From the Guidelines
Considerations for Occupational Medicine in Workers at High Altitude
Workers at high altitude should ascend gradually to allow acclimatization, with a maximum ascent of 1000 feet per day, to minimize the risk of acute mountain sickness (AMS) and other high-altitude illnesses 1.
Medical Screening and Precautions
Workers should be medically screened before starting high-altitude work, with particular attention to pre-existing medical conditions such as heart disease, lung disease, and anemia 1.
- Acetazolamide, 125-250 mg orally twice a day, can be used as a preventative measure for AMS in workers who will be ascending rapidly to high altitudes 1.
- Workers at high altitude should also be educated on the symptoms of AMS, including headache, fatigue, nausea, and shortness of breath, and should be instructed to descend immediately if symptoms occur 1.
- Oxygen supplementation may be necessary for workers who will be working at extremely high altitudes or for extended periods 1.
Monitoring and Treatment
Regular monitoring of workers' health, including blood oxygen levels and blood pressure, is also recommended 1.
- Workers with pre-existing medical conditions may require additional precautions, such as more gradual ascent or closer medical monitoring 1.
- In cases of severe AMS, workers should be immediately descended to a lower altitude and given oxygen supplementation, and if necessary, nifedipine, 10-20 mg orally every 6 hours, can be used to treat pulmonary hypertension, and dexamethasone, 8 mg orally every 6 hours, can also be used to treat cerebral edema 1.
Sex-Specific Considerations
There may be sex-specific differences in responses to high altitude, with women potentially being at higher risk for AMS and other high-altitude illnesses 1.
- Respiratory muscle training prior to or during altitude/hypoxic sojourn may be more beneficial for women due to larger expiratory flow limitations during hyperventilation 1.
- Women may also be at higher risk for iron deficiency, and early and appropriate iron supplementation prior to and during altitude/hypoxic sojourn may be necessary 1.
From the Research
Considerations for Occupational Medicine in Workers at High Altitude
The following considerations are important for occupational medicine in workers at high altitude:
- Acute Mountain Sickness (AMS): AMS is a common syndrome occurring after acute ascent to over 2,500 m and is caused by increased capillary permeability 2. Factors that increase the risk of AMS include exercise, and avoiding rapid ascent, undue exercise, and the use of acetazolamide are useful preventative measures 2, 3.
- Prevention and Treatment: Acetazolamide is the drug of choice for pharmacologic prophylaxis, and descent to lower elevation is the definitive treatment for altitude illness 3. Doses of 500-750 mg/day within 24 hours of altitude exposure appear to be the most effective for minimizing symptoms of AMS 4.
- Acclimatization and Adaptation: Gradual ascent to allow acclimatization can lessen or prevent symptoms of AMS 2, 3. Acclimatization and adaptation are important for workers and residents at high altitude, and the improvement seen in maximum exercise has been incorporated into some training schedules for endurance athletes 2.
- Health Effects: High altitude is associated with various adverse health effects, including:
- Cardiovascular effects: increased sympathetic tone, elevated blood pressure, and decreased exercise tolerance in workers with pre-existing hypertension or coronary artery disease 5.
- Pulmonary effects: high-altitude pulmonary edema, pulmonary hypertension, subacute mountain sickness, and chronic mountain sickness 2, 5.
- Neurological effects: acute mountain sickness, high-altitude cerebral edema, and poor sleep quality 2, 5.
- Ophthalmological effects: increased exposure to ultraviolet light and xerophthalmia 5.
- Renal effects: high altitude is associated with a protective effect in patients with renal disease, although the effect on miners with a history of chronic renal disease is unknown 5.
- Hematological effects: advanced age increases the risk of erythrocytosis and chronic mountain sickness, and thrombotic and thromboembolic events are more common at high altitude 5.
- Musculoskeletal effects: miners are at increased risk for low back pain due to occupational factors, and easy fatigue at altitude further predisposes workers to this disorder 5.
- Toxic Exposures: Diesel emissions at altitude contain more carbon monoxide due to increased incomplete combustion of fuel, and miners with a diagnosis of chronic obstructive pulmonary disease may be at higher risk for morbidity from exposure to diesel exhaust at altitude 5.
- Pre-placement Screening and Surveillance: Careful selection of workers, appropriate acclimatization, and limited on-site surveillance can help control most health risks, but further research is necessary to more completely understand the risks of mining at altitude and delineate what characteristics of potential employees put them at risk for altitude-related morbidity or mortality 5.