Study sets tracheal pressure benchmarks in harness racehorses: full analysis

A new Equine Veterinary Journal study gives equine clinicians a clearer physiologic baseline for evaluating upper-airway function in harness racehorses under load. In 76 clinically normal horses, investigators measured inspiratory and expiratory tracheal pressures during a standardized high-speed treadmill test and reported reference values across successive exercise phases. Their central finding was that inspiratory pressures became progressively more negative with harder work and dropped further during poll flexion, while expiratory pressures were comparatively stable. (pmc.ncbi.nlm.nih.gov)

That matters because exercise-related upper respiratory tract disorders are a well-recognized cause of poor performance in racehorses, but objective functional benchmarks have been harder to standardize than endoscopic observations alone. The authors note that tracheal pressure measurement is considered a minimally invasive and reliable way to assess upper-airway function in a clinical setting, and that prior comparisons across studies have been limited by differences in methods and test conditions. (pmc.ncbi.nlm.nih.gov)

The study enrolled Standardbreds and Norwegian-Swedish coldblooded trotters with clinically normal upper respiratory tracts and used a 7-minute treadmill protocol with alternating one-minute phases of free head carriage and poll flexion. Standardbreds were exercised at 9 m/s, while Norwegian-Swedish coldblooded trotters worked at 8.5 m/s, with treadmill incline increased to 3% before the test. Most horses reached heart rates above 200 beats per minute within the first minute and hit maximal heart rate after about 3 to 4 minutes, according to the study background. (pmc.ncbi.nlm.nih.gov)

The pressure findings were notable less for expiratory changes than for inspiratory load. Inspiratory tracheal pressures became significantly more negative relative to the opening phase of the test, with the steepest declines in the first half of exercise and during poll flexion. The authors did not find significant breed-related differences in inspiratory or expiratory tracheal pressures during the exercise test, suggesting the reference ranges may have broader utility across the two harness-racing populations studied. (pmc.ncbi.nlm.nih.gov)

The paper also fits into a longer line of Norwegian work linking head-neck position to upper-airway obstruction in harness horses. Earlier studies found that poll flexion can worsen tracheal pressure abnormalities and is associated with dynamic laryngeal collapse in Norwegian Coldblooded Trotters, a disorder described as severe and performance-limiting. Related reports have also tied poll flexion to other dynamic upper-airway problems in harness racehorses, including epiglottic compression. Taken together, the new study appears to strengthen the physiologic foundation for interpreting those disorders by defining what “normal” pressure patterns look like first. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, especially those working in equine sports medicine and referral diagnostics, reference values can make tracheal pressure testing more clinically actionable. A more objective benchmark may improve confidence when distinguishing normal exercise-related pressure shifts from abnormal inspiratory loading caused by dynamic upper-airway collapse. It could also help when discussing prognosis, selecting horses for treadmill endoscopy, or comparing pre- and post-intervention function after medical management or surgery. That’s particularly relevant in poor-performance workups, where respiratory findings can be subtle, multifactorial, and influenced by head-neck position during exercise. (pmc.ncbi.nlm.nih.gov)

No outside expert commentary or formal industry reaction surfaced clearly in accessible sources, but the surrounding literature points to growing interest in more quantitative respiratory assessment during equine exercise. In that context, this study’s contribution is less about introducing a new technology than about giving clinicians a better reference frame for one already used in specialized centers. That interpretation is an inference based on the study’s stated aim and the prior literature on dynamic upper-airway obstruction in racehorses. (pmc.ncbi.nlm.nih.gov)

What to watch: The practical question now is whether these reference values are incorporated into routine treadmill-based upper-airway evaluations, and whether future studies test how well they discriminate normal horses from those with confirmed dynamic obstruction in real-world referral populations. Publication timing also suggests the work is newly entering the clinical literature, after being listed as accepted in June 2025 and appearing in the journal’s 2025-2026 cycle. (login.lantbruksforskning.se)