SPONTANEOUS PLATELET ACTIVATION AND AGGREGATION DURING OBSTRUCTIVE SLEEP-APNEA AND ITS RESPONSE TO THERAPY WITH NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE

Study objective: To determine whether alterations of platelet reactivi ty occur during obstructive sleep apnea (OSA) and, if so, whether ther apy with nasal-continuous positive airway pressure (N-CPAP) alters thi s reactivity. Design: Patients with suspected moderate to severe OSA h ad blood drawn for spontaneous platelet aggregation (sAGG) and activat ion (sACT) measurements at hourly intervals during diagnostic polysomn ography (PSG) and, in those with confirmed OSA, on a separate night du ring which N-CPAP was applied. Setting: Tertiary care center sleep lab oratory. Patients: Six patients with OSA had matched blood samples dra wn on both diagnostic and N-CPAP treatment nights. Five patients witho ut confirmed OSA served as controls. Interventions: N-CPAP was applied to those patients with OSA and pressures adjusted with goals of elimi nating apneas; IV-CPAP was then maintained through the night. Measurem ents and results: sACT and sAGG were measured using flow cytometric de termination of P-selectin expression using a monoclonal antibody. Plat elet aggregation was assessed by measuring the proportion of platelets larger than resting platelets by light scatter techniques. Mean value s for sACT and sAGG were higher on the diagnostic night compared with treatment night (p=0.001 and p=0.003, analysis of variance, respective ly). The mean baseline supine sACT compared with completion supine sAC T for both diagnostic and N-CPAP nights also revealed significant diff erences (mean=16.6+/-3.5% vs 36.9+/-7.5%, p=0.04; and 11.9+/-3% vs 39. 5+/-9.1%, p=0.04). Platelet activation during sleep in five subjects w ithout OSA resembles that found in patients with OSA during N-CPAP. Co nclusions: Increased platelet sACT and sAGG occur during sleep in pati ents with OSA. This effect is greatly reduced by N-CPAP.