2,5,50 The extent of this risk is not well understood or easily predicted. Some individuals have demonstrated the

ability to function well at high altitude whereas others suffer the consequences of increased pulmonary hypertension, HAPE, or right heart failure even at moderate altitudes.50–56 Symptoms with ascent may include dyspnea, weakness on exertion, and syncope.5 For people with symptomatic pulmonary hypertension at sea level, altitude exposure is contraindicated.2 click here Asymptomatic patients with CHD should be warned of the potential for developing HAPE and take nifedipine prophylactically to reduce their risk. Travelers with a brisk hypoxic pulmonary vasoconstrictor response may be identified in the clinic by observing their response to inhalation of a low oxygen mixture.5 These recommendations equally apply to patients with primary or secondary pulmonary hypertension.5 People with chronic obstructive pulmonary disease (COPD) may be hypoxemic at sea level and thus may develop altitude-related BIRB 796 cost symptoms at lower elevations than healthy people (Figure 2).2,8,27 Blunted carotid body

response due to chronic hypercapnia may reduce their ability to produce a hypoxic ventilatory response, thus further exacerbating the hypoxia.7 Breathing cold air results in pulmonary vasoconstriction and increased pulmonary artery pressure.8,57 Elevated levels of carboxyhemoglobin due to smoking may further compromise oxygen-carrying capacity in this cohort.58 Depending on baseline oxygen saturation and the PAK6 pathological condition

of the lungs, risks associated with altitude exposure include profound hypoxemia, pulmonary hypertension, disordered ventilatory control, impaired respiratory muscle function, and sleep-disordered breathing.2 No studies have been conducted on patients with COPD at high altitude. However, studies of patients with mild to moderate COPD at 1,920 m concluded that it is safe for such patients to travel to intermediate altitude.33,58 Altitude exposure is contraindicated for patients with severe COPD who have dyspnea at rest or on mild exertion at sea level. Patients with moderate disease should undergo individualized risk assessment and ascend with caution.2,7 Hypoxic challenge, spirometry testing, and the British Thoracic Society’s (BTS)59 guidelines for respiratory patients planning air travel may provide useful guidance for physicians.2,7,27 To minimize the risk of adverse effects, patients with COPD should avoid strenuous exercise at altitude and ensure optimal health prior to ascent.27 Maintenance of hydration at altitude is important to avoid problems associated with thickened mucosal secretions.60 Altitude can influence bronchial hyperresponsiveness, and thus, the likelihood of an acute asthma attack.