Human heart rate variability and sleep stages

With the aim of better understanding the dynamic changes in sympatho-vagal tone occurring during the night, human heart rate variability (HRV) during the various sleep stages was evaluated by means of autoregressive spectral analysis.Each recording consisted of an electroencephalogram, an electrooculogram, and electromyogram, an electrocardiogram, and a spirometry trace. All of the data were sampled and stored in digital form.Sleep was analysed visually, but HRV was analysed off-line by means of original software using Burg's algorithm to calculate the LF/HF ratio (LF: 0.04–0.12 Hz; HF: 0.15–0.35 Hz) for each sleep stage.Seven healthy subjects (four males; mean age 35 years) were enrolled in the study.Our findings show a progressive and significant reduction in the LF/HF ratio through sleep stages S1–S4, as a result of an increase in the HF component; this indicates the prevalence of parasympathetic activity during slow-wave sleep. During wakefulness, S1 and REM, the LF/HF values were similar and close to 1.SommarioAllo scopo di comprendere meglio le modificazioni del tono del sistema nervoso autonomo durante la notte, è stata valutata la variabilità del ritmo cardiaco (HRV) negli stadi del sonno, impiegando una metodica autoregressiva di analisi spettrale.Ciascuna registrazione consisteva di elettroencefalogramma, elettro-oculogramma, elettromiografia, spirometria ed elettrocardiogramma, campionati e registrati in forma digitale.L'ipnogramma è stato ottenuto ispettivamente, mentre l'analisi dell'HRV è stata eseguita con un software dedicato, utilizzando l'algoritmo di Burg e calcolando il rapporto LF/HF (LF: 0.04–0.12 Hz; HF: 0.15–0.35 Hz) per ciascuno stadio del sonno.Sono stati arruolati nello studio 7 soggetti sani (4 maschi, età media 35 anni). I nostri risultati mostrano una progressiva e significativa diminuzione di LF/HF dallo stadio 1 al 4, imputabile ad un aumento del tono del parasimpatico (aumento della componente HF), mentre il valore del rapporto durante veglia, REM e fase 1 è risultato simile (circa 1).

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