methods: There were 10 men who volunteered to perform up to 8 cold water immersions (CWI) at combinations of 2 water temperatures (10 degrees C and 15 degrees C), 2 depths [waist (W), chest (C)], and 2 walking speeds (0.44 or 0.

Dietary tyrosine benefits cognitive and psychomotor performance during body cooling.

Supplemental tyrosine is effective at limiting cold-induced decreases in working memory, presumably by augmenting brain catecholamine levels, since tyrosine is a precursor for catecholamine synthesis. The effectiveness of tyrosine for preventing cold-induced decreases in physical performance has not been examined. This study evaluated the effect of tyrosine supplementation on cognitive, psychomotor, and physical performance following a cold water immersion protocol that lowered body core temperature.

Heart rate variability and electrocardiogram waveform as predictors of morbidity during hypothermia and rewarming in rats.

This study examined electrocardiogram (ECG) waveform, heart rate (HR), mean blood pressure (BP), and HR variability as potential autonomic signatures of hypothermia and rewarming. Adult male Sprague-Dawley rats had telemetry transmitters surgically implanted, and 2 weeks were allowed for recovery prior to induction of hypothermia. Rats were lightly anesthetized (sodium pentobarbital, 35 mg/kg i.

Tissue-specific extravasation of albumin-bound Evans blue in hypothermic and rewarmed rats.

The effects of hypothermia and rewarming on endothelial integrity were examined in intestines, kidney, heart, gastrocnemius muscle, liver, spleen, and brain by measuring albumin-bound Evans blue loss from the vasculature. Ten groups of twelve rats, normothermic with no pentobarbital, normothermic sampled at 2, 3, or 4 h after pentobarbital, hypothermic to 20, 25, or 30 degrees C, and rewarmed from 20, 25, or 30 degrees C, were cooled in copper coils through which water circulated. Hypothermic rats were cooled to the desired core temperature and maintained there for 1 h; rewarmed rats were cooled to the same core temperatures, maintained there for 1 h, and then rewarmed.

Treatment of hyperthermia-induced extravasation with hypertonic saline (7.5%) in 6% dextran 70 (HSD) in Wistar/Furth rats.

This study determined the effectiveness of hypertonic saline (7.5%) in 6% Dextran 70 (HSD) in reducing hyperthermia-induced extravasation in Wistar/Furth (WF) rats and compared this extravasation with that previously reported in Sprague-Dawley (SD) rats. Wistar/Furth rats (male, n = 12/group, 300-325 g) were placed unrestrained in a chamber (41.

Flunarizine pretreatment attenuates hyperthermia-induced extravasation in rats.

Previous work has established that there is an increase in endothelial permeability in hyperthermic rats. This work assessed the potential of the calcium channel blocker (E)-1-bis(4-fluorophenyl)methyl-4-(3-phenyl-2-propenyl)piperazine dihydrochloride (flunarizine) as a pretreatment to ameliorate this extravasation. Five groups of male rats (n=12 rats per group, 400-500 g) were given 0, 0.

Effect of nitric oxide synthase inhibition on regional blood flow during hyperthermia.

The loss of compensatory splanchnic vasoconstriction during hyperthermia was assessed in rats after administration of either 0, 10, 30, or 100mg/kg N(w)-nitro-L-arginine methyl ester,L-NAME. Rectal temperature (T(re)), heart rate (HR), mean arterial blood pressure (MAP), breathing frequency (BF), and renal, mesenteric and caudal blood flows (Q(R), Q(M) and Q(C)) were measured until irreversible cardiovascular collapse occurred. HR, MAP and BF increased as T(re) rose to 42 degrees C, then fell as circulatory collapse occurred.

Hyperthermic effects on reticuloendothelial system particulate uptake.

Reticuloendothelial system (RES) particulate uptake (PU) of vascular debris influences survival from extreme hyperthermia. Little is known of the effect of extreme hyperthermia, unrelated to fever, on RES PU shortly after reaching a maximum core temperature (T(c)). Relative to normothermic rats (T(c)=38.

Hyperthermia-induced changes in the vascular permeability of rats: a model system to examine therapeutic interventions.

Extravasation in the heart, liver, lung, kidney, spleen, gastrocnemius, and duodenum was quantified in normothermic and hyperthermic (core temperature (T(c))=41.5, 42, or 42.6 degrees C) rats.

Effects of almitrine bismesylate in a microswine model of hypoxemic hypothermia.

We have developed an anesthetized microswine model of hypoxemic hypothermia and rewarming for testing prophylaxes and treatments. The respiratory stimulant almitrine bismesylate (ALM) was considered as a potential field expedient therapy for hypoxemic hypothermia. Preliminary experiments demonstrated that five consecutive 100 micrograms.

A miniswine model of acute exertional heat exhaustion.

Method: We examined the thermoregulatory and hemodynamic responses of 12 miniswine (31 +/- 3.9 kg) during 25-30 min of treadmill exercise (5.4 km.

Splenic effects on hemodynamics induced by hypothermia and rewarming in miniature swine.

Central arterial hemodynamic changes were assessed during cooling, hypothermia, and rewarming in splenectomized (SPX, n = 4) and unsplenectomized (SP, n = 4) 8-10 month old male Yucatan miniature swine (34.0 +/- 1.4 kg).

Chronic implantation of nonocclusive catheters and flow probes in the splanchnic and hindlimb vasculature of the rabbit.

Flow probes and nonocclusive catheters were simultaneously implanted in the splanchnic and hindlimb vasculature to measure regional blood flows and arteriovenous differences of individual organs in the conscious rabbit. Pulsed Doppler flow probes were constructed by modifying the technique of Haywood et al., and nonocclusive catheters were designed and constructed from Silastic tubing (0.

Effects of exercise modality on patterns of ventilation and respiratory timing.

Ventilatory patterns and respiratory timing were measured in 14 subjects during cycling (CYC) and treadmill exercise (TM) at similar leg frequencies (fLEG) to determine if mode of exercise affects patterns of ventilation and respiratory timing. Measurements of breathing frequency (fR), tidal volume (VT), expired ventilation (VE), and inspiratory (TI) and expiratory (TE) time were obtained at fLEG of 50, 70, and 90 rev.min-1 (rpm) for CYC and at similar incremental fLEG (strides.

Fluid-electrolyte losses in uniforms during prolonged exercise at 30 degrees C.

The effects of several uniform configurations on fluid and electrolyte losses in a hot environment (30 degrees C db, 18 degrees C wb) were studied in 15 healthy males, during 6 h of intermittent treadmill exercise (1.56 m.s-1, 0% grade, 50 min.

Incidence of hypohydration when consuming carbohydrate-electrolyte solutions during field training.

Carbohydrate-electrolyte solutions (CE1, CE2) were evaluated for their ability to reduce the incidence of hypohydration during field training in hot weather (max Tamb = 88 degrees-100 degrees F). Hydration status was monitored twice daily in Army reservists who consumed ad libitum CE1, or CE2, or water, or a flavored water placebo. The water group had the highest percentage incidence of urine specific gravity greater than or equal to 1.

Prediction of the exercise-heat tolerance of soldiers wearing protective overgarments.

The purpose of this investigation was to see whether subject characteristics and physiologic measurements predicted exercise-heat tolerance (EHT) and voluntary tolerance time in young soldiers. A total of 18 unacclimatized males attempted six 50-min periods of treadmill walking (4.0 km.

Patterns of human drinking: effects of exercise, water temperature, and food consumption.

The effects of exercise, water temperature, and food consumption on patterns of ad libitum drinking were studied in 33 men during 6 consecutive cycles of 30 min walking (4.8 km.h-1, 5% grade) and 30 min rest in a climatic chamber (40 degrees C, 40% relative humidity).

Plasma renin activity and aldosterone: correlations with moderate hypohydration.

Adult male test subjects (n = 16) were assigned to one of three clothing configurations (Army fatigues, fatigues with impermeable chemical protective garments, and fatigues with protective garments plus protective masks) prior to exercise (level treadmill, 1.11 m/s, 50 min/h, 6 h) in a moderate (wet bulb globe temperature, WBGT = 23 degrees C) environment with ad lib water consumption. When protective masks were worn, two through-mask drinking systems were evaluated: the current gravity-fed system for fluid delivery and a new system utilizing a small hydraulic pump (Fist-Flex).