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A new model of chronic intermittent hypoxia in humans: effect on ventilation, sleep, and blood pressure

¹Sleep Laboratory and Exploration Fonctionnelle Cardio Respiratoire, Pôle Rééducation et Physiologie, University Hospital Grenoble, Grenoble; ²Institut National de la Santé et de la Recherche Médicale ERI 17, EA 3745, HP2 Laboratory (Hypoxia: Pathophysiology), Joseph Fourier University, Grenoble, France; and ³Pulmonary and Sleep Research Laboratory, Division of Pulmonary, Critical Care and Sleep Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts

Submitted 1 September 2008 ; accepted in final form 16 February 2009

Obstructive sleep apnea is characterized by repetitive nocturnal upper airway obstructions that are associated with sleep disruption and cyclic intermittent hypoxia (CIH) The cyclic oscillations in O₂ saturation are thought to contribute to cardiovascular and other morbidity, but animal and patient studies of the pathogenic link between CIH and these diseases have been complicated by species differences and by the effects of confounding factors such as obesity, hypertension, and impaired glucose metabolism. To minimize these limitations, we set up a model of nocturnal CIH in healthy humans. We delivered O₂ for 15 s every 2 min during sleep while subjects breathed 13% O₂ in a hypoxic tent to create 30 cycles/h of cyclic desaturation-reoxygenation [saturation of peripheral O₂ (Sp_O2) range: 95–85%]. We exposed subjects overnight for 8–9 h/day for 2 wk (10 subjects) and 4 wk (8 subjects). CIH exposure induced respiratory disturbances (central apnea hypopnea index: 3.0 ± 1.9 to 31.1 ± 9.6 events/h of sleep at 2 wk). Exposure to CIH for 14 days induced an increase in slopes of hypoxic and hypercapnic ventilatory responses (1.5 ± 0.6 to 3.1 ± 1.2 l·min^–1·% drop in Sp_O2 and 2.2 ± 1.0 to 3.3 ± 0.9 l·min^–1·mmHg CO₂^–1, respectively), consistent with hypoxic acclimatization. Waking normoxic arterial pressure increased significantly at 2 wk at systolic (114 ± 2 to 122 ± 2 mmHg) and for diastolic at 4 wk (71 ± 1.3 to 74 ± 1.7 mmHg). We propose this model as a new technique to study the cardiovascular and metabolic consequences of CIH in human volunteers.

sleep apnea; pathophysiology; cardiovascular

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