7,8,27 Furthermore, bronchoconstriction at low barometric RAD001 mouse pressure exacerbates hypoxia and thus theoretically predisposes asthmatics to HAPE and AMS.2 At altitudes up to 2,000 m, asthmatic travelers receive the benefits of decreased airborne allergens and reduced resistance to airflow.7,8,27,61 At altitudes

above 2,500 m, conditions may be more conducive to induce an asthma attack due to the cold, dry air.61 Travelers at highest risk are those who use inhaled bronchodilators more than three times per week at their living altitude and those who participate in strenuous aerobic activity at altitude.61,62 Between 3,500 and 5,000 m, it has been shown that asthmatics have a reduced risk of suffering an asthma attack. Whereas the cold, dry air provides a stimulus for an asthma attack, changes in physiologic mediators that occur with acclimatization are thought to exert a modulatory effect over airway hyperresponsiveness.7,61,63 While at altitude, use of volumetric spacers is recommended for metered dose BTK inhibitors high throughput screening inhalers, and the mouth should be protected against cold and wind.8,61 It is notable that high altitude natives routinely use silk scarves to protect their airways from exposure to cold air. Exertion at altitude should be moderate to avoid excessive hyperventilation and passive ascent to high altitude should be avoided as sudden exposure to hypoxia can increase airway irritability.61,64 Peak expiratory flow rate is a practical

method for monitoring asthmatic status at PI-1840 altitude.8 Hypobaric hypoxia associated with high altitude is likely to exacerbate the effects of obstructive sleep apnea (OSA). Richalet and colleagues suggest that individuals with Down syndrome and OSA have significantly impaired chemoreceptor sensitivity to hypoxia and are thus at increased risk of HAPE with exposure to even moderate altitudes.65 Thus, high altitude travel is contraindicated for people with OSA who demonstrate arterial oxygen desaturation at sea level.31 It is of interest that

acetazolamide has been shown to reduce the apnea–hypopnea index in patients with OSA.66 Should a patient with OSA choose to travel to altitude, it is reasonable to prescribe acetazolamide prophylaxis in an effort to improve the symptoms of OSA and reduce the risk of developing AMS. Patients who travel with their continuous positive airway pressure machine may need to adjust the pressure setting to accommodate for the decrease in barometric pressure at altitude.8 No baseline data exist to help the physician predict which patients with interstitial lung disease (ILD) are most likely to suffer deterioration in their respiratory status at high altitude. It is recommended that patients with ILD in whom the presence of pulmonary hypertension has not been confirmed should undergo echocardiography before traveling to high altitude. Symptomatic pulmonary hypertension is a contraindication to high altitude travel.