Sleep-related hypoxaemia and excessive erythrocytosis in Andean high-altitude natives

Sleep-related hypoxaemia and excessive erythrocytosis in Andean high-altitude natives. L. Spicuzza * , N. Casiraghi # , A. Gamboa } , C. Keyl z , A. Schneider z , A. Mori § , F. Leon-Velarde } , G.U. Di Maria * , L. Bernardi # *Dept of Internal Medicine and Medical Specialities, University of Catania, # Dept of Internal Medicine and § Pathology, IRCCS S. Matteo and University of Pavia, Italy. } University Cayetano Heredia, Lima, Peru. z Dept of Anaesthesiology, University of Regensburg, Germany. To determine whether nocturnal hypoxaemia contributes to the excessive erythrocytosis (EE) in Andean natives, standard polysomnographies were performed in 10 patients with EE and in 10 controls (mean haematocrit 76.6 +/- 1.3% and 5.4 +/- 0.8%, respectively) living at an altitude of 4,380 m. In addition, the effect of O2 administration for 1 h prior to sleep, and the relationship between the hypoxic/hypercapnic ventilatory response and the apnoea/hypopnoea index (AHI) during sleep were studied. Awake arterial oxygen saturation (Sa,O2) was significantly lower in patients with EE than in controls (83.7 +/- 0.3% versus 85.6 +/- 0.4%). In both groups, the mean Sa,O2 significantly decreased during sleep (to 80.0 +/- 0.8% in EE and to 82.8 +/- 0.5% in controls). The mean Sa,O2 values remained significantly lower in patients with EE than in controls at all times of the night, and patients with EE spent significantly more time than the controls with an Sa,O2 of