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Fractal fluctuations in human respiration
Paul J Fadel1, Susan M Barman, Shaun W Phillips
1Dept. of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|August 3, 2004
Summary
Healthy human breathing patterns exhibit fractal dynamics, indicating time-scale-invariant correlations rather than randomness. These complex respiratory fluctuations suggest underlying regulatory processes.
Area of Science:
- Physiology
- Complex Systems Analysis
- Human Respiration
Background:
- Breathing patterns in healthy humans at rest are typically analyzed as random fluctuations.
- Understanding the underlying dynamics of respiratory control is crucial for physiological research.
Purpose of the Study:
- To characterize respiratory fluctuations in awake, healthy adult humans under resting conditions.
- To determine if fluctuations in breath number, respiratory period, and breath amplitude exhibit fractal (time-scale-invariant) properties.
Main Methods:
- Respiratory movements recorded using a strain-gauge pneumograph in 20 healthy adults.
- Analysis of fluctuations using Allan factor, Fano factor, and dispersional analysis.
- Comparison of original time series with randomized surrogates and calculation of the Hurst exponent.
Main Results:
- Fractal fluctuations were observed in at least one respiratory parameter in 18 out of 20 subjects.
- Time-scale-invariant behavior was absent in only two subjects.
- Results suggest separate regulatory processes control fractal fluctuations in breath number, respiratory period, and breath amplitude.
Conclusions:
- Apparently random respiratory pattern fluctuations are often correlated over multiple time scales.
- The findings indicate complex, non-random dynamics govern human breathing at rest.
- Fractal analysis provides novel insights into the physiological control of respiration.