CO2 Supplement for Treatment of Acute Mountain Sickness

Overview

It was reported that up to 76% people who rapidly ascend to the altitude higher than 4500 m without sufficient acclimatization will have AMS which often develops 6-8 hours after reaching at high altitude. AMS could be improved if there is no continuous ascent although central sleep apnea may persist much longer. It has also been well documented that exercise capacity was impaired at high altitude. Oxygen inhalation is the most effective treatment method, but it is impractical for outdoor activities because of the large volume required. There are some drugs such as acetazolamide, and ibuprofen for relieving AMS but side effects and inconsistent treatment effect made them to be difficulty for routine use. It is noted that adding CO2 might be useful for improvement of hypoxia and exercise ability and eliminating CSA. There is no available device which can accurately supply constant CO2 and is functionally free of dead space. We innovated a portable device with a special mask for supplement of CO2 for prophylaxis and treatment of AMS.

Description

Objective: To determine whether, after rapid ascent to high altitude the device could reduce the incidence and severity of AMS as defined by AMS scores, improve sleep quality and reduce central sleep apnea events.

Methods: A randomized placebo-controlled study will be performed in 36 healthy adults with no history of travelling to high altitude (>1000m) a year before the study. Subjects will be randomly and blindly given either CO2 mixed with air or air alone during daytime and sleep. Blood gases will be measured 30 minutes after inhalation of air or CO2. SaO2, heart rate, and respiratory rate will be recorded every two hours. AMS (Lake Louise Acute Mountain Sickness Score) will be recorded before and after sleep. PSG including diaphragm EMG would be recorded under CO2 or air. Exercise time, ventilation heart rate, respiratory rate, and SaO2 will be recorded and maximal load and peak ventilation will be measured during incremental cycle exercise with inhalation of CO2 or ambient air.

Eligibility

Inclusion Criteria:

1. BMI less than 25kg/m2
2. normal lung function.
3. Healthy lowlanders (<500m) who have no history to travel to high altitude (>1000m) a year before the study.

Exclusion Criteria:

1. insomnia,
2. moderate or severe OSA based on PSG at sea level (AHI> 15 events/hr).
3. visited to an altitude >2500 m in the preceding year.
4. Currently using medicines for diabetes, hypertension et al.