Environmental Symptoms Questionnaire Research Articles

Imparied insulin sensitivity in the early hours following either active or passive ascent to 3600m is associated with acute mountain sickness susceptibility

Reduced insulin sensitivity (a higher glucose level for the same insulin concentration) at baseline residence (BLR) has been associated with increased susceptibility to acute mountain sickness. (AMS) at high altitude (HA). The objective of this study was to determine whether fasting blood glucose (GLU), lactate (LAC) and insulin (INS) were impacted during an active versus passive ascent to 3600m in AMS-susceptible and AMS-resistant individuals. We hypothesized that insulin sensitivity would be reduced at BLR in the AMS-susceptible cohort based on previous research. To test this hypothesis, 78 active-duty Soldiers were tested at baseline residence (BLR), transported to Taos, New Mexico (2,845m), then hiked (n=39) or were driven (n=39) to 3600m, and stayed for four days. AMS-C was assessed using the Environmental Symptoms Questionnaire (ESQ) at HA twice on day 1, five times on days 2 and 3 and once on day 4. If AMS-C was ≥0.7 at any timepoint, individuals were categorized as AMS-susceptible (AMS+, n=33); others categorized as resistant (AMS−, n=45). Fasting rested blood GLU and LAC responses collected at 06:00 were measured using a blood gas analyzer and serum INS responses were measured using an ELISA assay at BLR, HA2 (14-h post-ascent), HA3 (38-h post ascent), and HA4 (62-h post ascent). An additional sample for blood GLU and LAC was collected on HA1 at 18:00 (2-h post ascent). As expected, the active compared to passive ascent group demonstrated an increase (p<0.05) in GLU (113.6±14.3 vs. 101.9±15.1) and LAC (2.56±0.93 vs. 1.73±0.78) on HA1 most likely due to sympathetic stimulation following active ascent. However, differences in fasting GLU and LAC between ascent groups did not persist on HA2 through HA4. There were also no ascent group differences INS in any of the conditions. Fasting GLU levels on HA2 were higher in the AMS+ vs. AMS− cohorts (99.8±9.8 vs 95.3±7.9 mg/dl; p<0.05) but fasting INS levels on HA2 did not differ between cohorts (9.8±5.4 vs.7.1±3.4 mIU/ml; p>0.05) indicating impaired insulin sensitivity in those susceptible to AMS early in the HA exposure. There were no differences, however, in GLU and INS levels between AMS+ vs. AMS− cohorts on BLR, HA3 or HA4. Fasting LAC also demonstrated no differences in any of the conditions in the active vs. passive ascent groups or AMS+ vs. AMS− cohorts. In conclusion, the increase in blood GLU and LAC at HA1 following active compared to passive ascent was expected. Contrary to our hypothesis, however, a reduction in insulin sensitivity was not found in AMS-susceptible individuals at BLR but was found at 14-h post ascent to 3600m and quickly resolved thereafter. The inability to effectively utilize glucose as an O2-effcient fuel in the early hours of HA exposure may contribute to AMS symptoms. USAMRDC. Authors’ views not offcial U.S. Army or DoD policy. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Elevated sympathoadrenal response following active ascent to 3,600m is not associated with acute mountain sickness

Previous reports have suggested an increase in plasma epinephrine (EPI) and either an increase, no change or decrease in norepinephrine (NE) following acute (< 4 h) exposure to high altitude (HA). In addition, previous research has demonstrated an exercise-induced increase in EPI and NE during exercise initiated following arrival at HA. Last, some but not others have reported an association between increased sympathoadrenal activity and acute mountain sickness (AMS). We hypothesized that elevated sympathoadrenal activity induced from active ascent on foot to 3,600m may contribute to the development of AMS. Thirty-seven Soldiers (mean ± SD; 6 women; age=25.5±4.9 years) were tested at their baseline residence (BLR; Fort Bliss, TX, 1,190m), transported to Taos, NM (2,845m), then hiked (n=18) or were driven (n=19) to the HA data collection site where they resided for four days (68hrs). AMS Cerebral Factor Score (AMS-C) was determined using the Environmental Symptoms Questionnaire (ESQ-III) recorded twice at HA on day 1 (HA1), five times on days 2 (HA2) and 3 (HA3) and once on day 4 (HA4). If AMS-C was ≥0.7 on any measurement occasion, individuals were categorized as AMS-susceptible (AMS+, n=11) others were AMS-resistant (AMS─, n=26). Plasma EPI (pg/ml) and NE (pg/ml) were measured from venous blood draws at 06:00 at BLR, a non-fasted blood draw at 18:00 following ascent on HA1, and subsequent fasted blood samples at 06:00 on each morning at HA (HA2, HA3, HA4). AMS-susceptibility was not associated with the EPI or NE response in any condition so both cohorts were combined. The EPI response to active vs. passive ascent was similar with an increase (p<0.05) from BLR (28.0±26.8) to HA1 (47.5±40.3) followed by a subsequent decrease (p<0.05) from HA1 to HA2 (28.0±18.6) through HA4 (25.4±16.9). NE, however, increased (p<0.05) only in the active ascent group from BLR (413±216) to HA1 (729±281) and remained stable from HA1 through HA4 (644±192). The passive ascent group demonstrated no change in NE from BLR (327±126) to HA1 (413±181) through HA4 (466±144). NE levels were similar (p>0.05) in the active vs passive ascent group at BLR but higher (p<0.05) in the active ascenders on HA1 through HA4. In conclusion, contrary to our hypothesis, the sympathoadrenal response to HA was not impacted by AMS susceptibility but active ascent induced a greater NE response following ascent and throughout the duration of the HA stay. USAMRDC. Authors’ views not offcial U.S. Army or DoD policy. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Pro- and Anti-Inflammatory Responses Following Active and Passive Ascent to 3600 m

Lowlanders who develop acute mountain sickness (AMS) following rapid ascent to high altitude (HA) demonstrate increased levels of both pro-inflammatory (tumor necrosis factor α (TNFα), Interleukin (IL)- 1β, IL-6, IL-8, and IL-17α) and anti-inflammatory biomarkers (IL-10 and IL-1 receptor agonist; IL-1ra). Whether ascending by self-locomotion (i.e., active ascent) modulates these pro- and anti-inflammatory cytokine responses at HA is unknown. We hypothesized a greater pro-inflammatory response in the AMS-susceptible group following active ascent. To test this hypothesis, 78 healthy Soldiers (mean±SD; age, 26±5yr) were tested at baseline residence (BLR), transported to Taos, NM (2845m), then hiked (n=39) or were driven (n=39) to HA (3600m), and stayed for 4 days. AMS-Cerebral factor score (AMS-C) was assessed using the Environmental Symptoms Questionnaire (ESQ) at HA twice on day 1 (HA1). If AMS-C was ≥0.7 at either assessment, individuals were categorized as AMS-susceptible (AMS+; n=24); others were AMS-resistant (AMS−; n=54). Fasting blood samples were taken at 06:00 at BLR, HA2, HA3 and HA4 and analyzed to determine cytokine (TNFα, IL-1β, IL-6, IL-8, IL-10, IL-17α, and IL-1ra) responses following the initial hypoxic insult. Blood values (pg/mL) were log-transformed and adjusted for plasma volume changes from BLR to HA. The active group expended a greater ( p<0.05) amount of energy (745±435 kcal) than the passive group (55±10 kcal) during ascent. There were no differences in biomarkers between ascent groups, so data were combined. In the AMS-susceptible group, IL-17α increased ( p<0.05) from BLR to HA2 (63.3±8.8 to 73.1±8.8, p=0.002) and remained increased at HA3 (70.1±8.8) and HA4 (73.1±8.8). In the AMS-resistant group, IL-17α did not change from BLR to any of the days at HA. Independent of AMS susceptibility, the anti-inflammatory marker IL-1ra increased from BLR to HA2 (63.5±11.4 to 89.9±11.4, p=0.013) and then fell back down to BLR values on HA3 (70.4±11.4, p=0.560) and HA4 (71.8±11.4, p=0.537). When all days were combined, TNFα (+15%, p=0.036), IL-6 (+50%, p=0.042), and IL-10 (+36%, p=0.040) were increased in the AMS-susceptible compared to the AMS-resistant group. IL-1β and IL-8 did not change ( p>0.05) from BLR to any time point at HA in either group. In conclusion, both a robust pro- (TNFα, IL-6, IL-17α) and anti-inflammatory (IL-10) response occurred at HA in those susceptible to AMS most likely due to inflammation following the initial hypoxic insult followed quickly by an anti-inflammatory response. However, ascent strategy on HA1 had no impact on pro- or anti-inflammatory cytokines on days 2-4 at HA. Authors’ views not offcial U.S. Army or DoD policy. Funding: USAMRDC. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Prevalence and knowledge about acute mountain sickness in the Western Alps.

To assess the prevalence of acute mountain sickness (AMS) in 1370 mountaineers at four different altitudes in the Western Alps. We also examined the influence of potential risk factors and the knowledge about AMS on its prevalence. In this observational cross-sectional study AMS was assessed on the day of ascent by the Lake Louise score (LLS, cut-off ≥3, version 2018) and the AMS-Cerebral (AMS-C) score of the environmental symptom questionnaire (cut-off ≥0,70). The latter was also obtained in the next morning. Knowledge regarding AMS and high-altitude cerebral edema (HACE) and the potential risk factors for AMS were evaluated by questionnaires. On the day of ascent, the prevalence of AMS assessed by the LLS and AMS-C score was 5.8 and 3.9% at 2850 m, 2.1 and 3.1% at 3050 m, 14.8 and 10.1% at 3650 m, and 21.9 and 15% at 4559 m, respectively. The AMS prevalence increased overnight from 10.1 to 14.5% and from 15 to 25.2% at 3650 m and 4559 m, respectively, and was unchanged at 2850 m and 3050 m. A history of AMS, higher altitude, lower degree of pre-acclimatization, and younger age were identified as risk factors for developing AMS. Slow ascent was weakly associated with AMS prevalence, and sex and knowledge about AMS and HACE were indistinct. AMS is common at altitudes ≥ 3650 m and better knowledge about AMS and HACE was not associated with less AMS in mountaineers with on average little knowledge.

Personal protective equipment for COVID-19 among healthcare workers in an emergency department: An exploratory survey of workload, thermal discomfort and symptoms of heat strain.

To examine workload, thermal discomfort and heat-related symptoms among healthcare workers (HCWs) in an Australian ED during the COVID-19 pandemic. A cross-sectional study design was employed among HCWs in an ED at a metropolitan hospital in Brisbane, Australia. Respondents provided demographic information including their self-reported age, sex, height, weight, role (e.g. doctor, nurse), and whether they wore personal protective equipment (PPE) during their shift, rated as either Full PPE, Partial PPE, or usual uniform or scrubs. The workload of HCWs was assessed with the National Aeronautics and Space Administration's task load index (NASA-TLX). Thermal discomfort was evaluated using scales from the International Organisation for Standardisation. Responders rated their subjective heat illness using the Environmental Symptoms Questionnaire. Fifty-nine HCWs completed the survey (27 male, 31 female, one prefer not to answer). Overall workload from the NASA-TLX was 64.6 (interquartile range [IQR] 56.5-73.3) for doctors, 72.5 (IQR 63.3-83.3) for nurses and 66.7 (IQR 58.3-74.17) for other staff, representing moderate to high ratings. Eighty-one percent reported thermal sensation to be slightly warm, warm, or hot, and 88% reported being uncomfortable, ranging from slightly to extremely. Ninety-seven percent reported at least one heat-strain symptom. More than 50% reported light-headedness or headache and approximately 30% reported feeling dizzy, faint, or weak. ED HCWs experience thermal discomfort when wearing PPE. Combined with their workloads, HCWs experienced symptoms related to heat strain. Therefore, careful consideration should be given to managing heat strain among HCWs when wearing PPE in an ED.

Rectal Temperature Cooling Using 2 Cold-Water Immersion Preparation Strategies.

Cold-water immersion (CWI) is essential to treat patients with exertional heatstroke (EHS). Experts recommend that patients with EHS be immersed in water between 1.7°C and 15°C within 30 minutes of collapse. Some clinicians fill cooling tubs several hours before exercise, keep the tub in hot conditions, and then add ice in the event of an EHS emergency. No data exist on whether adding ice to water at the time of treatment is as effective as keeping water in the recommended range. To (1) compare the cooling rates of individuals immersed in a water bath kept at 10°C (CON) or 17°C water with 75.7 L (20 gal) of ice added to it immediately upon immersion (ICE) and (2) examine perceptual responses before, during, and after cooling. Crossover study. Laboratory. Twelve individuals (7 men, 5 women; age = 22 ± 2 years, height = 176.0 ± 12.8 cm, mass = 74.5 ± 10.6 kg). Participants exercised in the heat until rectal temperature was 39.5°C. They then immersed themselves in CON (initial water volume = 681 ± 7.6 L, 10.0°C ± 0.03°C) or ICE (initial water volume = 605.7 ± 7.6 L water at 17.0°C ± 0.03°C with 75.7 L ice) until rectal temperature was 38°C. Thermal sensation and environmental symptoms questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling. Rectal temperature cooling rates, thermal sensation, ESQ responses. Participants exercised for similar durations (CON = 39.6 ± 18.2 minutes, ICE = 38.8 ± 14.3 minutes, Z11 = 0.94, P = .38) and had similar thermal sensation and ESQ scores immediately postexercise each day (P values > .05). They cooled quickly and at similar rates in both conditions (CON = 0.20°C ± 0.06°C/min, ICE = 0.21°C ± 0.12°C/min, t12 = 0.72, P = .49). Perception data were similar between conditions during and after cooling (P < .05). Clinicians can cool patients with EHS quickly by adding ice to water that has warmed to above expert recommendations. Adding ice to a water bath at the time of EHS emergencies could save time, energy, and resources instead of always maintaining water bath temperatures within expert-recommended ranges.

Excellent Rectal Temperature Cooling Rates in the Polar Life Pod Consistent With Stationary Tubs.

Several tools exist to reduce rectal temperature (TREC) quickly for patients experiencing exertional heatstroke (EHS). Stationary tubs effectively treat EHS but are bulky and impractical in some situations. More portable cold-water immersion techniques, such as tarp-assisted cooling with oscillation, are gaining popularity because of their benefits (eg, less water needed, portability). The Polar Life Pod (PLP) may be another portable way to reduce TREC, but few researchers have examined its effectiveness. To determine whether the PLP and stationary tub reduced TREC at acceptable or ideal rates, whether TREC cooling rates differed by method, and how participants felt before, during, and after cooling. Randomized crossover study. Laboratory. Thirteen individuals (8 men, 5 women; age = 21 ± 2 years, mass = 73.99 ± 11.24 kg, height = 176.2 ± 11.1 cm). Participants exercised in the heat until TREC was 39.5°C. They immersed themselves in either the PLP (202.7 ± 23.8 L, 3.2 ± 0.6°C) or a stationary tub (567.8 ± 7.6 L, 15.0 ± 0.1°C) until TREC was 38°C. Thermal sensation and environmental symptom questionnaire (ESQ) responses were recorded before, during, and after exercise and cooling. Rectal temperature cooling rates, thermal sensation, and ESQ responses. Participants had similar exercise durations (PLP = 41.6 ± 6.9 minutes, tub = 42.2 ± 9.3 minutes, t12 = 0.5, P = .31), thermal sensation scores (PLP = 7.0 ± 0.5, tub = 7.0 ± 0.5, P > .05), and ESQ scores (PLP = 25 ± 13, tub = 29 ± 14, P > .05) immediately postexercise each day. Although TREC cooling rates were excellent in both conditions, the PLP cooled faster than the stationary tub (PLP = 0.28 ± 0.09°C/min, tub = 0.20 ± 0.09°C/min, t12 = 2.5, P = .01). Thermal sensation in the PLP condition was lower than that in the tub condition halfway through cooling (PLP = 1 ± 1, tub = 2 ± 1, P < .05) and postcooling (PLP = 2 ± 1, tub = 3 ± 1, P < .05). The ESQ scores were higher for PLP than for the stationary tub postcooling (PLP = 25 ± 14, tub = 12 ± 9, P < .05). The PLP and the stationary tub cooled individuals with hyperthermia at ideal rates for treating patients with EHS (ie, >0.16°C/min). The PLP may be an effective tool for treating EHS when limited water volumes and portability are concerns. Clinicians should have rewarming tools and strategies (eg, heating blankets) available to improve patients' comfort after PLP use.

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

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 ≥ 0.7 indicated sickness. While sleeping for one night both at sea level (SL) and high altitude (HA), a wrist motion detector was used to measure awakenings (Awak, events/h) and sleep efficiency (Eff, %). If Eff was ≥85%, individuals were considered a good sleeper (Sleep+). Mood and cognition were assessed using the Automated Neuropsychological Assessment Metric and Mood Scale (ANAM‐MS). The ESQ and ANAM‐MS were administered in the morning both at SL and after 20 h at HA. AMS severity (mean ± SE; 1.82 ± 0.27 vs. 0.20 ± 0.27), AMS prevalence (90% vs. 10%), depression (0.63 ± 0.23 vs. 0.00 ± 0.24) Awak (15.6 ± 1.6 vs. 10.1 ± 1.6 events/h), and DeSHr (38.5 ± 6.3 vs. 13.3 ± 6.3 events/h) were greater (p < 0.05) and Eff was lower (69.9 ± 5.3% vs. 87.0 ± 5.3%) at 4050 m compared to 3000 m, respectively. AMS presence did not impact cognition but fatigue (2.17 ± 0.37 vs. 0.58 ± 0.39), anger (0.65 ± 0.25 vs. 0.02 ± 0.26), depression (0.63 ± 0.23 vs. 0.00 ± 0.24) and sleepiness (4.8 ± 0.4 vs. 2.7 ± 0.5) were greater (p < 0.05) in the AMS+ group. The Sleep− group, compared to the Sleep+ group, had lower (p < 0.05) working memory scores (50 ± 7 vs. 78 ± 9) assessed by the Sternberg 6‐letter memory task, and lower reaction time fatigue scores (157 ± 17 vs. 221 ± 22), assessed by the repeated reaction time test. Overall, AMS, depression, DeSHr, and Awak were increased (p < 0.05) at 4050 m compared to 3000 m. In addition, AMS presence impacted mood while poor sleep impacted cognition which may deteriorate teamwork and/or increase errors in judgement at HA.

Impact of 2 days of staging at 2500-4300m on sleep quality and quantity following subsequent exposure to 4300m.

The impact of 2 days of staging at 2500–4300 m on sleep quality and quantity following subsequent exposure to 4300 m was determined. Forty‐eight unacclimatized men and women were randomly assigned to stage for 2 days at one of four altitudes (2500, 3000, 3500, or 4300 m) prior to assessment on the summit of Pikes Peak (4300 m) for 2 days. Volunteers slept for one night at sea level (SL), two nights at respective staging altitudes, and two nights at Pikes Peak. Each wore a pulse oximeter to measure sleep arterial oxygen saturation (sSpO2, %) and number of desaturations (DeSHr, events/hr) and a wrist motion detector to estimate sleep awakenings (Awak, awakes/hr) and sleep efficiency (Eff, %). Acute mountain sickness (AMS) was assessed using the Environmental Symptoms Questionnaire and daytime SpO2 was assessed after AMS measurements. The mean of all variables for both staging days (STG) and Pikes Peak days (PP) was calculated. The sSpO2 and daytime SpO2 decreased (p < 0.05) from SL during STG in all groups in a dose‐dependent manner. During STG, DeSHr were higher (p < 0.05), Eff was lower (p < 0.05), and AMS symptoms were higher (p < 0.05) in the 3500 and 4300 m groups compared to the 2500 and 3000 m groups while Awak did not differ (p > 0.05) between groups. At PP, the sSpO2, DeSHr, Awak, and Eff were similar among all groups but the 2500 m group had greater AMS symptoms (p < 0.05) than the other groups. Two days of staging at 2500–4300 m induced a similar degree of sleep acclimatization during subsequent ascent to 4300 m but the 2500 m group was not protected against AMS at 4300 m.

Comparing Acute Mountain Sickness Definitions to Examine Differences in Systemic Inflammation

Acute mountain sickness (AMS) occurs when individuals rapidly ascend to high altitudes, but its exact cause remains unknown. Additionally, AMS is assessed using a subjective questionnaire with a variety of criteria used for diagnosis so there is no precise, objective method for determining if a subject has AMS. Hypoxia, or low oxygen, at altitude results in a proinflammatory state and AMS is associated with systemic inflammation as determined by elevated plasma levels of some cytokines. Thus, we wanted to determine if the association between AMS and inflammation was altered based on how AMS was defined. To examine this, 17 women and 17 men were exposed to 10 hours of normobaric hypoxia (11.5% O2) simulating 15600 feet. Blood samples taken before and at 10 hours of hypoxia were assayed for 13 inflammatory cytokines. AMS was defined by the following definitions: 1) Lake Louise Questionnaire (LLQ) score ≥3 and a headache score ≥1 at the 10-hour time point, 2) maximum LLQ score ≥3 and a maximum headache score of ≥1, 3) maximum LLQ score ≥3 and a maximum Environmental Symptoms Questionnaire (ESQ) score of 0.7 or maximum LLQ ≥3, a maximum headache score ≥2, and a maximum ESQ ≥0.4, 4) maximum LLQ ≥3, 5) LLQ score ≥3 at the 10-hour time point. We found that Interleukin (IL) 8 significantly increased in AMS- but not AMS+ participants regardless of AMS definition. Additionally, AMS- but not AMS+ participants significantly increased IL-1β and IL-33 concentration from baseline to 10 hours of hypoxia under only three out of the five definitions (#1, #3 & #5 above for IL-1β and #3, #4, & #5 above for IL-33). Furthermore, the change in IL-1β concentration after 10 hours of hypoxia was significantly different between AMS- and AMS+ participants under definition #3 above. These data suggest that how AMS is defined may influence whether or not there are differences in circulating inflammatory cytokines between those with and without AMS. Therefore, the relationship between systemic inflammation and AMS may be more complex than previously thought.

Measures Of Autonomic Cardiac Function Are Associated With Acute Mountain Sickness At High Altitude.

PURPOSE: Evidence suggests acute mountain sickness (AMS) aligns to heart rate variability (HRV) suppression at high altitude. This study explored associations between measures of autonomic cardiac function and AMS scores in normobaric hypoxia (NH) and during ascent to very high altitude in the natural environment. METHODS: Thirty participants (17 male and 13 female, aged 20-62 years) trekked from 2800m to 5350m (Himalaya, Nepal) over 14 days. Short term temporal and spectral measures of HRV were recorded at rest (paced breathing, 12 breaths per minute), in NH (FIO2=0.124, ~4100m) and in hypobaric hypoxia (HH) at 4356m and 5350m, during ascent. RMSSD and 60 second heart rate recovery (HRR60) following stepping exercise (3 min at 50-60% maximal aerobic capacity) were accepted measures of parasympathetic neural activity. The heart rate response (∆HR) to an orthostatic postural challenge (two minutes supine followed by two minutes standing), reflective of sympathetic neural activity, was measured at the same time points (∆HR = HR [peak stand] - HR [mean supine]). AMS diagnosis was confirmed for scores ≥ 5.0 (Lake Louise Survey, LLS) or ≥ 0.70 (Environmental Symptoms Questionnaire, ESQ-c) at least once during the ascent. Institutional ethical approval was gained. RESULTS: Data analysis reflects 24 participants. Eleven (46%) developed AMS. Peak LLS AMS scores ranged between 1-5, 0-10 and 2-11 units in the AMS group at 2800m, 4356m and 5350m respectively, and 0-4 for the non-AMS group. No significant interaction (P=0.161) nor a main effect for altitude (P=0.093) was observed, however a significantly greater LLS score was observed in the AMS group at 5300m (P<0.001). Peak LLS scores at 2800m correlated with RMSSD (NH) (r=.483, P=.020) and at 4300m correlated with RMSSD at 4300m (-.487, P=.025). Postural ∆HR at 2800m correlated significantly with the ESQ-c and peak LLS scores at 4300m (r=-.601, P=.002 and r=-.579, P=.004), and the ∆HR at 4300m correlated with ESQ-c and LLS scores at 4300m (r=.-570, P=.005 and r=-.471, P=.023). HRR60 (NH) correlated with LLS score at 4300 m and peak LLS score at this altitude (r=-.495, P=.026 and r=-.450, P=.047 respectively). CONCLUSION: AMS-susceptible individuals show vagal suppression at high altitude. Vagal measures may be useful indicators for AMS susceptibility at very high altitude.

Mood State Is Related To Acute Mountain Sickness At Both 3000m And 4050m Altitude

PURPOSE: The purpose of this study was to further explicate the relationship between changes in mood states, assessed using the Automated Neuropsychological Assessment Metrics Mood Scale (ANAM-MS), and severity of acute mountain sickness (AMS) without the confounding factors of acetazolamide, climbing rate and environmental conditions. METHODS: Nineteen healthy lowlanders (16 men, 3 women; mean±SE; 22 ±1yr, 76.6 ±3.1 kg, 173.2 ±2.1cm, 46.0 ±1.2 ml · kg−1 · min−1) were randomly exposed to either 3000m (526mmHg) or 4050m (460mmHg) in a hypobaric chamber for 20h. Seven mood states (anger, anxiety, happiness, fatigue, depression, restlessness, and vigor) were assessed using the ANAM-MS; a series of 42 questions answered on a 0-6 Likert Scale. AMS severity was assessed using the AMC-Cerebral Factor Score (AMS-C) of the Environmental Symptoms Questionnaire. Both tests were administered on 8 occasions at sea level (SL), and after 2h and 20h at each altitude (HA2 and HA20). The SL baseline scores for ANAM-MS and AMS-C were calculated as the mean of the 7th (morning) and 8th (afternoon) assessments. RESULTS: There were no differences between altitude groups in mood at SL, HA2 or HA20 so data were combined. There was differences between altitude groups in AMS-C score so data was analyzed separately. No mood state changed significantly from SL to HA2. However, fatigue and restlessness increased (P<0.05) from SL (0.57 ±0.13; 0.07 ±0.03) to HA20 (1.41 ±0.32; 0.52 ±0.20), respectively. In addition, vigor decreased (P<0.05) from SL (1.97 ±0.30) to HA20 (0.88 ±0.21). Happiness, anxiety, depression and anger did not change over time. AMS-C was elevated (P<0.05) at 4050m (1.82 ±0.27) compared to 3000m (0.22 ±0.29) at HA20. Restlessness (r=0.66; P=0.037) and anxiety (r=0.65; P=0.044) correlated with AMS-C at HA20 in the 4050m group. Fatigue (r=0.77; P<0.016) and anger (r=0.95; P=0.0001) correlated with AMS-C at HA20 in the 3000m group. CONCLUSION: ANAM-MS ratings of fatigue, restlessness and decreased vigor emerge as low as 3000m due to hypobaric hypoxia alone. Mood disturbances were related to AMS severity; subjects with the highest ratings of fatigue and anger at 3000m, and restlessness and anxiety at 4050m possessed the highest AMS-C scores in their respective groups. Authors’ views not official U.S. Army or DoD policy. Funding: USAMRDC

New metric of hypoxic dose predicts altitude acclimatization status following various ascent profiles.

Medical personnel need practical guidelines on how to construct high altitude ascents to induce altitude acclimatization and avoid acute mountain sickness (AMS) following the first night of sleep at high altitude. Using multiple logistic regression and a comprehensive database, we developed a quantitative prediction model using ascent profile as the independent variable and altitude acclimatization status as the dependent variable from 188 volunteers (147 men, 41 women) who underwent various ascent profiles to 4 km. The accumulated altitude exposure (AAE), a new metric of hypoxic dose, was defined as the ascent profile and was calculated by multiplying the altitude elevation (km) by the number of days (d) at that altitude prior to ascent to 4 km. Altitude acclimatization status was defined as the likely presence or absence of AMS after ~24 h of exposure at 4 km. AMS was assessed using the Cerebral Factor Score (AMS‐C) from the Environmental Symptoms Questionnaire and deemed present if AMS‐C was ≥0.7. Other predictor variables included in the model were age and body mass index (BMI). Sex, race, and smoking status were considered in model development but eliminated due to inadequate numbers in each of the ascent profiles. The AAE (km·d) significantly (P < 0.0001) predicted AMS in the model. For every 1 km·d increase in AAE, the odds of getting sick decreased by 41.3%. Equivalently, for every 1 km·d decrease in AAE, the odds of getting sick increased by 70.4%. Age and BMI were not significant predictors. The model demonstrated excellent discrimination (AUC = 0.83 (95% CI = 0.79–0.91) and calibration (Hosmer‐Lemeshow = 0.11). The model provides a priori estimates of altitude acclimatization status resulting from the use of various rapid, staged, and graded ascent profiles.

Precooling, Hyperthermia, and Postexercise Cooling Rates in Humans Wearing American Football Uniforms.

Exertional heatstroke is one of the leading causes of death in American football players. Precooling (PC) with whole-body cold-water immersion (CWI) may prevent severe hyperthermia and, possibly, exertional heatstroke. However, it is unknown how much PC delays severe hyperthermia when participants wear American football uniforms during exercise in the heat. Does PC alter the effectiveness of CWI once participants become hyperthermic or affect perceptual variables during exercise? We asked 3 questions: (1) Does PC affect how quickly participants become hyperthermic during exercise in the heat? (2) Does PC before exercise affect rectal temperature (Trec) cooling rates once participants become hyperthermic? (3) Does PC affect perceptual variables such as rating of perceived exertion (RPE), thermal sensation, and environmental symptoms questionnaire (ESQ) responses? Crossover study. Laboratory. Twelve physically active males (age = 24 ± 4 years, height = 181.8 ± 8.4 cm, mass = 79.9 ± 10.3 kg). On PC days, participants completed 15 minutes of CWI (9.98°C ± 0.04°C). They donned American football uniforms and exercised in the heat (temperature = 39.1°C ± 0.3°C, relative humidity = 36% ± 2%) until Trec was 39.5°C. While wearing equipment, they then underwent CWI until Trec was 38°C. Control-day procedures were the same except for the PC intervention. Rectal temperature, heart rate, thermal sensation, RPE, and ESQ responses were measured throughout testing. The duration of cold-water immersion was used in conjunction with Trec to calculate cooling rates. Precooling allowed participants to exercise 17.6 ± 3.6 minutes longer before reaching 39.5°C (t11 = 17.0, P < .001). Precooling did not affect postexercise CWI Trec cooling rates (PC = 0.18°C/min ± 0.06°C/min, control = 0.20°C/min ± 0.09°C/min; t11 = 0.9, P = .17); ESQ responses (F2,24 = 1.3, P = .3); or RPE (F2,22 = 2.9, P = .07). Precooling temporarily lowered thermal sensation (F3,26 = 21.7, P < .001) and heart rate (F3,29 = 21.0, P < .001) during exercise. Because PC delayed hyperthermia without negatively affecting perceptual variables or CWI effectiveness, clinicians may consider implementing PC along with other proven strategies for preventing heat illness (eg, acclimatization).

Cooling Rates of Hyperthermic Humans Wearing American Football Uniforms When Cold-Water Immersion Is Delayed.

Treatment delays can be contributing factors in the deaths of American football athletes from exertional heat stroke. Ideally, clinicians begin cold-water immersion (CWI) to reduce rectal temperature (Trec) to <38.9°C within 30 minutes of collapse. If delays occur, experts recommend Trec cooling rates that exceed 0.15°C/min. Whether treatment delays affect CWI cooling rates or perceptual variables when football uniforms are worn is unknown. To answer 3 questions: (1) Does wearing a football uniform and delaying CWI by 5 minutes or 30 minutes affect Trec cooling rates? (2) Do Trec cooling rates exceed 0.15°C/min when treatment delays have occurred and individuals wear football uniforms during CWI? (3) How do treatment delays affect thermal sensation and Environmental Symptoms Questionnaire responses? Crossover study. Laboratory. Ten physically active men (age = 22 ± 2 y, height = 183.0 ± 6.9 cm, mass = 78.9 ± 6.0 kg). On 2 days, participants wore American football uniforms and exercised in the heat until Trec was 39.75°C. Then they sat in the heat, with equipment on, for either 5 or 30 minutes before undergoing CWI (10.6°C ± 0.1°C) until Trec reached 37.75°C. Rectal temperature and CWI duration were used to calculate cooling rates. Thermal sensation was measured pre-exercise, postexercise, postdelay, and post-CWI. Responses to the Environmental Symptoms Questionnaire were obtained pre-exercise, postdelay, and post-CWI. The Trec cooling rates exceeded recommendations and were unaffected by treatment delays (5-minute delay = 0.20°C/min ± 0.07°C/min, 30-minute delay = 0.19°C/min ± 0.05°C/min; P = .4). Thermal sensation differed between conditions only postdelay (5-minute delay = 6.5 ± 0.6, 30-minute delay = 5.5 ± 0.7; P < .05). Environmental Symptoms Questionnaire responses differed between conditions only postdelay (5-minute delay = 27 ± 15, 30-minute delay = 16 ± 12; P < .05). Treatment delays and football equipment did not impair CWI's effectiveness. Because participants felt cooler and better after the 30-minute delay despite still having elevated Trec, clinicians should use objective measurements (eg, Trec) to guide their decision making for patients with possible exertional heat stroke.

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

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. 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. Half in each group participated in ∼3 hours of daily physical activity while half were sedentary. Women accounted for ∼25% of each group. AMS incidence was assessed using the Environmental Symptoms Questionnaire. AMS was classified as mild (≥0.7 and <1.5), moderate (≥1.5 and <2.6), and severe (≥2.6). While staging, the incidence of AMS was lower (p < 0.001) in the 2500 m (0%), 3000 m (13%), and 3500 m (40%) staged groups than the direct ascent control group (83%). After ascent to 4300 m, the incidence of AMS was lower in the 3000 m (43%) and 3500 m (40%) groups than the 2500 m group (67%) and direct ascent control (83%). Neither activity level nor sex influenced the incidence of AMS during further ascent to 4300 m. Two days of staging at either 3000 or 3500 m, with or without physical activity, reduced AMS during subsequent ascent to 4300 m but staging at 3000 m may be recommended because of less incidence of AMS.

Ginkgo biloba extract for prevention of acute mountain sickness: a systematic review and meta-analysis of randomised controlled trials

ObjectiveTrials of ginkgo biloba extract (GBE) for the prevention of acute mountain sickness (AMS) have been published since 1996. Because of their conflicting results, the efficacy of GBE remains unclear....

Effect of Acute, Subacute, and Repeated Exposure to High Altitude (5050 m) on Psychomotor Vigilance.

Aim: High altitude (HA) hypoxia may affect cognitive performance and sleep quality. Further, vigilance is reduced following sleep deprivation. We investigated the effect on vigilance, actigraphic sleep indices, and their relationships with acute mountain sickness (AMS) during very HA exposure, acclimatization, and re-exposure.Methods: A total of 21 healthy altitude-naive individuals (25 ± 4 years; 13 females) completed 2 cycles of altitude exposure separated by 7 days at low altitude (LA, 520 m). Participants slept at 2900 m and spent the day at HA, (5050 m). We report acute altitude exposure on Day 1 (LA vs. HA1) and after 6 days of acclimatization (HA1 vs. HA6). Vigilance was quantified by reaction speed in the 10-min psychomotor vigilance test reaction speed (PVT-RS). AMS was evaluated using the Environmental Symptoms Questionnaire Cerebral Score (AMS-C score). Nocturnal rest/activity was recorded to estimate sleep duration using actigraphy.Results: In Cycle 1, PVT-RS was slower at HA1 compared to LA (4.1 ± 0.8 vs. 4.5 ± 0.6 s-1, respectively, p = 0.029), but not at HA6 (4.6 ± 0.7; p > 0.05). In Cycle 2, PVT-RS at HA1 (4.6 ± 0.7) and HA6 (4.8 ± 0.6) were not different from LA (4.8 ± 0.6, p > 0.05) and significantly greater than corresponding values in Cycle 1. In both cycles, AMS scores were higher at HA1 than at LA and HA6 (p < 0.05). Estimated sleep durations (TST) at LA, 1st and 5th nights were 431.3 ± 28.7, 418.1 ± 48.6, and 379.7 ± 51.4 min, respectively, in Cycle 1 and they were significantly reduced during acclimatization exposures (LA vs. 1st night, p > 0.05; LA vs. 5th night, p = 0.012; and 1st vs. 5th night, p = 0.054). LA, 1st and 5th nights TST in Cycle 2 were 477.5 ± 96.9, 430.9 ± 34, and 341.4 ± 32.2, respectively, and we observed similar deteriorations in TST as in Cycle 1 (LA vs. 1st night, p > 0.05; LA vs. 5th night, p = 0.001; and 1st vs. 5th night, p < 0.0001). At HA1, subjects who reported higher AMS-C scores exhibited slower PVT-RS (r = -0.56; p < 0.01). Subjects with higher AMS-C scores took longer time to react to the stimuli during acute exposure (r = 0.62, p < 0.01) during HA1 of Cycle 1.Conclusion: Acute exposure to HA reduces the PVT-RS. Altitude acclimatization over 6 days recovers the reaction speed and prevents impairments during subsequent altitude re-exposure after 1 week spent near sea level. However, acclimatization does not lead to improvement in total sleep time during acute and subacute exposures.

Electronic Nose Technology Fails to Sniff Out Acute Mountain Sickness.

The aim of the study was to evaluate whether an electronic nose can discriminate between individuals with and without acute mountain sickness (AMS) following rapid ascent to 4554 m. We recruited recreational climbers (19 women, 82 men; age 35 ± 10 years, mean ± standard deviation [SD]) upon arrival at 4554 m (Capanna Regina Margherita, Italy) for a proof of concept study. AMS was assessed with the Lake Louise self-report score (LLSRS) and the abbreviated Environmental Symptoms Questionnaire (ESQc); scores ≥3 and ≥0.7 were considered AMS, respectively. Exhaled air was analyzed with an electronic nose (Aeonose; The eNose Company, Netherlands). The collected data were analyzed using an artificial neural network. AMS prevalence was 44% with the LLSRS (mean score of those sick 4.4 ± 1.4 [SD]) and 20% with the ESQc (1.2 ± 0.5). The electronic nose could not discriminate between AMS and no AMS (LLSRS p = 0.291; ESQc p = 0.805). The electronic nose technology utilized in this study could not discriminate between climbers with and without symptoms of AMS in the setting of an acute exposure to an altitude of 4554 m. At this stage, we cannot fully exclude that this technology per se is not able to discriminate for AMS. The quest for objective means to diagnose AMS thus continues.

Temperate-Water Immersion as a Treatment for Hyperthermic Humans Wearing American Football Uniforms.

Cold-water immersion (CWI; 10°C) can effectively reduce body core temperature even if a hyperthermic human is wearing a full American football uniform (PADS) during treatment. Temperate-water immersion (TWI; 21°C) may be an effective alternative to CWI if resources for the latter (eg, ice) are unavailable. To measure rectal temperature (Trec) cooling rates, thermal sensation, and Environmental Symptoms Questionnaire (ESQ) scores of participants wearing PADS or shorts, undergarments, and socks (NOpads) before, during, and after TWI. Crossover study. Laboratory. Thirteen physically active, unacclimatized men (age = 22 ± 2 years, height = 182.3 ± 5.2 cm, mass = 82.5 ± 13.4 kg, body fat = 10% ± 4%, body surface area = 2.04 ± 0.16 m2). Participants exercised in the heat (40°C, 50% relative humidity) on 2 days while wearing PADS until Trec reached 39.5°C. Participants then underwent TWI while wearing either NOpads or PADS until Trec reached 38°C. Thermal sensation and ESQ responses were collected at various times before and after exercise. Temperate-water immersion duration (minutes), Trec cooling rates (°C/min), thermal sensation, and ESQ scores. Participants had similar exercise times (NOpads = 38.1 ± 8.1 minutes, PADS = 38.1 ± 8.5 minutes), hypohydration levels (NOpads = 1.1% ± 0.2%, PADS = 1.2% ± 0.2%), and thermal sensation ratings (NOpads = 7.1 ± 0.4, PADS = 7.3 ± 0.4) before TWI. Rectal temperature cooling rates were similar between conditions (NOpads = 0.12°C/min ± 0.05°C/min, PADS = 0.13°C/min ± 0.05°C/min; t12 = 0.82, P = .79). Thermal sensation and ESQ scores were unremarkable between conditions over time. Temperate-water immersion produced acceptable (ie, >0.08°C/min), though not ideal, cooling rates regardless of whether PADS or NOpads were worn. If a football uniform is difficult to remove or the patient is noncompliant, clinicians should begin water-immersion treatment with the athlete fully equipped. Clinicians should strive to use CWI to treat severe hyperthermia, but when CWI is not feasible, TWI should be the next treatment option because its cooling rate was higher than the rates of other common modalities (eg, ice packs, fanning).