Effect of breathing frequency and airflow on pulmonary function in high-intensity equine exercise.
Abstract: It has been postulated that the hypoxaemia and hypercapnoea that characterize strenuous equine exercise are partly due to flow limitations imposed by high breathing frequencies (fb), and that gas exchange would be improved if fb could be lowered. To evaluate this possibility, 6 Thoroughbred horses underwent 4 incremental treadmill exercise tests at inclines of 0, 5, 10 and 25%, respectively. In the test, horses were given a warm-up for 2 min, then ran sequentially for 1 min each at 60, 100 and 115% VO2max. Oxygen consumption (VO2), blood gas tensions (PaO2, PaCO2), fb, tidal volume (VT), minute ventilation (Ve), transpulmonary pressure (Ptp), peak inspiratory and expiratory airflows (VI, VE) and work of breathing (Wrm) were determined during the last 15 s of exercise at each intensity. The only effect of fb on PaO2 was seen at 60% VO2max. Also, maximal transpulmonary pressure difference (delta Ptpmax), and peak VI, and VE on a 25% slope were lower than those recorded at the other 3 inclines at 60% VO2max. At 100 and 115% VO2max, the effect of fb was less clear. While fb still differed, the only effects of fb at 100% VO2max were on delta Ptpmax. At 115% VO2max, fb on a 25% incline was lower than that for 0 and 5% slopes. The only other difference noted at this intensity was in VT on 10% slope. However, there was no difference between VTS recorded at inclines of 0, 5 or 25% at 115% VO2max. There was no effect of fb or exercise intensity on Ve at 100 or 115% VO2max. There was no change in PaO2, fb, VT, delta Ptpmax or VI and VE as exercise intensity increased from 60-115% VO2max on slopes of 0, 5 or 10%. However, for exercise on the 25% incline (i.e. with lower fb), each of these parameters increased (or decreased for PaO2) from 60-100%, but not from 100-115% VO2max. Failure of peak airflow and VT to increase when intensity increased was associated with the development of hypoxaemia and hypercapnoea, regardless of slope or fb. It is concluded that while a low fb may have some beneficial effect on gas exchange during submaximal exercise at approximately 60% VO2max, this effect disappears as exercise intensity increases. There appear to be limits to the peak airflows that can be generated by horses during strenuous exercise, and these limits may be reached regardless of fb. Flow limitation per se may play a greater role in the development of exercise-induced hypoxaemia and hypercapnoea in horses than dose fb.
Publication Date: 2000-02-05 PubMed ID: 10659215DOI: 10.1111/j.2042-3306.1999.tb05181.xGoogle Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- P.H.S.
Summary
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The research explores the impact of breathing frequency and airflow on the pulmonary function in horses during high-intensity exercise. It concludes that limitations on airflow may play a greater part in exercise-induced hypoxaemia and hypercapnoea in horses than breathing frequency.
Research Objectives and Methodology
- The study aimed to understand whether lower breathing frequencies in horses could improve gas exchange during strenuous exercise, in light of theories suggesting that hypoxaemia and hypercapnoea associated with intense equine exercise are partly due to high breathing patterns.
- The experiment involved six Thoroughbred horses who underwent four treadmill exercise tests with varying inclines (0, 5, 10, and 25%). The horses warmed up for two minutes each, followed by sequential running for a minute at 60, 100, and 115% VO2max respectively.
- The last 15 seconds of exercise at each level were analyzed in terms of oxygen consumption, blood gas tensions, breathing frequency, tidal volume, minute ventilation, transpulmonary pressure, peak inspiratory and expiratory airflows and work of breathing.
Key Findings
- The study found that reducing breathing frequency only had an impact on blood-gas tension (PaO2) in submaximal exercise at 60% VO2max.
- On steeper inclines (25%), horses had significantly lower peak inspiratory and expiratory airflows and maximal transpulmonary pressure difference compared to other inclines at 60% VO2max.
- At higher intensity (100 and 115% VO2max), the study found less clear effects of breathing frequency, with the only significant impacts observed on transpulmonary pressure difference at 100% VO2max and lower breathing frequency at 25% incline at 115% VO2max.
- No significant change in blood-gas tension, breathing frequency, tidal volume, maximal transpulmonary pressure difference or inspiratory and expiratory airflows was found as exercise intensity increased from 60-115% VO2max, except for at the steepest incline of 25%.
- The inability of peak airflow and tidal volume to increase with exercise intensity was associated with the onset of hypoxaemia and hypercapnoea, indicating that it wasn’t the breathing frequency that was primarily influencing these conditions during strenuous exercise.
Conclusions
- The study concludes that while lower breathing frequency may be beneficial for gas exchange during submaximal exercise, this effect disappears as the intensity of the exercise increases. It indicates that the constraints on peak airflows that can be generated by the horses during strenuous exercise seems to limit performance, rather than the breathing frequency per se.
- It strongly suggests that flow limitation plays a greater role in hypoxaemia and hypercapnoea development during intense exercise, guiding more attention towards managing airflow in horses under such conditions.
Cite This Article
APA
Bayly WM, Redman MJ, Sides RH.
(2000).
Effect of breathing frequency and airflow on pulmonary function in high-intensity equine exercise.
Equine Vet J Suppl(30), 19-23.
https://doi.org/10.1111/j.2042-3306.1999.tb05181.x Publication
Researcher Affiliations
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman 99164-6610, USA.
MeSH Terms
- Animals
- Blood Gas Analysis / veterinary
- Exercise Test / veterinary
- Horses / physiology
- Lung / physiology
- Oxygen Consumption
- Physical Conditioning, Animal / physiology
- Respiration
- Respiratory Function Tests / veterinary
Grant Funding
- T35 RR07049 / NCRR NIH HHS
Citations
This article has been cited 2 times.- Katz LM, Stallard J, Holtby A, Hill EW, Allen K, Sweeney J. Inspiratory muscle training in young, race-fit Thoroughbred racehorses during a period of detraining. PLoS One 2020;15(4):e0225559.
- Greco-Otto P, Bond S, Sides R, Kwong GPS, Bayly W, Léguillette R. Workload of horses on a water treadmill: effect of speed and water height on oxygen consumption and cardiorespiratory parameters. BMC Vet Res 2017 Nov 28;13(1):360.
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