We examined the effect of a short-term descent to low altitude on sleep-disordered breathing (SDB) in healthy moderate altitude residents. Forty-four healthy participants (50 Study impact: To our knowledge, the current study is the first to investigate the effect of a short-term descent to low altitude on sleep-disordered breathing (SDB) in healthy moderate altitude residents. In this paper, we show that a short-term, low-altitude stay leads to a reduction in nocturnal hypoxemia and less sleep-associated breathing disorders, especially in males. Moreover, the proportion of severe SDB is underestimated at lower-than-living sleep laboratory assessments.

Whether hypoxia during popular high-altitude travel negatively affects cerebral oxygenation in vulnerable patients with pulmonary vascular disease (PVD) is unknown. We studied overnight cerebral tissue oxygen saturation (CTO) and desaturation index (cODI) in PVD-patients at 2500 m and effects of supplemental oxygen therapy (SOT). In this randomized-controlled crossover trial, stable PVD-patients diagnosed with pulmonary arterial or distal chronic thromboembolic pulmonary hypertension (PAH/CTEPH) had CTO and cODI (decrease in CTO ≥ 4%) assessed overnight at 470 m and 2500 m along with fingertip pulseoximetry (SpO2) and desaturation index (aODI). For safety, SOT was given if SpO2 dropped < 80% for > 30 min and stratified analysis accordingly. Primary endpoint was the difference in CTO between 470 and 2500 m. 16 PVD-patients (7 women; 13 PAH, 3 CTEPH), (mean ± SD) 56 ± 14 years old, were included per-protocol. At 470 m, the mean nocturnal CTO was 66.3 ± 1.6% and SpO2 90.3 ± 0.8%. At 2500 m on ambient air, CTO was unchanged 65.9 ± 1.6% (mean difference -0.4%; 95% CI -4.0 to 3.2) despite a lower SpO2 of 83.6 ± 0.8; -6.7 (-8.7 to -4.6%). At 2500 vs. 470 m, cODI increased by 3.1 events/hour (-0.3 to 6.6). SOT needed by 50% of PH-patients improved SpO2 by +7.5 (4.9 to 10.0), but not CTO and cODI (+3.6% (-1.0 to 8.2)) and -3.8 events/hour (-8.1 to 0.5). In PVD-patients on ambient air at 2500 m, nocturnal CTO remained unchanged compared to 470 m despite lower SpO2. SOT promptly improved SpO2 without affecting cerebral oxygenation. These findings suggest sufficient nocturnal cerebral protection at 2500 m in PVD.

Traditional Chinese Medicine (TCM) is often applied in isolated TCM practices, making rigorous research and standardized real-world data collection challenging. The purpose of this study was to implement the general consent (GC) in TCM practices, investigate the issue and the acceptance rate of the GC, and the influencing demographic factors. GC forms were distributed to patients before appointments and collected during their first visits. Logistic regression analyses were performed to investigate demographic factors influencing GC issue and acceptance rates, considering variables such as age, sex, age * sex, and months since implementation. The study enrolled 2,603 patients who sought TCM treatment, of whom 77.5% returned a GC document. Overall, the GC acceptance rate was 1,558/2,603 (59.9%); of those returning the GC, the acceptance rate was 1,558/2,018 (77.2%). The median [IQR] age of patients was 52 years [37, 64], and the number of female patients was around twice that of male patients. Logistic regression analysis showed no association with the GC issue rate for older age (odds ratio, OR: 1.01, 95% CI: 0.99-1.03, p = 0.474), female sex (OR: 1.31, 95% CI: 0.71-2.38, p = 0.387), the interaction between age and female sex (OR: 1.00, 95% CI: 0.98-1.01, p = 0.379), or months since GC implementation (OR: 1.00, 95% CI: 0.98-1.01, p = 0.615). Similarly, for the acceptance rate, no effects were observed for older age (OR: 1.02, 95% CI: 1.00-1.04, p = 0.120), female sex (OR: 1.25, 95% CI: 0.63-2.46, p = 0.516), or the interaction between age and female sex (OR: 0.99, 95% CI: 0.97-1.01, p = 0.243). Months since GC implementation was associated with a slight decrease in acceptance rate over time (OR: 0.98, 95% CI: 0.97-1.00, p = 0.034). In conclusion, this study successfully implemented the GC in TCM practices and paves the way for real-world studies in the field of TCM. Patient acceptance was high and remained consistent across sex and age.

Background High altitude may adversely affect patients with pulmonary vascular disease (PVD), but acute cardiopulmonary effects remain unclear. Research Question How does 2-day high-altitude exposure affect pulmonary hemodynamics and oxygen delivery in patients with PVD defined as pulmonary arterial or chronic thromboembolic pulmonary hypertension? Study Design and Methods In this randomized, controlled crossover trial, stable, low-risk patients with PVD without resting hypoxemia at 470 m were transported by cable car to 2,500 m, where they stayed for 2 days. Systolic pulmonary arterial pressure (sPAP), total pulmonary resistance (TPR), right ventricular (RV) arterial coupling, pulmonary arterial elastance (EA), and pulmonary arterial compliance (PAC) were assessed by echocardiography, whereas oxygen content was measured in arterial blood gases. Results Twenty-seven patients with PVD (44% female; mean [SD] age, 61 [14] years) were included. Altitude exposure was associated with an increase in sPAP of 18 mm Hg (40%; 95% CI, 9-28 mm Hg; P < .001) and TPR of 2.8 Wood units (WU; 32%; 95% CI, 0.7-4.9 WU; P = .007). RV arterial coupling, assessed by tricuspid regurgitation velocity (TAPSE) to sPAP ratio, decreased from a mean (SD) of 0.55 (0.04) mm/mm Hg to 0.38 (0.04) mm/mm Hg (–31%; 95% CI, –0.27 to –0.07 mm/mm Hg; P < .001). EA increased by 0.2 mm Hg/mL (33%; 95% CI, 0.07-0.33 mm Hg/mL; P < .001) and PAC decreased by 1.6 mL/mm Hg (38%; –2.7 to –0.6 mL/mm Hg; P = .002). Although oxygen content was lower at high altitude, oxygen delivery was similar at both altitudes. Interpretation Our results show that 2-day exposure to 2,500 m in stable, low-risk patients with PVD increases RV resistive and pulsatile afterload and decreases TAPSE to sPAP ratio, indicating reduced RV arterial coupling. Despite attenuated cardiac adaptation, overall function seems to be sufficient to maintain oxygen delivery and to compensate partially for hypoxemia. Clinical Trial Registration ClinicalTrials.gov; No.: NCT05107700; URL: www.clinicaltrials.gov

Background/research question We investigated the increase in pulmonary artery pressure (PAP) with altitude gain in healthy low-altitude residents travelling to high altitude, analysing reported measures including systolic (sPAP) and mean pulmonary artery pressure (mPAP) and tricuspid regurgitation pressure gradient (TRPG). Methods A systematic literature search was performed in PubMed and Embase from database inception to 12 December 2024. Studies including healthy adults residing at <1000 m and reporting sPAP, mPAP or TRPG measured by echocardiography or right heart catheterisation at both low altitude and >1000 m within 30 days were included. Random effects meta-analyses and meta-regression assessed the increase in sPAP, mPAP and TRPG per 1000 m altitude gain. Results 60 articles with 1220 participants (75% males, age 34±4 years) were eligible; 54 were included into the meta-analysis. sPAP was reported in 38 studies, mPAP in nine and TRPG in 11. At high altitude, absolute sPAP ranged from 24 to 50 mmHg and mPAP from 20 to 26 mmHg. Meta-regression showed a linear increase per 1000 m: sPAP 3.4±0.5 mmHg, mPAP 2.5±0.7 mmHg and TRPG 3.3±1.0 mmHg. The estimated upper limit of normal for the increase per 1000 m was 4.5 mmHg for all three measures. Interpretation This systematic review and meta-analysis of healthy low-altitude residents travelling to high altitudes demonstrates a linear increase in PAP with altitude gain, based predominantly on data from elevations >2500 m and younger male populations. It defines upper reference limits for the increase in sPAP, mPAP and TRPG per 1000 m. These population-derived reference ranges may assist in the interpretation of PAP measurements and in counselling individuals evaluated at high altitude, but should be applied with consideration of the underlying population and exposure characteristics.

In patients with PH exposed to simulated ∼2500-m hypoxia, a single 50-mg sildenafil dose had no effect at rest but reduced exercise-induced pulmonary pressure and resistance, potentially improving exercise capacity during hypoxic exposure https://bit.ly/4rHhvFz.

Aims:Patients with pulmonary arterial and distal chronic thromboembolic pulmonary hypertension (PAH/CTEPH) frequently experience exertional dyspnoea with desaturation. Although ambulatory low-flow supplemental oxygen therapy (SOT) is commonly prescribed, its effect via portable concentrators in daily life has not been studied. We investigated the effect of ambulatory SOT on six-minute walk distance (6MWD). Methods and results:This was a randomized non-inferiority crossover study in patients with PAH or CTEPH desaturating by >3% during exercise. Patients performed two 6MWD tests in randomized order: one in ambient air and one with pulsed low-flow (1-2 L/min) nasal supplemental oxygen (SOT) by a portable back-packed concentrator. The primary outcome was 6MWD with a predefined non-inferiority margin of -35 m for ambient air vs. SOT. Forty patients (age 62 ± 15 years, 21 female, 20 PAH, 20 CTEPH) were included. The mean difference in 6MWD between ambient air and SOT was 0 m (95% CI: -15 to 14 m, P <0.001).Five patients exceeded the minimal clinically important difference of 35 m with SOT. At end-exercise, the cohort desaturated 2% less with SOT (95% CI -3 to -0.2%, P = 0.025) and reported 1 point less dyspnoea (95% CI 0.3 to 1, P < 0.002). These effects were also observed in PAH but not in CTEPH. Conclusion:Walking on ambient air was non-inferior to low-flow SOT during 6MWD in treated PAH/CTEPH patients with exercise-induced desaturation and relatively preserved exercise capacity. SOT reduced dyspnoea in PAH. Future research should identify SOT responders and develop lighter, more effective devices tailored to patient needs. Registration:ClinicalTrials.gov (NCT06384534).

Polyneuropathie ist eine einschränkende Erkrankung, die mit einer weitreichenden Schädigung der peripheren Nerven einhergeht und zu sensorischen, motorischen und autonomen Symptomen führt. Sie entsteht durch verschiedene Ursachen wie Stoffwechselstörungen, toxische Medikamente, Infektionen, genetische Konstellationen, Autoimmunerkrankungen, Tumoren, Traumata oder idiopathische Gegebenheiten und weist eine Prävalenz von 6–7

Müller, Julian, Anna Titz, Pascal Yoncaova, Michael Furian, Mona Lichtblau, Ruth McQuillan, Marshall Dozier, Evropi Theodoratou, and Silvia Ulrich.The association between chronic high-altitude exposure and increased pulmonary vascular resistance in healthy high-altitude residents. A systematic review and meta-analysis. High Alt Med Biol. 00:00-00, 2026. BACKGROUND:At high altitude, hypoxia triggers pulmonary vasoconstriction and vascular remodeling, potentially elevating pulmonary vascular resistance (PVR). Whether chronic high-altitude exposure raises PVR to clinically meaningful levels remain unclear, particularly in the context of long-term physiological adaptation. OBJECTIVES:To synthesize and assess the evidence of the association between chronic high-altitude exposure and PVR in healthy high-altitude residents. ELIGIBILITY CRITERIA:Peer-reviewed studies reporting PVR measured by echocardiography or right heart catheterization in healthy adults permanently residing at high altitude were eligible. Studies involving acute or intermittent hypoxia exposure, animal subjects, or pediatric populations were excluded. METHODS:A systematic literature search was conducted across four electronic databases (Medline, Embase, Scopus, and Web of Science) covering all records from database inception through October 2025. Two reviewers independently screened abstracts and full texts using Covidence software. Risk of bias was assessed using the modified National Heart, Lung, and Blood Institute Quality Assessment Tool. Random-effects meta-analyses were performed. A sensitivity analysis excluded studies with high risk of bias. RESULTS:Out of 464 identified records, 13 studies met eligibility criteria, comprising 854 participants (80% males) across different populations in South America, Asia, and Africa. Most studies were conducted between 3,500 and 4,000 m. The primary pooled PVR estimate was 2.4 WU (2.0-2.8 WU), which slightly exceeds the sea level upper limit of normal (2.0-2.2 WU). Following exclusion of high-risk-of-bias studies, the estimate decreased to 2.2 WU (1.9-2.5 WU), approaching the upper limit of normal. However, substantial heterogeneity was observed in all analyses. LIMITATIONS:The small number of included studies, heterogeneity, measurement technique, predominance of male participants, and narrow altitudinal range of most studies limit the generalizability of the findings. CONCLUSIONS:Chronic high-altitude exposure is associated with a slight elevation in PVR in otherwise healthy individuals. However, the clinical significance of this elevation remains unknown. These findings highlight the need for altitude-specific reference values, prospective studies, and further investigation into the role of blood viscosity in interpreting PVR at high altitude.

Polyneuropathy is a debilitating condition characterized by widespread damage to the peripheral nerves, leading to sensory, motor, and autonomic symptoms. It arises from various causes, including metabolic disorders, toxic medications, infections, genetic predisposition, autoimmune diseases, tumors, trauma, or idiopathic conditions. It has a prevalence of 6-7% in the general population and a higher prevalence in individuals with diabetes mellitus. This condition frequently causes chronic pain and disability, significantly impairs quality of life, and necessitates intensive clinical research. Regarding the scientific investigation of treatment methods such as acupuncture, while existing instruments improve reporting and bias assessment, they fall short in evaluating content validity, methodological appropriateness, or correctness of conclusions.This article discusses these data collection tools and proposes an initial two-stage roadmap for a new methodology for content and context validation. Step 1 involves a systematic literature search to identify relevant randomized controlled trials (RCTs). Step 2 includes an expert consensus process to develop a checklist for evaluating diagnosis, study design, results, and discussion.This proposed roadmap for a content- and context-based assessment tool closes gaps in current frameworks and promotes standardized, transparent assessments to strengthen polyneuropathy research and the clinical application of acupuncture.

BACKGROUND:High altitude may adversely affect patients with pulmonary vascular disease (PVD), but acute cardiopulmonary effects remain unclear. RESEARCH QUESTION:How does two-day high-altitude exposure affect pulmonary hemodynamics and oxygen delivery in patients with PVD defined as pulmonary arterial or chronic thromboembolic pulmonary hypertension? STUDY DESIGN AND METHODS:In this randomized, controlled crossover trial, stable, low-risk patients with PVD without resting hypoxemia at 470 m were transported by cable car to 2500 m, where they stayed for two days. Systolic pulmonary arterial pressure (sPAP), total pulmonary resistance (TPR), right ventricular (RV) -arterial coupling, pulmonary arterial elastance (EA) and compliance (PAC) were assessed by echocardiography, while oxygen content was measured in arterial blood gases. RESULTS:Twenty-seven patients with PVD (44% women, 61±14 years) were included. Altitude exposure was associated with an increase in sPAP of 18 mmHg (40%, 95%CI: 9 to 28 mmHg, p<0.001) and TPR of 2.8 WU (32%, 0.7 to 4.9 WU, p=0.007). RV-arterial coupling, assessed by TAPSE/sPAP ratio, decreased from 0.55±0.04 to 0.38±0.04 mm/mmHg (-31%, -0.27 to -0.07 mm/mmHg, p<0.001). EA increased by 0.2 mmHg/mL (33%, 0.07 to 0.33 mmHg/mL, p<0.001) and PAC decreased by 1.6 mL/mmHg (38%, -2.7 to -0.6 mL/mmHg, p=0.002). Although oxygen content was lower at high altitude, oxygen delivery was similar at both altitudes. INTERPRETATION:Two-day exposure to 2500 m in stable, low-risk patients with PVD increases RV resistive and pulsatile afterload and decreases TAPSE/sPAP, indicating reduced RV-arterial coupling. Despite attenuated cardiac adaptation, overall function appears sufficient to maintain oxygen delivery and partially compensate for hypoxemia. CLINICAL TRIAL REGISTRATION:Clinicaltrials.gov (NCT05107700).

Abstract The erythrocyte sedimentation rate (ESR) is one of the most widely used laboratory diagnostic parameters in the preliminary assessment of inflammation; indeed, every reader of this work has likely received an ESR assessment in their lifetime. A rapid ESR is a non-specific parameter that provides information about the inflammatory process. Although the origins of this methodology date back to antiquity, the prevailing view that ESR simply reflected particle settling of erythrocytes has recently undergone a paradigm shift: once cell aggregates form a system-spanning network, gravitational collapse of a weak and percolating gel reveals a more complex process reflecting the failure. The apparent non-specific nature of the cells and proteins involved also called into question the medical utility of ESR, at least in well-resourced environments. Here we show a new experimentally derived and physically modelled approach (“supraESR”) that enhances the value and accuracy of ESR for a variety of conditions that exhibit abnormally slow ESR (e.g., sickle cell disease, neuroacanthocytosis syndromes, chronic mountain sickness). We introduce a completely new diagnostic parameter that is based on an established and easily automated measurement method that promises low-cost screening for neuroacanthocytosis syndrome, a group of rare neurodegenerative diseases that are currently detectable only through integration of complex multimodal findings.

INTRODUCTION:Traditional Chinese medicine (TCM) is becoming popular in Switzerland; however, Swiss TCM research activity and scientific output have not been investigated. The objective of this work was to describe the Swiss TCM research activities and main health conditions studied. METHODS:A systematic literature search of PubMed (covering databases such as MEDLINE, life science journals and online books) and Embase was performed from database inception to December 31, 2023. Articles describing a TCM-related therapy modality in humans with at least one author affiliated with a Swiss institution were selected for the study. The primary outcome was the main health condition studied. Secondary outcomes were the total number of articles published over time, the TCM therapies used, and the Swiss institutions involved. RESULTS:Of the 223 published articles included in the final analysis, 68.2% originated from the top 3 of 73 Swiss institutions: the University of Zurich (32.3%), University of Bern (30.0%), and University of Basel (7.6%). Overall, 116 (52.0%) articles described original studies containing primary data. The top health category studied was pain management (16.4%). The most used TCM therapies were acupuncture and moxibustion (61.2%). CONCLUSION:Until 2023, the total number of scientific TCM output by Swiss authors is steadily increasing but remains small. More effort to conducted TCM research and elucidate the TCM therapy effects in Switzerland is warranted.

INTRODUCTION:Patients with pulmonary arterial hypertension (PAH) living at high altitudes experience exacerbated hypoxaemia. This study aimed to assess the effects of relocating PAH patients from high altitude (2,850 m) to sea level on nocturnal hypoxaemia, sleep-disordered breathing, and autonomic cardiovascular function. METHODS:In a repeated measures design, PAH patients underwent evaluations near their living altitude at 2,850 m and at sea level. The primary outcome was the change in mean nocturnal SpO2, while secondary outcomes included changes in time spent with SpO2 <90% (t < 90), apnoea-hypopnoea index (AHI), heart rate variability (HRV), and blood pressure. Measurements were taken using cardio-respiratory polygraphy at 2,850 m and during the first two nights following relocation f to sea level. RESULTS:A total of 8 patients (86% women) with a mean mean pulmonary artery pressure of 52 ± 17 mm Hg and PVR of 16.6 ± 8.8 Wood units were included. Relocation to sea level resulted in significant improvements in nocturnal hypoxaemia, with mean SpO2 increasing by 6.9% (95% CI 5.9-7.9) and t < 90 decreasing by -53% (95% CI -67.1 to -39.0). AHI and supine AHI decreased, and sleep quality significantly improved. HRV analysis showed increased parasympathetic activity, with root mean square of successive differences, pRR50, low frequency (LF), and high frequency (HF) rising, and the LF/HF ratio decreasing. Morning PaO2 increased by 3.0 kPa (95% CI 2.3-3.7), and blood pressure significantly decreased. CONCLUSION:Relocation of PAH patients from high to low altitude led to significant improvements in nocturnal oxygenation and SDB, and enhanced parasympathetic activity, suggesting that short-term exposure to sea level may offer benefits for PAH-patients living at high altitude.

Background/Objectives: It is widely acknowledged that healthy highlanders (HL) present with significantly higher pulmonary arterial pressure (PAP) compared to healthy lowlanders (LL). However, whether this elevated PAP solely signifies a response to hypoxia at altitude or is also linked to right ventricular (RV) dysfunction is still unknown. Therefore, we assessed RV function in HL and LL using speckle-tracking-derived strain analysis. Methods: This case-control study evaluates echocardiographic RV free wall strain (RVFWS) in LL and HL in Kyrgyzstan. A RVFWS over -20% for men and a RVFWS of -21% for women were considered indicators of RV dysfunction. Subgroup analysis included individuals with and without risk for pulmonary hypertension (PH), defined as a TRV > 2.8 m/s. Results: A total of 59 participants (21 LL, 38 HL), with a mean ± SD age of 43 ± 8 versus 48 ± 10 years, were included and assessed at their living altitude. RVFWS in HL and LL was -27.3% ± 4.7 versus -27.0% ± 6.0 (mean difference 0.13%, 95%CI -2.65 to 2.92, p = 0.852). The conventional RV indices RV FAC (42% ± 6 vs. 38% ± 8), TAPSE (2.2 cm ± 0.2 vs. 2.0 cm ± 0.3), and TDI S' (14.2 cm/s ± 1.9 vs. 12.1 cm/s ± 1.8), however, did differ significantly between LL and HL. HL with and without risk for PH did not differ in RVFWS and in the conventional RV indices. Conclusions: Despite significant differences in conventional RV markers, healthy highlanders generally did not differ in RVFWS compared with lowlanders, indicating maintained RV systolic function at high altitude. Our findings suggest that elevated PAP in HL reflects adaptation rather than RV dysfunction, underscoring the need for refined diagnostic criteria for clinically relevant high-altitude pulmonary hypertension.

Iron deficiency aggravates hypoxic pulmonary vasoconstriction, exacerbating the increase of pulmonary arterial pressure at high altitude (HA). This may be especially relevant for patients with pulmonary hypertension (PH) travelling to HA, who moreover have a high prevalence of iron deficiency. Currently, no data is available on iron parameters and their influence on HA adaptation in PH-patients. In a randomized cross-over trial, 27 patients (44% female, mean age 61.7 ± 13.6 y) with pulmonary arterial hypertension (67%) or chronic thromboembolic PH (33%) were assessed at baseline (Zurich, 470 m) and during a stay at 2500 m. Blood samples were taken at baseline and after 20 h at 2500 m. A significant increase in ferritin (131 ± 68 to 140 ± 75, p = 0.002), transferrin (28.0 ± 4.7 to 30.3 ± 4.4, p = 0.012) and soluble transferrin receptor (sTfR) levels (2.7 ± 0.7 to 2.9 ± 0.6, p = 0.014) was observed at HA, all of which correlated with decreasing hepcidin levels. Arterial partial pressure of carbon dioxide (PaCO2) was inversely correlated with transferrin levels (Pearson's r = -0.57, p < 0.001), and baseline transferrin concentration was an independent predictor of PaCO2 at baseline and HA (p = 0.037). Furthermore, transferrin levels < 30 µmol/L were an independent predictor of mean nocturnal oxygen saturation (SpO2) at baseline and HA. The need for oxygen supplementation at HA could be predicted using a model including baseline transferrin, achieving a positive predictive value of 84%, suggesting that transferrin may serve as a useful clinical marker to identify PH patients at risk of oxygen desaturation at HA.

We investigated whether three days of hypoxic exposure in a hypobaric chamber, and the associated nocturnal periodic breathing (nPB), reduce sympathetic nerve activity (MSNA) transduction to blood pressure (BP). While hypoxia did not affect MSNA transduction to BP, larger drops in BP occurred following cardiac cycles without sympathetic bursts, suggesting increased reliance on sympathetic vasoconstrictor support for beat-to-beat BP. Prevention of nPB by inspiratory carbon dioxide administration did not affect MSNA transduction to BP in hypoxia.

Background:Little is known about the effects of portable supplemental oxygen therapy (SOT) to improve exercise performance in highlanders at risk for high-altitude pulmonary hypertension (HAPH). We aimed to investigate whether SOT improves the 6-min walk distance (6MWD) and reduces perceived dyspnoea in highlanders at risk for HAPH. Methods:In a pragmatic randomised open-label crossover trial, adult highlanders, living >2500 m, with a peak tricuspid regurgitation velocity >2.8 m·s-1 corresponding to a tricuspid regurgitation pressure gradient (TRPG) ≥31 mmHg by echocardiography were included. Highlanders were randomised to perform two 6-min walk tests at 3250 m with and without SOT (50 mL pulse volume, via nasal cannula, provided by a portable device). The primary outcome was the effect of SOT on the 6MWD compared with ambient air (air). Secondary outcomes were vital parameters and dyspnoea assessed by the Borg Category-Ratio 10 (CR10) Scale with SOT versus air. Results:47 highlanders (44% male, mean±sd age of 52±12 years, TRPG of 41±10 mmHg and oxygen saturation (S pO2 ) of 88±3%) were included. SOT did not improve 6MWD compared with air (457±90 m versus 475±84 m; mean difference with SOT of -18 m (95% CI -30-8; p=0.241)). End-exercise dyspnoea was significantly lower with SOT compared with air, along with reduced heart rate and higher S pO2 . Conclusion:In hypoxaemic highlanders at risk for HAPH, portable low-dose SOT did not improve 6MWD, despite lower dyspnoea perception, lower heart rates and higher S pO2 at end-exercise. This indicates that low-dose SOT oxygen, as commonly applied in various clinical settings, does not increase 6MWD. Whether it reduces cardiovascular stress during exercise needs to be further studied.