Wakeham, Denis J., Andrew R. Tomlinson, Giorgio Manferdelli, Matthew M. Howrey, Anna K. Geib, Murugappan Ramanathan, Marcus Payne, Renie Guilliod, James Berry, Tony G. Babb, Peter Hackett, Benjamin D. Levine, and Christopher M. Hearon, Jr. The physiological and altitude lowering effects of different supplemental oxygen flow rates at extreme simulated altitude: a pilot study. High Alt Med Biol. 27:143-151, 2026. BACKGROUND:Approximately 80% of high-altitude climbers use supplemental oxygen >8,000 meters, yet optimal dosing strategies have not been established. METHODOLOGY:Therefore, in six unacclimatized individuals (34 ± 8 years; 2 F/4 M), we quantified the effects of supplemental oxygen flow rates (6, 4, 2, 1 and 0 L/min) using the SUMMIT Oxygen mask at 282 mmHg (rest and cycle ergometry: 60 and 120 Watts) and 253 mmHg (rest only) barometric pressure in a hypobaric chamber. We measured oxygen saturation (SpO2) and gas fractions in the mask during 4-minute exposures to each flow rate. RESULTS:Resting at 282 mmHg, SpO2 (6 L/min: 99% ± 0%; 0 L/min: 70% ± 8%, p < 0.001) and mean inspired oxygen fraction decreased (6 L/min: 65.87% ± 14.11%; 0 L/min: 21.50% ± 0.44%, p < 0.001) with lowering of supplemental oxygen. Exercise further decreased SpO2 and oxygen fractions across all flow rates at 282 mmHg. At 253 mmHg, SpO2 followed a similar trend to data collected at 282 mmHg (6 L/min: 96% ± 2%; 4 L/min: 93% ± 3%; 2 L/min: 87% ± 3%; 1 L/min: 71% ± 0%; 0 L/min: 66% ± 9%). Furthermore, at rest at 253 mmHg, 2 L/min of supplemental oxygen lowered the equivalent altitude to 4,489 meters. CONCLUSION:All unacclimatized participants were able to tolerate 253 mmHg at rest on as little as 2 L/min of supplemental oxygen.

BACKGROUND:Acute mountain sickness (AMS) is a debilitating condition that may occur on ascent to high altitude, with limited options for chemoprophylaxis. The pathophysiology of AMS is poorly understood, though it may be similar to migraine. This study aimed to determine the efficacy of prochlorperazine, a first-line agent for acute migraine, for AMS prophylaxis. METHODS:We performed a randomized, double-blind, placebo-controlled trial involving healthy, unacclimatized adult participants, primarily from the Denver area (1609 m), who received either oral prochlorperazine or placebo three times daily for 24 hours during rapid ascent to Mount Blue Sky, Colorado (4348 m). We evaluated individuals who received at least the first dose of placebo or intervention following a modified intent-to-treat approach. Participants travelled by vehicle to 3910 m, then hiked to the summit of Mount Blue Sky, where they slept overnight. The primary outcome was AMS incidence as defined by the 2018 Lake Louise Questionnaire, which was assessed on the evening of ascent and the following morning. RESULTS:We analysed 56 participants (25 women), with a mean age of 39 [IQR 28-49], with 28 participants in each study arm. Key baseline characteristics were equally distributed and well-matched between study arms. The incidence of AMS was 28 (50%), with 18 (64%) in the placebo arm and 10 (36%) in the prochlorperazine arm (P = 0.06). The absolute risk reduction was 28.6%, the number needed to treat was 4 and the odds ratio was 0.28 (95% C.I. 0.11-0.94). There were no serious adverse events, and there were no significant differences in the side effects between arms, including for drowsiness (P = 0.47). CONCLUSION:Our results suggest that prochlorperazine is effective in preventing AMS. Larger studies are warranted to validate our findings.

Background Altitude sojourns increasingly attract individuals of all ages and different health status due to the appeal of high-altitude destinations worldwide and easy access to air travel. The risk of acute mountain sickness (AMS) when flying to high altitude destinations remains underemphasized. Thus, this mini-review aims to evaluate the altitude-dependent AMS incidence depending on the mode of ascending, e.g. by air versus terrestrial travel.Methods A literature search was performed to identify observational studies assessing AMS incidence after acute ascent of primarily healthy adults to real high altitude. In addition, placebo arms of interventional trials evaluating the prophylactic efficacy of various drugs have been separately analysed to confirm or refute the findings from the observational studies. Linear regression analyses were used to evaluate altitude-dependent AMS incidence.Results Findings of 12 observational studies, in which the AMS incidence in 11 021 individuals ascending to 19 different altitudes (2200-4559 m) was evaluated, revealed an impressive 4.5-fold steeper increase in the AMS incidence for air travel as compared to slower ascent modes, i.e. hiking or combined car and/or air travel and hiking. The higher AMS incidence following transportation by flight versus slower means was also confirmed in placebo-treated participants in 10 studies of drug prophylaxis against AMS.Conclusions Due to the short time span in going from low to high altitude, reduced acclimatization likely is the main reason for a higher AMS risk when travelling to high altitude destinations by flight. To avoid frustrating travel experiences and health risks, appropriate and timely medical advice on how to prepare for air travel to high-altitude is of vital importance. Effective preparation options include the use of modern pre-acclimatization strategies and pharmacological prophylaxis by acetazolamide or dexamethasone, or even considering alternate itineraries with more gradual ascent.

Berendsen, Remco R., Peter Bartsch, Buddha Basnyat, Marc Moritz Berger, Peter Hackett, Andrew M. Luks, Jean-Paul Richalet, Ken Zafren, Bengt Kayser, and the STAK Plenary Group. Strengthening altitude knowledge: a Delphi study to define minimum knowledge of altitude illness for laypersons traveling to high altitude. High Alt Med Biol. 00:000-000, 2022.Introduction: A lack of knowledge among laypersons about the hazards of high-altitude exposure contributes to morbidity and mortality from acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) among high-altitude travelers. There are guidelines regarding the recognition, prevention, and treatment of acute-altitude illness for experts, but essential knowledge for laypersons traveling to high altitudes has not been defined. We sought expert consensus on the essential knowledge required for people planning to travel to high altitudes.Methods: The Delphi method was used. The panel consisted of two moderators, a core expert group and a plenary expert group. The moderators made a preliminary list of statements defining the desired minimum knowledge for laypersons traveling to high altitudes, based on the relevant literature. These preliminary statements were then reviewed, supplemented, and modified by a core expert group. A list of 33 statements was then presented to a plenary group of experts in successive rounds.Results: It took three rounds to reach a consensus. Of the 10 core experts invited, 7 completed all the rounds. Of the 76 plenary experts, 41 (54%) participated in Round 1, and of these 41 a total of 32 (78%) experts completed all three rounds. The final list contained 28 statements in 5 categories (altitude physiology, sleeping at altitude, AMS, HACE, and HAPE). This list represents an expert consensus on the desired minimum knowledge for laypersons planning high-altitude travel.Conclusion: Using the Delphi method, the STrengthening Altitude Knowledge initiative yielded a set of 28 statements representing essential learning objectives for laypersons who plan to travel to high altitudes. This list could be used to develop educational interventions.

High Altitude Medicine & BiologyVol. 21, No. 3 InterviewThe Experts Speak: An Interview with Dr. John WestInterview by Peter HackettInterview by Peter HackettSearch for more papers by this authorPublished Online:8 Sep 2020https://doi.org/10.1089/ham.2020.29018.wesAboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"The Experts Speak: An Interview with Dr. John West." High Altitude Medicine & Biology, 21(3), pp. 215–216FiguresReferencesRelatedDetails Volume 21Issue 3Sep 2020 InformationCopyright 2020, Mary Ann Liebert, Inc., publishersTo cite this article:Interview by Peter Hackett.The Experts Speak: An Interview with Dr. John West.High Altitude Medicine & Biology.Sep 2020.215-216.http://doi.org/10.1089/ham.2020.29018.wesPublished in Volume: 21 Issue 3: September 8, 2020Online Ahead of Print:July 27, 2020PDF download

Brodmann Maeder, Monika, Hermann Brugger, Matiram Pun, Giacomo Strapazzon, Tomas Dal Cappello, Marco Maggiorini, Peter Hackett, Peter Bartsch, Erik R. Swenson, Ken Zafren; (STAR Core Group) and the STAR Delphi Expert Group. The STAR data reporting guidelines for clinical high altitude research. High Alt Med Biol 00:000-000, 2018. Aims: The goal of the STAR (STrengthening Altitude Research) initiative was to produce a uniform set of key elements for research and reporting in clinical high-altitude (HA) medicine. The STAR initiative was inspired by research on treatment of cardiac arrest, in which the establishment of the Utstein Style, a uniform data reporting protocol, substantially contributed to improving data reporting and subsequently the quality of scientific evidence. Materials and Methods: The STAR core group used the Delphi method, in which a group of experts reaches a consensus over multiple rounds using a formal method. We selected experts in the field of clinical HA medicine based on their scientific credentials and identified an initial set of parameters for evaluation by the experts. Results: Of 51 experts in HA research who were identified initially, 21 experts completed both rounds. The experts identified 42 key parameters in 5 categories (setting, individual factors, acute mountain sickness and HA cerebral edema, HA pulmonary edema, and treatment) that were considered essential for research and reporting in clinical HA research. An additional 47 supplemental parameters were identified that should be reported depending on the nature of the research. Conclusions: The STAR initiative, using the Delphi method, identified a set of key parameters essential for research and reporting in clinical HA medicine.

We observed patients with chronic mountain sickness (CMS) in our clinic who developed progressive neurological deterioration (encephalopathy) and we wished to investigate this. We studied nine such CMS patients, and compared them to 21 CMS patients without encephalopathy, and to 15 healthy control subjects without CMS. All 45 subjects lived permanently at 3200–4000 m. Measurements at 2260 m included CMS symptom score, multi-slice CT, perfusion CT, pulse oximetry (SpO 2 %), and hemoglobin concentration (Hb). One patient had MRI imaging but not CT; 5 had CSF pressure measurements. CMS subjects had lower SpO 2, higher Hb, higher brain blood density, lower mean cerebral blood flow (CBF), and significant cerebral circulatory delay compared to controls. The nine CMS subjects with neurological deterioration showed diffuse cerebral edema on imaging and more deranged cerebral hemodynamics. CSF pressure was elevated in those with edema. We conclude that cerebral edema, a previously unrecognized complication, may develop in CMS patients and cause encephalopathy. Contributing factors appear to be exaggerated polycythemia and hypoxemia, and lower and sluggish CBF compared to CMS patients without cerebral edema; but what triggers this complication is unknown. Recognition and treatment of this serious complication will help reduce morbidity and mortality from CMS.

Iloprost With and Without rt-PA: Treatment of 131 Cases of Severe Frostbite Emmanuel Cauchy; Eric Chetaille; Emmanuel Pham; Hugo Nespoulet; Pascal Zellner; Francois Becker; Peter Hackett IFREMMONT (Institut de Formation et de Recherche en Medecine de Montagne), Hopital de Chamonix, Chamonix, France, Institute for Altitude Medicine, Telluride, CO, USA Introduction.—Both rt-PA and iloprost (prostacyclin) are effective treatments for severe frostbite, but it is unclear if using them in combination is more effective. Objective.—To evaluate combined treatment with rt-PA and iloprost in severe frostbite, compared with other therapies. Methods.—Retrospective case review of 131 patients with severe frostbite. Patients without contraindication or severe trauma were managed with rapid rewarming (381C bath water immersion þ aspirin IV [250mg] þ buflomedil IV [400 mg, alphalytic vasodilator] during 1 hour. Then 41 patients received daily treatment of aspirin and buflomedil (TT-A); 58 received aspirin and IV iloprost 2 ng/6 h (prostacyclin) (TT-B); and 20 received aspirin, IV tPA (100 mg, first day only) and iloprost (TT-C). Twelve patients did not receive any treatment (TT-D). The final level of amputation was measured 3 to 8 days later on bone scanning. Results.—For grade 3 frostbite, 100% of the patients required amputation in TT-D (4 of 4 patients), as did 62.5% with TT-A (10 of 16 patients), 4.9% with TT-B (2 of 41 patients) (P o .01), and 27.3% with TT-C (3 of 11 patients) (P o .03). For grade 4, 100% needed amputation in TT-D (3 of 3 patients), 100% in TT-A (4 of 4 patients), 66.7% TT-B (4 of 6 patients) (P o .001) and 44.4% with TT-C (4 of 9 patients) (P o 0.03). Of 407 digits, 183 frozen fingers lead to 22 amputations (TT-A 49%, TT-B 0%, TT-C 2%, TT-D 49%), and 224 frozen toes lead to 25 amputations (TT-A 34%, TT-B 0%; TT-C 4%, TT-D 62%). Analysis showed that tPA was effective up to 12 hours and iloprost up to 48 hours. Conclusion.—The efficacy of iloprost was significantly higher than buflomedil or no treatment. The addition of rt-PA to prostacycline seems to improve the prognosis only of stage 4 frostbite and only when the delay between rewarming and treatment was less than 12 hours.

Participation in wilderness and adventure sports is on the rise, and as such, practitioners will see more athletes seeking clearance to participate in these events. The purpose of this article is to describe specific medical conditions that may worsen or present challenges to the athlete in a wilderness environment.

High-altitude athletes and adventurers face a number of environmental and medical risks. Clinicians often advise participants or guiding agencies before or during these experiences. Preparticipation evaluation (PPE) has the potential to reduce risk of high-altitude illnesses in athletes and adventurers. Specific conditions susceptible to high-altitude exacerbation also important to evaluate include cardiovascular and lung diseases. Recommendations by which to counsel individuals before participation in altitude sports and adventures are few and of limited focus. We reviewed the literature, collected expert opinion, and augmented principles of a traditional sport PPE to accommodate the high-altitude wilderness athlete/adventurer. We present our findings with specific recommendations on risk stratification during a PPE for the high-altitude athlete/adventurer.

High-altitude athletes and adventurers face a number of environmental and medical risks. Clinicians often advise participants or guiding agencies before or during these experiences. Preparticipation evaluation (PPE) has the potential to reduce risk of high-altitude illnesses in athletes and adventurers. Specific conditions susceptible to high-altitude exacerbation also important to evaluate include cardiovascular and lung diseases. Recommendations by which to counsel individuals before participation in altitude sports and adventures are few and of limited focus. We reviewed the literature, collected expert opinion, and augmented principles of a traditional sport PPE to accommodate the high-altitude wilderness athlete/adventurer. We present our findings with specific recommendations on risk stratification during a PPE for the high-altitude athlete/adventurer.

OBJECTIVE:Increased intracranial pressure (ICP) may contribute to acute mountain sickness (AMS). Measuring optic nerve sheath diameter (ONSD) by ultrasound (US) is a noninvasive technique to detect elevated ICP, and increased ONSD has been associated with AMS. We hypothesized that ONSD would increase with acute, rapid ascent to 4300 m and that increased ONSD would be associated with symptoms of AMS. We further hypothesized that treatment with oxygen at 4300 m would reduce symptoms and ONSD.METHODS:A cohort study was performed comparing US measurement of ONSD in healthy subjects at 1400 m and 18 hours after rapid ascent to 4300 m, both before and after oxygen treatment and between subjects with and without AMS (Lake Louise Score ≥3).RESULTS:Among 57 subjects, 29 (51%) experienced AMS after rapid ascent to 4300 m. In subjects without AMS, mean ONSD did not increase at 4300 m. In subjects with AMS, mean ONSD increased at 4300 m and was higher than in those without AMS. Treatment with oxygen lowered mean ONSD in subjects with AMS but not in those without AMS. Individual responses to altitude and oxygen varied greatly within groups, and the relationship between ONSD and AMS symptoms was weak.CONCLUSIONS:In this controlled study, mean ONSD increased in subjects with AMS at high altitude. However, individual variation was high, and most ONSD values were below the clinical threshold for raised ICP. Observed differences were small, of questionable clinical importance, and within the range of precision of the US machine. Overall, our data do not support a role for increased ICP in mild to moderate AMS.

The diagnosis of acute mountain sickness (AMS) continues to pose problems to altitude sojourners, physicians, and researchers because of its subjective nature relying essentially on a subject’s appreciation of the presence and severity of symptoms (Roach and Kayser, 2007). Even though AMS is characterized by an ensemble of symptoms (Hackett and Roach, 2001), headache has been recognized as its key symptom at least since Ravenhill’s description in 1911 (Ravenhill, 1913). He described the experiences of ‘‘a majority of newcomers . . . . wake up the next morning with a severe frontal headache . . . . . any attempt at exertion increases the headache, which is nearly always confined to the frontal region.’’ This central role of headache was codified in the current version of the Lake Louise Questionnaire (Roach et al., 1993) that states that a ‘‘diagnosis of AMS is based on a recent gain in altitude, at least several hours at the new altitude, and the presence of headache and at least one of the following symptoms: gastrointestinal upset (anorexia, nausea or vomiting), fatigue or weakness, dizziness or lightheadedness and difficulty sleeping.’’ All surveys of AMS identify headache as the predominant and most prevalent symptom. Singh et al. (1969) noted from a survey of 1925 soldiers rapidly transported to high altitude that ‘‘Headache was not only the commonest but also the most persistent symptom.’’ In a study of 146 trekkers with AMS, Hackett et al. observed the following predominance of headache compared to other symptoms: headache (96%), insomnia (70%), anorexia (38%), nausea (35%), dizziness (27%), excessive breathlessness on exertion or at rest (25%), headache unrelieved by analgesics (26%), reduced urine (19%), marked lassitude (13%), vomiting (14%), incoordination (11%) (Hackett et al 1976). And finally, in a large survey at moderate altitudes, Honigman et al. confirmed the importance of headache in AMS with 62% of 3158 conference attendees reporting moderate to severe headache, and the next most common complaint being sleep disturbance at 31%, and anorexia at 11% and vomiting at only 3% (Honigman et al., 1993). Thus it seems clear that for AMS the cardinal symptom is headache in all studies, in all populations, and at a wide range of altitudes. Our position is that from a research perspective there are important advantages to defining AMS as a collection of symptoms that includes, always, a headache. The same is obviously not true for clinical management of altitude illness. This contrast between the needs for research versus best practice in clinical care forms the basis of our stance. In spite of several decades of sustained research efforts, the basic pathophysiology of AMS still remains elusive. We believe that a focus on high altitude headache will help unravel the puzzle of the pathophysiology of AMS. By stipulating for research purposes that headache be included in the definition of AMS, scientists seek to increase signal-to-noise ratio in AMS subjective symptom reporting. Unfortunately, subjective perception and reporting of symptoms is currently the only way to diagnose and quantify AMS. An example of excess noise is that without obligatory headache, a research subject who had a very bad night sleep and is dizzy at the time of completing the questionnaire could have a ‘‘severe’’ AMS score. Yet we know from several studies that poor sleep at altitude is not necessarily related directly to AMS. And dizziness can be secondary to hypoxemia, or to hypohydration, a common, non-AMS-related phenomenon at high altitude. Similarly, nausea and vomiting can be associated with the onset of AMS, or secondary to a bad headache of any cause, especially migraine, and in the field can also be secondary to gastrointestinal infection. Thus, obligatory presence of headache in the research scoring of AMS symptoms serves an important role by increasing the likelihood that the central symptom of AMS, first reported so clearly by Ravenhill, remains the focus of research studies. It should be noted that

High Altitude Medicine & BiologyVol. 12, No. 1 PRO and CON edited by Erik R. SwensonPro: RebuttalRobert Roach, Peter Hackett, and Bengt KayserRobert RoachDepartment of Emergency Medicine, Altitude Research Center, Denver, Colorado.Search for more papers by this author, Peter HackettThe Center for Altitude Medicine, Telluride Medical Center, Telluride, Colorado.Search for more papers by this author, and Bengt KayserInstitute of Movement Science and Sports Medicine, University of Geneva, Switzerland.Search for more papers by this authorPublished Online:31 Mar 2011https://doi.org/10.1089/ham.2010.1218AboutSectionsView articleView Full TextPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail View article"Pro: Rebuttal." , 12(1), p. 27FiguresReferencesRelatedDetails Volume 12Issue 1Apr 2011 InformationCopyright 2011, Mary Ann Liebert, Inc.To cite this article:Robert Roach, Peter Hackett, and Bengt Kayser.Pro: Rebuttal.High Altitude Medicine & Biology.Apr 2011.27-27.http://doi.org/10.1089/ham.2010.1218Published in Volume: 12 Issue 1: March 31, 2011PDF download

1. Overview of Travelers' Health 2. Trip Preparation 3. Vaccines for Travel 4. Jet Lag and Motion Sickness 5. Food and Drink Safety 6. Travelers' Diarrhea 7. Malaria 8. Insect Bite Prevention 9. Insect-Borne Diseases 10. Travel-Related Diseases 11. Lyme Disease 12. Hepatitis 13. Diabetes 14. HIV/AIDS and Sexually-Transmitted Diseases (STDs) 15. Altitude Illness 16. Medical Care Abroad 17. Travel Insurance 18. Medical Transport 19. Business Travel and Health 20. Travel and Pregnancy 21. Traveling with Children