Spontaneous Platelet Activation and Aggregation During Obstructive Sleep Apnea and Its Response to Therapy With Nasal Continuous Positive Airway Pressure*: A Preliminary Investigation

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Study objectiveTo determine whether alterations of platelet reactivity occur during obstructive sleep apnea (OSA) and, if so, whether therapy with nasal-continuous positive airway pressure (N-CPAP) alters this reactivity.DesignPatients with suspected moderate to severe OSA had blood drawn for spontaneous platelet aggregation (sAGG) and activation (sACT) measurements at hourly intervals during diagnostic polysomnography (PSG) and, in those with confirmed OSA, on a separate night during which N-CPAP was applied.SettingTertiary care center sleep laboratory.PatientsSix patients with OSA had matched blood samples drawn on both diagnostic and N-CPAP treatment nights. Five patients without confirmed OSA served as controls.InterventionsN-CPAP was applied to those patients with OSA and pressures adjusted with goals of eliminating apneas; N-CPAP was then maintained through the night.Measurements and resultssACT and sAGG were measured using flow cytometric determination of P-selectin expression using a monoclonal antibody. Platelet aggregation was assessed by measuring the proportion of platelets larger than resting platelets by light scatter techniques. Mean values for sACT and sAGG were higher on the diagnostic night compared with treatment night (p equals 0.001 and p equals 0.003, analysis of variance, respectively). The mean baseline supine sACT compared with completion supine sACT for both diagnostic and N-CPAP nights also revealed significant differences (mean equals 16.6 plus minus 3.5% vs 36.9 plus minus 7.5%, p equals 0.04; and 11.9 plus minus 3% vs 39.5 plus minus 9.1%, p equals 0.04). Platelet activation during sleep in five subjects without OSA resembles that found in patients with OSA during N-CPAP.ConclusionsIncreased platelet sACT and sAGG occur during sleep in patients with OSA. This effect is greatly reduced by N-CPAP.(CHEST 1995; 108:625-30)

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