Fluctuations of the fractal dimension of the electroencephalogram during periodic breathing in heart failure patients

Abstract

The physiological mechanisms responsible for periodic breathing (PB) in heart failure (HF) patients are still debated. A role for rhythmic shifts in the level of wakefulness has been suggested, but their existence has never been proven. In this study we investigated the existence of an oscillation in EEG activity during PB in these patients and assessed its relationship with the ventilatory oscillation. EEG activity was measured by the fractal dimension (FD) and by a spectral technique (weighted mean frequency, WMF) in 17 stable HF patients (mean age +/- SD: 57+/-10 yrs, NYHA class: 2.6 +/- 0.4, LVEF: 24 +/- 6%), with sustained PB during supine rest. The relationship between minute ventilation (MV) signal and FD and WMF was assessed by coherence analysis. Most patients (10/17) showed a well defined oscillation in FD and WMF at the frequency of PB closely linked (coherence > 0.7) with the oscillation of MV. In the remaining patients, neither FD nor WMF showed a clear oscillatory pattern synchronous with MV. Overall, the two EEG-derived parameters showed the same coherence with the ventilatory oscillation (mean coherence +/- SD: 0.65 +/- 0.25 vs 0.66 +/- 0.23, for FD and WMF respectively, p = 0.44). Our results provide evidence that during PB in HF patients, EEG activity often, but not always, fluctuates synchronously with the ventilatory oscillation. These fluctuations can be effectively detected by the fractal dimension, but classical spectral methods provide substantially the same information. Other mechanisms, particularly chemical instability in the respiratory control system, are likely to play a role in the genesis of PB.

A hybrid approach for continuous detection of sleep‐wakefulness fluctuations: validation in patients with Cheyne–Stokes respiration

“…In conclusion, in this study we have developed a hybrid method for continuous detection of state transitions, which integrates computer-based automatic analysis with visual microanalysis of major EEG ⁄ EOG features and events. We have tested our approach during Cheyne-Stokes respiration in patients with HF, a condition that is associated with repeated fluctuations in the level of wakefulness (Davies et al, 1999;Hanly et al, 1989;Maestri et al, 2010). The excellent agreement between the output of the statistical discriminator and the visual classification of unambiguous EEG activity supports the high reliability of the proposed method.…”

“…, 2000). In a previous study we found that in the majority of patients the ventilatory oscillation is accompanied by rhythmic changes in EEG activity, suggestive of fluctuations between wakefulness and light NREM sleep (Maestri et al. , 2010).…”

“…Patients were lying supine in a quiet laboratory environment during mid-morning hours, a condition that is often associated with the development of this abnormal breathing pattern (La Rovere et al, 2007;Pinna et al, 2000). In a previous study we found that in the majority of patients the ventilatory oscillation is accompanied by rhythmic changes in EEG activity, suggestive of fluctuations between wakefulness and light NREM sleep (Maestri et al, 2010).…”

Distinct polysomnographic and ECG-spectrographic phenotypes embedded within obstructive sleep apnea

“…Quantifying NREM vs. REM dominance may thus provide a pathophysiological phenotype. The oscillatory profile of respiratory oscillations or downstream respiration-driven or associated oscillations such as heart rate variability, blood pressure or even the electroencephalogram can be quantified (Maestri et al 2010). We present use of a ECG-derived cardiopulmonary coupling analysis to detect high loop gain apnea independent of conventional scoring.…”

Analysis of the three-dimensional TGS crystal spatial inhomogeneity of the fractal structure

“…In electronics, fractal conductance fluctuations in low-dimensional semiconductor devices [8][9][10], the chaotic nature of fractal conductance fluctuations in mesoscopic systems [11][12][13], and quantum-mechanical diffusion in semiconducting superlattices [14], were measured. In medical science, analyses of heart electroencephalograms for diagnostic purposes [15][16][17], or medical signals in general [18] are commonly used in clinical practice. Finally at a more global scale, in geoscience, fractal dimensions calculated for turbulence flow of atmospheric patterns are commonly used for weather prediction [19][20][21].…”