Nocturnal oximetry is an attractive option for the diagnosis of obstructive sleep apnoea (OSA) syndrome because of its simplicity and low cost compared to polysomnography (PSG). The present study assesses non-linear analysis of blood oxygen saturation (SaO 2 ) from nocturnal oximetry as a diagnostic test to discriminate between OSA positive and OSA negative patients. A sample of 187 referred outpatients, clinically suspected of having OSA, were studied using nocturnal oximetry performed simultaneously with complete PSG. A positive OSA diagnosis was found for 111 cases, while the remaining 76 cases were classified as OSA negative. The following oximetric indexes were obtained: cumulative time spent below a saturation of 90% (CT90), oxygen desaturation indexes of 4% (ODI4), 3% (ODI3) and 2% (ODI2), and the delta index (∆ index). SaO 2 records were subsequently processed applying two non-linear methods: central tendency measure (CTM) and Lempel-Ziv (LZ) complexity. Significant differences (p < 0.01) were found between OSA positive and OSA negative patients. Using CTM we obtained a sensitivity of 90.1% and a specificity of 82.9%, while with LZ the sensitivity was 86.5% and the specificity was 77.6%. CTM and LZ accuracy was higher than that provided by ODI4, ODI3, ODI2 and CT90. The results suggest that non-linear analysis of SaO 2 signals from nocturnal oximetry could yield useful information in OSA diagnosis.
The study in REF assessed analysis of a comprehensive feature set based on blood oxygen saturation (SaO 2 ) from nocturnal oximetry in order to evaluate sleep quality.
Nonlinear characteristics of blood oxygen saturation from nocturnal oximetry for obstructive sleep apnoea detection
Physiological measurement
Physiological measurement
Medicine