Objectives: We prospectively evaluate the spectral characteristics of nocturnal arterial oxygen saturation (Sao2) and heart rate variability obtained from pulse oximetric recording as a diagnostic test for obstructive sleep apnea (OSA).
Subjects and measurements: Three hundred referred outpatients with symptoms compatible with the diagnosis of OSA were studied using nocturnal pulse oximetric recording performed simultaneously with polysomnography. Power spectral analysis of Sao2 and heart rate data were analyzed using fast Fourier transformation of a Hamming-windowed signal.
Design and results: Recording test results were classified as abnormal (suspicion of OSA) if the periodogram showed a peak in the period 30 to 70 s in either of the signals. A normal test result was defined as the absence of this peak in the periodogram in both signals. Two independent observers performed a single-blind evaluation. The total area of the periodogram (Stot), the ratio of the area enclosed in the periodogram within the period 30 to 70 s (S30–70), the ratio of the area enclosed in the periodogram within the period 30 to 70 s with respect to the total area of the periodogram (S), and the peak amplitude of the periodogram in the period 30 to 70 s (PA) were measured in both signals. The presence of a peak in the periodogram in either of the signals has a sensitivity of 94%, a specificity of 82%, a positive predictive value of 87%, and a negative predictive value of 92% with respect to the OSA diagnosis. The patients in the OSA group had higher values for Stot, S30–70, S, and PA than the group without OSA.
Conclusions: Sao2 and heart rate spectral analysis obtained by nocturnal pulse oximetry as well as the identification of a peak within 30 to 70 s in either signal could be useful as a diagnostic technique for patient with OSA.