Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update.

To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention, diagnosis, and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches for managing each form of acute altitude illness that incorporate these recommendations as well as recommendations on how to approach high altitude travel following COVID-19 infection. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine in 2010 and the subsequently updated WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2014 and 2019.

High Altitude.

With ascent to high altitude, barometric pressure declines, leading to a reduction in the partial pressure of oxygen at every point along the oxygen transport chain from the ambient air to tissue mitochondria. This leads, in turn, to a series of changes over varying time frames across multiple organ systems that serve to maintain tissue oxygen delivery at levels sufficient to prevent acute altitude illness and preserve cognitive and locomotor function. This review focuses primarily on the physiological adjustments and acclimatization processes that occur in the lungs of healthy individuals, including alterations in control of breathing, ventilation, gas exchange, lung mechanics and dynamics, and pulmonary vascular physiology. Because other organ systems, including the cardiovascular, hematologic and renal systems, contribute to acclimatization, the responses seen in these systems, as well as changes in common activities such as sleep and exercise, are also addressed. While the pattern of the responses highlighted in this review are similar across individuals, the magnitude of such responses often demonstrates significant interindividual variability which accounts for subsequent differences in tolerance of the low oxygen conditions in this environment.

Unattended Hoist Extraction of an Intubated Patient From Mountainous Terrain.

Airway management and maintenance of adequate ventilation during a patient's unattended helicopter rescue hoist extraction present unique challenges to the air medical provider. We present the case of a critically injured patient requiring emergent airway management and subsequent extrication via hoist from challenging, near-vertical terrain, which illustrates the logistical challenges of providing high-quality, neuroprotective mechanical ventilation in an austere air medical scenario.

Clinical recommendations for high altitude exposure of individuals with pre-existing cardiovascular conditions: A joint statement by the European Society of Cardiology, the Council on Hypertension of the European Society of Cardiology, the European Society of Hypertension, the International Society of Mountain Medicine, the Italian Society of Hypertension and the Italian Society of Mountain Medicine.

Take home figureAdapted from Bärtsch and Gibbs2 Physiological response to hypoxia. Life-sustaining oxygen delivery, in spite of a reduction in the partial pressure of inhaled oxygen between 25% and 60% (respectively at 2500 m and 8000 m), is ensured by an increase in pulmonary ventilation, an increase in cardiac output by increasing heart rate, changes in vascular tone, as well as an increase in haemoglobin concentration. BP, blood pressure; HR, heart rate; PaCO2, partial pressure of arterial carbon dioxide.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2019 Update.

To provide guidance to clinicians about best preventive and therapeutic practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches to prevention and management of each form of acute altitude illness that incorporate these recommendations. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2010 and subsequently updated as the WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness in 2014.

Changes in acute pulmonary vascular responsiveness to hypoxia during a progressive ascent to high altitude (5300 m).

NEW FINDINGS: What is the central question of this study? Do the pulmonary vascular responses to hypoxia change during progressive exposure to high altitude and can alterations in these responses be related to changes in concentrations of circulating biomarkers that affect the pulmonary circulation? What is the main finding and its importance? In our field study with healthy volunteers, we demonstrate changes in pulmonary artery pressure suggestive of remodelling in the pulmonary circulation, but find no changes in the acute responsiveness of the pulmonary circulation to changes in oxygenation during 2 weeks of exposure to progressive hypoxia. Pulmonary artery pressure changes were associated with changes in erythropoietin, 8-isoprostane, nitrite and guanosine 3',5'-cyclic monophosphate. We sought to determine whether changes in pulmonary artery pressure responses to hypoxia suggestive of vascular remodelling occur during progressive exposure to high altitude and whether such alterations are related to changes in concentrations of circulating biomarkers with known or suspected actions on the pulmonary vasculature during ascent. We measured tricuspid valve transvalvular pressure gradients (TVPG) in healthy volunteers breathing air at sea level (London, UK) and in hypoxic conditions simulating the inspired O2 partial pressures at two locations in Nepal, Namche Bazaar (NB, elevation 3500 m) and Everest Base Camp (EBC, elevation 5300 m). During a subsequent 13 day trek, TVPG was measured at NB and EBC while volunteers breathed air and hyperoxic or hypoxic mixtures simulating the inspired O2 partial pressures at the other locations. For each location, we determined the slope of the relationship between TVPG and arterial oxygen saturation (SaO2) to estimate the pulmonary vascular response to hypoxia. Mean TVPG breathing air was higher at any SaO2 at EBC than at sea level or NB, but there was no change in the slope of the relationship between SaO2 and TVPG between locations. Nitric oxide availability remained unchanged despite increases in oxidative stress (elevated 8-isoprostane). Erythropoietin, pro-atrial natriuretic peptide and interleukin-18 levels progressively increased on ascent. Associations with TVPG were observed only with erythropoietin, 8-isoprostane, nitrite and guanosine 3',5'-cyclic monophosphate. Although the increased TVPG for any given SaO2 at EBC suggests that pulmonary vascular remodelling might occur during 2 weeks of progressive hypoxia, the lack of change in the slope of the relationship between TVPG and SaO2 indicates that the acute pulmonary vascular responsiveness to changes in oxygenation does not vary within this time frame.

Outdoor Activity and High Altitude Exposure During Pregnancy: A Survey of 459 Pregnancies.

OBJECTIVE: To evaluate whether women engage in outdoor activities and high altitude travel during pregnancy; the health care advice received regarding high altitude during pregnancy; and the association between high altitude exposure and self-reported pregnancy complications. METHODS: An online survey of women with at least 1 pregnancy distributed on websites and e-mail lists targeting mothers and/or mountain activities. Outcome measures were outdoor activities during pregnancy, high altitude (>2440 m) exposure during pregnancy, and pregnancy and perinatal complications. RESULTS: Hiking, running, and swimming were the most common activities performed during pregnancy. Women traveled to high altitude in over half of the pregnancies (244/459), and most did not receive counseling regarding altitude (355, 77%), although a small proportion (14, 3%) were told not to go above 2440 m. Rates of miscarriage and most other complications were similar between pregnancies with and without travel above 2440 m. Pregnancies with high altitude exposure were more likely to have preterm labor (odds ratio [OR] 2.3; 95% CI 0.97-5.4; P = .05). Babies born to women who went to high altitude during pregnancy were more likely to need oxygen at birth (OR 2.34; 95% CI 1.04-5.26; P < .05) but had similar rates of neonatal intensive care unit admission (P = not significant). CONCLUSIONS: Our results suggest pregnant women who are active in outdoor sports and travel to high altitude have a low rate of complications. Given the limitations of our data, further research is necessary on the risks associated with high altitude travel and physical activity and how these apply to the general population.

Wilderness and adventure travel with underlying asthma.

Given the high prevalence of asthma, it is likely that providers working in a pretravel setting will be asked to provide guidance for asthma patients about how to manage their disease before and during wilderness or adventure travel, while providers working in the field setting may need to address asthma-related issues that arise during such excursions. This review aims to provide information to assist providers facing these issues. Relevant literature was identified through the MEDLINE database using a key word search of the English-language literature from 1980 to 2013 using the term "asthma" cross-referenced with "adventure travel," "trekking," "exercise," "exercise-induced bronchoconstriction," "high-altitude," "scuba," and "diving." We review data on the frequency of worsening asthma control during wilderness or adventure travel and discuss the unique aspects of wilderness travel that may affect asthma patients in the field. We then provide a general approach to evaluation and management of asthma before and during a planned sojourn and address 2 particular situations, activities at high altitude and scuba diving, which pose unique risks to asthma patients and warrant additional attention. Although wilderness and adventure travel should be avoided in individuals with poorly controlled disease or worsening control at the time of a planned trip, individuals with well-controlled asthma who undergo appropriate pretravel assessment and planning can safely engage in a wide range of wilderness and adventure-related activities.

Wilderness Medical Society practice guidelines for the prevention and treatment of acute altitude illness: 2014 update.

To provide guidance to clinicians about best practices, the Wilderness Medical Society convened an expert panel to develop evidence-based guidelines for prevention and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. These guidelines present the main prophylactic and therapeutic modalities for each disorder and provide recommendations about their role in disease management. Recommendations are graded based on the quality of supporting evidence and balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches to prevention and management of each disorder that incorporate these recommendations. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine 2010;21(2):146-155.

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. 00:000-000, 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.

Clinical Conundrum: Return to High Altitude After Cerebral Venous Sinus Thrombosis.

Luks, Andrew M., Thomas G. DeLoughery, Jeffrey H. Gertsch, and Suzy Stokes. Clinical conundrum: return to high altitude after cerebral venous sinus thrombosis. High Alt Med Biol. 00:00-00, 2024.

Tension pneumocephalus: an uncommon cause of altered mental status.

BACKGROUND: Pneumocephalus is a rare cause of altered mental status in patients presenting to the Emergency Department. Occurring as a result of traumatic or iatrogenic violation of the dura, it can cause significant morbidity and mortality if tension physiology develops whereby air continues to accumulate with no mechanism for escape. OBJECTIVE: This case report will review the underlying pathophysiology, clinical presentation, diagnosis, and management of tension pneumocephalus. CASE REPORT: We present the case of an 89-year-old man who presented to the Emergency Department with declining mental status 9h after endoscopic sinus surgery. He was subsequently found to have tension pneumocephalus and underwent emergent burr hole evacuation. Despite resolution of the pneumocephalus, the patient had persistent neurologic deficits related to ischemic infarcts that occurred as a result of the tension physiology and subsequently expired in the hospital. CONCLUSION: This case illustrates the importance of considering tension pneumocephalus on the differential diagnosis for any patient presenting with altered mental status after surgical or diagnostic procedures with potential to violate the dural space.

Death Certification: An Interactive Teaching Session.

Introduction: Documentation of the cause of death is important for local and national epidemiology as well as for research and public health funding allocation. Despite this, many physicians lack the skills necessary to accurately complete a death certificate. Methods: We created a 45-minute virtual workshop to improve skills in completing death certificates. Participants examined the role of death certificates in disease epidemiology and resource allocation for research and public health interventions, reviewed the components of a death certificate, and practiced correcting and filling out death certificates from actual patient cases. To assess the workshop, participants completed sample death certificates immediately before and after the workshop for two representative cases. Results: Thirty-six internal medicine residents (17 PGY 1s, 12 PGY 2s, and seven PGY 3s) completed the workshop. Prior to the workshop, 89% of the sample death certificates contained one or more errors, compared with 46% postworkshop. Major errors, such as incorrect categorization of a cause of death, decreased from 58% preworkshop to 17% postworkshop. Learners expressed discomfort after realizing they had made errors in completing previous death certificates and noted a desire for continuing education and reference materials on this topic. Discussion: Death certification is a key competency for physicians. Our virtual workshop improved participants' skills in completing death certificates. Although a significant number of errors remained after the workshop, most of these residual errors were minor and would not affect cause-of-death reporting. The durability of these improvements over time requires further study.

Veno-venous Extracorporeal Membrane Oxygenation for COVID-19: A Call For System-Wide Checks to Ensure Equitable Delivery For All.

Extracorporeal membrane oxygenation (ECMO) has emerged in the COVID-19 pandemic as a potentially beneficial yet scare resource for treating critically ill patients, with variable allocation across the United States. The existing literature has not addressed barriers patients may face in access to ECMO as a result of healthcare inequity. We present a novel patient-centered framework of ECMO access, providing evidence for potential bias and opportunities to mitigate this bias at every stage between a marginalized patient's initial presentation to treatment with ECMO. While equitable access to ECMO support is a global challenge, this piece focuses primarily on patients in the United States with severe COVID-19-associated ARDS to draw from current literature on VV-ECMO for ARDS and does not address issues that affect ECMO access on a more international scale.