How to take care of your Asthma in Higher Altitudes? - Dr Udaya S

Who doesn’t want to experience a walk through snow-capped mountains and flower valleys, or just a trek up the hill outside the city?

While trekking mostly involves walking, it is not a walk in the park. It requires stamina, lung power and strong legs. Travelling to a destination at a higher altitude for leisure or an adventure might prove to be, or should I say, is considered to be a challenge for people suffering from asthma. So let us today discuss the issues and myths associated.

Asthma is an inflammatory disorder of airways. The main physiological feature of asthma is episodic airway obstruction characterised by reversible airflow limitation and accompanied by episodic dyspnea, cough, and wheezing, chest tightness.

Asthma comprises a range of diseases and has a variety of heterogeneous phenotypes. Genetic predisposition, specifically a personal or family history of atopy (propensity to allergy, commonly shown as eczema, hay fever, and asthma), is one of the recognised factors related with asthma.

Exposure to tobacco smoke and other inflammatory gases or particulate matter is also linked to asthma. Other triggers for asthma include acute viral respiratory tract infections, exercise, gastro-oesophageal reflux disease, chronic sinusitis, environmental allergens, use of aspirin, beta-blockers, insects, plants, chemical fumes, obesity, emotional factors or stress.

Some studies have found an inverse relationship between geographic altitude and the prevalence and morbidity of asthma (Vargas et al., 1999; Gourgoulianis et al., 2001). Asthma control at high altitude is affected by several environmental factors including allergen burden, cold air, hypoxia and air density. Eventually it is a balance of risk versus benefits.

Benefits

The decreased presence of allergens and lower air pollution at high altitude, the absence of house dust mite allergens at altitudes >1,600m may explain the beneficial effect of high altitude in subjects with asthma.

Two studies, one in children and one in adults, have shown that high-altitude treatment also reduces airway inflammation in patients with allergies other than house dust mite, or no allergies at all the change in environmental exposure from a polluted, industrialised environment at sea level to the low-trigger environment at high altitude.

The environment at high altitudes may be directly beneficial to health due to the reduced air viscosity and oxygen pressure. Breathing becomes easier because of the reduced air density, which lowers lung resistance and promotes full lung expansion by increasing inspiratory and expiratory flows and decreasing respiratory resistances.

One explanation could be that at higher altitudes the more severe hypoxia stimulates the release of catecholamines and cortisol i.e. natural steroids, which in turn have a protective effect on bronchial hyper responsiveness thus reducing symptoms.

Also moving to the mountains, the patients are moved away from psychological stress at home or at work. Such places are also well known for their abundance of sunshine. UV radiation exposure increases the skin's production of vitamin D and may alter the immune system, which may lessen the severity of long-term conditions like asthma.

Risks

Cold air is a known trigger for asthma, especially in combination with increased ventilation during exercise, which may explain the increased prevalence of asthma among cross-country skiers and emphasises the need for optimal treatment in these athletes.

Exposure to cold air at high altitude may thus counteract the beneficial effects of improved air quality. A variable percentage (60% to 80%) of asthmatics suffer from exercise-induced bronchoconstriction (EIB), which is the acute transient airway narrowing that occurs during and most often after exercise.

In fact, dehydration of the airways results in a release of mediators, especially from mast cells.

Upper respiratory tract infection is a common event during high

altitude trekking. It is known that bronchial responsiveness increases for up to 6 weeks after an upper respiratory tract infection (Heir et al., 1995).

As far as the incidence of acute mountain sickness (AMS), there is no evidence to conclude it is more as compared to normal population.

Screening and Health Checks

For people with asthma planning for such trips two independent risk factors for attacks during travel were determined:

1. Frequent use (3 times weekly) of inhaled bronchodilators before travel.

2. Participation in intense physical exertion during treks.

3. Hypoxia altitude simulation test and other such tests can be used to screen high risk patients by Pulmonologists.

We believe that people with asthma who are under control and who take the necessary precautions shouldn't be prohibited from ascending to high altitudes.

Specific recommendations are as follows:

1. Patients with mild intermittent or mild persistent disease may ascend up to 5000 m.

2. Patients with moderate to severe asthma should be cautioned against travelling to high altitude (above 3000 to 3500 m), especially in remote areas.

3. Patients should not discontinue regular therapy and should always have rescue drugs. At high altitude, the use of a spacer for a metered dose inhaler is recommended, even more than at sea level as the reduced density of air and hypobaria might affect the delivery of drugs.

4. To guarantee proper operation, inhalers should be stored in a warm, dry environment.

5. It is best to bring new inhalers to avoid the risk of running out of this therapy.

6. The same medications that are used at sea level should always be utilised to premedicate patients before they exercise.

7. As at sea level, during very cold and windy days, patients should protect the mouth (e.g., with a scarf).

8. Trekking to high altitudes in remote areas is better done in the presence of a medical doctor.

In any event, the patient should be instructed to bring enough medication, perhaps packaged in two separate locations in case of loss; a list of what to do in case of worsening asthma should be included with the medication (i.e., oral corticosteroids, with an inhaled short-acting b-2 agonist, such as salbutamol 200–400 mg every 20 min after taking oral glucocorticoids for two to six hours, there is no improvement and the early bronchodilators do not produce a quick and persistent response for at least three hours, it is better to seek medical care (GINA guidelines). To end, “Not all who wander are lost!”