Variation in the arousal pattern after obstructive events in obstructive sleep apnea

The relationship between the severity of obstructive sleep apnea (OSA) (mea sured by steep study) and daytime sleepiness is poor. Variation in the degr ee of arousal accompanying obstructive respiratory events might help explai n this poor correlation. Polysomnographic records from patients with OSA we re reviewed in order to extract representative examples of apneas and hypop neas tin 10 patients), as well as events both supine and decubitus (in 12 p atients). The EEC accompanying each obstructive event was processed with a neural network technique to describe sleep depth on a second-by-second basi s. The lengths of any visually evident microarousals were also measured man ually. There was considerable interindividual variation in the degree of sl eep disturbance using the neural network technique (p < 0.005), but not usi ng the lengths of the visually scored microarousals (p = 0.6). The arousals accompanying apneic events caused greater variabitity in sleep depth quant ified using the neural network technique (p = 0.03), and also lasted longer based on the visual scoring (mean, 12.6; SD, 1.7 s) than the hypopneic eve nts (mean, 9.9; SD, 2.4 s; p = 0.02). There were no significant differences between events occurring supine versus decubitus with either technique (p = 0.7). These differences in arousal magnitude may explain some of the poor correlations between conventional measures of sleep apnea severity and day time sleepiness.