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Nonlinear measures of respiration: Respiratory irregularity and increased chaos of respiration in patients with panic disorder

Yeragani, VK and Radhakrishna, RKA and Tancer, M and Uhde, T (2002) Nonlinear measures of respiration: Respiratory irregularity and increased chaos of respiration in patients with panic disorder. In: Neuropsychobiology, 46 (3). pp. 111-120.

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Official URL: http://content.karger.com/produktedb/produkte.asp?...

Abstract

Background. Respiratory irregularity has been previously reported in patients with panic disorder using time domain measures. However, the respiratory signal is not entirely linear and a few previous studies used approximate entropy (APEN), a measure of regularity of time series. We have been studying APEN and other nonlinear measures including a measure of chaos, the largest Lyapunov exponent (LLE) of heart rate time series, in some detail. In this study, we used these measures of respiration to compare normal controls (n = 18) and patients with panic disorder (n = 22) in addition to the traditional time domain measures of respiratory rate and tidal volume. Methods: Respiratory signal was obtained by the Respitrace system using a thoracic and an abdominal belt, which was digitized at 500 Hz. Later, the time series were constructed at 4 Hz, as the highest frequency in this signal is limited to 0.5 Hz. We used 256 s of data (1,024 points) during supine and standing postures under normal breathing and controlled breathing at 12 breaths/min. Results: APEN was significantly higher in patients in standing posture during normal as well as controlled breathing (p = 0.002 and 0.02, respectively). LLE was also significantly higher in standing posture during normal breathing (p = 0.009). Similarly, the time domain measures of standard deviations and the coefficient of variation (COV) of tidal volume (TV) were significantly higher in the patient group (p = 0.02 and 0.004, respectively). The frequency of sighs was also higher in the patient group in standing posture (p = 0.02). In standing posture, LLE (p < 0.05) as well as APEN (p < 0.01) contributed significantly toward the separation of the two groups over and beyond the linear measure, i.e. the COV of TV. Conclusion: These findings support the previously described respiratory irregularity in patients with panic disorder and also illustrate the utility of nonlinear measures such as APEN and LLE as additional measures toward a better understanding of the abnormalities of respiratory physiology in similar patient populations as the correlation between LLE, APEN and some of the time domain measures only explained up to 50-60% of the variation. Copyright (C) 2002 S. Karger AG, Basel.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to S. Karger AG.
Keywords: Respiration;Irregularity;Linear;Nonlinear;Anxiety;Approximate entropy
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 21 Jul 2011 06:15
Last Modified: 21 Jul 2011 06:15
URI: http://eprints.iisc.ernet.in/id/eprint/39308

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