Safety and efficacy of electro-thumbtack needle for acute mountain sickness patients: a protocol of a randomized, single-blinded, and placebo-controlled study.

BACKGROUND: Acute mountain sickness (AMS) is considered the most common altitude sickness. It can be detrimental to the health of tourists who rapidly ascend high mountains, and can also impair the performance of individuals who move to the plateau for work or education. Acupuncture has been shown to improve AMS as a simple, safe, and effective nonpharmacological method, in case electro-thumbtack needle (ETN) is a more convenient form of acupuncture for both doctor and patient. There are no studies validating the effectiveness of electro-thumbtack needle in improving symptoms in participants with AMS. In this study, we will conduct a randomized controlled trial to evaluate the clinical efficacy and safety of electro-thumbtack needle in participants with AMS. Our hypothesis is that electro-thumbtack needle is safe and effective in treating participants with AMS. METHODS: This study is a single-center, randomized, single-blinded, and placebo-controlled study involving at least 114 participants who were diagnosed with AMS. The participants randomly assigned in a 1:1 ratio to the electro-thumbtack needle group and the sham acupuncture group. The treatment protocol involved stimulation of seven predefined acupuncture points, including Zhong Wan (RN12), bilateral Nei Guan (PC6), bilateral He Gu (LI4), and bilateral Tai Yang (EX-HN5), for approximately one minute each, with continuous application over 48 h. The primary outcome was improvement in 2018 Lake Louise score (LLS) after 48 h of treatment. Secondary outcome indicators included the incidence of participants with moderate-to-severe AMS (AMS > 5)and AMS, the LLS, visual analogue scale of headache, clinical functioning scores, the Groningen Sleep Quality Survey, the Stanford Somnolence Scale, blood pressure, oxygen saturation, and heart rate, in addition to treatment-related adverse events were also captured. DISCUSSION: This trial aims to ascertain the therapeutic benefits of ETN in mitigating AMS symptoms, thereby contributing to the evidence base for traditional medical practices, particularly acupuncture, in high-altitude medicine. TRIAL REGISTRATION: Chinese Clinical Trials Registry: ChiCTR2300073882. Registered on 24 July 2023.

[Expert consensus on Tibetan medicine diagnosis and treatment for high altitude polycythemia].

High altitude polycythemia(HAPC) is one of the most common chronic high-altitude diseases and a prominent public health issue in the Qinghai-Xizang Plateau region of China. Tibetan medicine has provided a safe and effective treatment approach for HAPC, but there is currently no expert consensus on Tibetan medicine diagnosis and treatment for the disease. This consensus followed the principles of evidence-based medicine and learned the procedure and methods of Technical specifications on developing expert consensus for clinical practice guideline in traditional Chinese medicine recommended by China Association of Chinese Medicine. Five clinical issues were identified through literature search, expert interviews, clinical research, and conference consensus. The PICO principle was used for evidence retrieval, screening, and synthesis, and the opinions of experts on high-altitude diseases and cardiovascular and cerebrovascular diseases from major Tibetan medical institutions in China, as well as some traditional Chinese medicine(TCM), western medicine, and evidence-based experts, were widely solicited. Recommendations and consensus suggestions were formed through one expert consensus meeting and two rounds of Delphi expert questionnaire surveys. The consensus included disease diagnosis, etiology and pathogenesis, syndrome classification, clinical treatment, outcome evaluation, prevention and care, and other contents. Therapies for HAPC included Tibetan medicine treatments based on syndrome differentiation, single formula or patent medicine, and external treatment. Each treatment had corresponding levels of evidence and recommendations. This consensus was guided by solving clinical problems, combining disease diagnosis and syndrome differentiation and highlighting the characteristics and advantages of Tibetan medicine, with a view to promoting the standardization of Tibetan medicine diagnosis, treatment, and research on HAPC and improving the level of prevention and treatment.

[Research progress of traditional Chinese and Western medicine non-pharmacological prevention strategies for acute high altitude disease].

Acute high altitude disease (AHAD) is a general term for a series of clinical reactions that occur when the body fails to adapt to the low-pressure hypoxic environment of high altitudes. Mild cases can cause symptoms such as headache, nausea and vomiting, while more severe cases can lead to life-threatening conditions such as pulmonary edema, cerebral edema and other critical conditions that can be fatal. With the increasing demand for high altitudes deployment, understanding the common preventive measures of AHAD can reduce its morbidity or mortality to a certain extent, which is of great benefit to those who reside temporarily at high altitudes. In recent years, as people's health awareness has improved, there has been a growing attention towards non-pharmacological methods of disease prevention. At the same time, non-pharmacological therapy has significant therapeutic effects in preventing and treating high-altitude diseases, which has attracted the attention of researchers in this field. This review summarizes the major non-pharmacological preventive components of modern medicine and outlines the current non-pharmacological approaches to AHAD from the perspective of traditional Chinese medicine, intending to serve clinical purposes and improve the onset and prognosis of AHAD.

Effect of oxygen supplementation on cognitive performance among HEMS providers after acute exposure to altitude: the HEMS II randomized clinical trial.

IMPORTANCE: Emergency medical services (EMS) providers transiently ascend to high altitude for primary missions and secondary transports in mountainous areas in helicopters that are unpressurised and do not have facilities for oxygen supplementation. The decrease in cerebral oxygen saturation can lead to impairment in attention and reaction time as well as in quality of care during acute exposure to altitude. OBJECTIVE: The primary aim of the current study was to investigate the effect of oxygen supplementation on cognitive performance in Helicopter EMS (HEMS) providers during acute exposure to altitude. DESIGN, SETTING, AND PARTICIPANTS: This interventional, randomized, controlled, double-blind, cross-over clinical trial was conducted in October 2021. Each trial used a simulated altitude scenario equivalent to 4000 m, in which volunteers were exposed to hypobaric hypoxia with a constant rate of ascent of 4 m/s in an environmental chamber under controlled, replicable, and safe conditions. Trials could be voluntarily terminated at any time. Inclusion criteria were being members of emergency medical services and search and rescue services with an age between 18 and 60 years and an American Society of Anesthesiologists physical status class I. EXPOSURES: Each participant conducted 2 trials, one in which they were exposed to altitude with oxygen supplementation (intervention trial) and the other in which they were exposed to altitude with ambient air supplementation (control trial). MAIN OUTCOMES AND MEASURES: Measurements included peripheral oxygen saturation (SpO2), cerebral oxygenation (ScO2), breathing and heart rates, Psychomotor Vigilance Test (PVT), Digit-Symbol Substitution Test (DSST), n-Back test (2-BACK), the Grooved Pegboard test, and questionnaires on subjective performance, stress, workload, and positive and negative affect. Paired t-tests were used to compare conditions (intervention vs. control). Data were further analyzed using generalized estimating equations (GEE). RESULTS: A total of 36 volunteers (30 men; mean [SD] age, 36 [9] years; mean [SD] education, 17 [4] years) were exposed to the intervention and control trials. The intervention trials, compared with the control trials, had higher values of SpO2 (mean [SD], 97.9 [1.6] % vs. 86 [2.3] %, t-test, p = 0.004) and ScO2 (mean [SD], 69.9 [5.8] % vs. 62.1 [5.2] %, paired t-test, p = 0.004). The intervention trials compared with the control trials had a shorter reaction time (RT) on the PVT after 5 min (mean [SD], 277.8 [16.7] ms vs. 282.5 [15.3] ms, paired t-test, p = 0.006) and after 30 min (mean [SD], 276.9 [17.7] ms vs. 280.7 [15.0] ms, paired t-test, p = 0.054) at altitude. While controlling for other variables, there was a RT increase of 0.37 ms for each % of SpO2 decrease. The intervention trials showed significantly higher values for DSST number of correct responses (with a difference of mean [SD], 1.2 [3.2], paired t-test, p = 0.035). Variables in the intervention trials were otherwise similar to those in the control trials for DSST number of incorrect responses, 2-BACK, and the Grooved Pegboard test. CONCLUSIONS AND RELEVANCE: This randomized clinical trial found that oxygen supplementation improves cognitive performance among HEMS providers during acute exposure to 4000 m altitude. The use of oxygen supplementation may allow to maintain attention and timely reaction in HEMS providers. The impact of repeated altitude ascents on the same day, sleep-deprivation, and additional stressors should be investigated. Trial registration NCT05073406, ClinicalTrials.gov trial registration.

Pulmonary vascular diseases at high altitude - is it safe to live in the mountains?

PURPOSE OF REVIEW: This review addresses the concern of the health effects associated with high-altitude living and chronic hypoxia with a focus on pulmonary hypertension. With an increasing global population residing at high altitudes, understanding these effects is crucial for public health interventions and clinical management. RECENT FINDINGS: Recent literature on the long-term effects of high-altitude residence and chronic hypoxia is comprehensively summarized. Key themes include the mechanisms of hypoxic pulmonary vasoconstriction, the development of pulmonary hypertension, and challenges in distinguishing altitude-related pulmonary hypertension and classical pulmonary vascular diseases, as found at a low altitude. SUMMARY: The findings emphasize the need for research in high-altitude communities to unravel the risks of pulmonary hypertension and pulmonary vascular diseases. Clinically, early and tailored management for symptomatic individuals residing at high altitudes are crucial, as well as access to advanced therapies as proposed by guidelines for pulmonary vascular disease. Moreover, identifying gaps in knowledge underscores the necessity for continued research to improve understanding and clinical outcomes in high-altitude pulmonary vascular diseases.

Altitude-Related Illness.

Altitude-related illness occurs as a result of inadequate acclimatization. The mainstay of prevention is a slow, graded ascent profile which gives the body time to respond to a low-oxygen environment. The diagnosis of these conditions is often difficult in resource-limited environments, so history and a physical exam are key in identifying patients who will require descent and evacuation. Treatment modalities such as supplemental oxygen, portable hyperbaric chambers, and medications, are all temporizing measures until the patient can be safely evacuated to a lower elevation.

Superoxide dismutase 1-modified dental pulp stem cells alleviate high-altitude pulmonary edema by inhibiting oxidative stress through the Nrf2/HO-1 pathway.

High-altitude pulmonary edema (HAPE) is a deadly form of altitude sickness, and there is no effective treatment for HAPE. Dental pulp stem cells (DPSCs) are a type of mesenchymal stem cell isolated from dental pulp tissues and possess various functions, such as anti-inflammatory and anti-oxidative stress. DPSCs have been used to treat a variety of diseases, but there are no studies on treating HAPE. In this study, Sprague-Dawley rats were exposed to acute low-pressure hypoxia to establish the HAPE model, and SOD1-modified DPSCs (DPSCsHiSOD1) were administered through the tail vein. Pulmonary arterial pressure, lung water content (LWC), total lung protein content of bronchoalveolar lavage fluid (BALF) and lung homogenates, oxidative stress, and inflammatory indicators were detected to evaluate the effects of DPSCsHiSOD1 on HAPE. Rat type II alveolar epithelial cells (RLE-6TN) were used to investigate the effects and mechanism of DPSCsHiSOD1 on hypoxia injury. We found that DPSCs could treat HAPE, and the effect was better than that of dexamethasone treatment. SOD1 modification could enhance the function of DPSCs in improving the structure of lung tissue, decreasing pulmonary arterial pressure and LWC, and reducing the total lung protein content of BALF and lung homogenates, through anti-oxidative stress and anti-inflammatory effects. Furthermore, we found that DPSCsHiSOD1 could protect RLE-6TN from hypoxic injury by reducing the accumulation of reactive oxygen species (ROS) and activating the Nrf2/HO-1 pathway. Our findings confirm that SOD1 modification could enhance the anti-oxidative stress ability of DPSCs through the Nrf2/HO-1 signalling pathway. DPSCs, especially DPSCsHiSOD1, could be a potential treatment for HAPE. Schematic diagram of the antioxidant stress mechanism of DPSCs in the treatment of high-altitude pulmonary edema. DPSCs can alleviate oxidative stress by releasing superoxide dismutase 1, thereby reducing ROS production and activating the Nrf2/HO-1 signalling pathway to ameliorate lung cell injury in HAPE.

Evaluation and Management of the Individual with Recurrent High Altitude Pulmonary Edema.

Luks AM, Grissom CK. Evaluation and Management of the Individual with Recurrent HAPE. High Alt Med Biol. 25:238-246, 2024. Individuals with a history of acute altitude illness often seek recommendations from medical providers on how to prevent such problems on future ascents to high elevation. Although many of these cases can be managed with pharmacologic prophylaxis and counseling about the appropriate rate of ascent alone, there are some situations in which further diagnostic evaluation may also be warranted. One such situation is the individual with recurrent episodes of high altitude pulmonary edema (HAPE), as one of several predisposing factors may be present that warrants additional interventions beyond pharmacologic prophylaxis and slow ascent and may even preclude future travel to high altitude. This review considers this situation in greater detail. Structured around the case of an otherwise healthy 27-year-old individual with recurrent episodes of HAPE who would like to climb Denali (6,190 m), the review examines the known risk factors for disease and then provides guidance regarding when and how to evaluate such individuals and appropriate steps to prevent HAPE on further ascents to high elevation. Except in rare circumstances, a history of recurrent HAPE does not preclude further ascent to high elevation, as a multipronged approach including pharmacologic prophylaxis, careful planning about the rate of ascent, and the degree of physical effort and other strategies, such as preacclimatization, staged ascent, and use of hypoxic tents, can be employed to reduce the risk of recurrence with future travel.

Continuous Positive Airway Pressure in the Treatment of Pediatric High Altitude Pulmonary Edema: A Case Study.

Treatment of high altitude pulmonary edema (HAPE) can be challenging and is further complicated in the pediatric patient in the prehospital environment. The following case presents a decompensating pediatric patient with HAPE in the prehospital aeromedical environment. It illustrates the potential benefit of continuous positive airway pressure (CPAP) as a treatment modality in the treatment of HAPE.

Characteristics of neonatal hypoxic-ischemic encephalopathy at high altitude and early results of therapeutic hypothermia.

BACKGROUND: Altitude hypoxia and limited socioeconomic conditions may result in distinctive features of neonatal hypoxic-ischemic encephalopathy (HIE). Therapeutic hypothermia (TH) has not been used at altitude. We examined characteristics of HIE and early outcomes of TH in 3 centers at two high altitudes, 2 at 2,261 m and 1 at 3,650 m. METHODS: The incidence of HIE at NICUs was noted. TH was conducted when personnel and devices were available in 2019~2020. Standard inclusion criteria were used, with the addition of admission age >6 hours and mild HIE. Demographic and clinical data included gestational age, gender, weight, Apgar score, ethnics, age on admission, age at TH and clinical degree of HIE. EEG was monitored for 96 hours during hypothermia and rewarming. MRI was performed before discharge. RESULTS: There was significant difference in ethnics, HIE degree, age at TH across 3 centers. The overall NICU incidence of HIE was 4.0%. Among 566 HIE patients, 114 (20.1%) received TH. 63 (55.3%) patients had moderate/severe HIE. Age at TH >6 hours occurred in 34 (29.8%) patients. EEG discharges showed seizures in 7~11% of patients, whereas spikes/sharp waves in 94~100%, delta brushes in 50~100%. After TH, MRI showed moderate to severe brain injury in 77% of patients, and correlated with center, demographic and clinical variables (Ps≤0.0003). Mortality was 5% during hospitalization and 11% after discharge until 1 year. CONCLUSIONS: At altitude, the incidence of HIE was high and brain injury was severe. TH was limited and often late >6 hours. EEG showed distinct patterns attributable to altitude hypoxia. TH was relatively safe. TRIAL REGISTRATION: The study was registered on February 23, 2019 in Chinese Clinical Trial Register (ChiCTR1900021481).

Challenges in the management of high-altitude illnesses and emergencies in Bhutan and Nepal.

Many popular tourist attractions and trekking routes in Bhutan and Nepal are situated between 3000 and 6000 m in elevation. High-altitude emergencies are becoming more common and medical providers must be aware of the practical and medical issues in managing these disorders. We reflect on the challenges in providing high-altitude emergency medical services in Bhutan and Nepal.

Endotracheal Intubation at 3,600 Meters Above Sea Level for High-Altitude Pulmonary Edema Followed by Helicopter Evacuation in Nepal.

Ranging from 64 to 8848 m above sea level, Nepal is a country rich in hilly and mountainous terrain.1 24.8% of Nepal's land area is above 3000 m, 18.9% is between 3000 and 5000 m, and 5.9% is above 5000 m.2 Hikers and trekkers are increasingly attracted to this challenging altitude and terrain, which presents risks for altitude sickness and other physical complications. Responding to medical emergencies in high-altitude areas in Nepal is highly challenging. This difficulty is often exacerbated by inclement weather, unavailability of helicopters, and poor communication regarding the location and condition of patients requiring medical attention and evacuation. High-altitude pulmonary edema (HAPE) is an illness characterized by non-cardiogenic pulmonary edema, which occurs not infrequently in individuals who rapidly ascend above 2500-3000 m in elevation,3 and which has a high mortality rate if not treated in a timely manner. Improved outcomes would be likely if skilled and equipped medical staff had better access to the sites of high-altitude expeditions in Nepal, so that life-saving interventions could be performed promptly. We report the case of a patient with HAPE who was intubated in the field at an altitude of 3600 m, and then evacuated via helicopter to a healthcare facility.

Initial Treatment of High-Altitude Pulmonary Edema: Comparison of Oxygen and Auto-PEEP.

BACKGROUND: Improvement of oxygenation is the aim in the therapy of high-altitude pulmonary edema (HAPE). However, descent is often difficult and hyperbaric chambers, as well as bottled oxygen, are often not available. We compare Auto-PEEP (AP-Pat), a special kind of pursed lips breathing, against the application of bottled oxygen (O2-Pat) in two patients suffering from HAPE. METHODS: We compare the effect of these two different therapies on oxygen saturation measured by pulse oximetry (SpO2) over time. RESULT: In both patients SpO2 increased significantly from 65-70% to 95%. Above 80% this increase was slower in AP-Pat compared with O2-Pat. Therapy started immediately in AP-Pat but was delayed in O2-Pat because of organizational and logistic reasons. CONCLUSIONS: The well-established therapies of HAPE are always the option of choice, if available, and should be started as soon as possible. The advantage of Auto-PEEP is its all-time availability. It improves SpO2 nearly as well as 3 L/min oxygen and furthermore has a positive effect on oxygenation lasting for approximately 120 min after stopping. Auto-PEEP treatment does not appear inferior to oxygen treatment, at least in this cross-case comparison. Its immediate application after diagnosis probably plays an important role here.

Companion Rescue and Risk Management of Trekkers on the Everest Trek, Solo Khumbu Region, Nepal.

BACKGROUND: Trekking to high-altitude locations presents inherent health-related hazards, many of which can managed with specific first aid (FA) training. This study evaluates the trip preparation, FA knowledge, and FA self-assessment of trekkers (organized by tour operators vs. individually planned tours). Data obtained shall be used for specific FA trip preparation and management of emergencies en route for this population. METHODS: A total of 366 trekkers on the Everest Base Camp Trek, Nepal, were interviewed using a questionnaire specifically designed to evaluate their FA knowledge and management of emergencies. Data evaluation was performed using descriptive statistics. RESULTS: A total of 40.5% of trekkers experienced at least one medical incident during their trip, of which almost 50% were due to acute mountain sickness (AMS). There was more AMS in commercially organized groups than in individually planned ones (55% vs. 40%). For more than 50%, no medical care was available during their trip. A total of 80% could answer only 3/21 FA questions completely correctly. Only 1% showed adequate knowledge concerning FA strategies. A total of 70% were willing to enroll in an FA class specialized towards the needs of trekkers. CONCLUSIONS: The importance of high-altitude FA knowledge and trip preparation is widely underestimated. There is an unmet demand amongst trekkers for specific wilderness FA classes.

Accessory Climbing Routes Associated With More Rescue Operations Than the Main Climbing Route: A Retrospective 12-Year Report of Yushan National Park.

INTRODUCTION: This study compared the casualties and types of rescues conducted on the main climbing route (MCR) and accessory climbing routes (ACRs) in Yushan National Park (YSNP) between 2008 and 2019. METHODS: We collected the following information for all documented mountain rescue operations conducted on the MCRs and ACRs in YSNP between 2008 and 2019: accident location, casualty type, victim number, and type of rescue. The victims were categorized as to injury, illness, mortality, or no medical problem (NMP) groups according to their condition at the time of rescue. RESULTS: Two-hundred forty-four rescue operations involving 329 victims were conducted during the 12-y study period. Among them, 105 (32%) did not require medical treatment, 102 (31%) were injured, 82 (25%) were ill, and 40 (12%) were deceased. Of the 82 individuals with illness, 69 (84%) had acute altitude sickness. The accident and mortality rates on the ACRs were significantly higher than those on the MCR (P<0.001; χ2). The ACR incidents involved significantly higher percentages of helicopter-based rescues and victims in the NMP group (P<0.001). CONCLUSIONS: Acute altitude sickness accounted for most of the rescues. ACRs had higher injury and mortality rates and required more helicopter-based rescues for patients who did not have medical problems. This study may serve as a reference to reduce casualties and overuse of helicopters by educating tourists on the appropriate use of maps and the evaluation of trails in relation to weather conditions.

Clinician's Corner: Counseling Patients with Pulmonary Vascular Disease Traveling to High Altitude.

Ulrich, Silvia, Mona Lichtblau, Simon R. Schneider, Stéphanie Saxer, and Konrad E. Bloch, Clinician's corner: counseling patients with pulmonary vascular disease traveling to high altitude. High Alt Med Biol. 23:201-208, 2022.-Pulmonary vascular diseases (PVDs) with precapillary pulmonary hypertension (PH), such as pulmonary arterial or chronic thromboembolic PH, impair exercise performance and survival in patients. Vasodilators and other treatments improve quality of life and prognosis to an extent in patients who have PVDs as chronic disorders. Obviously, patients with PVD wish to participate in usual daily activities, including travel to popular settlements and mountainous regions located at high altitude. However, the pulmonary hemodynamic impairment due to PVD leads to blood and tissue hypoxia, particularly during exercise and sleep. It is thus of concern that alveolar hypoxia at higher altitude may exacerbate patients' symptoms and lead to decompensation. Current PH guidelines discourage high-altitude exposure for fear of altitude-related adverse health effects. However, several recent well-designed prospective and randomized trials show that despite altitude-induced hypoxemia, pulmonary hemodynamic changes and impairment of exercise performance in patients with PVD are similar to the responses in healthy people or in patients with mild chronic obstructive pulmonary disease. The vast majority of patients with PVD can tolerate short-term exposure to moderate altitudes up to 2,500 m. For the roughly 10% of patients with stable disease who develop severe hypoxemia when ascending to 2,500 m, they respond well to low-level supplemental oxygen support. The best low-altitude predictors for adverse health effects at high altitude are the known clinical risk factors for PVD such as symptoms, functional class, exercise capacity, and exertional oxygen desaturation, whereas hypoxia altitude simulation testing is of little additive value. In any case, patients should be instructed that altitude-related adverse health effects may be difficult to predict and that in case of worsening symptoms, immediate accompanied descent to lower altitude and oxygen therapy are required. Patients with severe hypoxemia near sea level may safely visit high-altitude regions up to 1,500-2,000 m while continuing oxygen therapy and avoiding strenuous exercise. All PH patients should be counseled before any high-altitude sojourn by doctors with experience in PVD and high-altitude medicine and have an action plan for the occurrence of severe hypoxemia and other altitude-related conditions such as acute mountain sickness.

Isovolemic hemodilution in chronic mountain sickness acutely worsens nocturnal oxygenation and sleep apnea severity.

STUDY OBJECTIVES: Chronic mountain sickness (CMS) is commonly observed among Andean and other highland populations. Sleep-disordered breathing (SDB) is highly prevalent at high altitude, and SDB and nocturnal hypoxemia have been observed in CMS. Phlebotomy is commonly performed to treat CMS, but it is unknown whether reducing hematocrit improves SDB. We hypothesized that isovolemic hemodilution (IVHD) in CMS would reduce SBD severity and improve sleep efficiency. METHODS: Six participants with CMS and 8 without CMS, all residents of Cerro de Pasco, Peru (altitude 4340 m), completed baseline nocturnal sleep studies. CMS participants then underwent IVHD, and nocturnal sleep studies were repeated 24-48 hours after IVHD. We analyzed sleep apnea severity, nocturnal oxygenation, and sleep quality in those with CMS relative to those without CMS, and the effects of IVHD in CMS participants. RESULTS: Participants with CMS did not have altered sleep architecture, sleep apnea severity, or nocturnal oxygenation relative to non-CMS participants. However, IVHD in CMS increased apnea-hypopnea index (40.9 ± 6.9 events/h to 61.5 ± 7.7 events/h, P = .009). IVHD increased oxyhemoglobin desaturation index (P = .008) and the percentage of sleep time spent with oxyhemoglobin saturation at or below 80% (P = .012). There was no effect of IVHD on sleep efficiency, arousal index, or sleep staging. CONCLUSIONS: In this cohort, CMS was not associated with worsened SDB or changes in sleep architecture. IVHD, a putative therapeutic option for participants with CMS, appears to worsen nocturnal oxygenation and SDB within 48 hours post-IVHD. CITATION: Sanchez-Azofra A, Villafuerte FC, DeYoung PN, et al. Isovolemic hemodilution in chronic mountain sickness acutely worsens nocturnal oxygenation and sleep apnea severity. J Clin Sleep Med. 2022;18(10):2423-2432.

Respiratory physiology at high altitude and considerations for pediatric patients.

Over 150 million people, including many children, live at high altitude (>2500 m) with the majority residing in Asia and South America. With increases in elevation, the partial pressure of oxygen (pO2) is reduced, resulting in a hypobaric hypoxic environment. Fortunately, humans have evolved adaptive processes which serve to acclimate the body to such conditions. These mechanisms, occurring along a specific time course, result in tachypnea, tachycardia, diuresis, and hematopoiesis, and a shift in the oxygen dissociation curve favoring an increased affinity for oxygen. These, along with other physiological effects, including increased pulmonary vascular resistance, alterations in cerebral blood flow, and changes in sensitivity to opioids, must be considered when administering anesthesia at high altitudes. Susceptible individuals or those who ascend too quickly may outpace the body's ability to acclimate resulting in one or more forms of high-altitude sickness ranging from the milder acute mountain sickness to the more serious conditions of high-altitude pulmonary edema and cerebral edema, either of which can be life-threatening if not promptly recognized and treated. Since the adaptive mechanisms for acclimatization greatly affect the cardiopulmonary systems, patients with underlying health issues such as sleep apnea, congenital heart disease, and asthma may have susceptibilities and warrant special consideration. Clinicians should have an understanding of the physiologic adaptations, anesthetic considerations, and special concerns in these populations in order to offer the best care possible.