Different physiopsychological changes between AMS-susceptible and AMS-resistant pre-selected Antarctic expeditioners in Tibet

Does Ibuprofen Prevent Acute Mountain Sickness?

Pro: pulse oximetry is useful in predicting acute mountain sickness.

The role of intracranial hypertension in acute mountain sickness (AMS) is a matter of debate. Distortion product otoacoustic emissions (DPOAEs) can be used to monitor the intracranial pressure (ICP) noninvasively with a level decrease at the frequencies f2=1 and 1.5 kHz indicating elevated ICP. DPOAEs (f2=1, 1.5, 2, 3, and 4 kHz), oxygen saturation (Sao2) and the Lake Louise score (LLS) to assess AMS were measured in trekking tourists on the Mount Everest trek in Nepal at 2610 m and 5170 m. Paired data of both altitudes could be obtained of 187 subjects. All results are given in mean±SD. Sao2 was 94.8±2.7% at 2610 m and 79.0±6.9% at 5170 m. While at 2610 m, none of the study subjects had AMS (LLS 0.04±0.02), at 5170 m 82 (43.9%) had AMS when defined as LLS>2, and 31 (16.6%) when defined as LLS>4 (LLS 2.8±2.2). DPOAE levels decreased at altitude in all frequencies without a difference between trekkers with AMS and without AMS. Low Sao2 correlated with high LLS. Low Sao2 correlated with larger DPOAE level decrease only at f2=1 kHz, while the other frequencies showed no correlation. DPOAE level decrease and LLS showed no correlation. Our data suggest that subjects with AMS symptoms did not have higher ICP compared to healthy subjects. Consequently, it seems unlikely that intracranial hypertension accounts for the symptoms of AMS.

ABSTRACTS 7th World Congress of Mountain & Wilderness Medicine A combined meeting of the International Society for Mountain Medicine and the Wilderness Medical Society July 30-August 4, 2016 Telluride, Colorado.

The Chinese AMS score (CAS) is used in clinical medicine and research to diagnosis acute mountain sickness (AMS). However, the Lake Louise Score (LLS) is the well-accepted standard for diagnosing AMS. The difference between the CAS and LLS questionnaires is that the CAS considers more nonspecific symptoms. The aim of the present study was to evaluate differences in AMS prevalence according to the LLS and CAS criteria. We surveyed 58 males who traveled from Chongqing (300 m) to Lhasa (3658 m) via the Qinghai-Tibet train. Cases of AMS were diagnosed using LLS and CAS questionnaires in a few railway stations at different evaluation areas along the road. We subsequently evaluated discrepancies in values related to the prevalence of AMS determined using the 2 types of questionnaires (CAS and LLS). The prevalence of CAS-diagnosed AMS indicated that the percentage of AMS cases among the 58 young men was 29.3% in Golmud, 60.3% in Tanggula, 63.8% in Lhasa, 22.4% on the first day after arrival in Lhasa, 27.6% on the second day, 24.1% on the third day, and 12.1% on the fourth day. The prevalence of LLS-diagnosed AMS in Golmud was 10.3%, 38% in Lhasa, and 6.9% on day 1, the prevalence in each station was lower than that as assessed by the CAS. Our experimental data indicate that AMS diagnoses ascertained using the CAS indicate a higher AMS prevalence than those ascertained using the LLS. Through statistical analysis, the CAS seems capable of effectively diagnosing AMS as validated by LLS (sensitivity 61.8%, specificity 92.7%).

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 25:164-173, 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 (AMS) is common at high altitude and may lead to high altitude cerebral edema (HACE) if not properly recognized. Previous studies have suggested that AMS is associated with increases in intracranial pressure (ICP). Increased ICP has been associated with increased intra-ocular pressure (IOP). This study was designed to determine the association between IOP and AMS. Subjects were recruited from a convenience sample of travelers in the Khumbu region of Nepal, elevation 14,410 ft (4392 m). Study participation involved completion of a questionnaire to assess for AMS by the Lake Louise Score (LLS), followed by three IOP measurements in each eye. Investigators were blinded to the LLS. Subjects with a history of ocular surgery were excluded. Three IOP measurements per eye were made using an applanation tonometer (Tono-Pen XL(®), Reichart Technologies) and averaged across both eyes. Multivariable logistic regression analysis was used to estimate the association between IOP and AMS while adjusting for age, ascent or descent, and use of acetazolamide. IOP and blood O2 saturation were compared using a Spearman correlation coefficient. 161 subjects were enrolled with a median age of 36 (IQR: 29-45) years; 60% were male, 75% were ascending, and 64% were taking acetazolamide; additionally, 38%, (95% CI: 31%-47%) were diagnosed with AMS (LLS ≥3). The median IOP was 21 (IQR 18-24) mmHg. The logistic regression model demonstrated no association between IOP and AMS as measured by LLS (odds ratio [OR] 1.0, 95% CI: 0.9-1.1),age (OR 1.0, 95% CI: 0.9-1.0) or with use of acetazolamide (OR 1.4, 95% CI: 0.6-2.6). Ascent (OR 0.4, 95% CI: 0.2-0.9) was negatively associated with IOP but not significantly so. IOP and O2 saturation were not correlated (p=0.93). IOP measured at high altitude is not associated with the diagnosis of AMS. Other approaches to diagnose AMS easily and accurately are needed.

Acute mountain sickness (AMS) causes serious illness for many individuals ascending to high altitude (HA), although preventable with appropriate acclimatisation. AMS is a clinical diagnosis, with symptom severity evaluated using the Lake Louise Score (LLS). Reliable methods of predicting which individuals will develop AMS have not been developed. This systematic review evaluates whether a predictive relationship exists between oxygen saturation and subsequent development of AMS. PubMed, PubMed Central, MEDLINE, Semantic Scholar, Cochrane Library, University of Birmingham Library and clinicaltrials.gov databases were systematically searched from inception to 15 June 2023. Human studies involving collection of peripheral blood oxygen saturation (SpO2) from healthy lowlanders during ascent to HA that evaluated any relationship between SpO2 and AMS severity were considered for eligibility. Risk of bias was assessed using a modified Newcastle–Ottawa Tool for cohort studies (PROPSPERO CRD42023423542). Seven of 980 total identified studies were ultimately included for data extraction. These studies evaluated SpO2 and AMS (via LLS) in 1406 individuals during ascent to HA (3952–6300 m). Risk of bias was ‘low’ for six and ‘moderate’ for one of the included studies. Ascent profiles and SpO2 measurement methodology varied widely, as did the statistical methods for AMS prediction. Decreasing oxygen saturation measured with pulse oximetry during ascent shows a positive predictive relationship for individuals who develop AMS. Studies have high heterogeneity in ascent profile and oximetry measurement protocols. Further studies with homogeneous methodology are required to enable statistical analysis for more definitive evaluation of AMS predictability by pulse oximetry.

BackgroundAcute mountain sickness (AMS) occurs in non-acclimatized people after an acute ascent to an altitude of 2,500 m or higher. The aim of this study was to examine the incidence and severity of AMS and associated symptoms in children.MethodsThe prospective observational study included 197 healthy, non-acclimatized 11 and 12-year-old children trekking the round-trip from the trailhead to the summit of Xue Mountain, Taiwan (2,179 m to 3,886 m) over 3 days. AMS was evaluated at Qika Hut (2,460 m) on Day 1, at Sanliujiu Hut on Day 2 (3,100 m), and at the same altitude (3,100 m) after reaching the summit on Day 3. We used the Lake Louise Score (LLS) to diagnose AMS and record daily AMS-associated symptoms. We gave acetazolamide to children with mild to moderate AMS. Dexamethasone was reserved for individuals suffering from severe AMS. Acetaminophen was administrated to children with headache, and metoclopramide for those with nausea or vomiting.ResultsThere were 197 subjects eligible for analysis. The overall incidence of AMS was 40.6%, which was higher in males and in subjects with a higher body mass index (BMI) (p < 0.05). The prevalence of AMS on Day 1 was 5.6%, which was significantly lower than that on Day 2 (29.4%) and Day 3 (23.4%). The mean LLS of all subjects was 1.77 ± 2.08. The overall incidence of severe AMS (LLS ≥ 5) was 12.5%. The mean LLS of the AMS group (3.02 ± 2.46) was significantly higher than that of the non-AMS group (0.92 ± 1.16, p < 0.001). Among the AMS group, the mean LLS was 1.00 ± 1.55 on Day 1, 4.09 ± 1.97 on Day 2, and 3.98 ± 2.42 on Day 3. The most common symptom was sleep disturbance followed by dizziness, and headache. The prevalence of headache was 46.2% on Day 2 at 3,100 m, and 31.3% on Day 3 at the same altitude after climbing the summit (3,886 m). Males experienced significantly more headache and fatigue than females (p < 0.05). The LLS and prevalence of all AMS symptoms were significantly higher in the AMS than the non-AMS group (p < 0.05).ConclusionsThe AMS incidence among children trekking to Xue Mountain was 40.6%. AMS is common and mostly manifests as mild symptoms. Gender (male) and a higher BMI could be considered two independent risk factors of higher AMS incidence. Sleep disturbance is the most common symptom, and the lower prevalence of headache on Day 3 may be due to the effects of medication and/or acclimatization.

This study was intended to demonstrate a biologically important association between acute mountain sickness (AMS) and sleep disordered breathing. A total of 14 subjects (eight males, six females aged 36 +/- 10 years) were studied at six different altitudes from sea level to 5050 m over 12 days on a trekking route in the Nepal Himalaya. AMS was quantified by Lake Louise (LL) score. At each altitude, sleep was studied by 13 channel polysomnography (PSG). Resting arterial blood gases (ABG) and exercise SaO2 were measured. Ventilatory responses (VR) were measured at sea level. Individual data were analysed for association at several altitudes and mean data were analysed for association over all altitudes. ABG showed partial acclimatization. For the mean data, there were strong positive correlations between LL score and altitude, and periodic breathing, as expected. Strong negative correlations existed between LL score and PaO2, PaCO2, sleep SaO2 and exercise SaO2, but there was no correlation with sea level VR. There were equally tight correlations between LLs/PaO2 and LL score/sleep SaO2. The individual data showed no significant correlations with LL score at any altitude, probably reflecting the non-steady state nature of the experiment. In addition, mean SaO2 during sleep was similar to minimum exercise SaO2 at each altitude and minimum sleep SaO2 was lower, suggesting that the hypoxic insult during sleep was equivalent to or greater than walking at high altitude. It is concluded that desaturation during sleep has a biologically important association with AMS, and it is speculated that under similar conditions (trekking) it is an important cause of AMS.

The Lake Louise Score (LLS) is a common tool for diagnosing acute mountain sickness (AMS) after a recent gain in altitude. Required symptoms (headache, dizziness, fatigue or gastrointestinal symptoms) are unspecific, subjective and not detectable by physiological parameters. (Talks et al., 2022; Boos et al., 2018) This study aimed to enhance present knowledge concerning the impact of mental health on LLS. In a cross-sectional questionnaire study, we assessed 3 groups: 100 inpatients (Ward for psychosomatic medicine – Innsbruck, PSY), 73 mentally healthy individuals (Innsbruck, Austria at an altitude of 570 m, CO) and 223 mountaineers in Nepal (Pheriche 4,371 m and Dingboche 4,410 m, NEPAL). Beside social demographics and LLS 2018 (cutoff for LLS-positivity: LLS ≥ 3 including at least 1 point for headache), we examined symptoms of anxiety (Zung Self-Rating Anxiety Scale [SAS], General Anxiety Disorder Questionnaire 7 [GAD-7]), affective states (International Positive and Negative Affect Schedule Short form [I-PANAS-SF]) and sleep (Insomnia Severity Index [ISI]). In this preliminary analysis, the average age was 39 ± 16 years in PSY, 34 ± 16 years in CO and 40 ± 14 years in NEPAL. Gender distribution showed greater portion of women in PSY and CO (PSY: 72% female 24% male 3% non-binary, CO: 64% female 36% male) contrary to NEPAL (36% female 64% male). At sea level, 67% scored LLS-positive in PSY and 12% in CO (Fishers exact test, p &lt; 0.001). In NEPAL 25% met AMS-criteria by LLS. CO and NEPAL score significantly lower in LLS than PSY (ANOVA: diff = -3.70, p &lt; 0.0001; diff = -3.68, p &lt; 0.0001, respectively). PSY and CO showed significant weak to moderate correlations (Spearman-Rho, p &lt; 0.001) of anxiety (SAS, GAD), affective states (I-PANAS-SF) and sleep impairment (ISI) with LLS-sum. NEPAL showed significant very-weak to weak correlations of insomnia, anxiety and negative affect with LLS-sum. Using logistic regression analysis (Figure 1), higher odds of LLS-positivity are significantly associated with insomnia and anxiety (ISI, SAS) in PSY, with anxiety in CO (SAS) and insomnia and negative affect in NEPAL. While of course a recent gain in altitude is a prerequisite for the diagnosis of AMS this study shows that patients with pre-existing mental illness at low altitude score more frequently false-positive on the LLS than a mentally healthy cohort. Symptoms of anxiety, negative affect and sleep disturbance can affect the AMS-defining questionnaire of LLS both at sea level and at high altitude. There is still uncertainty on a possible common pathophysiological pathway of psychiatric diseases and AMS since there is no Gold Standard in diagnosing AMS. Concerning (well-)established risk-factors for AMS like speed of ascent (Berger et al., 2023) and female sex (Hou et al., 2019), we see no evident data. The data presented here suggest that strength of expression of negative affect can cause positive LLS scoring. Acute mountain sickness and psychiatric disorders show overlapping symptoms at sea level. At high altitudes, negative affect seems to be a possible cause for the development of AMS. Further research focus should be placed on mountaineers in high altitude with psychiatric disorders and their mental state.

Acute Mountain Sickness Is Not Repeatable Across Two 12-Hour Normobaric Hypoxia Exposures

The clinical evaluation of acute mountain sickness (AMS) is often performed in remote settings with minimal equipment. The purpose of this study was to examine the utility of heart rate variability and other cardiovascular parameters in a high-altitude clinical setting. Forty-one participants were recruited from the patient population of the clinic, and from festivalgoers [those who attended the Janai Purnima festival held at Lake Gosainkunda (4380 m) in Langtang, Nepal] in the vicinity of the clinic. Twenty-one participants were diagnosed with AMS; remaining participants were free from altitude illness. Heart rate variability (both time and frequency domain measures), arterial oxygen saturation (SpO2), blood pressure and Lake Louise Score were evaluated in all the participants. Oxygen saturation and diastolic blood pressure were negatively and positively correlated with Lake Louise Score, respectively. Receiver operating characteristic analysis indicated that an SpO2 of 86% or greater was associated with a very low likelihood of AMS at this altitude. No heart rate variability parameters were different in the AMS group as compared with the control group. In conclusion, in patients with SpO2 of 86% or more at 4380 m or higher, the likelihood of AMS is low. Diastolic blood pressure correlated with AMS severity, whereas heart rate variability was not useful in the diagnosis of AMS.

Risk Determinants of Acute Mountain Sickness and Summit Success on a 6-Day Ascent of Mount Kilimanjaro (5895 m)

Acute mountain sickness (AMS) is a common condition in individuals who ascend to altitudes over 2 500 m. There is no measurements that can reliably predict or diagnose this condition. We therefore determined whether pulse oximetry data are associated with the development of AMS and can help diagnose AMS. We studied 58 young male undergraduates who traveled from Chongqing (300 m) to Lhasa (3 658 m) by train. We collected data on the ascent profiles and AMS symptoms based on the Lake Louise Score (LLS). The resting arterial oxygen saturation (R-SpO2) and pulse rate were then measured using finger pulse oximetry. In Golmud(2 800 m) and Tanggula(5 200 m), R-SpO2 was significantly lower in the AMS group than in the group without AMS (P<0.05). However, upon arrival in Lhasa (3 658 m), the R-SpO2 was higher in the AMS group than in the non-AMS group (P<0.05). In Tanggula, the change in the SpO2 (CR-SpO2) in the AMS group was higher than that in the non-AMS group (P<0.05). But in Lhasa, the CR-SpO2 in the AMS group was lower than that in the non-AMS group (P<0.05). We also monitored heart rate (HR) throughout the study. In Xining(2 200 m) and Golmud, the HRs in the AMS group were higher than those in the non-AMS group. However, the HRs in the AMS group were lower than those in the non-AMS group in Tanggula and Lhasa. Based on the results of this study, the R-SpO2 graph was not consistent. We can thus conclude that the utility of SpO2 remains limited in the diagnosis of AMS. The results suggest that using pulse oximetry to diagnose AMS is not valuable in people ascending to Lhasa on the Qinghai-Tibet train.