Ascent schedules, acute altitude illness, and altitude acclimatization： Observations on the Yushu Earthquake

During the Yushu Earthquake on April 14, 2010, a large number of rescuers from sea level or lowlands ascended to the quake areas very rapidly or rapidly less than 24 h. However, Yushu Earthquake is the highest quake in the world at altitudes between 3 750 m and 4 878 m where is a serious hypoxic environment. A high incidence of acute altitude illness was found in the unacclimatized rescuers; the mountain rescue operation changed as ＂rescue the rescuers＂. Lesson from the Yushu Earthquake is that the occurrence of acute altitude illness may be closely related to the ascent schedules. This prompted us to study the relationship between ascent rate and the incidence and severity of acute altitude illness ; five different groups were compared. The first group was 42 sea level male young soldiers who ascended to quake area very rapidly within 8 h at 4 000 m; the second group was 48 sea level male young soldiers who ascended to 4 000 m rapidly less than 18 h; the third group was 66 acclima- tized medical workers from 2 261 m who ascended to 4 000 m rapidly within 12 h; the fourth group was 56 Tibetan medical workers from 2 800 m who ascended to 4 000 m rapidly within 8 h; the fifth group was 50 male sea level workers who ascended to 4 000 m gradually over a period of 4 d. The results showed that the sea level rescuers ascended to 4 000 m very rapidly or rapidly had the highest incidence of acute mountain sickness （AMS） with the greatest AMS scores and the lowest arterial oxygen saturation （SaO2）; the sea level workers ascended to 4 000 m gradually had moderate incidence of AMS with moderate AMS scores and SaO2 values; whereas the acclimatized and adapted rescuers had the lowest incidence of AMS, lowest AMS scores and higher SaO2 ; especially none AMS occurred in Tibetan rescuers. AMS score is inversely related to the ascent rate （r=- 0.24, p〈0.001）. Addi- tionally, acute altitude illness is significantly influenced by altitude acclimatization. The ascent rate is inversely related to the period of altitude acclimatization whereas the time of perfect recovered from AMS is positively correlated to the time taken to acclimatize. Generally, the best means of preventing acute altitude illness is slow and gradual ascent to high altitude, as this allows time for establishing altitude acclimatization and tolerance to the hy- poxic environment. However, during an emergency circumstance, such as mountain rescue operation, the rescuers must rapidly ascend to high altitude, so