Background: Portable sleep apnea monitors are often used to screen for sleep-disordered breathing in chronic heart failure patients (CHF), but night-to-night repeatability of obtained measurements of nocturnal breathing disorders has not been fully assessed.
Methods: Fifty-six stable, moderate-to-severe CHF patients [male, 87%; age, 57 ± 9 years; NYHA class, 2.6 ± 0.6; left ventricular ejection fraction (LVEF), 32% ± 9%] underwent an unattended in-hospital cardiorespiratory recording using a portable sleep apnea monitor during two consecutive nights. The apnea/hypopnea index (AHI), apnea index (AI), oxygen desaturation index (ODI), and periodic breathing (PB) duration were computed. Intra-subject night-to-night variability was assessed by the 95% limits of random variation (LoV). We also estimated the contribution of intra-rater variability to the overall intra-subject variability. Dichotomizing the AHI and PB duration according to conventional cutoffs of, respectively, ≥5 events per hour, ≥15 events per hour, and ≥120 min, the percentage of patients concordantly classified by the two measurements was finally computed.
Results: The 95% LoV were ±10.6, ±7.7, ±11.3 events per hour for AHI, AI and ODI, and ±63.2 min for PB duration, respectively. The contribution of intra-rater variability to total intra-subject variability was 1.7%, 1.4%, 2.5%, and 1.3% for AHI, AI, ODI, and PB duration, respectively. Most patients (85%, 82%, and 95% for AHI ≥ 5, AHI ≥ 15, and PB duration, respectively) were classified concordantly by the two measurements.
Conclusions: In patients with heart failure, measurements of severity of sleep-disordered breathing derived from portable sleep apnea monitors show significant night-to-night intra-subject variation with a negligible contribution from intra-rater variability; however, using the same measurements for classification purposes, as commonly performed in clinical practice to screen patients for sleep-disordered breathing, very stable results are obtained.