Fractal behaviour of heart rate variability reflects abnormal respiration patterns in OSAS patients

Abstract

Although heart rate variability (HRV) decreasing has
\nbeen usually described in obstructive sleep apnea
\nsyndrome (OSAS), some studies have recently questioned
\nthe validity of spectral HRV analysis in presence of
\nrespiratory and arrhythmic disorders. Fractal analysis of
\nHRV is an emerging nonlinear technique overcoming
\nthese limitations and allowing short term HRV
\nassessment during hypo/apnea phases. The aim of this
\nstudy is to analyse the Fractal features in sleep apnea in
\norder to find as these characteristics could change during
\nabnormal respiration patterns in OSAS. We studied 30
\npolysomnographic recordings of severe OSAS (AHl30)
\npts. (age 55±9) and 10 PR of normal subjects (age 46±4).
\nHypo/apnea phases and related beat-to-beat time series
\nhave been detected and classified by automated
\nalgorithms and manually verified by expert technicians.
\nFractal analysis was performed by the Higuchi algorithm
\n(FD). Results showed that while FD does not significantly
\ndiffer between Normals (l.6J±0.09) and normal breath
\nepochs in OSAS, it significantly (p<0.005) tends to a less
\nfractal structure from normal breath (l.60±0.15) to
\nhypopneas (l.52±0.13), obstructive (l.50±0.12) and
\nmixed apneas (l.48±0.1l) epochs, with a significant
\nDunn's multiple comparisons post test only between
\nnormal breath vs. obstructive and mixed apneas.