Acute Mountain Sickness Scores Research Articles

SLAB51 Probiotic Improves Oxygen Saturation and Acute Mountain Sickness Score at High Altitude

Hypobaric hypoxia imposes various challenges at high altitude that initiate differentphysiological responses as part of the acclimatization process. Current interventions foraccelerating and/or improving acclimatization to high altitude are limited. Preliminarystudies of the multi-strain probiotic SLAB51 (O2booster; Hecto, Seoul, South Korea)have shown its potential to improve oxygenation, a crucial component ofacclimatization, in clinical conditions of hypoxemia. We hypothesized that treatment withSLAB51 at high altitude will lead to improved acclimatization as measured by oxygensaturation (SpO2) and scores from the Acute Mountain Sickness (AMS) survey (2018Lake Louise Questionnaire). A group of 17 (9 males, 8 females) healthy Latino/a adultsfrom the San Diego area, ranging from ages 19-63, were taken from sea-level to WhiteMountain Barcroft Station (3800 m) for up to four days. Participants underwent adouble-blind, placebo-controlled study where nine participants consumed the SLAB51probiotic and eight consumed a placebo up to three times a day. SpO2 was measuredusing a forehead pulse oximeter, and an AMS survey score was attained daily. Ouranalyses revealed that SpO2 was significantly higher in participants who received theSLAB51 probiotic at high altitude versus those who received the placebo (Two-wayANOVA, p-value < 1.12e-05). Furthermore, AMS scores were significantly lower inparticipants treated with SLAB51 than those who received the placebo (Two-wayANOVA, p-value < 0.007). Our results indicate that SLAB51 ingestion at high altitudeimproved SpO2 compared to a placebo and may improve acclimatization to high altitude. Funding: LEA Altitude Performance Fund. 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.

Assessment of Acute Mountain Sickness: Comparing the Chinese AMS Score to the Lake Louise Score.

Wu, Yu, Wenqi Zhao, Bao Liu, Jianyang Zhang, Zhifeng Zhong, Simin Zhou, Jiaxin Xie, Yuqi Gao, Peng Li, and Jian Chen. Assessment of Acute Mountain Sickness: Comparing the Chinese Ams Score to the Lake Louise Score. High Alt Med Biol 00:000-000, 2024. Objective: To compare the ability of the Chinese AMS Score (CAS) to detect acute mountain sickness (AMS) using the 2018 version of the Lake Louise Score (LLS) as reference. Methods: After flying from Chengdu (altitude: 500 m) to Lhasa (3,658 m), 2,486 young men completed a questionnaire. The questionnaire contained LLS and CAS items. An LLS ≥3 and/or a CAS ≥cutoff were used as the criteria for AMS. Hierarchical cluster analysis and two-step cluster analysis were used to investigate relationships between the symptoms. Results: AMS incidence rates were 33.8% (n = 840) with the LLS and 59.3% (n = 1,473) with the CAS (χ2 = 872.5, p < 0.001). The LLS and CAS had a linear relationship (orthogonal regression, Pearson r = 0.91, p < 0.001). With the LLS as the standard, the CAS had high diagnostic accuracy (area under the curve = 0.95, 95% confidence interval: 0.94-0.96). However, with the CAS, 25.5% (n = 633) more participants were labeled as having AMS than with the LLS (false positives). Two clusters were identified: one with headache only (419 participants, 66.2%) and one without headache but with other symptoms (214 participants, 33.8%). Reducing the weight of headache in the CAS allowed to align CAS and LLS. Conclusion: In comparison to the LLS, the CAS has a sensitivity close to 100% but lacks specificity given the high rate of false positives. The different weight of headaches may be the main reason for the discrepancy.

Acute mountain sickness predicts the emotional state of amateur mountaineers.

Research on amateur mountaineers is scarce, and this study aims to delve into the emotional experiences of ten amateur mountaineers during their ascent using the "Befindlichkeitsskala" (BFS) and Lake Louise Acute Mountain Sickness scoring system (LLS). These subjects were exposed to altitudes of 3140m, 4300m, and 5276m, respectively. We found that LLS scores were negatively correlated with positive emotions (β = -27.54, p < 0.05) and positively correlated with negative emotions (β = 21.97, p < 0.05). At an altitude of 4300m, individuals with AMS exhibited significant differences in depression, anger, excitement, and inactivity compared to climbers without AMS. Upon returning to 3140m after completing the climb, significant differences were observed in emotions such as happiness, calmness, anger, excitement, and depression. Throughout the three-day climb, noteworthy differences emerged in activity, happiness, calmness, inactivity, positive emotions (p < 0.01), negative emotions, and overall emotional scores (p < 0.05). Our study suggests a decline in the emotional well-being of amateur climbers with increasing altitude, highlighting AMS as a pivotal predictive factor for emotional experiences while climbing.

The effects of the menstrual cycle on the physiological responses to exercise in eumenorrheic women at high-altitude

Introduction&#x0D; The acute mountain sickness (AMS) prevalence increases with altitude; i.e.,10-25% at 2,500 m and 50-85% at ~5,000 m (Bärtsch &amp; Swenson, 2013). Women are more likely affected by AMS than men (Richalet et al., 2012). AMS can affect exercise performance. However, the effects of the menstrual cycle (MC) on physiological responses to exercise and on tolerance to high-altitude (HA) remain underexplored. It has been reported that ovarian hormones stimulate ventilation in normoxic conditions (Saaresranta &amp; Polo, 2002). Early findings suggest that running economy is lower in the mid-luteal (ML) compared to the early-follicular (EF) phase in normoxia (Goldsmith &amp; Glaister, 2020). However, cycling efficiency at HA has not been explored yet. Thus, we investigated the effects of acute HA exposure on ventilatory responses at rest and during exercise in healthy females during two different phases of their MC.&#x0D; Methods&#x0D; Sixteen eumenorrheic women (age: 33 ± 7 yr; MC length: 27 ± 2 days; not taking any hormonal contraceptive) took part in this study. First, over a 6-month period, the participants’ MC were monitored using a calendar method. Then, they reached the Torino Hut (3,375 m) by cable car and spent one night at HA on two different MC phases; i.e., during the early-follicular (EF; MC day 4 ± 1) and the mid-luteal (ML; day 20 ± 2) phases. Each time, they underwent a submaximal (1.2 W/kg) test on a cycle ergometer ~17 h after arrival at HA. In addition to this, participants filled in two questionnaires, the Lake Louise AMS Score and the Groningen Sleep Quality Scale, ~16 h after arrival at HA.&#x0D; Results&#x0D; Resting ventilation was significantly higher during EF compared to ML (15.2 ± 1.9 vs. 13.2 ± 2.5 L/min, p = 0.039), while no differences were found for ventilation during exercise (53.9 ± 13.2 vs. 53.5 ± 13.4 L/min, p = 0.695), cycling efficiency (21.7 ± 0.0% vs. 19.8 ± 0.0%, p = 0.244), saturation at rest (92.4 ± 1.3 vs. 91.3 ± 3.2%, p = 0.142) and during exercise (87.2 ± 5.7 vs. 89.0 ± 4.0%, p = 0.528). Moreover, no differences in the Lake Louise AMS (2.2 ± 1.5 vs. 1.7 ± 1.5, p = 0.266) or Groningen (8.0 ± 3.3 vs. 7.5 ± 3.4, p = 0.668) scores were noted between the two MC phases.&#x0D; Discussion/Conclusion&#x0D; Despite a slightly higher resting ventilation during EF, when both oestrogens and progesterone are at their lowest levels, there were no differences in ventilatory responses to exercise and in AMS between the different phases of the MC. Consequently, there is currently very little evidence to aptly recommend a specific MC phase for mountaineering or any other HA activities (Burtscher et al., 2023). Further investigations are requested to assess whether other physiological responses to HA may be influenced by hormonal variations.&#x0D; References&#x0D; Bärtsch, P., &amp; Swenson, E. R. (2013). Acute high-altitude illnesses. New England Journal of Medicine, 368, 2294–2302. https://doi.org/10.1056/NEJMcp1214870&#x0D; Burtscher, J., Raberin, A., Brocherie, F., Malatesta, D., Manferdelli, G., Citherlet, T., Krumm, B., Bourdillon, N., Antero, J., Rasica, L., Burtscher, M. &amp; Millet, G. P. (2023). Recommendations for women in mountain sports and hypoxia training/conditioning. Sports Medicine. Advance online publication. https://doi.org/10.1007/s40279-023-01970-6&#x0D; Goldsmith, E., &amp; Glaister, M. (2020). The effect of the menstrual cycle on running economy. The Journal of Sports Medicine and Physical Fitness, 60(4), 610–617. https://doi.org/10.23736/s0022-4707.20.10229-9&#x0D; Richalet, J.-P., Larmignat, P., Poitrine, E., Letournel, M., &amp; Canouï-Poitrine, F. (2012). Physiological risk factors for severe high-altitude illness: A prospective cohort study. American Journal of Respiratory and Critical Care Medecine, 185(2), 192–198. https://doi.org/10.1164/rccm.201108-1396OC&#x0D; Saaresranta, T., &amp; Polo, O. (2002). Hormones and breathing. American College of Chest Physicians, 122(6), 2165–2182. https://doi.org/10.1378/chest.122.6.2165

Patterns of Structural Changes in the Fundus Measured by Optical Coherence Tomography Angiography as Potential Markers of Acute Mountain Sickness.

To use optical coherence tomography angiography (OCTA) to assess the pattern of changes in retinal and choroidal blood flow and structure in healthy volunteers who quickly went from sea level to a plateau and to determine the parameters associated with acute mountain sickness (AMS). Forty-five individuals (89 eyes) were examined by OCTA and filled out the AMS questionnaire. One baseline examination was performed on the plain, followed by examinations at days 1, 3, and 5 after entering the plateau. Parameters were self-controlled to explore patterns of change, analyzed for correlation with AMS score, and modeled as a nomogram of AMS risk. On the plateau compared to the plain, vascular morphology showed dilated superficial macular retinal vessels and constricted deeper layers with increased vessel length density and fractal dimension; vessel density increased in all retinal strata and decreased in the choroidal macrovascular layer; and thickness increased except for a decrease in mean retinal thickness in the central macular sulcus. The rate of increase in retinal nerve fiber layer (RNFL) thickness in the inner and outer macular rings correlated with AMS score (r = -0.211). The nomogram showed moderate accuracy (AUC = 0.672) and consistency (C-index = 0.659) in assessing AMS risk. In high-altitude hypoxia, retinal vessels dilate and distort, resulting in increased blood flow density and thickness. Increased RNFL thickness in the paracentral macula may be a marker of low AMS risk. The changes in the retinal structure of the fundus can be used to assess the risk of developing AMS.

High Altitude Illness among Rapidly Ascending Pilgrims to Kailash Mansarovar.

High altitude pilgrims typically ascend rapidly, are not well prepared for the austere environment and tend to have multiple co-morbidities. Here, we list the trend of altitude and other illnesses who visited Humla district hospital (2,950 meters) following very rapid ascent to Kailash Mansarovar (4,500 meters). A prospective study was conducted among 55 patients at the Humla District Hospital from September 2019 - August 2022. Patients who fell ill during pilgrimage and brought to the hospital were included. The patients were assessed with medical history and clinical examination. Lake Louise Score Acute Mountain Sickness Score (2018) was used for the diagnosis of Acute Mountain Sickness. A total of 56 evacuees visited the hospital which included 55 patients and 1 brought dead. The mean age was 50.63 ±10.91 years. Sixteen patients (29.1%) developed symptoms within 24 hours and 15 patients (27.3%) within 48 hours of ascent. Headache 42 (76.4%) was the most common complain. Mild acute mountain sickness (30.9%; 17 patients) was the most common altitude related illness while 14 patients (25.4%) were diagnosed with non-altitude related illnesses. Twelve patients (21.8%) had co-morbidities like hypertension and diabetes mellitus. In the rapidly ascending pilgrims, majority of travelers requiring medical attention are suffering from some form of altitude illnesses. Hence, proper planning and public awareness about slow and gradual ascent profile is necessary to make the travel safer.

Effects of age on hypoxic tolerance in women

Effects of age on hypoxic tolerance in women

Hypoxia-altitude simulation test to predict altitude-related adverse health effects in COPD patients.

Amongst numerous travellers to high altitude (HA) are many with the highly prevalent COPD, who are at particular risk for altitude-related adverse health effects (ARAHE). We then investigated the hypoxia-altitude simulation test (HAST) to predict ARAHE in COPD patients travelling to altitude. This prospective diagnostic accuracy study included 75 COPD patients: 40 women, age 58±9 years, forced expiratory volume in 1 s (FEV1) 40-80% pred, oxygen saturation measured by pulse oximetry (S pO2 ) ≥92% and arterial carbon dioxide tension (P aCO2 ) <6 kPa. Patients underwent baseline evaluation and HAST, breathing normobaric hypoxic air (inspiratory oxygen fraction (F IO2 ) of 15%) for 15 min, at low altitude (760 m). Cut-off values for a positive HAST were set according to British Thoracic Society (BTS) guidelines (arterial oxygen tension (P aO2 ) <6.6 kPa and/or S pO2 <85%). The following day, patients travelled to HA (3100 m) for two overnight stays where ARAHE development including acute mountain sickness (AMS), Lake Louise Score ≥4 and/or AMS score ≥0.7, severe hypoxaemia (S pO2 <80% for >30 min or 75% for >15 min) or intercurrent illness was observed. ARAHE occurred in 50 (66%) patients and 23 out of 75 (31%) were positive on HAST according to S pO2 , and 11 out of 64 (17%) according to P aO2 . For S pO2 /P aO2 we report a sensitivity of 46/25%, specificity of 84/95%, positive predictive value of 85/92% and negative predictive value of 44/37%. In COPD patients ascending to HA, ARAHE are common. Despite an acceptable positive predictive value of the HAST to predict ARAHE, its clinical use is limited by its insufficient sensitivity and overall accuracy. Counselling COPD patients before altitude travel remains challenging and best focuses on early recognition and treatment of ARAHE with oxygen and descent.

Could Orthostatic Stress Responses Predict Acute Mountain Sickness Susceptibility Prior to High Altitude Travel? A Pilot Study.

Bellovary, Bryanne N., Andrew D. Wells, Zachary J. Fennel, Jeremy B. Ducharme, Jonathan M. Houck, Trevor J. Mayschak, Ann L. Gibson, Scott N. Drum, and Christine M. Mermier. Could orthostatic stress responses predict acute mountain sickness susceptibility before high altitude travel? A pilot study. High Alt Med Biol. 24:19-26, 2023. Purpose: This study assessed head-up tilt (HUT) responses in relation to acute mountain sickness (AMS)-susceptibility during hypoxic exposure. Materials and Methods: Fifteen participants completed three lab visits: (1) protocol familiarization and cycle maximal oxygen consumption (VO2max) test; (2) HUT test consisting of supine rest for 20 minutes followed by 70° tilting for ≤40 minutes; and (3) 6 hours of hypobaric hypoxic exposure (4,572 m) where participants performed two 30-minute cycling bouts separated by 1 hour at a 50% VO2max workload within the first 3 hours and rested when not exercising. During HUT, systolic blood pressure (SBP), diastolic blood pressure, heart rate (HR), and variability (blood pressure variability [BPV] and HR variability [HRV]) were measured continuously. The AMS scores were determined after 6 hours of exposure. Correlations determined relationships between HUT cardiovascular responses and AMS scores. Repeated-measures analysis of variance (ANOVA) assessed differences between those with and without AMS symptoms during HUT. Results: Higher AMS scores correlated with greater change in SBP variability (r = 0.52, p = 0.048) and blunted changes in HRV (root mean square of successive differences between normal heartbeats r = 0.81, p = 0.001, percentage of adjacent normal sinus intervals that differ by more than 50 milliseconds [pNN50] r = 0.87, p < 0.001) during HUT. A pNN50 interaction (p = 0.02) suggested elevated cardiac sympathetic activity at baseline and a blunted increase in cardiac sympathetic influence throughout HUT in those with AMS (pNN50 baseline: AMS = 26.2% ± 15.3%, no AMS = 51.0% ± 13.5%; first 3 minutes into HUT: AMS = 17.2% ± 19.1%, no AMS = 17.1% ± 10.9%; end of HUT: AMS = 6.2% ± 9.1%, no AMS 11.0% ± 10.0%). Conclusions: The results suggest autonomic responses via HUT differ in AMS-susceptible individuals. Changes in HRV and BPV during HUT may be a promising predictive measurement for AMS-susceptibility, but further research is needed for confirmation.

Assessment of hypoxia tolerance to high-altitude exposure following sleep deprivation

Objectives: The adverse effects of hypoxia and sleep deprivation (SD) have been studied separately but there is little literature on their effects when acting in conjunction. Hence, the effects of SD on hypoxia tolerance and cognitive performance when exposed to altitude were investigated. Material and Methods: In a cross-sectional repetitive measure design, 15 healthy volunteers assessed on cognitive performance were made to perform cognitive tests (Dual Task Test, Stroop Test [ST], and Digit Symbol Substitution Test [DSST] of Psychometric Evaluation Designed for Aviators test battery) on the ground and at a simulated altitude of 17,000 ft in a hypobaric chamber on 4 days. On the 2nd and 3rd day, the tests were done following 2 h of SD the previous night, and on the 4th day, the same was repeated following normal recovery sleep. Heart rate (HR) and respiratory rate (RR) were measured on the ground and 17,000 ft. The Lake Louise Acute Mountain Sickness (LLAMS) scores were used to assess the severity of symptoms of hypoxia and time to arterial oxygen desaturation of 75% was used to measure hypoxia tolerance. Results: Although not statistically significant, the LLAMS scores showed an increasing trend on SD days with an improvement in recovery of sleep. No statistically significant differences in the HR (F = 0.569, P = 0.637) and RR (F = 0.569, P = 0.637) were observed across the days of SD or recovery. The time to oxygen desaturation to 75% also showed no significant effect (F = 0.587, P = 0.625). A statistically significant increase in response times of two cognitive tests (ST and DSST) was observed on exposure to altitude on all 4 days. The three cognitive tests did not show any statistically significant effect following 2 h of SD or recovery. Conclusion: The study could not elicit a statistically significant effect of 2 h of SD across 2 consecutive nights on the cognitive performance measures on exposure to hypoxia.

Association of Pre-existing Mental Health Conditions with Acute Mountain Sickness at Everest Base Camp.

Hüfner, Katharina, Fabio Caramazza, Evelyn R. Pircher Nöckler, Agnieszka E. Stawinoga, Paolo Fusar-Poli, Sanjeeb S. Bhandari, Buddha Basnyat, Monika Brodmann Maeder, Giacomo Strapazzon, Iztok Tomazin, Ken Zafren, Hermann Brugger, and Barbara Sperner-Unterweger. Association of pre-existing mental health conditions with acute mountain sickness at Everest Base Camp. High Alt Med Biol. 23:338-344, 2022. Background: Mental health disorders are common, but limited data are available regarding the number of people with a past medical history of psychiatric diagnoses going to high altitude (HA). It is also unknown whether mental health conditions are associated with an increased risk of acute mountain sickness (AMS). Methods: We analyzed data from a previous study at Everest Base Camp. Participants self-reported their past medical history and history of substance use and had a brief history taken by a physician. AMS was assessed using the self-reported 2018 Lake Louise AMS Score. Results: Eighty-five participants (66 men and 19 women, age 38 ± 9 years) were included. When questioned by a physician, 28 participants reported prior diagnoses or symptoms compatible with depression (23%), anxiety disorder (6%), post-traumatic stress disorder (1%), and psychosis/psychotic experiences (9%). The prevalence of psychiatric diagnoses in the past medical history was much lower in the self-reported data (2/85) compared to data obtained via physician assessment (28/85). Increased risks of AMS were associated with a past medical history of anxiety disorder (odds ratio [OR] 22.7; confidence interval [95% CI] 2.3-220.6; p < 0.001), depression (OR 3.6; 95% CI 1.2-11.2; p = 0.022), and recreational drug use ever (OR 7.3; 95% CI 1.5-35.5; p = 0.006). Conclusions: Many people who travel to HA have a past medical history of mental health conditions. These individuals have an increased risk of scoring positive for AMS on the Lake Louise Score compared with people without a history of mental health conditions.

Matrix metalloproteinase-9 and substance-P as predictors for early-stage diagnosis of acute mountain sickness

IntroductionAlthough acute mountain sickness (AMS) can be a life-threatening condition, early diagnosis is difficult due to vague and non-specific symptoms. The aim of this study is to investigate biochemical markers that can detect high-altitude diseases in advance. Eight different biomarkers (BNP, HIF-1α, NGAL, MMP-3, MMP-9, SESN2, substance P (SP), and U-II) were studied, and their relationship with AMS was investigated. MethodsOf the 84 mountaineers who participated in the mountaineering training organized by the Turkish Mountaineering Federation in the Rize Kaçkar Mountains in 2018, 52 volunteered to participate in the study. Twelve hours after the participants reached an altitude of 2200 m (exposed to moderate hypoxia), their vital parameters were measured, and blood samples were taken for biochemistry tests. Vital signs and Lake Louise (LL) AMS scores were recorded every 24 h during the following 72 h. The participants were divided into two groups according to their LL scores: those with AMS and those without (AMS+ and AMS −), and the vital parameters and biomarker levels of both groups were compared and evaluated. ResultsOf the volunteers participating in the study, 35 (67.3%) were male and 17 (32.7%) were female, although there was no gender difference in terms of susceptibility to AMS. Among the investigated markers in the AMS + group, MMP-9 and SP were statistically significantly higher (p = 0.037 and p = 0.038, respectively). There were no statistical differences between AMS− and AMS+ groups with regard to heart rate, oxygen saturation, and systolic and diastolic blood pressure values (p = 0.507, p = 0.929, p = 0.955, p = 0.572, respectively). ConclusionThere were significant differences between the AMS− and AMS+ groups in terms of MMP-9 and SP. However, differences in physical indexes between the groups were not statistically significant. This could provide objective indexes for scanning and screening individuals susceptible to AMS in the early stages of rapid ascending.

Baseline Psychological Traits Contribute to Lake Louise Acute Mountain Sickness Score at High Altitude

Talks, Benjamin James, Catherine Campbell, Stephanie J. Larcombe, Lucy Marlow, Sarah L. Finnegan, Christopher T. Lewis, Samuel J.E. Lucas, Olivia K. Harrison, and Kyle T.S. Pattinson. Baseline psychological traits contribute to Lake Louise Acute Mountain Sickness score at high altitude. High Alt Med Biol. 23:69–77, 2022.Background:Interoception refers to an individual's ability to sense their internal bodily sensations. Acute mountain sickness (AMS) is a common feature of ascent to high altitude that is only partially explained by measures of peripheral physiology. We hypothesized that interoceptive ability may explain the disconnect between measures of physiology and symptom experience in AMS.Methods:Two groups of 18 participants were recruited to complete a respiratory interoceptive task three times at 2-week intervals. The control group remained in Birmingham (140 m altitude) for all three tests. The altitude group completed test 1 in Birmingham, test 2 the day after arrival at 2,624 m, and test 3 at 2,728 m after an 11-day trek at high altitude (up to 4,800 m).Results:By measuring changes to metacognitive performance, we showed that acute ascent to altitude neither presented an interoceptive challenge, nor acted as interoceptive training. However, AMS symptom burden throughout the trek was found to relate to sea level measures of anxiety, agoraphobia, and neuroticism.Conclusions:This suggests that the Lake Louise AMS score is not solely a reflection of physiological changes on ascent to high altitude, despite often being used as such by researchers and commercial trekking companies alike.

No effect of patent foramen ovale on acute mountain sickness and pulmonary pressure in normobaric hypoxia.

What is the central question to this study? Is there a relationship between a patent foramen ovale and the development of acute mountain sickness and an exaggerated increase in pulmonary pressure in response to 7-10h of normobaric hypoxia? What is the main finding and its importance? Patent foramen ovale presence did not increase susceptibility to acute mountain sickness or result in an exaggerated increase in pulmonary artery systolic pressure with normobaric hypoxia. This suggests hypobaric hypoxia is integral to the increased susceptibility to acute mountain sickness previously reported in those with patent foramen ovale, and patent foramen ovale presence alone does not contribute to the hypoxic pulmonary pressor response. Acute mountain sickness (AMS) develops following rapid ascent to altitude, but its exact causes remain unknown. A patent foramen ovale (PFO) is a right-to-left intracardiac shunt present in ∼30% of the population that has been shown to increase AMS susceptibility with high altitude hypoxia. Additionally, high altitude pulmonary oedema (HAPE) is a severe type of altitude illness characterized by an exaggerated pulmonary pressure response, and there is a greater prevalence of PFO in those with a history of HAPE. However, whether hypoxia per se is causing the increased incidence of AMS in those with a PFO and whether a PFO is associated with an exaggerated increase in pulmonary pressure in those without a history of HAPE is unknown. Participants (n=36) matched for biological sex (18 female) and the presence or absence of a PFO (18 PFO+) were exposed to 7-10h of normobaric hypoxia equivalent to 4755m. Presence and severity of AMS was determined using the Lake Louise AMS scoring system. Pulmonary artery systolic pressure, cardiac output and total pulmonary resistance were measured using ultrasound. We found no significant association of PFO with incidence or severity of AMS and no association of PFO with arterial oxygen saturation. Additionally, there was no effect of a PFO on pulmonary pressure, cardiac output or total pulmonary resistance. These data suggest that hypobaric hypoxia is necessary for those with a PFO to have increased incidence of AMS and that presence of PFO is not associated with an exaggerated pulmonary pressor response.

Blood Pressure Load: An Effective Indicator of Systemic Circulation Status in Individuals With Acute Altitude Sickness.

Background: Acute high altitude (HA) exposure results in blood pressure (BP) variations in most subjects. Previous studies have demonstrated that higher BP is potentially correlated with acute mountain sickness (AMS). The BP load may be of clinical significance regarding systemic circulation status.Objectives: This study aimed to examine HA-induced BP changes in patients with AMS compared to those in healthy subjects. Further, we provided clinical information about the relationship between variations in 24-h ambulatory parameters (BP level, BP variability, and BP load) and AMS.Methods: Sixty-nine subjects were enrolled and all participants ascended Litang (4,100 m above sea level). They were monitored using a 24-h ambulatory blood pressure device and underwent echocardiography within 24 h of altitude exposure. The 2018 Lake Louise questionnaire was used to evaluate AMS.Results: The AMS group comprised more women than men [15 (65.2%) vs. 13 (28.3%), P < 0.001] and fewer smokers [4 (17.4%) vs. 23 (50.0%), P = 0.009]. The AMS group exhibited significant increases in 24-h BP compared to the non-AMS group (24-h SBP variation: 10.52 ± 6.48 vs. 6.03 ± 9.27 mmHg, P = 0.041; 24-h DBP variation: 8.70 ± 4.57 vs. 5.03 ± 4.98 mmHg, P = 0.004). The variation of mean 24-h cBPL (cumulative BP load) (mean 24-h cSBPL: 10.58 ± 10.99 vs. 4.02 ± 10.58, P = 0.016; 24-h mean cDBPL: 6.03 ± 5.87 vs. 2.89 ± 4.99, P = 0.034) was also obviously higher in AMS subjects than in non-AMS subjects after HA exposure. 24-h mean cSBPL variation (OR = 1.07, P = 0.024) and 24-h mean cDBPL variation (OR = 1.14, P = 0.034) were independent risk factors of AMS. Moreover, variation of 24-h mean cSBPL showed a good correlation with AMS score (R = 0.504, P < 0.001).Conclusions: Our study demonstrated that patients with AMS had higher BP and BP load changes after altitude exposure than healthy subjects. Excessive BP load variations were associated with AMS. Thus, BP load could be an effective indicator regarding systemic circulation status of AMS.

Using machine learning to determine the correlation between physiological and environmental parameters and the induction of acute mountain sickness

BackgroundRecent studies on acute mountain sickness (AMS) have used fixed-location and fixed-time measurements of environmental and physiological variable to determine the influence of AMS-associated factors in the human body. This study aims to measure, in real time, environmental conditions and physiological variables of participants in high-altitude regions to develop an AMS risk evaluation model to forecast prospective development of AMS so its onset can be prevented.ResultsThirty-two participants were recruited, namely 25 men and 7 women, and they hiked from Cuifeng Mountain Forest Park parking lot (altitude: 2300 m) to Wuling (altitude: 3275 m). Regression and classification machine learning analyses were performed on physiological and environmental data, and Lake Louise Acute Mountain Sickness Scores (LLS) to establish an algorithm for AMS risk analysis. The individual R2 coefficients of determination between the LLS and the measured altitude, ambient temperature, atmospheric pressure, relative humidity, climbing speed, heart rate, blood oxygen saturation (SpO2), heart rate variability (HRV), were 0.1, 0.23, 0, 0.24, 0, 0.24, 0.27, and 0.35 respectively; incorporating all aforementioned variables, the R2 coefficient is 0.62. The bagged trees classifier achieved favorable classification results, yielding a model sensitivity, specificity, accuracy, and area under receiver operating characteristic curve of 0.999, 0.994, 0.998, and 1, respectively.ConclusionThe experiment results indicate the use of machine learning multivariate analysis have higher AMS prediction accuracies than analyses utilizing single varieties. The developed AMS evaluation model can serve as a reference for the future development of wearable devices capable of providing timely warnings of AMS risks to hikers.

Effect of intermittent normobaric hypoxia exposure on acclimatization to high altitude by air induction

Background: In emergency like condition, defence personnel are deployed to high altitude without proper acclimatization. Maladaption at high altitude leads to high altitude illness like acute mountain sickness (AMS), high altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE) which hampers the operational capabilities. Aims and Objectives: The aim of the present study was to assess the effect of intermittent normobaric hypoxia exposure (IHE) at sea level on different physiological responses during initial days of acclimatization at 3500m and 4000m altitudes in acute induction. Materials and Methods: The IHE subjects were exposed to 12% FIO2 (equivalent altitude 14500 ft) for 4 hrs/day for 4 consecutive days at sea level and 5th day they were inducted by air to 3500m altitude. Baseline recording of different physiological parameters like cardiovascular, respiratory, oxygen saturation and AMS score were measured at sea level as well as 3500m altitude on daily basis for 6 days to assess acclimatization status. To confirm acclimatization status at 3500m, on fifth day the IHE group subjects were transported by road to 4000m and again measured different basal physiological parameters (like cardiovascular, oxygen saturation and AMS score) for four consecutive days. Results: Different physiological parameters of IHE treated group were stabilized by day 4 of air induction at 3500m altitude. Whereas, at 4000m altitude, these parameters were stabilized by day 2 of induction. Conclusion: Acclimatization schedules of four days at 3500m and two days at 4000m are essential to avoid malacclimatization/or high-altitude illness.

Normobaric Hypoxia Exposure During Treadmill Aerobic Exercise After Stroke: A Safety and Feasibility Study.

ObjectiveTo evaluate the safety and feasibility of performing treadmill aerobic exercise in moderate normobaric hypoxia among chronic hemiparetic stroke survivors.DesignObservational study using convenience sampling.SettingResearch laboratory in a tertiary rehabilitation hospital.ParticipantsChronic hemiparetic stroke survivors who could walk at least 10-m with or without assistance and had no absolute contraindications to exercise testing.InterventionParticipants (three male and four female) were asked to complete three normobaric hypoxia exposure protocols within a single session. First, they were passively exposed to normobaric hypoxia through gradual reductions in the fraction of inspired oxygen (FIO2 = 20.9, 17.0, and 15.0%) while seated (5-min at each level of FIO2). Participants were then exposed to the same reductions in FIO2 during constant-load exercise performed on a treadmill at 40% of heart rate reserve. Finally, participants completed 20-min of exercise while intermittently exposed to moderate normobaric hypoxia (5 × 2-min at FIO2 = 15.0%) interspaced with 2-min normoxia intervals (FIO2 = 20.9%).Outcome MeasuresThe primary outcome was occurrence of adverse events, which included standardized criteria for terminating exercise testing, blood oxygen saturation (SpO2) <80%, or acute mountain sickness score >2. The increased cardiovascular strain imposed by normobaric hypoxia exposure at rest and during exercise was evaluated by changes in SpO2, heart rate (HR), blood pressure, and rating of perceived exertion (RPE).ResultsOne participant reported mild symptoms of nausea during exercise in normobaric hypoxia and discontinued participation. No other adverse events were recorded. Intermittent normobaric hypoxia exposure was associated with reduced SpO2 (MD = −7.4%, CI: −9.8 to −5.0) and increased HR (MD = 8.2, CI: 4.6 to 11.7) compared to intervals while breathing typical room air throughout the 20-min constant-load exercise period. The increase in HR was associated with a 10% increase in relative effort. However, reducing FIO2 had little effect on blood pressure and RPE measurements.ConclusionModerate normobaric hypoxia appeared to be a safe and feasible method to increase the cardiovascular strain of submaximal exercise in chronic hemiparetic stroke survivors. Future studies evaluating the effects of pairing normobaric hypoxia exposure with existing therapies on secondary prevention and functional recovery are warranted.

Integrated respiratory chemoreflex-mediated regulation of cerebral blood flow in hypoxia: Implications for oxygen delivery and acute mountain sickness.

What is the central question of this study? To what extent do hypoxia-induced changes in the peripheral and central respiratory chemoreflex modulate anterior and posterior cerebral oxygen delivery, with corresponding implications for susceptibility to acute mountain sickness? What is the main finding and its importance? We provide evidence for site-specific regulation of cerebral blood flow in hypoxia that preserves oxygen delivery in the posterior but not the anterior cerebral circulation, with minimal contribution from the central respiratory chemoreflex. External carotid artery vasodilatation might prove to be an alternative haemodynamic risk factor that predisposes to acute mountain sickness. The aim of the present study was to determine the extent to which hypoxia-induced changes in the peripheral and central respiratory chemoreflex modulate anterior and posterior cerebral blood flow (CBF) and oxygen delivery (CDO2 ), with corresponding implications for the pathophysiology of the neurological syndrome, acute mountain sickness (AMS). Eight healthy men were randomly assigned single blind to 7h of passive exposure to both normoxia (21% O2 ) and hypoxia (12% O2 ). The peripheral and central respiratory chemoreflex, internal carotid artery, external carotid artery (ECA) and vertebral artery blood flow (duplex ultrasound) and AMS scores (questionnaires) were measured throughout. A reduction in internal carotid artery CDO2 was observed during hypoxia despite a compensatory elevation in perfusion. In contrast, vertebral artery and ECA CDO2 were preserved, and the former was attributable to a more marked increase in perfusion. Hypoxia was associated with progressive activation of the peripheral respiratory chemoreflex (P<0.001), whereas the central respiratory chemoreflex remained unchanged (P>0.05). Symptom severity in participants who developed clinical AMS was positively related to ECA blood flow (Lake Louise score, r=0.546-0.709, P=0.004-0.043; Environmental Symptoms Questionnaires-Cerebral symptoms score, r=0.587-0.771, P=0.001-0.027, n=4). Collectively, these findings highlight the site-specific regulation of CBF in hypoxia that maintains CDO2 selectively in the posterior but not the anterior cerebral circulation, with minimal contribution from the central respiratory chemoreflex. Furthermore, ECA vasodilatation might represent a hitherto unexplored haemodynamic risk factor implicated in the pathophysiology of AMS.

Relationship Between Orthostatic Stress Response And Acute Mountain Sickness Susceptibility At High Altitude: Pilot Study

PURPOSE: To determine whether there is a difference in hemodynamic responses to head-up tilt (HUT) in subjects who do, and do not, experience acute mountain sickness (AMS) during exposure to hypobaric hypoxia. We also aimed to determine if those hemodynamic variables altered during HUT correlated with AMS severity. METHODS: Fifteen participants completed three testing sessions: 1) VO2max test to determine workload at 50% VO2max for hypoxia exposure; 2) HUT test consisted of supine rest for 20 min followed by 70° upright tilt for ≤40 min; and 3) six hours of hypobaric hypoxic exposure simulating 4572 m where participants performed two, 30-min cycling bouts and rested when not exercising. During HUT, continuous blood pressure (BP) monitoring was used to assess systolic and diastolic blood pressure (SBP, DBP); mean arterial pressure (MAP); variability in SBP, DBP, and MAP; and heart rate. AMS scores were reported before and after six hours of hypoxic exposure. Statistical analysis included mixed effects ANOVA to determine changes between supine rest and end of HUT and those who scored a ≥ 3 AMS positive (AMS+) and < 3 AMS negative (AMS-) groups. Correlations by linear regression determined associations between HUT hemodynamic responses and AMS scores. Statistical significance was set to p < 0.05. RESULTS: Systolic, diastolic, and mean arterial blood pressure variability (BPV) increased from supine rest to end of HUT (BPV mean difference ± SD for AMS+ & AMS- groups: SBP = 3.5 ± 3.0, 1.2 ± 1.9: DBP = 1.7 ± 1.5, 0.6 ± 0.9: MAP = 2.8 ± 2.9, 1.1 ± 1.4; p = 0.004, 0.004, & 0.006, respectively). Those with higher AMS scores tended to have a greater magnitude of change in SBP, DBP, and MAP variability during the HUT test (r = 0.65, 0.64, & 0.60, respectively). CONCLUSIONS: Increased BPV indicates BP dysregulation, suggesting that AMS+ individuals may have greater disruptions in BP control that could be observable during a postural change prior to hypoxic exposure. BPV during HUT may be a promising predictive variable for AMS but further research is needed. In the future, researchers should consider using sea-level residents and a range of simulated elevations to determine the predictability of AMS susceptibility by BPV.