Abstract
Introduction
Mount Aconcagua (6961 m) is the highest peak in the Western Hemisphere and attempted by over 3000 climbers annually. Aconcagua Provincial Park (APP) and the APP medical service oversee all rescues and medical care. This study aims to describe patients and conditions requiring rescue medical evacuation on Aconcagua.
Methods
Demographic, medical, and logistics data provided by APP on all park evacuations were retrospectively reviewed from the 2022–23 and 2023–24 climbing seasons.
Results
Of 6494 total Aconcagua climbers over the study period, 302 required an evacuation response from APP (mean 151 per year), yielding an evacuation rate of 4.7%. Mean age was 43.0. Male climbers had twice the risk of requiring rescue than female climbers (OR 2.01). Most evacuees were European (40%) or North American (33%), though climbers from Africa, Asia, and Australia had over twice the incidence of rescue (OR 2.26). Most frequent reasons for evacuation included altitude illness of all types (62%), high-altitude pulmonary edema (HAPE) (49%), trauma/musculoskeletal (15%), general medical (11%), and acute mountain sickness (11%). Most were flown by helicopter (95%), with flight location primarily from 4200 to 4300 m base camps (77%) and between 5300 and 5970 m (16%).
Conclusions
On Aconcagua, 4.7% of climbers required medical evacuation. Altitude illness frequently required rescue, with HAPE representing the single most common reason for evacuation. Male sex and certain continents of origin showed increased risks. Helicopter evacuation and medical oversight by APP appear to contribute to climber safety on Aconcagua. Opportunities exist for future study and climber education of risks.
Introduction
Mount Aconcagua (6961 m) is the highest peak in the Western Hemisphere and located in the Andes of Argentina. Annually, over 3000 climbers attempt to summit Aconcagua during a peak austral summer season lasting from November to February. Climbing Aconcagua maintains widespread global interest, partially due to its status as one of the world's seven highest continental summits (Seven Summits).
Aconcagua Provincial Park (APP) manages climbing and rescues on Aconcagua through a system of park rangers, police rescuers, and a physician medical service. The Aconcagua medical service is comprised of a park-contracted private medical group of Argentinian physicians that staff camp medical clinics. Lead physicians have years of experience, while newer doctors undergo orientation and have oversight. The medical service supervises the medical aspect of all rescues and evacuations on Aconcagua and performs mandatory medical checks on all climbers during their ascent. Medical checks occur at base camps and generally include a basic history and exam with vital signs and assessment of the acclimatization status of each climber.
Aconcagua is most often climbed by its nontechnical Normal Route ascending from the Horcones Valley trailhead (2950 m) and gaining the summit via the northwest ridge. The medical service and park rangers maintain a presence at base camps including Confluencia (3400 m), Plaza de Mulas (4300 m), and Plaza Argentina (4200 m on the Vacas Valley approach), as well as at Nido de Condores (5500 m), where a police rescue patrol is also stationed. The highest camp commonly used by climbers prior to summiting is Cólera (5970 m).
Aconcagua is unique with its high-altitude environment, substantial climber volume, and park database from which to study mountaineering rescues. However, few recent studies have been published on Aconcagua climbers. One prior study looked at acute mountain sickness (AMS) and summit success of climbers, noting an AMS rate of 39%. 1 Other studies have assessed prior altitude experience of Aconcagua climbers, 2 walk-testing to predict summit success, 3 mountaineering fatalities, 4 a single evacuation for acute coronary syndrome, 5 and characteristics of patients with high-altitude pulmonary edema (HAPE). 6 To date, no comprehensive data have been published regarding search and rescue evacuations on Aconcagua, and few other studies exist specific to rescues of mountaineers on other Seven Summits peaks internationally.7–9 Many studies of the world's highest peaks focus primarily on fatalities but not on other climbers requiring rescue.4,10–12 Some studies look at rescue records on mountains within parks or other high mountains, but those records may not always be specific to mountaineers.8,13–15 An Aconcagua study on nonfatal reasons for rescue would add depth to broad international reviews of emergency care in the high-altitude environment. 16
This study aims to characterize climbers and conditions requiring rescue evacuation on Aconcagua to assist with safety and prevention and to add to global knowledge of rescue in the high-altitude mountaineering environment.
Methods
Demographic, medical, and logistics data of all climbers and non-climbers requiring rescue evacuation are recorded annually by APP. De-identified data were provided by APP for the two most recent climbing seasons spanning 2022–24 and retrospectively reviewed. Data included age, country of origin, medical diagnosis, location of evacuation, and mode of transport. Sex of all evacuees was provided separately by the park as a ratio but not included in the aggregate data due to the de-identification process. Thus, male-to-female ratio of all evacuees (including nonclimbers) was used to represent evacuated climbers for purposes of analysis. Country of origin was recorded but grouped into continent of origin for the purposes of the current analysis, and Russia was grouped with Europe. Guided-party versus independent-party status of climbers was not recorded by APP and was not able to be determined. Location and elevation of rescue evacuation was defined as the initial onset of the condition requiring evacuation when reported or the site of transport for the evacuation if not otherwise specified by APP records. Elevation of rescue was grouped by 1000 m increments.
Medical diagnoses recorded by APP were made by park medical service physicians in nearly all cases of climbers and excluding cases of fatality. Medical diagnoses were grouped into categories. If there were multiple medical diagnoses listed by APP, the most severe or likely was considered as the primary reason for evacuation. An exception was made if both high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE) were present, in which case both were included in this analysis. Frostbite was categorized separately from trauma/musculoskeletal.
Background demographic information on all registered climbers was obtained directly from staff at APP for purposes of comparing to those requiring evacuation. All climbers attempting to summit Aconcagua must register with APP and provide this limited demographic information to obtain an “ascent” permit. Smaller numbers of trekkers not attempting to summit obtained permits termed “long trekking,” and baseline climber demographic age and sex data included these minority of permits, though they were felt by APP to be generally representative of climber data. Age of all registered climbers was reported by the park by number of climbers in decade age brackets, and a weighted average from these brackets was used to calculate mean age of all climbers. Continent of origin was known for 99% of all registered climbers, and the 1% unknown were assumed to have the same distribution for purposes of analysis.
Permit type of each rescue subject was recorded by APP; therefore, climbers with ascent permits, termed “climbers” for the purposes of this study, were able to be analyzed separately from subjects with lower mountain permits or guide service employees. Climbing guides actively working on the mountain were included as climbers if evacuated. However, nonclimbers such as camp staff, porters, muleteers, hikers with trekking permits, trekking guides, and climbers on a non-Aconcagua route but still within APP were termed “nonclimbers” for the purposes of this study and excluded from the analysis of Aconcagua climbers. Total number of nonclimbers was not available to use as a denominator for incidence calculations of nonclimbers.
An evacuation, or rescue, was defined by APP as any incident requiring park assistance to exit the park for the purposes of an emergent concern, including medical, trauma, lost, nonmedical aid, and fatalities. Any private party self-evacuation that did not contact or involve APP resources was not recorded by APP and is not included in this study. For the purposes of this analysis and discussion the terms rescue, medical evacuation, and evacuation are used interchangeably. The term medical evacuation also includes those evacuated for reasons related to trauma.
Outcomes were compared using Fisher's exact test, with odds ratios (OR) and 95% confidence intervals (CI) reported for effect sizes. Mean ages were compared with one-sample t-test. Analyses were performed using Stata 18.5 (College Station, TX: StataCorp).
This study was determined to be exempt from Institutional Review Board review at the University of Vermont (UVM). Permission to conduct the study was granted by the medical service of APP.
Results
During the two-season study period, 6494 climbers registered to summit Aconcagua. Of these, 302 required evacuation, yielding an evacuation rate of 4.7% (95% CI 4.2–5.2%) and an average of 151 (95% CI 116–186) climbers rescued annually, including fatalities. During the second year of the study period, the evacuation rate declined to 3.9% (95% CI 3.3–4.6%). Mean age of evacuated climbers was 43.0 (95% CI 41.6–44.4%). Most evacuees were from Europe (n = 119, 40%) or North America (n = 100, 33%). Two guides were evacuated in separate instances. An additional 38 nonclimbers were evacuated over the study period. Of evacuated climbers and nonclimbers in aggregate, 87% were male and 13% were female. Characteristics of climbers requiring medical evacuation are displayed in Table 1.
Descriptive characteristics of evacuated climbers on Aconcagua. (Continent not reported for two climbers.)
Abbreviations: confidence interval (CI).
Table 2 lists the primary medical diagnoses of climbers requiring evacuation. Evacuations for any high-altitude illness-related cause comprised 62% of evacuees (n = 187), with high-altitude pulmonary edema (HAPE) representing 48% (n = 146) of total evacuees and AMS 11% (n = 33). HAPE was the single most common medical diagnosis of climbers requiring rescue. The overall incidence of climber evacuation from Aconcagua for HAPE was 2.3% (n = 148, 95% CI 1.9–2.7%), including two patients experiencing both HAPE and high-altitude cerebral edema (HACE). Trauma and musculoskeletal diagnoses (frostbite excluded) represented 15% (n = 45) of those requiring evacuation, and frostbite separately represented 8% (n = 23) of reasons for rescue. General medical causes comprised 11% (n = 34) of cases and included diagnoses such as cardiac or chest pain, abdominal pain, ear nose throat emergencies, and seizure. The cardiac etiology subset (n = 12, 4%) is also listed separately in Table 2 as it was the single largest general medical cause. Evacuation for fatality occurred in 3% (n = 8) of climbers requiring an evacuation response from APP, with an overall incidence of 0.12% (95% CI 0.05 to 0.24). Etiology of fatality was not reported, but in each case, there was no report of trauma.
Primary Medical Diagnosis of Climbers Requiring Evacuation on Aconcagua (n = 302).
Abbreviations: Acute mountain sickness (AMS), high-altitude pulmonary edema (HAPE), high-altitude cerebral edema (HACE).
Characteristics of evacuations by method and altitude of rescue are displayed in Table 3. Most rescued climbers were evacuated by helicopter (n = 287, 95%). Flight location occurred primarily from 4200 to 4300 m base camps (n = 233, 77%) and between 5300–5970 m (n = 48, 16%) and are categorized in Table 3 by 1000 m intervals.
Characteristics of Evacuations on Aconcagua by Method and Altitude of Rescue (n = 302).
Of the 38 nonclimbers evacuated during the study period, mean age was 28.0 (95% CI 25.5-30.5) and most were from South America (n = 37, 97%). Reasons for evacuation included primarily altitude illness (n = 13, 34%), including HAPE (n = 10, 26%), and trauma (n = 13, 34%).
Age and sex of evacuees were compared to all Aconcagua climbers. Mean age of rescued climbers did not differ from all climbers (43.0 vs 42.0 years, p = .14). Similarly, climbers over 50 (n = 84/1565) versus those 50 years old and under (n = 216/4929) did not differ in evacuation rate (5.4% vs 4.4%, p = .11, OR 1.24, 95% CI 0.94–1.61) or in rate of any specific medical cause (data not shown). Age was not recorded in the case of two rescued climbers. Using aggregate data on the sex of all evacuees (sex of climbers and nonclimbers were reported together by APP) and extrapolating those data ratios to climbers only, male climbers (n = 264/5069) had twice the incidence of rescue than female climbers (n = 38/1425) (5.2% vs 2.7%, p < .001, OR 2.01, 95% CI 1.41–2.91).
Continent of origin of rescued climbers was compared to all registered climbers. Climbers from Asia, Australia, and Africa were over twice as likely to require evacuation as climbers from Europe, North America, and South America (9.1% vs 4.2%, p < .001, OR 2.26, 95% CI 1.60–3.13), including from altitude illness (5.7% vs 2.6%, p < .001, OR 2.29, 95% CI 1.49–3.42). More specifically, climbers from Asia were more than twice as likely to require rescue as those from the rest of the world (9.0% vs 4.4%, p < .001, OR 2.17, 95% CI 1.43–3.20), also specifically from altitude illness (6.2% vs 2.7%, p < .001, OR 2.42, 95% CI 1.46–3.85). Despite small numbers, climbers from Africa were more likely to require rescue for trauma than climbers from the rest of the world (7.4% vs 0.7%, p = .02, OR 11.95, 95% CI 1.33–50.45). Climbers from Asia and North America were rescued at a higher rate at elevations over 5000 m, though this effect was small (1.2% vs 0.5%, p = .0004, OR 2.37, 95% CI 1.29–4.38). Only climbers from Europe and North America died during the study period (n = 8, 0.2%).
Climber evacuations on Aconcagua were compared to published data from Denali and Everest, as displayed in Table 4.7,17 Of rescued climbers on Aconcagua compared to both Denali and Everest, HAPE was more common on Aconcagua (p < .001 for both) and frostbite was less common (p < .01 for both). Rescues on Aconcagua compared with Denali were more often for altitude illness in general (p < .001) and less often than for trauma in general (p < .001).
Evacuations on Aconcagua Compared with Denali and Everest.
See text for references. Abbreviations: Confidence interval (CI), high-altitude pulmonary edema (HAPE). Significant difference from Aconcagua (p < .05) marked with asterisk (*).
Overall climber rates of reasons for rescue were able to be calculated and compared with Denali (Table 5). 7 Overall incidence of evacuation was four times higher on Aconcagua than Denali (4.7% vs 1.2%, p < .001, OR 4.14, CI 3.49–4.91). The incidence of rescue evacuation for HAPE (2.3% vs 0.2%) and all altitude causes (2.9% vs 0.2%) was markedly higher on Aconcagua than Denali (p < .001 for both). The incidence of rescue for trauma (0.7% vs 0.5%) and frostbite (0.4% vs 0.2%) were slightly higher on Aconcagua than Denali (p = .02 for both).
Incidence of Evacuation for Medical Diagnosis on Aconcagua Versus Denali.
See text for reference. Abbreviations: Odds ratio (OR), confidence interval (CI), high-altitude pulmonary edema (HAPE). Significant difference (p < .05) marked with asterisk (*).
Discussion
This study represents the first comprehensive review of medical evacuations on Aconcagua and a unique opportunity for global comparisons.
Overall Rate of Rescue
Of all climbers on Aconcagua, 4.7% required medical evacuation but only 3.9% in the second year of the study. The reason for this lower rate is uncertain and would require more years of study to determine if it represents an anomaly or trend. No major changes were made in the APP evacuation response protocol, though the first year of the study was noted to receive relatively high snowfall, and the medical service had just undergone leadership change with base camp facilities upgrades.
Rate of rescue is not always straightforward to calculate for the world's highest mountains, as accurate data of all climbers rescued and all climbers attempting to summit may not be easily obtainable or tracked. Both Aconcagua and Denali are exceptional in this manner. Denali (6190 m) is another Western Hemisphere “Seven Summits” mountain with a comparable elevation and located within a park that records all climbers and all rescues. Prior to 2010, Denali was found to have an evacuation rate of 1.2%, significantly lower than Aconcagua, but this Denali rate did not include body recoveries. 7 Other important factors could be responsible for this rate difference from Aconcagua, noting also that Denali data were collected over 18 years versus two years on Aconcagua despite a higher number of rescues on Aconcagua over the study periods.
First, Denali is more arctic and remote. Rapid access to helicopter evacuation is straightforward on Aconcagua, with near-daily flights to 4300 m base camp and routinely to 5500 m high camp for park operations. Rescue helicopter flights to extract an ill or injured climber at base camp on Aconcagua travel up a single valley for less than 25 km from a staging area at the park entrance (2950 m) to access a staffed base camp helipad. By contrast, access to the 4300 m camp on Denali is more remote and less routinely traveled. Thus, helicopter evacuations may be technically easier on Aconcagua and could partially explain some of this rescue frequency difference.
Second, climbers may have less experience on Aconcagua than Denali, which may affect rescue rates. A prior study of Aconcagua climbers found that most climbers had not slept over 5000 m or climbed over 6000 m. 2 That study suggested that climbers from Europe and North America may not have access to training or pre-acclimatization on peaks over 5000 m and that the nontechnical aspect of the Aconcagua Normal Route attracts less experienced climbers. Anecdotally, many climbers on Aconcagua report using the climb there to gain experience prior to attempting Denali's more technical summit. Therefore, less experience of Aconcagua climbers could make them more prone to illness, leading to an increased evacuation rate compared with Denali.
Third, the Normal Route on Aconcagua is technically less demanding than the most frequently climbed West Butress route of Denali. Though ascent rates were not tracked by APP data, climbers may ascend more rapidly on Aconcagua due to easier terrain, leading to higher rates of altitude illness and a subsequent higher rescue rate. A study of 17 HAPE patients on Aconcagua requiring evacuation found that they spent fewer nights acclimatizing at 4300 m base camp than controls, 6 consistent with the concept that more rapid ascent may lead to increased evacuations on Aconcagua.
Regarding evacuation rate over time on Aconcagua, the two most current years were studied as they represent the two most recent full seasons since the COVID-19 pandemic disrupted climbing on the mountain. However, for historical context, the annual mean of 151 evacuees (or 170 per year if nonclimbers are included) does fall within the range of total number of annual evacuations of 112–204 per year from 2010 to 2020, with these numbers provided by staff at APP.
Climber Characteristics
Regarding age, the current study found that the age of rescued climbers did not differ from all climbers. Further, climbers over 50 did not have a significantly higher rate of rescue than younger climbers. These data contrast those from other mountains, which have noted that older age is associated with a higher rate of rescue, such as on Denali, and a higher rate of death, such as on Everest.7,11 However, deaths on Denali were not associated with age. 10 In 2013, Aconcagua fatalities had a mean age of 42 years, which approximates the current mean of rescued climbers of 43 years. 4
Male climbers were found to be twice as likely as female climbers to require medical evacuation (OR 2.01). This finding of male predominance in rescues and fatalities is consistent throughout mountaineering literature but rarely calculated as an accurate relative risk such as with the current analysis.4,7,9–11,13,15,18,19
Looking at the continent of origin of rescued climbers, the highest rates of evacuation were found among climbers from Africa, Asia, and Australia. Mortality rate or evacuation rate by continent has not been previously calculated for Aconcagua or many other mountains, but it has been calculated for Denali.4,7,10 Similar to Aconcagua, on Denali climbers from Asia were more likely to require rescue. 7 However, during the study period, there were no deaths of climbers from Asia despite the higher rate of rescue, which contrasts with fatality data from Denali showing a higher risk of death in Asian climbers. 10 Thus, perhaps the higher evacuation rate of Asian climbers is affecting climber safety on Aconcagua in a manner different from on Denali, based on differing reasons for rescues and fatalities between the two mountains.
Medical Causes and Rescue Implications
This study found a remarkable percentage of climbers requiring medical evacuation for altitude illness (62%) and specifically HAPE (49%) and AMS (11%). Of all climbers attempting to summit Aconcagua, 2.3% were evacuated for HAPE, which represents the single largest reason for medical evacuation during the study period. A study of climbers on Aconcagua in 2001 estimated the incidence of HAPE requiring rescue to be 1.5%, but this rate was calculated using a partial year estimate of climbers at risk. 1 A prior mortality study found that the single largest medical cause of death on Aconcagua was HAPE. 4 The current data show much higher rates of altitude illness rescues on Aconcagua compared with Denali, and a higher percent of evacuations for HAPE than on Everest. Thus, altitude illness and HAPE are frequent and life-threatening on Aconcagua. The APP medical service has remained central to the diagnosis, treatment, and evacuation of these patients with high-altitude illnesses. 6
Rapid access to helicopter facilitated descent has been present for years on Aconcagua. Additionally, the descent from the Aconcagua 4300 m Plaza de Mulas base camp to the Horcones trailhead is an arduous 25 km hike not amenable to foot travel by an ill or injured climber. With a high prevalence of HAPE on Aconcagua, it is important to note that increased sympathetic tone from exertion, such as with self-evacuation over a difficult land route, could lead to clinical deterioration of HAPE and death. For this reason, helicopter evacuation is generally recommended for HAPE, 20 and a recent study found that all HAPE patients attended to by the APP medical service were evacuated by helicopter and survived. 6 Note that many helicopter rescues on Aconcagua are also preceded by limited self-rescue or assisted rescue on foot from a higher location to a landing zone, but this on-foot component is generally not captured by APP registry data. Though this study does not examine the mortality effect of helicopter evacuation, the presence of helicopter-assisted descent appears to frequently benefit climbers requiring evacuation with life-threatening diagnoses such as HAPE.
As mentioned, climber inexperience or route characteristics may make Aconcagua climbers more susceptible to altitude illness. However, on many other large mountains worldwide, rescues and fatalities are commonly due to trauma.7,10,11,18,19 One notable exception is Mount Kilimanjaro, where HAPE caused the majority of deaths. 9 Like Mount Kilimanjaro, the Normal Route on Aconcagua is nontechnical, which appears to explain the predominance of altitude illness evacuations over traumatic etiologies on these mountains.
Details of fatalities were not able to be determined for the current study, but the fatality rate near 0.1% approximates that of an older study on Aconcagua. 4 A larger sample size of recent deaths over more years since the older study may be beneficial to verify a current fatality rate.
Future Considerations
With such frequent evacuations for HAPE, including at the 4300 m base camp, a more aggressive education campaign could be considered to reduce HAPE incidence. Helicopter-facilitated rescue and an active medical presence on Aconcagua appear to benefit climbers requiring rescue, though a more specific study regarding mortality may be beneficial. Helicopter access and physician medical oversight in APP can be continued to benefit climber safety. With its current high incidence, an opportunity exists for further study of HAPE risk factors, such as ascent profiles, which may contribute to its high prevalence on Aconcagua. Though the diagnosis of HAPE remains primarily clinical, other life-threatening medical conditions may also coexist, 5 and the continued use of base camp medical clinic diagnostic tools and post-evacuation patient follow-up may assist with defining future patient care needs.
Additionally, prevention and treatment of all altitude illnesses, as well as frostbite prevention, appear to be other important opportunities for climber education by APP in order to avoid both illness and rescue evacuation in future years. Climbers from certain regions with increased rate of evacuation may benefit from additional education. The importance of gradual acclimatization and adequate summit day clothing should continue to be emphasized. Due to large numbers of climbers, obtaining a summit permit for Aconcagua currently involves a registration process with no mandatory education component, but APP could consider developing this element. On Denali, mortality fell after the initiation of a climber registration program focused on planning and education, 10 which suggests that a similar effort by APP could be both effective and measurable in a future study. Resource allocation and rescue preparation efforts by APP can also be informed by this study, noting a higher percentage of evacuations for altitude causes versus less commonly from trauma, though traumatic reason for rescue was still not an insignificant finding.
Finally, the high rate of rescue evacuation at 4.7% should emphasize to climbers the dangers and seriousness of an Aconcagua climb, despite the nontechnical nature of its Normal Route.
Limitations
Study limitations include retrospective review of data, the brief two-year study period, as well as the need to combine certain baseline demographic data from long trekking permits with climbers using ascent permits based on reporting from APP. The incidence of nonclimber evacuations was unable to be calculated due to the absence of a denominator. Due to the de-identification process, climber sex was also reported separately from each evacuated climber. Thus, specific testing for sex versus medical diagnosis could not be performed. Despite these limitations, these results appear to be generalizable to the entire current climber population and representative of the current post-COVID pandemic medical practice on Aconcagua. Limited fatality data is reported but would be more thoroughly evaluated over a longer timeframe.
Conclusion
Climbing Aconcagua involves significant dangers despite the nontechnical nature of its Normal Route. This study documents the medical and traumatic conditions leading to medical evacuation on Aconcagua in recent years. Of all climbers in the 2022–24 seasons, 4.7% required rescue and 49% of these were for HAPE. Male climbers and climbers from Africa, Asia, and Australia had a higher risk of requiring rescue. A higher rate of evacuation for altitude illness than Denali and Everest is an important consideration for APP resource allocation and preparation. APP could consider adding educational components to the current registration process to enhance climber safety. Additional opportunities exist for future study of HAPE, as well as mortality. Climbers should remain aware of these risks and the importance of acclimatization to avoid the need for medical evacuation when climbing Aconcagua.
Footnotes
Acknowledgments
The authors thank Pablo Perelló, Chief Ranger of the High Mountain Zone at Aconcagua Provincial Park, and the staff of the Government of Mendoza Department of Renewable Natural Resources for assistance with data acquisition. Peter Callas from the UVM Department of Mathematics and Statistics assisted with statistical analysis. Roz King and Miles Lambertson of UVM assisted with study coordination.
Author Contribution(s)
Conceptualization, methodology, investigation, validation, writing review and editing: AB, BA, RD, RP, SS, JS. Supervision, formal analysis, and original draft preparation: AB.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article, other than BA, RD, RP, and JS work for the medical service of APP.
Data Availability
Data were made available to the research team only by APP.
Ethical Considerations
The study was determined to be exempt from Institutional Review Board review at UVM. Permission to conduct the study was granted by the medical service of APP.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
