Roach, Robert C., Peter H. Hackett, Oswald Oelz, Peter Bärtsch, Andrew M. Luks, Martin J. MacInnis, J. Kenneth Baillie, and The Lake Louise AMS Score Consensus Committee. The 2018 Lake Louise Acute Mountain Sickness Score. High Alt Med Biol 19:1–4, 2018.— The Lake Louise Acute Mountain Sickness (AMS) scoring system has been a useful research tool since first published in 1991. Recent studies have shown that disturbed sleep at altitude, one of the five symptoms scored for AMS, is more likely due to altitude hypoxia per se, and is not closely related to AMS. To address this issue, and also to evaluate the Lake Louise AMS score in light of decades of experience, experts in high altitude research undertook to revise the score. We here present an international consensus statement resulting from online discussions and meetings at the International Society of Mountain Medicine World Congress in Bolzano, Italy, in May 2014 and at the International Hypoxia Symposium in Lake Louise, Canada, in February 2015. The consensus group has revised the score to eliminate disturbed sleep as a questionnaire item, and has updated instructions for use of the score.
Karl, J. Philip, Renee E. Cole, Claire E. Berryman, Graham Finlayson, Patrick N. Radcliffe, Matthew T. Kominsky, Nancy E. Murphy, John W. Carbone, Jennifer C. Rood, Andrew J. Young, and Stefan M. Pasiakos. Appetite suppression and altered food preferences coincide with changes in appetite-mediating hormones during energy deficit at high altitude, but are not affected by protein intake. High Alt Med Biol. 19:156–169, 2018.—Anorexia and unintentional body weight loss are common during high altitude (HA) sojourn, but underlying mechanisms are not fully characterized, and the impact of dietary macronutrient composition on appetite regulation at HA is unknown. This study aimed to determine the effects of a hypocaloric higher protein diet on perceived appetite and food preferences during HA sojourn and to examine longitudinal changes in perceived appetite, appetite mediating hormones, and food preferences during acclimatization and weight loss at HA. Following a 21-day level (SL) period, 17 unacclimatized males ascended to and resided at HA (4300 m) for 22 days. At HA, participants were randomized to consume measured standard-protein (1.0 g protein/kg/d) or higher protein (2.0 g/kg/d) hypocaloric diets (45% carbohydrate, 30% energy restriction) and engaged in prescribed physical activity to induce an estimated 40% energy deficit. Appetite, food preferences, and appetite-mediating hormones were measured at SL and at the beginning and end of HA. Diet composition had no effect on any outcome. Relative to SL, appetite was lower during acute HA (days 0 and 1), but not different after acclimatization and weight loss (HA day 18), and food preferences indicated an increased preference for sweet- and low-protein foods during acute HA, but for high-fat foods after acclimatization and weight loss. Insulin, leptin, and cholecystokinin concentrations were elevated during acute HA, but not after acclimatization and weight loss, whereas acylated ghrelin concentrations were suppressed throughout HA. Findings suggest that appetite suppression and altered food preferences coincide with changes in appetite-mediating hormones during energy deficit at HA. Although dietary protein intake did not impact appetite, the possible incongruence with food preferences at HA warrants consideration when developing nutritional strategies for HA sojourn.
Lundeberg, Jenny, John R. Feiner, Andrew Schober, Jeffrey W. Sall, Helge Eilers, and Philip E. Bickler. Increased cytokines at high altitude: lack of effect of ibuprofen on acute mountain sickness, physiological variables or cytokine levels. High Alt Med Biol. 19:249–258, 2018. Introduction: There is no consensus on the role of inflammation in high-altitude acclimatization. Aims: To determine the effects of a nonsteroidal anti-inflammatory drug (ibuprofen 400 mg every 8 hours) on blood cytokines, acclimatization, acute mountain sickness (AMS, Lake Louise Score), and noninvasive oxygenation in brain and muscle in healthy volunteers. Materials and Methods: In this double-blind study, 20 volunteers were randomized to receive ibuprofen or placebo at sea level and for 48 hours at 3800 m altitude. Arterial, brain, and leg muscle saturation with near infrared spectroscopy, pulse oximetry, and heart rate were measured. Blood samples were collected for cytokine levels and cytokine gene expression. Results: All of the placebo subjects and 8 of 11 ibuprofen subjects developed AMS at altitude ( p = 0.22, comparing placebo and ibuprofen). On arrival at altitude, the oxygen saturation as measured by pulse oximetry (S p O 2 ) was 84.5% ± 5.4% (mean ± standard deviation). Increase in blood interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels occurred comparably in the placebo and ibuprofen groups (all not significant, univariate test by Wilcoxon rank sum). Increased IL-6 was associated with higher AMS scores ( p = 0.002 by Spearman rank correlation). However, we found no difference or association in AMS score and blood or tissue oxygenation between the ibuprofen and placebo groups. Conclusions: We found that ibuprofen, at the package-recommended adult dose, did not have a significant effect on altitude-related increases in cytokines, AMS scores, blood, or tissue oxygenation in a population of healthy subjects with a high incidence of AMS.
To compare a program based on intermittent hypoxia-hyperoxia training (IHHT) consisting of breathing hypoxic-hyperoxic gas mixtures while resting to a standard exercise-based rehabilitation program with respect to cardiorespiratory fitness (CRF) in older, comorbid cardiac outpatients. Thirty-two cardiac patients with comorbidities were randomly allocated to IHHT and control (CTRL) groups. IHHT completed a 5-week program of exposure to hypoxia-hyperoxia while resting, CTRL completed an 8-week tailored exercise program, and participants in the CTRL were also exposed to sham hypoxia exposure. CRF and relevant hematological biomarkers were measured at baseline and after treatment in both groups. After intervention, CRF in the IHHT group was not significantly different (n = 15, 19.9 ± 6.1 mlO minutes kg ) compared with the CTRL group (n = 14, 20.6 ± 4.9 mlO minutes kg ). CRF in IHHT increased significantly from baseline (6.05 ± 1.6 mlO minutes kg ), while no difference was found in CTRL. Systolic and diastolic blood pressures were not significantly different between groups after treatment. Hemoglobin content was not significantly different between groups. Erythrocytes and reticulocytes did not change pre/post interventions in both experimental groups. IHHT is safe in patients with cardiac conditions and common comorbidities and it might be a suitable option for older patients who cannot exercise. A 5-week IHHT is as effective as an 8-week exercise program in improving CRF, without hematological changes. Further studies are needed to clarify the nonhematological adaptations to short, repeated exposure to normobaric hypoxia-hyperoxia.
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.
Promising benefits on cardiometabolic risk factors have been reported with prolonged programs of cyclic hypoxia. The aim of this study was to examine whether cyclic hypoxia exposure while exercising through two protocols of high-intensity interval training in overweight/obese women is more effective to improve cardiometabolic risk markers than exercising in normoxia. Participants included 86 overweight/obese women, who started a 12-week program of 36 sessions, and were randomly divided into four groups: (1) interval training in hypoxia (IHT; FIO = 17.2%; n = 13), (2) interval training in normoxia (INT; n = 15), which included 3-minute high-intensity exercise (90% Wmax) followed by 3 minutes of active recovery (55%-65% Wmax), (3) repeated-sprint training in hypoxia (RSH; FIO = 17.2%; n = 15), and (4) repeated-sprint training in normoxia (RSN; n = 18), which included 30 seconds of all-out effort (130% Wmax) followed by 3 minutes of active recovery (55%-65% Wmax). Body composition, anthropometric, biochemical, and clinical parameters were assessed at baseline (A), after 18 training sessions (B), and during the 7 days after the last session (C). IHT and RSH showed a significant (p < 0.001 and p = 0.016, respectively) decrease in the waist circumference at both B and C assessments compared with A. Hypoxia groups presented a significant reduction in the percentage of trunk fat with a moderate effect size (IHT: d = 0.56; RSH: d = 0.93). In the normoxia groups, total cholesterol (CHOL) tended to decrease (INT: -4.21% and RSN: -5.18%), whereas it tended to increase in the hypoxia groups (IHT: +2.91% and RSH +4.07%). An interaction effect between conditions (through pooled data) on waist circumference (p = 0.01), percentage of trunk fat mass (p < 0.001), and CHOL (p = 0.019) was observed. Both training regimens under normobaric cyclic hypoxia were more effective at causing decreased abdominal fat in overweight/obese women than the same protocols in normoxia.
We sought to characterize the mental health morbidity associated with avalanche rescue, and to generate hypotheses as to how such morbidity may be mitigated. Avalanche first responders were recruited through online advertisements, social media, direct outreach, and e-mail solicitation. Thirteen subjects were selected for inclusion. Each subject participated in a semistructured interview. Transcripts were coded and thematically analyzed. Themes identified from interviews fell into three broad categories: long-term effects of rescue participation, assessments of psychological support, and recommendations for change. Symptoms of substance use disorder, depression, anxiety, panic, acute stress disorder, and posttraumatic stress disorder were evident in the interviews, as was evidence of adverse effects on subjects' personal relationships. Many respondents described a deficiency of formal psychological support for avalanche first responders, often limited to after-action debriefs of varying effectiveness. Nevertheless, subjects who received high-quality professional psychological support considered it helpful. Participants' suggestions for improvement focused on formalizing preincident psychological preparation and postincident support. Avalanche responders may experience long-lasting, work-related psychological effects. There is a paucity of effective psychological preparation and support for this population of first responders. Formal psychological support is positively received when available. Further study is required to evaluate particular interventions in this specific population.
High-altitude (HA) pregnancies have been associated with decreased glucose levels and increased insulin sensitivity versus sea level. Our objective was to determine if the prevalence of gestational diabetes mellitus (GDM) and the impact of demographic characteristics on GDM diagnosis differed at moderate altitude (MA) versus HA. Using a retrospective cohort design, we compared women living at HA (>8250 ft) and MA (4000-7000 ft) during pregnancy. Exclusion criteria were as follows: multiple gestation, preexisting diabetes, unavailable GDM results, or relocation from a different altitude during pregnancy. GDM diagnosis was determined using Carpenter and Coustan criteria. Data were compared by t-test (continuous variables) or chi-squared tests (categorical variables). Univariate, multivariate, and stepwise regression models were used to assess the impact of various factors on GDM prevalence. There was no difference in GDM prevalence between altitudes in these populations; the relationship between altitude and GDM was nonsignificant in all regression analyses. At MA, maternal age, Hispanic ethnicity, body mass index (BMI), and gestational age (GA) at testing increased GDM incidence in univariate analyses. At HA, maternal age, Hispanic ethnicity, and multiparity increased GDM incidence in univariate analyses. While GDM prevalence did not differ between MA and HA, the impact of maternal demographic characteristics on GDM risk varied by altitude group. Higher BMI and greater GA at testing increased the incidence of GDM at MA, but not at HA. Multiparity had an effect at HA, but not MA. These differences may represent subtle differences in glucose metabolism at HA.
Frostbite and other cold-related injuries commonly develop during prolonged exposure to the low environmental temperatures of polar and mountainous regions. Hypoxia is a potent sympathetic stimulus that causes vasoconstriction of the peripheral blood vessels, which may further compound the risk of developing a cold-related injury during high-altitude exposure. To investigate this, we utilized portable infrared thermographic technology to quantitatively measure changes in the surface temperature of the hands during exposure to increasing levels of normobaric hypoxia in a temperature-controlled high-altitude simulation. Surface temperature was assessed at four anatomical locations on both the left and right hands in a cohort of 10 healthy male participants at a series of predetermined levels of hypoxia (0.20 fraction of inspired oxygen [FIO2] [pre- and postexposure], 0.172 FIO2, 0.145 FIO2, 0.128 FIO2). Thermographic analysis revealed an overall decrease in peripheral temperature across the anatomical regions of the hands as the hypoxic stimulus increased, with statistically significant reductions observed at all four anatomical sites during exposure to 0.128 FIO2 (p < 0.05). These findings demonstrate that portable infrared thermography can be used to detect reductions in peripheral surface body temperature during exposure to normobaric hypoxia.
The present study was designed to define the hemoglobin [Hb] increase with altitude in Peruvian children. We suggest the normal range of [Hb] as means ±2 standard deviations (SD), with a value less than - 2 SD as a possible threshold to detect anemia. The prevalence of anemia was calculated. These values were compared to the World Health Organization (WHO) altitude correction parameter and the threshold for anemia of 11 g/dL. Likewise, polycythemia is suggested as [Hb] greater than 2 SD. 2,028,701 children aged 6–59 months were analyzed. The quadratic regression analysis shows that [Hb] is constant between sea level and 999 m. Thereafter, [Hb] increases from 11.32 g/dL (1000 m) up to ∼14.54 g/dL at 4000 m. Applying the threshold for anemia defined by WHO (11 g/dL) results in a prevalence of ∼35% for children living at altitudes 4000 m. After [Hb] altitude correction, the prevalence was ∼36% (1000 m) and increases to ∼66% above 4000 m. With our proposed threshold for anemia, the prevalence was ∼15% below 1000 m and ∼5% above 4000 m. For polycythemia ([Hb] >14.5 g/dL), increases were from 1.2% at 19 g/dL shows the highest values at 4000 m, while polycythemia defined as [Hb] greater than 2 SD was reduced at high altitude (HA). In conclusion, using WHO thresholds for anemia and [Hb] correction by altitude most likely overestimates the prevalence of anemia and may underestimate polycythemia in Peruvian children living at HA. Therefore, new threshold values for anemia and polycythemia as mean [Hb] less than 2 SD and greater than 2 SD for populations living at a specific altitude are suggested.
Objective: Clinical studies have shown that oral vitamin C supplementation can reduce serum uric acid levels in multiple populations and may also improve acute mountain sickness. However, it is unclear whether this protocol can improve high-altitude hyperuricemia. Therefore, we aimed to evaluate the role of vitamin C supplementation on high-altitude hyperuricemia. Methods: A preliminary prospective control study was performed in 2015. Young male army recruits (n = 66), who had recently arrived on the Tibetan Plateau for the first time, were recruited for study I. Subjects were assigned to either the vitamin C group, who took an oral daily dose of 500 mg vitamin C for 1 month, or the blank control group, who had no intervention. The levels of serum uric acid, serum creatinine, and blood urea nitrogen were monitored at baseline and at the end of 1 month. In a second study II in 2016 (n = 120), the effect of 500 mg/d vitamin C on high-altitude hyperuricemia was compared with 75 IU/d of vitamin E. Results: In study I, the level of serum uric acid at 1 month was significantly higher than at baseline (436.1 +/- 79.3 mu mol/L vs. 358.0 +/- 79.8 mu mol/L, p 0.05). The change in serum uric acid was positively correlated with both the changes in serum creatinine (r = 0.599, p < 0.001) and blood urea nitrogen (r = 0.207, p = 0.005). Conclusions: These findings indicate that healthy young men develop an increase in serum uric acid within a month of moving from low to high altitude. Oral vitamin C supplementation can safely reduce this increase at a low cost.
Frostbite is a common injury in high altitude medicine. Intravenous vasodilators have a proven efficacy and, recently, have been proposed as a safe outpatient treatment. Nevertheless, the lack of availability and consequently delayed application of this treatment option can result in poor clinical outcomes for patients. We present the case of a 60-year-old Chilean man with severe frostbite injuries suffered while climbing Mount Everest. The patient was initially given field treatment to the extent permitted by conditions and consensus guidelines. Unfortunately, advanced management was delayed, with iloprost administered 75 hours after the initial injury. The patient also underwent 5 days of hyperbaric and analgesic/antibiotic therapies. An early bone scan predicted a poor clinical outcome, and five of the patient's fingers, between both hands, were incompletely amputated. We present this case to exemplify the importance of advanced in-field management of frostbite injuries.
The goals of this study were to characterize headache at high altitude in relation to the severity of acute mountain sickness (AMS), to investigate whether a history of migraine or nonmigrainous headache at low altitude is a risk factor for AMS and to estimate its effect size in relation to established major risk factors. We performed a secondary, extended analysis of data obtained from 1320 mountaineers staying overnight at the Capanna Margherita (4559 m). Headache at low and high altitude was classified according to the criteria of the International Headache Society. About 45% of the mountaineers suffered from headache in the evening of the arrival day at 4559 m. In those with headache, tension type headache decreased from 62% to 29% and 13% with no AMS (AMS-C = 1.5), while headache fulfilling the criteria of migraine increased correspondingly from 14% to 34% and 69%. A history of migraine or any type of headache at low altitude is a minor predictor of AMS that does not significantly contribute to AMS risk in a multivariate analysis including the major risk factors such as history of AMS, rate of ascent, and degree of preacclimatization in this population of alpine mountaineers. The association between more severe AMS and migrainous headache may be due to common nonspecific symptoms but a common underlying pathophysiology of AMS and migraine cannot be excluded. Despite this association a history of migraine or other headache at low altitude is not a major risk factor for AMS.
Objectives: Frostbite is a cold injury mostly affecting the extremities. The objective of this study was to reveal the incidence of frostbite injuries in the Austrian Alps, to search for frostbite risk factors, and thereby optimize prevention and treatment. Methods: Out-of-hospital data in the National Registry of Alpine Accidents from January 1, 2005, to December 31, 2015, were screened for frostbite injuries. Cases in the registry were merged with clinical data from the major trauma center in western Austria, Innsbruck Medical University Hospital, and statistically analyzed. Results: Documented in the National Registry are 114,595 injured persons in the 11-year study period. Thirty-one frostbite cases were documented nationwide, 18 (58%) of which occurred in the western states of Austria and were therefore potentially referred to the Innsbruck Medical University Hospital. Six (19.6%) patients were female. Frostbite was almost exclusively related to fingers and toes (90% of cases). Conclusions: Frostbite injuries in the Austrian Alps are rare. With an incidence of 0.07/100,000, three to four clinically relevant frostbite injuries occur annually. Men are at greater risk for frostbite injuries than women. Fingers and toes are at greatest risk. Proper preparation of outdoor activities and cold-protective gear can help prevent frostbite injuries.
Yang, Ying, Duo-Ji Zha-Xi, Wei Mao, Guang Zhi, Bin Feng, and Yun-Dai Chen. Comparison of echocardiographic parameters between healthy highlanders in Tibet and lowlanders in Beijing. High Alt Med Biol . 19:259–264, 2018.—The hearts of highlanders exhibit distinct features compared with the hearts of lowlanders. However, previous findings have not been verified in a large-scale Tibetan population study. The aim of this study was to present differences in echocardiography results among healthy native Tibetans, acclimatized Han highlanders, and Han lowlanders at sea level. A total of 1820 healthy Tibetans and 224 healthy Han highlanders were drawn from a representative sample of residents in Tibet. Echocardiography was performed on each participant at the sampled local medical centers. Echocardiographic data from 2332 healthy Han lowlanders were obtained from a database of a medical examination center in Beijing. Using propensity score matching to balance differences in demographic features, we evaluated the effects of altitude and ethnicity in three paired comparisons. The results revealed that the great arteries were larger in the Han population than in the Tibetan population regardless of altitude (all p < 0.05). No differences were found in the right atrium between different altitudes and ethnicities. The diameters and thicknesses of the right ventricle (RV) were larger in the Tibetans than in the Han lowlanders (i.e., 30.0 mm (26.0, 34.0) versus 28.6 mm (25.5, 31.8) for the basal right ventricular linear dimension). The left heart in diastole was largest in the Han lowlanders (i.e., 46.3 ± 3.9 mm versus 43.0 mm [40.0, 44.0] in Han highlanders and 45.8 mm [43.0, 48.8] versus 42.0 mm [39.0, 45.0] in Tibetans for the diameter of the left ventricle [LV] at end-diastole). Moreover, the interventricular septum was thicker in the high-altitude population than in the low-altitude population (all p < 0.05). Compared with the Tibetans, the Han highlanders exhibited enhanced ventricular functions (65.0% [60.0, 69.0] versus 68.0% [63.0, 69.0] for LV ejection fraction and 22.0 mm [20.0, 26.0] versus 24.0 mm [21.0, 27.0] for tricuspid annular plane systolic excursion, both p < 0.05). In conclusion, a small left heart and a large RV may be consequences of hypoxic exposure at high altitudes irrespective of ethnic origin.
Berendsen, Remco R., Marieke E. van Vessem, Marcel Bruins, Luc J.S.M. Teppema, Leon P.H.J. Aarts, and Bengt Kayser. Electronic nose technology fails to sniff out acute mountain sickness. High Alt Med Biol. 19:232–236, 2018. Aim: 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. Results: 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). Conclusion: 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.
Hamm, Wolfgang, Lukas von Stülpnagel, Mathias Klemm, Monika Baylacher, Konstantinos D. Rizas, Axel Bauer, and Stefan Brunner. Deceleration capacity of heart rate after acute altitude exposure. High Alt Med Biol 19:299–302, 2018. Background: The autonomic nervous system plays a crucial role in adaptive changes after high-altitude exposure. Deceleration capacity (DC) of heart rate is an advanced marker of heart rate variability (HRV) that predominantly reflects the vagal activity of the cardiac autonomic nervous system. The impact of high-altitude exposure on DC has not been investigated yet. Methods: In eight healthy individuals we performed a high-resolution digital 30-min electrocardiography in Frank leads configuration at baseline (521 m altitude), immediately after ascent to the Environmental Research Station Schneefernerhaus (UFS) at Zugspitze (2650 m altitude) and after a sojourn of 24 hours at this altitude. DC of heart rate was assessed using customized software. In addition, standard parameters of HRV were assessed. Results: DC decreased significantly from 10.2 ± 0.8 ms to 8.9 ± 1.0 ms ( p < 0.05) after acute altitude exposure. After a sojourn of 24 hours at high altitude, DC remained low at 8.6 ± 1.2 ms. There were no significant changes in standard parameters of HRV. Conclusion: Our findings show for the first time a decrease of DC of heart rate providing a novel insight into the dysbalance of autonomic nervous system at high altitude.
Cabrera-Aguilera, Ignacio, David Rizo-Roca, Elisa A. Marques, Garoa Santocildes, Teresa Pagès, Gines Viscor, António A. Ascensão, José Magalhães, and Joan Ramon Torrella. Additive effects of intermittent hypobaric hypoxia and endurance training on bodyweight, food intake, and oxygen consumption in rats. High Alt Med Biol . 19:278–285, 2018.—We used an animal model to elucidate the effects of an intermittent hypobaric hypoxia (IHH) and endurance exercise training (EET) protocol on bodyweight (BW), food and water intake, and oxygen consumption. Twenty-eight young adult male rats were divided into four groups: normoxic sedentary (NS), normoxic exercised (NE), hypoxic sedentary (HS), and hypoxic exercised (HE). Normoxic groups were maintained at an atmospheric pressure equivalent to sea level, whereas the IHH protocol consisted of 5 hours per day for 33 days at a simulated altitude of 6000 m. Exercised groups ran in normobaric conditions on a treadmill for 1 hour/day for 5 weeks at a speed of 25 m/min. At the end of the protocol, both hypoxic groups showed significant decreases in BW from the ninth day of exposure, reaching final 10% (HS) to 14.5% (HE) differences when compared with NS. NE rats also showed a significant weight reduction after the 19th day, with a decrease of 7.4%. The BW of hypoxic animals was related to significant hypophagia elicited by IHH exposure (from 8% to 12%). In contrast, EET had no effect on food ingestion. Total water intake was not affected by hypoxia but was significantly increased by exercise. An analysis of oxygen consumption at rest (mL O 2 /[kg·min]) revealed two findings: a significant decrease in both hypoxic groups after the protocol (HS, 21.7 ± 0.70 vs. 19.1 ± 0.78 and HE, 22.8 ± 0.80 vs. 17.1 ± 0.90) and a significant difference at the end of the protocol between NE (21.3 ± 0.77) and HE (17.1 ± 0.90). These results demonstrate that IHH and EET had an additive effect on BW loss, providing evidence that rats underwent a metabolic adaptation through a reduction in oxygen consumption measured under normoxic conditions. These data suggest that the combination of IHH and EET could serve as an alternative treatment for the management of overweight and obesity.
Summerfield, Douglas T., Kirsten E. Coffman, Bryan J. Taylor, Amine N. Issa, and Bruce D. Johnson. Exhaled nitric oxide changes during acclimatization to high altitude: a descriptive study. High Alt Med Biol. 19:215–220, 2018. Aims: This study describes differences in the partial pressures of exhaled nitric oxide (PeNO) between subjects fully acclimatized (ACC) to 5300 m and those who have just arrived to high altitude. Methods: PeNO was determined in eight subjects newly exposed and nonacclimatized (non-ACC) to high altitude and compared with that in nine subjects who had ACC to high altitude for 1 month. In addition, systolic pulmonary artery pressure (sPAP) and arterial oxygen saturation (SaO 2 ) were measured in all participants. These measurements were repeated in the non-ACC group 5 and 9 days later. Results: PeNO levels on day 1 were significantly higher in the non-ACC versus ACC cohort (8.7 ± 3.5 vs. 3.9 ± 2.2 nmHg, p = 0.004). As the non-ACC group remained at altitude, PeNO levels fell and were not different when compared with those of the ACC group by day 9 (5.9 ± 2.4 vs. 3.9 ± 2.2 nmHg, p = 0.095). Higher sPAP was correlated with lower PeNO levels in all participants ( R = −0.50, p = 0.043). PeNO levels were not correlated with SaO 2 . Conclusions: As individuals acclimatized to high altitude, PeNO levels decreased. Even after acclimatization, PeNO levels continued to play a role in pulmonary vascular tone.