HEART-RATE-VARIABILITY IN PATIENTS WITH DAYTIME SLEEPINESS SUSPECTED OF HAVING SLEEP-APNEA SYNDROME - A RECEIVER-OPERATING CHARACTERISTIC ANALYSIS

1. Periodic breathing is known to be associated with cyclic fluctuatio ns in heart rate, The purpose of this study was to evaluate the capabi lity of spectral analysis of heart rate variability to identify episod es with periodic breathing in patients suspected of having sleep apnoe a syndrome. 2. Forty-eight subjects complaining of chronic daytime sle epiness were studied using polysomnography and additional monitoring o f Holter-ECG and synchronized pulse oximetry, The recordings were divi ded into 20 min episodes which were identified as recordings registere d during normal breathing, periodic breathing, and periods of both nor mal and abnormal breathing. Power spectral analysis was performed on e pisodes which met the criteria of stationarity of data (313 episodes w ith normal breathing, 264 episodes with continuous periodic breathing, 80 episodes with both normal and periodic breathing pattens). 3. The ability of parameters, derived from analysis of heart rate variability , to discriminate between episodes with normal and periodic breathing was assessed by receiver-operating characteristic analysis. 4. The spe ctral power component in the frequency range 0.01-0.07 Hz revealed the greatest accuracy for discriminating between normal and periodic brea thing (area under the receiver-operating characteristic curve = 0.929; standard error = 0.009). The analysis of the episodes classified as f alse-positive at a given test sensitivity of 90% and a corresponding s pecificity of 77% revealed that half of these episodes had been record ed during transient central nervous arousal reactions related to perio dic leg movements or heavy snoring. 5. We concluded that power spectra l analysis of heart rate variability offers a possible means of identi fying episodes of sleep-related breathing disorders or periodic leg mo vements. Therefore, analysis of heart rate variability may be a valuab le additional diagnostic tool in patients undergoing Holter-ECG record ing.