Published ahead of print on October 3, 2002, doi:10.1164/rccm.200202-096OC Am. J. Respir. Crit. Care Med., Volume 167, Number 2, January 2003, 128-136 A more recent version of this article appeared on January 15, 2003
Submitted on February 8, 2002 Model-based assessment of autonomic control in obstructive sleep apnea syndrome during sleepJavier A Jo1,1 Biomedical Engineering, University of Southern California, Los Angeles, CA, USA, 2 Medicine, University of Southern California, Los Angeles, CA, USA * To whom correspondence should be addressed. E-mail: khoo{at}bmsr.usc.edu.
Respiration, R-R interval, blood pressure and other polysomnographic variables were recorded in 8 normals and 9 patients with untreated obstructive sleep apnea syndrome in wakefulness and sleep. To increase respiratory and cardiovascular variability, a computer-controlled ventilator delivered randomly-modulated inspiratory pressures that were superimposed on a baseline continuous positive airway pressure. A mathematical model allowed heart rate variability to be partitioned into a component mediated by respiratory-cardiac coupling and one mediated by the baroreflexes. Respiratory-cardiac coupling gain was lower in patients vs. normals (36.9 ± 3.3 vs 66.1 ± 5.6 ms L-1 , P<0.03). Baroreflex gain in patients was also depressed relative to normal (2.3 ± 0.4 vs. 4.9 ± 0.7 ms mmHg-1; P<0.02). Baroreflex gain increased two-to- threefold from wakefulness to sleep in normals, but was relatively unaffected by state change in patients. Along with results derived from spectral analysis of cardiovascular variability, these findings confirm previous reports that obstructive sleep apnea syndrome is associated with reduced parasympathetic and elevated sympathetic activity. The model-based approach provides a more precise characterization of heart rate variability that can be employed in conjunction with spectral analysis for the noninvasive detection and assessment of autonomic cardiovascular abnormality in obstructive sleep apnea syndrome. Key words: Cardiovascular control, mathematical model, heart rate variability, baroreflex sensitivity, respiratory sinus arrhythmia, system identification
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