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 calcu- lated 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 (inci- dence) 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
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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 find- ings could be helpful to the HRA in its endeavor to keep the mountains safe for trekkers and porters. The other pur- pose was to compare altitude sickness at the two aid posts.
Himalayan Rescue Association aid posts data were col- lected 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 medi- cine. 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 loca- tions (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
AMSS Patients: (Trekker+Nepali) % Of Total Aid Post 15.3 14.4
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
173 248 453 504
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
271 253 320 265
'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
'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 deter- mine 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 analy- sis of the proportion of mountain sickness at the two aid posts.
Hence, these data were pooled and the total num- ber of patients presenting with AMS, HAPE, or HACE was used to calculate the proportion of high altitude sick- ness 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.
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
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 ill- ness 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, pro- vide 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 sick- ness, 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 inci- dence 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 num- ber 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 num- ber 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 ear- lier 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 expla- nation for this could be the rigor with which organiza- tions like the Himalayan Rescue Association preach prevention of A M S in the Himalayas.
The authors w...