High altitude pulmonary edema, down syndrome, and obstructive sleep apneas.

A 24-year-old adult with a Down syndrome was admitted in December 2006 at the Moutiers hospital in the French Alps for an acute inaugural episode of high altitude pulmonary edema (HAPE) that occurred in the early morning of day 3 after his arrival to La Plagne (2000 m). This patient presented an interventricular septal defect operated on at the age of 7, a hypothyroidism controlled by 50 microg levothyrox, a state of obesity (BMI 37.8 kg/m(2)), and obstructive sleep apneas with a mean of 42 obstructive apneas or hypopneas per hour, treated with continuous positive airway pressure (CPAP). The patient refused to use his CPAP during his stay in La Plagne. At echocardiography, resting parameters were normal, with a left ventricular, ejection fraction of 60%, a normokinetic right ventricle, and an estimated systolic pulmonary artery pressure (sPAP) of 30 mmHg. At exercise, sPAP rose to 45 mmHg and the right ventricle was still normokinetic and not dilated. An exercise hypoxic tolerance test performed at 60 W and at the equivalent altitude of 3300 m revealed a severe drop in arterial oxygen saturation down to 60%, with an abnormal low ventilatory response to hypoxia, suggesting a defect in peripheral chemosensitivity to hypoxia. In conclusion, patients with Down syndrome, including adults with no cardiac dysfunction and regular physical activity, are at risk of HAPE even at moderate altitude when they suffer from obstructive sleep apneas associated with obesity and low chemoresponsiveness. This observation might be of importance since an increasing number of young adults with Down syndrome participate in recreational or sport activities, including skiing and mountaineering.