Oximetry spectral analysis in the diagnosis of obstructive sleep apnoea

Abstract

Using spectral analysis of oximetry data, we prospectively evaluated the validity of this methodology in patients clinically suspected of suffering from obstructive sleep apnoea (OSA). A total of 233 outpatients were studied. Nocturnal oximetry was performed simultaneously with conventional polysomnography for all participants. The power density of oxygen saturation was analysed using Fast-Fourier transformation of the oximetric signal. Nocturnal oximetry test results were considered as abnormal (suspicion of OSA) if a peak in the spectrum between the period boundaries 30 and 70 s was observed. A normal test result was defined as the absence of the 30-70 s peak from the spectrum. Single-blind evaluation was performed by three independent observers, and agreement of two or more of these was considered definitive. The peak amplitude and the ratio of the area enclosed in the 30-70 s peak to the total area of the spectrum (r(S)) were measured. The presence of a peak has a sensitivity of 78%, a specificity of 89%, a positive predictive value of 89% and a negative predictive value of 78%. Apnoea-hypopnoea indexes were correlated significantly with peak amplitude (r=0.74; P<0.001) and with r(S) (r=0.69; P<0.001). For a peak amplitude threshold of 0.7%(2), the sensitivity was 94% and the specificity was 65% for OSA diagnosis. Using a threshold for r(S) of 0.15, the sensitivity was 91% and the specificity was 67%. Thus the spectral analysis of nocturnal oximetry and identification of a peak at 30-70 s could be useful as a diagnostic technique for OSA subjects.

Nonlinear characteristics of blood oxygen saturation from nocturnal oximetry for obstructive sleep apnoea detection

“…The studies by Rodríguez et al (1996), Lacassagne et al (1997), Zamarrón et al (1999), Olson et al (1999) and Magalang et al (2003) provided higher sensitivity but lower specificity, whereas Ryan et al (1995) and Brouillette et al (2000) achieved higher specificity but lower sensitivity. Our results demonstrate that both CTM and LZ methods provide significant sensitivity and specificity values.…”

“…The PSG register was analyzed over periods of 30 s and during sleep phases I, II, III, IV and rapid eye movement, according to R&K rules (Rechtschaffen and Kales 1968). Apnoea was defined as the absence of airflow for more than 10 seconds and hypopnoea as the reduction of respiratory flow for at least 10 seconds accompanied by a 4% or more decrease in the saturation of haemoglobin (Zamarrón et al 1999, Meoli et al 2001. The average apnoea-hypopnoea index (AHI) was calculated for hourly periods of sleep.…”

“…In OSA, classical spectral analysis based on Fourier Transform has been performed to analyze the periodic nature of desaturation dips to extract features from power spectrum (Zamarrón et al 1999(Zamarrón et al , 2003. Other studies try to provide additional information not based on periodicity but on the changes of physiological series.…”

Multimodal detection of sleep apnoea using electrocardiogram and oximetry signals

“…Similar features were considered in this study. For the SpO2 signal, previous studies have used temporal features including the percentage time below a certain level, the sum of the differences between successive readings (delta index), the number of dips in oxygen saturation per hour and frequency-based features such as the spectral peak in the SpO2 spectrum and pulse rate periodogram in the range of 30-70 s (Gyulay et al 1993;Golpe et al 1999;Zamarron et al 1999;Oeverland et al 2002).…”

“…Yamashiro & Kryger (1995) used nocturnal oximetry as a screener for OSA and achieved a sensitivity of 90 per cent and specificity of 75 per cent; however, they had to reject 10 per cent of subjects from the study due to poor SpO2 signal quality. In an adult population, Zamarron et al (1999) used spectral analysis of the oximetry signal to screen for OSA and found a sensitivity of 78 per cent and a specificity of 89 per cent.…”