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THE CLINICAL SIGNIFICANCE OF SPONTANEOUS AROUSALS INDEX (SAI) DURING POLYSOMNOGRAPHY

The University of Oklahoma, Health Sciences Center, Oklahoma City, OK

PURPOSE: Sleep arousals are important for reestablishing a patent airway subsequent to an obstructive event and to protect against prolonged hypoxemia. Spontaneous arousals (SA) are also considered among the clinical indicators of upper airway resistance syndrome (UARS). We examined the frequency and clinical significance of SA in patients referred for evaluation of obstructive sleep apnea (OSA).

METHODS: This was a retrospective study of 118 consecutive adult patients presenting for polysomnography from October 2002 till March 2003. A multivariate logistic regression was constructed with the rate of SA as the dependent variable. Apnea Hypopnea Index (AHI), Sleep efficiency (SE), mean SaO2, and stage 1 were independent variables. Arousals were defined according to the American Academy of Sleep Medicine established criteria. Data are presented as mean ± SEM.

RESULTS: The mean total recording time was 396±6 with a total sleep time of 308±10 min. An increased SAI (>10/hr) was present in 20 patients (19%). Age, gender, Epworth Sleepiness Scale, sleep onset latency, periodic limb movement index were similar in patients with high and normal SAI. A higher SAI was associated with a higher AHI (57.8±6 vs.32.5±3; p=0.0002)(r=0.4; p<0.05), a lower SE (57±3 vs. 77±2%; p=0.002), a higher stage 1 sleep (11.5±1.2 vs. 6.5±0.6 %; p=0.0003) and a lower mean SaO2 (90.4±0.8 vs.92.1±0.4; p=0.04). There was a trend towards a higher respiratory arousal index (35±5 vs. 25±3; p=0.1) and hypoxemia (time SaO2<90%) (72±15 vs. 43±8; p=0.09) with a higher SAI. In the multivariate analysis, a higher SAI was associated with increased AHI (OR=7.6; 95 CI:2.7-34.7). In the high SAI group, while on CPAP , SAI improved from 17±2 to 3.2±1.2 events /hour (p<0.001), and correlated significantly with the improvement in AHI (r=0.6; p<0.05).

CONCLUSION: High SAI is a marker of severe sleep apnea and correlates with the AHI.

CLINICAL IMPLICATIONS: The SAI variable does not add appreciably to the available clinical information except when the SAI is high with substantially lower AHI, which would increase the index of suspicion for the presence of UARS.

DISCLOSURE: Joe Zein, None.