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Equine veterinary journal2025; doi: 10.1111/evj.14557

Inspiratory and expiratory tracheal pressures during high-intensity exercise in harness racehorses.

Abstract: Exercise-related upper respiratory tract (URT) disorders are common in racehorses. Objective assessment of URT mechanics is essential to quantify degrees of obstruction caused by URT disorders identified upon dynamic endoscopy. Objective: To establish reference values for inspiratory and expiratory tracheal pressures (cmHO) during high-speed treadmill endoscopy in harness racehorses with clinically normal URTs. Methods: Prospective observational study. Methods: Tracheal pressures were measured in harness racehorses (Standardbreds and Norwegian-Swedish coldblooded trotters) in which no URT abnormalities were detected. Peak inspiratory and expiratory tracheal pressures were determined for each minute (phase) of a standardised treadmill test, which alternated between trotting with free head carriage (phases 1, 3, 5 and 7) and with poll flexion (phases 2, 4 and 6). Linear mixed-effects models assessed changes in tracheal pressures across the exercise test, and effects of breed, racing experience, respiratory rate and head-neck position (free vs. poll flexion). Results: Seventy-six horses were included. Mean (SD) peak inspiratory tracheal pressures ranged from -21.8 (5.0) cmHO in phase 1 to -34.9 (5.3) and -34.3 (5.7) cmHO in phases 6 and 7. Inspiratory pressures became significantly more negative across phases (p < 0.001) and were -3.5 cmHO (95% CI: -4.0 to -3.0, p < 0.001) lower during poll flexion versus free head carriage. Expiratory tracheal pressures remained stable across exercise phases (11.5 [2.8] to 12.5 [2.6] cmHO) with no significant changes. There were no significant differences between the two breeds. Respiratory rate ranged from 79.8 (12.6) to 90.8 (15.0) breaths/min and remained stable between 89.6 and 90.8 breaths/min through phases 3-7. Conclusions: Simultaneous airflow measurements were not performed. Conclusions: Inspiratory pressures became more negative with exercise progression and were significantly lower during poll flexion versus free head carriage. Reference values for tracheal pressures from clinically normal horses provide an objective tool for evaluating URT function during exercise. Background: Les problématiques de voies respiratoires supérieures (URT) associées à l'exercice sont communes chez les chevaux de course. L'évaluation objective de la mécanique des voies respiratoires supérieures est essentielle afin de quantifier les degrés d'obstruction causés par ces problématiques, identifiées en endoscopie dynamique/embarquée. Objective: Établir des valeurs de référence pour les pressions trachéales (cmH20) inspiratoires et expiratoires durant l'endoscopie au tapis roulant à haute vitesse, chez les chevaux de course attelés avec voies respiratoires supérieures cliniquement normales. TYPE D'ÉTUDE: Étude prospective observationnelle. MÉTHODES: Les pressions trachéales sont mesurées chez les chevaux des course attelés (trotteurs Standardbreds et coldbloods Norvégien‐Suédois) sans anomalie des voies respiratoires supérieures détectées. Les pressions trachéales inspiratoires et expiratoires maximales ont été déterminées à chaque minute (phase) d'un test de tapis roulant standardisé, qui alternait entre du trot avec le port de tête libre (phases 1, 3, 5 et 7) et avec la nuque fléchie (phases 2, 4, 6). Des modèles linéaires à effets mixtes évaluent des changements de pressions trachéales durant le test d'exercice et les effets de race, expérience en course, fréquence respiratoire et position de la tête et du cou (libre vs fléchi). RÉSULTATS: Soixante‐seize chevaux ont été inclus. La moyenne (SD) des pressions trachéales inspiratoires maximales s'étendait de −21.8 (5.0) mcH20 en phase 1 à −34.9 (5.3) et −34.3 (5.7) cmH20 en phases 6 et 7. Les pressions inspiratoires sont devenues significativement plus négatives au travers des phases (p < 0.001) et étaient −3.5 cmH20 (95% CI: −4.0 to −3.0, p < 0.001) inférieures durant la flexion de la nuque par rapport au positionnement de la tête. Les pressions trachéales expiratoires sont demeurées stable au travers des phases (11.5 [2.8] to 12.5 [2.6] cmH2O) sans changement significatif. Il n'y avait pas de différence significative entre les 2 races de chevaux. La fréquence respiratoire s'étendait de 79.8 (12.6) à 90.8 (15.0) respirations/minute et est demeurée stable entre 89.6–90.8 respirations/minutes au travers des phases 3 à 7. Unassigned: Aucune mesure de débit d'air enregistrée simultanément. Conclusions: Les pressions inspiratoires sont devenues plus négatives lors de la progression de l'exercice et étaient significativement diminuées durant la flexion de la nuque par rapport à un positionnement de tête libre. Les valeurs de référence pour les pressions trachéales provenant de chevaux cliniquement normaux constituent un outil objectif pour évaluer la fonction des voies respiratoires supérieures durant l'exercice.
© 2025 The Author(s). Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2025-07-21 PubMed ID: 40686083DOI: 10.1111/evj.14557Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This study aimed to establish tracheal pressure reference values during high-speed exercise for racehorses without upper respiratory tract (URT) disorders. The findings revealed that inspiratory pressures became increasingly negative as exercise intensity increased and were significantly lower when horses had their necks flexed compared to a free head carriage. Expiratory pressures remained unaltered, and there were no significant differences between breeds.

Objective of the Study

  • The primary aim of the study was to derive reference values for inspiratory and expiratory tracheal pressures in harness racehorses during high-intensity exercise. These values could serve as a benchmark for identifying degrees of obstruction caused by URT disorders in horses during dynamic endoscopy.

Study Methods

  • The researchers used a prospective observational study design, where tracheal pressures were measured during a standardized treadmill test in two breeds of harness racehorses without any URT abnormalities.
  • Peak inspiratory and expiratory tracheal pressures were measured for each minute of the exercise session which alternated between free head carriage and poll flexion.
  • A linear mixed-effects model was used to evaluate changes in tracheal pressures across the exercise test, considering factors such as breed, racing experience, respiratory rate, and head-neck position.

Results of the Study

  • A total of seventy-six horses were included in this study, and the results showed that inspiratory pressures increasingly turned negative with the progression of the exercise, and were more pronounced during poll flexion as compared to a free head carriage position.
  • The expiratory pressures, on the other hand, remained consistent across all exercise phases with no significant changes.
  • There were no distinctions observed between the two horse breeds. The respiratory rate remained relatively stable through the majority of the phases ranging between 89.6 and 90.8 breaths per minute.

Conclusions of the Study

  • The research concluded that inspiratory pressures become more negative as the exercise intensity increases and were notably lower during poll flexion when compared to free head carriage.
  • However, it should be noted that simultaneous airflow measurements were not performed which could affect the absolute understanding of URT function during exercise.
  • Despite this, the derived reference values for tracheal pressures in clinically normal horses offer a solid tool for assessing URT function in horses during vigorous exercise.

Cite This Article

APA
Vermedal H, Hellings IR, Fretheim-Kelly ZL, Fintl C, Olsen HMB, Strand E. (2025). Inspiratory and expiratory tracheal pressures during high-intensity exercise in harness racehorses. Equine Vet J. https://doi.org/10.1111/evj.14557

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Vermedal, Hanna
  • Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Hellings, Ingunn Risnes
  • Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Fretheim-Kelly, Zoe Louise
  • Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Fintl, Constanze
  • Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Olsen, Hanna Margrethe Berg
  • Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.
Strand, Eric
  • Faculty of Veterinary Medicine, Norwegian University of Life Sciences, Oslo, Norway.

Grant Funding

  • 311955 / Norwegian Research Council
  • H-19-47-472 / Swedish-Norwegian Foundation for Equine Research

References

This article includes 55 references
  1. Art T, Serteyn D, Lekeux P. Effect of exercise on the partitioning of equine respiratory resistance.. Equine Vet J 1988;20:268–273.
  2. Franklin SH, Van Erck‐Westergren E, Bayly WM. Respiratory responses to exercise in the horse.. Equine Vet J 2012;44:726–732.
  3. Marlin DJ, Roberts CA. Qualitative and quantitative assessment of respiratory airflow and pattern of breathing in exercising horses.. Equine Vet Educ 1998;10:178–186.
  4. Morris E, Seeherman H. Clinical evaluation of poor performance in the racehorse: the results of 275 evaluations.. Equine Vet J 1991;23:169–174.
  5. Kannegieter NJ, Dore ML. Endoscopy of the upper respiratory tract during treadmill exercise: a clinical study of 100 horses.. Aust Vet J 1995;72:101–107.
  6. Lane JG, Bladon B, Little DR, Naylor JR, Franklin SH. Dynamic obstructions of the equine upper respiratory tract. Part 1: observations during high‐speed treadmill endoscopy of 600 Thoroughbred racehorses.. Equine Vet J 2006;38:393–399.
  7. Strand E, Fjordbakk CT, Sundberg K, Spangen L, Lunde H, Hanche‐Olsen S. Relative prevalence of upper respiratory tract obstructive disorders in two breeds of harness racehorses (185 cases: 1998–2006).. Equine Vet J 2012;44:518–523.
  8. Tan RH, Dowling BA, Dart AJ. High‐speed treadmill videoendoscopic examination of the upper respiratory tract in the horse: the results of 291 clinical cases.. Vet J 2005;170:243–248.
  9. Kelly PG, Reardon RJ, Johnston MS, Reardon RJM, Pollock PJ. Comparison of dynamic and resting endoscopy of the upper portion of the respiratory tract in 57 Thoroughbred yearlings.. Equine Vet J 2013;45:700–704.
  10. Lane JG, Bladon B, Little DR, Naylor JR, Franklin SH. Dynamic obstructions of the equine upper respiratory tract. Part 2: comparison of endoscopic findings at rest and during high‐speed treadmill exercise of 600 Thoroughbred racehorses.. Equine Vet J 2006;38:401–407.
  11. Van Erck‐Westergren E, Franklin SH, Bayly WM. Respiratory diseases and their effects on respiratory function and exercise capacity.. Equine Vet J 2013;45:376–387.
  12. Allen KJ, van Erck‐Westergren E, Franklin SH. Exercise testing in the equine athlete.. Equine Vet Educ 2016;28:89–98.
  13. Martin BB Jr, Reef VB, Parente EJ, Sage AD. Causes of poor performance of horses during training, racing, or showing: 348 cases (1992–1996).. J Am Vet Med Assoc 2000;216:554–558.
  14. Petsche VM, Derksen FJ, Berney CE, Robinson NE. Effect of head position on upper airway function in exercising horses.. Equine Vet J 1995;27:18–22.
  15. Strand E, Hanche‐Olsen S, Grønvold AMR, Mellum CN. Dynamic bilateral arytenoid and vocal fold collapse associated with head flexion in 5 Norwegian Coldblooded Trotter racehorses.. Equine Vet Educ 2004;16:242–250.
  16. Vermedal H, O'Leary JM, Klemsdal AE, Roen GM, Fretheim‐Kelly Z, Strand E. Unilateral and bilateral compression of the epiglottis during poll flexion in harness racehorses.. Equine Vet Educ 2024;36:465–472.
  17. Vermedal H, Strand E. Dynamic laryngeal collapse associated with poll flexion as a complication of laryngeal tie‐forward surgery in three harness racehorses.. Vet Surg 2020;49:600–606.
  18. Davidson EJ, Martin BB, Boston RC, Parente EJ. Exercising upper respiratory videoendoscopic evaluation of 100 nonracing performance horses with abnormal respiratory noise and/or poor performance.. Equine Vet J 2011;43:3–8.
  19. Van Erck E. Dynamic respiratory videoendoscopy in ridden sport horses: effect of head flexion, riding and airway inflammation in 129 cases.. Equine Vet J 2011;43(S40):18–24.
  20. Joó K, Duque Betancourt D, Vasquez Marin T, Parra Moyano LA. Evaluation of overground endoscopy findings in Colombian Criollo Paso horses.. J Equine Vet Sci 2021;99:103374.
  21. Ducharme NG, Hackett RP, Ainsworth DM, Erb HN, Shannon KJ. Repeatability and normal values for measurement of pharyngeal and tracheal pressures in exercising horses.. Am J Vet Res 1994;55:368–374.
  22. Rehder RS, Ducharme NG, Hackett RP, Nielan GJ. Measurement of upper airway pressures in exercising horses with dorsal displacement of the soft palate.. Am J Vet Res 1995;56:269–274.
  23. Kästner SBW, Michael A, Townsend HGG. Evaluation of the upper respiratory tract in the horse during treadmill exercise—a review. Part I: endoscopy.. Pferdeheilkunde 1998;14:33–40.
  24. Strand E, Ossurardottir S, Wettre KB, Fjordbakk CT. Alar fold resection in 25 horses: clinical findings and effect on racing performance and airway mechanics (1998–2013).. Vet Surg 2019;48:835–844.
  25. Fretheim‐Kelly Z, Fjordbakk CT, Fintl C, Krontveit R, Strand E. A bitless bridle does not limit or prevent dynamic laryngeal collapse.. Equine Vet J 2021;53:44–50.
  26. Williams JW, Meagher DM, Pascoe JR, Hornof WJ. Upper airway function during maximal exercise in horses with obstructive upper airway lesions. Effect of surgical treatment.. Vet Surg 1990;19:142–147.
  27. Williams JW, Pascoe JR, Meagher DM, Hornof WJ. Effects of left recurrent laryngeal neurectomy, prosthetic laryngoplasty, and subtotal arytenoidectomy on upper airway pressure during maximal exertion.. Vet Surg 1990;19:136–141.
  28. Strand E, Fjordbakk CT, Holcombe SJ, Risberg A, Chalmers HJ. Effect of poll flexion and dynamic laryngeal collapse on tracheal pressure in Norwegian Coldblooded Trotter racehorses.. Equine Vet J 2009;41:59–64.
  29. Kästner SBW, Michael A, Townsend HGG. Evaluation of the upper respiratory tract in the horse during treadmill exercise—a review. Part ll: measurement of upper airway flow mechanics.. Pferdeheilkunde 1998;14:43–50.
  30. Nielan GJ, Rehder RS, Ducharme NG, Hackett RP. Measurement of tracheal static pressure in exercising horses.. Vet Surg 1992;21:423–428.
  31. Holcombe SJ, Beard WL, Hinchcliff KW. Effect of a mask and pneumotachograph on tracheal and nasopharyngeal pressures, respiratory frequency, and ventilation in horses.. Am J Vet Res 1996;57:250–253.
  32. R‐Core‐Team. R: A language and environment for statistical computing.. Vienna, Austria: R Foundation for Statistical Computing; 2024. [cited 2025 Apr 21].
  33. Bates D, Mächler M, Bolker B, Walker S. Fitting linear mixed‐effects models using lme4.. J Stat Softw 2015;67:1–48.
  34. Kuznetsova A, Brockhoff PB, Christensen RHB. lmerTest package: tests in linear mixed effects models.. J Stat Softw 2017;82(13):1–26.
  35. Wickham H, François R, Henry L. dplyr: a grammar of data manipulation (R package version 1.1.4).. 2023. [cited 2025 Apr 21].
  36. Wickham H. ggplot2: elegant graphics for data analysis.. 2nd ed. New York, NY: Springer‐Verlag; 2016.
  37. Kassambara A. ggpubr: ‘ggplot2’ Based Publication Ready Plots (R package version 0.6.0).. 2023. [cited 2025 Apr 21].
  38. Bolker B, Robinson D. broom.mixed: tidying methods for mixed models (R package version 0.2.9.6).. 2024. [cited 2025 Apr 21].
  39. Bartoń K. MuMIn: multi‐model inference (R package version 1.48.4).. 2024. [cited 2025 Apr 21].
  40. Lenth R. emmeans: estimated marginal means, aka least‐squares means (R package version 1.10.7).. 2025. [cited 2025 Apr 21].
  41. McCluskie LK, Franklin SH, Lane JG, Tremaine WH, Allen KJ. Effect of head position on radiographic assessment of laryngeal tie‐forward procedure in horses.. Vet Surg 2008;37:608–612.
  42. Cehak A, Rohn K, Barton AK, Stadler P, Ohnesorge B. Effect of head and neck position on pharyngeal diameter in horses.. Vet Radiol Ultrasound 2010;51:491–497.
  43. Fjordbakk CT, Chalmers HJ, Holcombe SJ, Strand E. Results of upper airway radiography and ultrasonography predict dynamic laryngeal collapse in affected horses.. Equine Vet J 2013;45:705–710.
  44. Lumsden JM, Derksen FJ, Stick JA, Robinson NE. Use of flow‐volume loops to evaluate upper airway obstruction in exercising standardbreds.. Am J Vet Res 1993;54:766–775.
  45. Holcombe SJ, Derksen FJ, Stick JA, Robinson NE, Boehier DA. Effect of nasal occlusion on tracheal and pharyngeal pressures in horses.. Am J Vet Res 1996;57:1258–1260.
  46. Butler PJ, Woakes AJ, Smale K, Roberts CA, Hillidge CJ, Snow DH. Respiratory and cardiovascular adjustments during exercise of increasing intensity and during recovery in thoroughbred racehorses.. J Exp Biol 1993;179:159–180.
  47. Curtis RA, Kusano K, Evans DL, Lovell NH, Hodgson DR. Reliability of cardiorespiratory measurements with a new ergospirometer during intense treadmill exercise in Thoroughbred horses.. Vet J 2005;169:223–231.
  48. Lafortuna CL, Reinach E, Saibene F. The effects of locomotor‐respiratory coupling on the pattern of breathing in horses.. J Physiol 1996;492(Pt 2):587–596.
  49. Cotrel C, Leleu C, Courouce‐Malblanc A. Factors influencing variation in locomotor‐respiratory coupling in standardbred trotters in the field.. Equine Vet J 2006;38(S36):562–566.
  50. Radcliffe CH, Woodie JB, Hackett RP, Ainsworth DM, Erb HN, Mitchell LM. A comparison of laryngoplasty and modified partial arytenoidectomy as treatments for laryngeal hemiplegia in exercising horses.. Vet Surg 2006;35:643–652.
  51. Fretheim‐Kelly Z, Halvorsen T, Heimdal JH, Strand E, Vollsæter M, Clemm H. Feasibility and tolerability of measuring translaryngeal pressure during exercise.. Laryngoscope 2019;129:2748–2753.
  52. Vermedal H, O'Leary JM, Fjordbakk CT, McAloon CG, Løkslett H, Stadnes B. Outcome analysis of 95 harness racehorses with confirmed dorsal displacement of the soft palate treated with laryngeal tie‐forward surgery.. Equine Vet J 2021;54(4):693–702.
  53. Woodie JB, Ducharme NG, Kanter P, Hackett RP, Erb HN. Surgical advancement of the larynx (laryngeal tie‐forward) as a treatment for dorsal displacement of the soft palate in horses: a prospective study 2001–2004.. Equine Vet J 2005;37:418–423.
  54. Cheetham J, Pigott JH, Thorson LM, Mohammed HO, Ducharme NG. Racing performance following the laryngeal tie‐forward procedure: a case‐controlled study.. Equine Vet J 2008;40:501–507.
  55. Barakzai SZ, Dixon PM. Conservative treatment for thoroughbred racehorses with intermittent dorsal displacement of the soft palate.. Vet Rec 2005;157:337–340.

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