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Trends in the Workload of the Two High Altitude Aid Posts in the Nepal Himalayas Buddha Basnyat, Gabrielle K. Savard, and Ken Zafren

6ackground:Acute mountain sickness (AMS), High altitude pulmonary edema (HAPE) and High Altitude Cerebral Edema (HACE) are well known problems in the high altitude region of the Nepal Himalayas.To assess the proportion of AMS, HAPE, and HACE from 1983 to 1995 in the Himalaya Rescue Association (HRA) aid posts' patients at the Everest (Pheriche 4243 m) and Annapurna (Manang 3499 m ) regions, the two most popular trekking areas in the Himalayas. A retrospec- tive study was conducted at the HRA medical aid posts in Manang (3499 m) and Pheriche (4243 m) in the Himalayas, where 4655 trekkers (tourists, mostly Caucasians) and 4792 Nepalis (mostly porters and villagers) were seen at the two high-altitude clinics from 1983 to 1995, for a variety of medical problems, including AMS.

Methods:The number of trekking permits issued for entering the two most popular regions in the Himalayas was calculated and referenced to the proportion of trekkers with medical conditions. Well established guidelines like the Lake Louise Diagnostic Criteria were used in the assessment of AMS, HAPE and HACE. Linear regression analyses were performed on data collected from the two aid posts to determine the effect of time on each variable. For comparison between the aid posts, angular transformation (arcsine) and analysis of variance (ANOVA) were performed on all proportional (incidence) data.

ResukApproximately 20% of all visitors (Nepali plus trekkers) who visited the higher Pheriche aid post were diagnosed with AMS compared to around 6% at the lower Manang aid post.There was a linear increase over time in the number of trekkers entering the Everest (r=0.904, p<.OOl) and the Annapurna (r=0.887, p<.OOl) regions.The proportion of trekker patients with any medical condition visiting the two HRA aid posts at Manang and Pheriche, expressed as a function of the total number of trekkers entering the Everest and Annapurna regions, was not significantly different between Pheriche (average 4%) and Manang (average 1%). However, the proportion of AMS, HAPE and HACE in patients (Nepali plus trekkers) t o the aid posts was greater in those visiting the higher Pheriche aid post compared to the lower Manang aid post (f=56.74, n=13; p<.OOI). Importantly, only the proportion of AMS (r=0.568; p<.05) and not HAPE or HACE increased over time in Pheriche, alongside an unchanged proportion of trekker patients, amongst all Pheriche aid post patients.There was no increase of AMS, HAPE or HACE in Manang.

Conclusions: HAPE and HACE are the life-threatening forms of AMS and although there is a linear increase of trekkers entering the Himalayas in Nepal, the findings revealed that HAPE and HACE have not increased over time. One possible explanation may be that awareness drives by organizations like the Himalayan Rescue Association may be effective in preventing the severe forms of AMS.

When lowlanders ascend to intermediate or high altitudes (2000 m and >3000 m, respectively), they may expe- rience symptoms of acute mountain sickness (AMS), (i.e., a complex of headache, insomnia, and anorexia which may progress to nausea and vomiting, ataxia, mental

Buddha Basnyat, MD, MSc, FACP: Medical Director, Himalayan Rescue Association and Medical Attending, Patan Hospital, Kathmandu, Nepal; Gabrielle K. Savard, MD, PhD: University of Calgary, Calgary, Alberta Canada; Ken Zafren, MD, FACP: Medical Director, Denali National Park, Associate Director, Himalayan Rescue Association, Anchorage, Alaska.

Reprint requests: Buddha Basnyat, MD, Nepal International Clinic, PO. Box 3596, La1 Durbar, Kathmandu, Nepal.

JTravel Med 1999; 6:217-222.

confusion and extensive fatigue, and ultimately appear in its most severe form known as high altitude cerebral edema (HACE) Acute Mountain Sickness is exacer- bated with rapid ascent and it is associated with high altitude pulmonary edema (HAPE) in 5-10% of case^.^'^ Since 1976, the Himalayan Rescue Association (HRA) in Nepal has been operating high altitude aid posts in order to provide assistance primarily in the prevention and treatment of altitude sickness in foreign trekkers and Nepalis (mostly porters) traveling within the Ever- est and Annapurna National Park regions, two of the most popular trekking sites in Nepal. Other limited medical services are also provided. Documentation on patients (Nepali plus trekkers) presenting to the two aid posts with altitude sickness (i.e., AMS, HAPE or HACE) has been made since 1983, both in the spring and fall seasons.

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2 1 8 Journa l o f Travel Medicine, Volume 6, Number 4

The purpose ofthis study was to determine whether the proportion ofAMS, HAPE, and HACE in patients to the Pheriche (Everest region) and Manang (Annapurna region) aid posts has changed since 1983, so that the findings could be helpful to the HRA in its endeavor to keep the mountains safe for trekkers and porters. The other purpose was to compare altitude sickness at the two aid posts.

Methods

Himalayan Rescue Association aid posts data were collected from the two HRA aid posts in Nepal: Pheriche (4243 m) in the Everest region, and Manang (3499 ni) in the Annapurna region. Twice a year, in the spring (March to May) and in the fall (October to December), foreign trekkers and Nepalese porters and local villagers may visit the clinic for a consult with one of the attending physi- cians regarding a medical problem, or to ask questions and attend lectures hosted by the HRA on altitude sickness and its prevention.

The medical staff are volunteer doctors fluent in English who are registered practitioners in their own countries and have a special interest in mountain medicine. They attend a detailed orientation session on moun-

tain sickness in Kathmandu before going to the aid posts. This session is run by the Medical Director for the HRA, using established guidelines for the prevention, recogni- tion, and treatment of altitude sickness.'" The posting is considered prestigious and volunteers are chosen after a careful selection process. A significant assignment for the doctors is the daily educational talks on the prevention of altitude sickness given by them to visitors to the aid posts.

Table 1 Data on Aid Post Patients at Pheriche Location, Everest Region

Study Group Subjects of this study were trekkers and Nepali

porters and villagers who were seen at the two clinics between 1983 and 1995 for medical reasons including altitude sickness, gastroenteritis, upper and lower respi- ratory tract infection, dermatological problems,and sus- pected typhoid, dengue, and malaria. Data presented on the total number of aid post patients and specifically on altitude sickness at both Pheriche and Manang locations (Tables l and 2) relate to all patients (Nepali and/or trekkers).

For many, the culmination of the trek beyond Pheriche in the Everest region was going to the higher altitude of Kala Pattar (altitude 5545 m) for a panoramic view; and, beyond Manang in the Annapurna region, the high point of the trek was going over the Thorang La

Year 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

Total Everest Treklung NA NA Permits' Dispensed

Aid Post Patients Nepalist 154 240 Trekkerst 238 301

Trekker Patients % Of Total Everest NA NA Trekking Permits

Trekker Patients (Trekker+Nepali) % Of Total Aid Post 60.7 55.6

Patients

AMSS Patients: (Trekker+Nepali) % Of Total Aid Post 15.3 14.4

Patients

HAPE' Patients (Trekker+Nepali) % Of Total A d Post Patients 1.5 1.7

HACE" Patients (Trekker+Nepali) % Of Total A d Post Patients 2.0 2.4

NA

204 181

NA

65.1

20.0

2.2

3.4

6906

171 384

5.6

69.2

15.3

0.5

0.9

9117 8430

173 248 453 504

5.0 6.0

72.4 66.8

16.9 13.7

0.6 3.8

0.6 1.5

7383

185 371

5.0

66.7

21.2

3.4

1.1

7985 10343 10110 12124

168 293 305 159 315 395 359 118

4.0 3.8 3.6 NA

63.9 57.4 54.0 NA

29.4 18.9 17.9 23.6

1.0 2.5 3.0 2.7

2.4 2.6 2.4 NA

12996 14150

271 253 320 265

2.5 2

54 51

32.5 18.5

1.7 2.5

2.0 1.1

'Permits are only necessary for non-Nepalis who enter the Everest National Park. +Nepalis=Non-trekkei-, usually porters or local villagers. >Trekkers=tourists, mostly Caucasians. $AMS=acute mountain sickness; this category includes all forms of A M S . 'HAPE=high altitude pulmonary edema. "HACE=high altitude cerebral edema. Many with predominant HACE also had HAPE and vice versa. NA = Not available

Basnyat e t a l . , Aid Posts i n the Nepal Himalayas 219

Table 2 Data on Aid Post Patients at Manang Location, Annapurna Region

Year 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995

Total AnnapurnaTrekkmg NA NA NA NA NA NA 26,470 25,042 27,683 29,626 28,715 30,378 30,370 Permits' Dispensed

Aid Post Patients Nepalist 89 307 297 408 238 632 200 549 626 838 618 879 Trekkers' 88 190 149 488 146 419 162 246 397 435 369 337

Trekker Patients %OfTotalAnnapurna NA NA NA NA NA NA 0.6 1.0 1.4 1.5 1.3 1.1 Treklung Permits

Trekker Patients % OfTotal Aid Post Patients 49.7 38.2 33.4 54.5 38.0 39.9 44.8 30.9 38.8 34.2 37.4 27.7

AMSs Patients (Trekker+Nepali) % O f Total Post Patients 0 5.0 8.5 4.7 5.5 6.6 6.1 1.3 6.7 7.3 9.6 5.8

HAPE' Patients (Trekker+Nepali) % Of Total Post Patienrs 0 0.4 0.4 0 1.0 0.1 0.8 0 0 0.4 0 0.1

HACE" Patients (Trekker+Nepah) % Of Total Post Patients 0 1.2 0.2 0 0.8 0.3 0.3 0 0 0.5 0 0.2

696 330

1.1

32.2

8.9

0.3

0

'Permits are only necessary for non-Nepahs who enter the Annapurna National Park. tNepalis = Non-trekkers, usually porters or local villagers. *Trekkers = tourists, mostly Caucasians. DAMS = acute mountain sickness; this category includes all forms of AMS. 'HAPE = high alotude pulmonary edema; "HACE = high altitude cerebral edema. Many with predominant HACE also had HAPE and vice versa. NA = Not available.

pass (altitude 5400 m). The study sample therefore included people who may have slept higher than 4243 m at Pheriche or 3499 m at Manang but returned to lower altitudes for medical treatment.

Acute Mountain Sickness Scoring System Established guideline^'^^ were used for the diagno-

sis of AMS and its more severe forms: HAPE and HACE. AMS was diagnosed if in conjunction with headache, the patient had any one of these: nausea, dizziness, fatigue, or sleeplessness. HACE was diaganosed if in addition to AMS, the patient had ataxia or mental changes.

HAPE was diagnosed if patients had a cough, short- ness of breath at rest, or decreased exercise performance, in addition to rales and wheezes in the lungs and cyanosis or tachypnea and tachycardia. Although patients with HACE and HAPE have been categorized separately, this only denotes predominance of either symptom complex, as many patients diagnosed with HAPE or HACE had symptoms relating to both.

Data Analysis Linear regression analyses were performed on data

collected from Pheriche and Manang aid posts to determine the effect of time (ie., years) on each variable. Sta- tistical comparison of data collected &om the two aid posts over time was also made for the various variables which were assessed. This analysis was limited to those data for which an incidence could be calculated based on the avail- ability of a denominator. The total number of trekking

permits dispensed each year for Everest (data available &om 1986 to 1995) and Annapurna (data available from 1989 to 1995) National Parks, was used as the denominator for determining the incidence of visits by trekkers to each aid post. N o such denominator was available for the number of Nepalis entering each of the National Park regions as they can enter the parks freely without requir- ing a permit. Thus, the incidence of Nepalis visiting the aid posts between 1983 and 1995 was not assessed. The proportion of total aid post patients represented by trekkers in a given year and season (spring and fall) was established using the number of aid post patients as the denominator. Despite an attempt by the HRA doctors to distinguish between Nepali and trekkers in terms of mountain sickness (AMS, W E , HACE), insufficient data were available to separate these two groups for the analysis of the proportion of mountain sickness at the two aid posts.

Hence, these data were pooled and the total number of patients presenting with AMS, HAPE, or HACE was used to calculate the proportion of high altitude sickness over time at each aid post, using the total number of aid post patients at each of the locations as the denominator.

An angular transformation (arcsine) was performed on all proportional (incidence) data before using a one- way repeated measures analysis of variance (ANOVA) for comparisons between aid posts. In cases where the data did not follow a normal distribution, as determined by skewness and kurtosis analysis, a Friedman repeated

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measures ANOVA was used. Significance was set at the p=.05 level.

Results

All data collected from both the aid posts in the Ever- est and Annapurna regions are presented in Table 1 and Table 2 respectively.

Proportion of Trekkers Visiting Aid Posts The total number of trekking visas dispensed in

the period 1986 to 1995 (Everest) and 1989 to 1995 (Annapurna) increased linearly over time in both National Parks (Everest: r = 0.904,p<.OOl;Annapurna: r = 0.887, p<.OI). The number of visas was approximately 3-fold greater in the Annapurna region than in the Everest region (f =1000, n = 7; p<.OOl). The proportion of trekkers visiting either Pheriche or Manang aid posts, expressed as a function of the total number of trekkers entering either Everest or Annapurna National Park, was not significantly different between the two aid posts in the period 1989-1995.

Of all patients to each aid post (Nepali plus trekker), the proportion of trekkers (as opposed to Nepali) visiting the higher elevation aid post at Pheriche was unchanged over time whereas it decreased linearly over time at Manang ( ~ 0 . 5 9 7 ; p<.05). This proportion was greater in Pheriche (4243 m; around 61% of all patients to the Pheriche aid post) than that at Manang (3499 m; around 38% of all patients to the Manang aid post) (f=5.31, n=13;p<.05).

Proportion of Acute Mountain Sickness in Visitors to Aid Posts

Approximately 20% of all patients (Nepali plus trekkers) who visited the Pheriche aid post, were diagnosed with AMS compared to around 6% at Manang.

Approximately 2% of all patients to Pheriche and 0.26% of all patients to Manang were diagnosed with HAPE and/or HACE. When this incidence ofAMS was compared between the two locations, it was found to be greater at the higher altitude Pheriche aid post compared to Manang (f=56.74, n=13; pc.001). Similarly, the incidence ofboth HAPE and HACE were hgher at Pheriche than Manang (HAPE: fz55.18, n=13; p<.OOl; HACE: f=47.96, n=13; p<.OOl).

There was a linear increase in the proportion of AMS amongst the Pheriche aid post visitors (Nepali plus trekkers) since 1983 ( ~ 0 . 5 6 8 ; pc.05); no other linear trend was found.

Finally spring or fall season did not impact on the proportion of patients with A M S in either of the aid posts.

Discussion

The major findings of this study were: 1) there has been a linear increase in the number of trekkers entering both Everest and Annapurna National Parks since 1986 and 1989, respectively; 2) the proportion of trekkers visiting HRA aid posts was not significantly different between the lower (Manang in Annapurna National Park) and the higher (Pheriche in Everest National Park) altitude locations; 3) however, the proportion of AMS, HAPE and HACE, expressed as a function of the total number of aid post patients, was greater in patients (Nepali plus trekkers) to the Pheriche aid post compared to those visiting the Manang aid post; 4) the incidence of AMS in aid post patients (Nepali plus trekkers) has increased linearly in Pheriche (but not Manang) since 1983 but; 5 ) the proportion of HAPE and HACE in Pheriche and Manang has not increased over time. Adventure travel is a growth industry which allows an increasing number of people of all ages, with little expe- rience or physical preparation, and who are very often unaware of the potential problems, to undertake remote treks at high elevations: the risk of developing AMS and its associated complications therefore is great.2

In the present study, the observed proportion of AMS in visitors (Nepali plus trekkers) to the Pheriche aid post of around 20% is the first published data of this kind from this aid post.

Interestingly a common hunch amongst the volunteer doctors staffing the aid posts is that anyone who has attended an educational talk has not developed HACE. The observation, however, that the incidence of AMS in all visitors to the Pheriche aid post has been increasing since 1983, suggests that either a) individuals at increased risk for developing AMS are visiting the higher altitude locations in the Nepal Himalayan, and/or b) the AMS awareness and prevention drives are in fact helping to make visitors at high altitude more aware of AMS and its initial symptoms (i.e., they would present earlier in the course of the illness, before the develop- ment' of the more serious forms of AMS, such as HACE or even HAPE).

In keeping with this latter possibility in the present study, the incidence of HACE and HAPE has not increased since 1983, unlike that ofAMS in Pheriche. This finding also suggests that the earlier detection of AMS (i.e., as may be indicated by the observed increased incidence in AMS since 1983) may be helping to reduce the risk of serious forms of AMS. This finding is in accordance with a recent study which showed that even in terms of altitude illness, trekking in Nepal is a relatively safe activity.' One possible explanation for this could be that the main emphasis given to the prevention of AMS by the HRA is taking effect, thus creating

B a s n y a t e t al., A i d Pos ts in t h e N e p a l H i m a l a y a s 2 2 1

a greater awareness of the four “golden rules”’ for both tourists and porters. The rules are: 1) Understand the symptoms of AMS and at high altitude assume any illness to be AMS unless proven otherwise. 2) Do not ascend with symptoms. 3) Descend if symptoms worsen. 4) Emphasize the responsibility of members of a group for each other.

Nepal has the magnificent Himalayas which attract thousands of tourists every year, but being a financially strapped, developing country with a minimum ofsophis- ticated health infrastructures, the emphasis on these “golden rules” m y be of the utmost importance for safety in the Himalayas.

Ofinterest is the observation that there was a greater proportion of trekkers than Nepalis visiting the higher altitude aid post in Pheriche compared to that in Man- ang. Ths suggests that Nepahs who visit the Everest region present less frequently in Pheriche. One factor which may contribute to this latter observation is that, as many of these Nepalis are lowland porters, there is a fear that they might lose their job if they report ill with altitude illness as they will need to descend. Anecdotal observation a t the Pheriche aid post over the years has revealed that the porters that visit the aid post usually have severe forms of AMS (i.e., they have waited too long)!

co-authored by one of us (B.B.) have focused on the plight of the different Nepah ethnic people at high altitude (e.g., Rais, Limbu, Chetris) and it is clear they are certainly not immune to A M S . Although significantly more tourists travel to the Anna- purna region, than the Everest region there is a paucity of data on AMS from the Annapurna region and this is the first set of data published from the Manang aid post.

Indeed two recent

limitations of the Study There are several important limitations to this first

analysis which, together with the present findings, provide a groundwork for subsequent studies at the aid posts.

In particular, details on the rate of ascent to altitude, the age, gender, level of fitness, place of residence (sea level or altitude), medical history, and the previous hptory of mountain sickness at high altitude of each patient, would be required for a more comprehensive assessment and comparison of AMS, HAPE and HACE, in visitors to Everest and Annapurna National Parks.

Indeed, Honigman et a1.12 suggested that physical fitness (low to average), age under 60 years, lung disease, residence at sea level, and.previous history of altitude sickness, are independent predictors of increased risk of AMS in visitors to high altitudes. Obesity and strenu- ous overexertion in the first few days at high altitudes have also been linked to increased risk of AMS and HAPE.2.12

A second limitation of this study was that the incidence of trekker patients visiting the aid posts, expressed as a function of all trekkers entering either National Park, could not be calculated precisely, as the exact number of trekkers entering either Everest or Annapurna National Park, who actually reached the destination of Pheriche or Manang, respectively, was not obtained. Nevertheless, the reasonable assumption was made in this study that this proportion has not changed significantly since 1983 (i.e., a similar proportion of the total number of trekkers entering Everest or Annapurna has reached either Pheriche or Manang, between 1983 and 1995).

Finally, another limitation may be inter-observer variability as many doctors volunteered at the aid post over this time period. However all the doctors were given thorough orientation lectures and uniformity in the approach to A M S was strongly emphasized, although it is true that a portion of the study here predates the gold standard Lake Louise Consen~us.~ Guidelines from earlier references’,$ which resemble the Lake Louise Con- sensus, were followed for the earlier years.

In conclusion, HAPE and HACE, the severe forms of AMS, have not increased overtime at Pheriche (4243 m) and Manang (3499 m) high altitude aid posts in the Himalayas despite a linear increase in the trekker population to these areas. One plausible explanation for this could be the rigor with which organizations like the Himalayan Rescue Association preach prevention of A M S in the Himalayas.

Acknowledgments

The authors wish to acknowledge Dr. Lynn Con- lon for providing the original idea for this work and for her assistance with the initial gathering of the data.

The authors wish to acknowledge the invaluable assistance of the many volunteer doctors, and the Sherpa staff (Namka and Ang Rita) without whom this study would have been impossible. We are also grateful to the Kathmandu office staff (Prakash Adhikari, Nimesh Singh Dhar, and Govind Bashyal) of the Himalayan Rescue Association. In particular, our special thanks to Nimesh, who spent many hours cleaning the dust and painstak- ingly gathering the data.

The authors also wish to thank Drs. Quentin Pittman and Gordon Ford of the Departments of Medical Phys- iology and of Medicine, respectively, of the University of Calgary, Calgary, Alberta, Canada, for their encour- agement. Finally, thanks to Pramila Rai and Sharmila Maharjan for typing this manuscript.

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A hanging signboard of a German pharmacy. Photo submitted by Dr. lsao Ebisawa.