Breathing strategy of the adult horse (Equus caballus) at rest.
Abstract: To investigate the mechanism underlying the polyphasic airflow pattern of the equine species, we recorded airflow, tidal volum, rib cage and abdominal motion, and the sequence of activation of the diaphragm, intercostal, and abdominal muscles during quiet breathing in nine adult horses standing at rest. In addition, esophageal, abdominal, and transdiaphragmatic pressures were simultaneously recorded using balloon-tipped catheters. Analysis of tidal flow-volume loops showed that, unlike humans, the horse at rest breathes around, rather than from, the relaxed volume of the respiratory system (Vrx). Analysis of the pattern of electromyographic activities and changes in generated pressures during the breathing cycle indicate that the first part of expiration is passive, as in humans, with deflation toward Vrx, but subsequent abdominal activity is responsible for a second phase of expiration: active deflation to below Vrx. From this end-expiratory volume, passive inflation occurs toward Vrx, followed by a second phase of inspiration: active inflation to above Vrx, brought about by inspiratory muscle contraction. Under these conditions the abdominal muscles appear to share the principal pumping duties with the diaphragm. Adoption of this breathing strategy by the horse may relate to its peculiar thoracoabdominal anatomic arrangement and to its very low passive chest wall compliance. We conclude that there is a passive and active phase to both inspiration and expiration due to the coordinated action of the respiratory pump muscles responsible for the resting adult horse's biphasic inspiratory and expiratory airflow pattern. This unique breathing pattern perhaps represents a strategy of minimizing the high elastic work of breathing in this species, at least at resting breathing frequencies.
Publication Date: 1988-01-01 PubMed ID: 3356653DOI: 10.1152/jappl.1988.64.1.337Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research investigates how adult horses breathe while at rest, specifically the role of various muscles and pressures in creating their unique polyphasic airflow pattern, which is significantly different from the pattern seen in humans.
Research Context and Methodology
- The study seeks to understand the underlying mechanism of the distinct polyphasic airflow pattern seen in the equine species, which differentiates their breathing methods from those of humans.
- Various data was recorded from nine adult horses standing at rest – airflow, tidal volume, rib cage and abdominal motion, and the sequence of activation of the diaphragm, intercostal, and abdominal muscles during normal breathing.
- The team used balloon-tipped catheters to simultaneously record esophageal, abdominal, and transdiaphragmatic pressures.
Findings and Analysis
- Analysis of tidal flow-volume loops revealed that unlike in humans, a resting horse breathes around the relaxed volume (Vrx) of the respiratory system, not from it.
- The generated patterns of electromyographic activity and changes in pressure during the breathing cycle, shows the first part of expiration is passive resembling humans. It includes deflation towards Vrx.
- This is followed by a second phase of active expiration, driven by abdominal activity which contributes to further deflation to below Vrx.
- From this point, a cycle of passive inflation begins towards Vrx, succeeded by an active inflation phase above Vrx triggered by inspiratory muscle contraction.
Conclusion
- Both inspiration and expiration entail active and passive phases wrought by the coordinated operation of the respiratory pump muscles. This coordinated activity results in the resting adult horse’s bifurcated inspiratory and expiratory airflow.
- The horse’s adoption of this unique breathing strategy is hypothesized to relate to its unique thoracoabdominal anatomical arrangement and notably low passive chest wall compliance.
- Thus, this distinctive pattern possibly signifies a strategy to minimize the high elastic work of breathing in horses, particularly at resting breathing frequencies.
Cite This Article
APA
Koterba AM, Kosch PC, Beech J, Whitlock T.
(1988).
Breathing strategy of the adult horse (Equus caballus) at rest.
J Appl Physiol (1985), 64(1), 337-346.
https://doi.org/10.1152/jappl.1988.64.1.337 Publication
Researcher Affiliations
- Department of Physiological Sciences, College of Veterinary Medicine, University of Florida, Gainesville 32610.
MeSH Terms
- Animals
- Electromyography
- Female
- Horses / physiology
- Male
- Respiration
- Respiratory Muscles / physiology
- Rest
- Tidal Volume
Citations
This article has been cited 11 times.- Juvin L, Colnot E, Barrière G, Thoby-Brisson M, Morin D. Neurogenic mechanisms for locomotor-respiratory coordination in mammals. Front Neuroanat 2022;16:953746.
- Moreno-Martinez F, Byrne D, Raisis A, Waldmann AD, Hosgood G, Mosing M. Comparison of Effects of an Endotracheal Tube or Facemask on Breathing Pattern and Distribution of Ventilation in Anesthetized Horses. Front Vet Sci 2022;9:895268.
- Stefanik E, Drewnowska O, Lisowska B, Turek B. Causes, Effects and Methods of Monitoring Gas Exchange Disturbances during Equine General Anaesthesia. Animals (Basel) 2021 Jul 9;11(7).
- Secombe C, Adler A, Hosgood G, Raisis A, Mosing M. Can bronchoconstriction and bronchodilatation in horses be detected using electrical impedance tomography?. J Vet Intern Med 2021 Jul;35(4):2035-2044.
- Burnheim K, Hughes KJ, Evans DL, Raidal SL. Reliability of breath by breath spirometry and relative flow-time indices for pulmonary function testing in horses. BMC Vet Res 2016 Nov 28;12(1):268.
- Le Gal JP, Juvin L, Cardoit L, Morin D. Bimodal Respiratory-Locomotor Neurons in the Neonatal Rat Spinal Cord. J Neurosci 2016 Jan 20;36(3):926-37.
- Pacheco AP, Paradis MR, Hoffman AM, Hermida P, Sanchez A, Nadeau JA, Tufts M, Mazan MR. Age effects on blood gas, spirometry, airway reactivity, and bronchoalveolar lavage fluid cytology in clinically healthy horses. J Vet Intern Med 2014 Mar-Apr;28(2):603-8.
- Drummond G. Like breathing out and breathing in. J Physiol 2010 Sep 15;588(Pt 18):3345.
- Lafortuna CL, Saibene F, Albertini M, Clement MG. The regulation of respiratory resistance in exercising horses. Eur J Appl Physiol 2003 Oct;90(3-4):396-404.
- Guthrie AJ, Beadle RE, Bateman RD, White CE. Characterization of normal tidal breathing flow-volume loops for thoroughbred horses. Vet Res Commun 1995;19(4):331-42.
- Gallivan GJ, Viel L, McDonell WN. An evaluation of the multiple-breath nitrogen washout as a pulmonary function test in horses. Can J Vet Res 1990 Jan;54(1):99-105.
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