Journal Mobile Options
Table of Contents
Vol. 46, No. 3, 2002
Issue release date: November 2002
Section title: Biological Psychiatry. Main Editor: J. Mendlewicz (Brussels) / Original Paper
Neuropsychobiology 2002;46:111–120

Nonlinear Measures of Respiration: Respiratory Irregularity and Increased Chaos of Respiration in Patients with Panic Disorder

Yeragani V.K.a · Radhakrishna R.K.A.b · Tancer M.a · Uhde T.a
aDepartment of Psychiatry, Wayne State University School of Medicine, Detroit, Mich., USA; bDepartment of ECE, Indian Institute of Science, Bangalore, India
email Corresponding Author

Dr. V.K. Yeragani, Professor of Psychiatry

Wayne State University School of Medicine

Flat No. 16, K.C.N. Mansion, Madhava Nagar

Bangalore 560001 (India)

Tel. +91 80 2287715, Fax +91 80 3610085, E-Mail

Do you have an account?

Register and profit from personalized services (MyKarger) Login Information

Please create your User ID & Password

Contact Information

I have read the Karger Terms and Conditions and agree.


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.

© 2002 S. Karger AG, Basel

Article / Publication Details

First-Page Preview
Abstract of Biological Psychiatry. Main Editor: J. Mendlewicz (Brussels) / Original Paper

Published online: 11/11/2002

Number of Print Pages: 10
Number of Figures: 2
Number of Tables: 5

ISSN: 0302-282X (Print)
eISSN: 1423-0224 (Online)

For additional information:

Copyright / Drug Dosage / Disclaimer

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.