Bronchial asthma and high-altitude expeditions is a controversial combination. On one hand, cold dry air and exertion are classic asthma triggers — on the other hand, above 2000 m there are far fewer allergens (pollen, dust mites), which theoretically improves many patients’ condition. In clinical practice: WELL-controlled asthma (no exacerbations >12 mo, FEV1 >80%) is compatible with expeditions up to 5500 m. Severe, poorly controlled asthma or frequent exacerbations require individual assessment. This article: mechanisms, HAST as hypoxia tolerance test, medication protocol, when absolutely not to go.
In a nutshell — asthma at altitude
- Well-controlled asthma (FEV1 >80%, no exacerbations >12 mo) — compatible with expeditions up to 5500 m
- Cold dry air + exertion = classic triggers of exercise-induced asthma
- Fewer allergens at altitude — some patients feel BETTER than in the lowlands
- HAST (Hypoxia Altitude Simulation Test) — recommended before expedition for asthma
- Double medication supply — always 2× larger than standard plan
- Buff / scarf covering mouth — reduces exposure to cold dry air
How altitude affects asthma — mechanisms
1. Cold dry air — main trigger
Above 3000 m air is typically <0°C and dry (humidity 10–30%). Inhaling dry cold air cools airway mucosa and dries it out. Mechanism of exercise-induced bronchoconstriction (EIB): damaged mucosa releases inflammatory mediators (leukotrienes, histamine) that constrict bronchial smooth muscle. Effect: exertional dyspnea, wheezing, cough — especially 10–15 min after exertion begins.
2. Reduced allergens — paradoxical benefit
Above 2000 m pollen concentrations from grasses, trees, weeds drop to practically zero. House dust mites (Dermatophagoides) don’t survive above 1500–2000 m. Consequence: many allergic asthma patients report improvement in the mountains — fewer attacks, lower medication needs. This is the basis of historical “climate therapy” in Davos (Switzerland).
3. Hypoxia — respiratory paradox
Altitude causes compensatory hyperventilation — the body breathes faster and deeper. In a healthy person this improves oxygen saturation. In an asthmatic, exertion + rapid ventilation can worsen bronchospasm by exposing a greater volume of cold air to the mucosa.
4. High-altitude dry cough (“Khumbu cough”)
All trekkers >4000 m are exposed to dry, exhausting cough from dust and cold air. In asthmatics the cough is amplified and can trigger a full asthma attack. Prophylaxis: buff scarf covering mouth and nose (moistens and warms inhaled air).
HAST — hypoxia test before expedition
HAST (Hypoxia Altitude Simulation Test) is a test where you breathe a 15% O₂ mixture (simulating 2500 m) for 20 minutes. During the test saturation, spirometry, subjective symptoms are monitored. For asthma it is a recommended pre-expedition test:
- Normal result: SpO₂ >85%, no FEV1 drop >15%, no wheezing — expedition to 4000 m possible
- Borderline result: SpO₂ 80–85%, FEV1 drop 15–20% — expedition limited to <3500 m or with intensive treatment
- Pathologic result: SpO₂ <80%, severe dyspnea, need for salbutamol — expedition discouraged
HAST is performed by pulmonology labs — available in some academic hospitals, not routine. Worth asking a travel medicine physician for a referral.
Medications — supply and strategy
Rescue medications (SABA)
- Salbutamol (Ventolin) inhaler 100 μg/dose — 2 backups (original + backup)
- Standard dosing: 2 puffs every 4–6 h as needed; in exacerbation 4–6 puffs every 20 min for first hour
- Spacer / chamber — strongly recommended, increases lung-delivered dose 2–3×
- Alternative: formoterol in pressurized inhaler (fast onset + long duration)
Controller medications (ICS, ICS+LABA)
- Continue all chronic medications — inhaled corticosteroids (fluticasone, budesonide), ICS+LABA combinations (Seretide, Symbicort, Fostair)
- Do not reduce doses during the expedition, even if you feel better (fewer allergens)
- Increase controller dose by 50–100% 7 days before departure if your asthma is “poorly stable” (step-up plan discussed with pulmonologist)
- Supply: 2× monthly consumption
Emergency medications — oral steroids
- Prednisolone 20–40 mg/day or methylprednisolone 16 mg/day — 5–7 day course for SABA-refractory asthma exacerbation
- Written plan from pulmonologist: when to start, when to descend
- Always radio/satellite consultation with pulmonologist before initiating steroid course
Exercise-induced asthma (EIB) prophylaxis
- Salbutamol 2 puffs 15–20 min before exertion — classic prophylaxis
- Montelukast 10 mg evening — for EIB-dominant patients; added to standard treatment for expedition duration (pulmonology consultation)
- Buff / scarf — warms and humidifies inhaled air, significant improvement in tolerance
- Warm-up — 10–15 min of light walking before intense exertion
When expedition is contraindicated
- Severe asthma (GINA step 4–5) with daily SABA use
- FEV1 <60% on resting spirometry
- Exacerbation within past 3 months requiring hospitalization or steroid courses
- Asthma with past intubation — history of resuscitation from severe asthma
- Pathologic HAST (SpO₂ <80% on 15% O₂)
- No SABA response in spirometry tests
In these cases, reasonable limit: expeditions to 2500–3000 m with pulmonology consultation; target expeditions >4000 m are discouraged.
Frequently asked questions
Does asthma rule out Everest Base Camp?
No, if well-controlled. Well-controlled asthma (FEV1 >80%, no exacerbations >12 months, low SABA use) is compatible with EBC trek (5364 m). Conditions: normal HAST result, double supply of rescue and controller meds, oral steroid plan for exacerbation, pulmonologist consultation 3 months pre-expedition. Many asthmatic patients have reached EBC without issue.
Why do some patients feel BETTER at altitude?
Allergic asthma is typically triggered by grass, tree, weed pollen and house dust mites. These allergens essentially disappear above 2000 m (mites >1500 m don’t survive due to low humidity and temperature; pollen is sparse). Consequence: allergic asthma patients often experience improvement in the Alps, Andes, Himalayas. This is the basis of historical ‘climatotherapy’ in Davos and high-altitude spas.
Can I bring extra salbutamol on expedition?
Yes, absolutely. 2 backup inhalers plus a spacer (inhalation chamber) is recommended. Cost of extra inhaler: $10-15. On foreign expeditions (Nepal, Peru, Tanzania) salbutamol is available without prescription, but counterfeit risk is significant — better to bring from home. Double prophylactic dose (4 puffs instead of 2) before intense exertion is fine.
What to do for asthma exacerbation during trekking?
Graduated protocol: 1) Immediately salbutamol 4-6 puffs with spacer. No improvement in 20 min — repeat. 2) Observation 60-90 min. If improved — stay at current location, do not ascend further today. 3) No improvement or worsening dyspnea — start prednisolone 40 mg/day, call satellite support, prepare evacuation. 4) Resting SpO2 <85%, resting dyspnea, cyanosis — immediate evacuation.
Does a buff really help with Khumbu cough in asthmatics?
Yes, significantly. A buff or scarf covering mouth and nose acts as a pre-warmer and humidifier — you inhale air at temperature and humidity much higher than ambient. Effect: 70-80% reduction in Khumbu cough episodes for trekkers, significantly fewer exercise-induced asthma attacks. The Sherpa technique has been common for decades among Himalayan trekkers. Unconditionally mandatory element of an asthmatic’s kit in the Himalayas.
References
- GINA (Global Initiative for Asthma) 2024 Guidelines. ginasthma.org.
- Torres-Duque CA, et al. Tropical high altitude and severe asthma in adults: house dust mite sensitization. J Asthma. 2024;61(3):222–231.
- Cogo A, Fischer R, Schoene RB. Respiratory diseases and high altitude. High Alt Med Biol. 2004;5(4):435–444.
- Luks AM, Auerbach PS, Freer L, et al. Wilderness Medical Society Clinical Practice Guidelines: 2019 Update. Wilderness Environ Med. 2019;30(4S):S3–S18.
Note: Every high-altitude expedition for an asthmatic patient requires individual pulmonology consultation 3 months before. This article is orientational.