Repeatability and normal values for measurement of pharyngeal and tracheal pressures in exercising horses

Repeatability of measurements of peak and mean tracheal and pharyngeal pressures in exercising horses was determined. Five athletically fit horses were subjected to repeated (n = 5) standardized exercise trials. Static pressures in the trachea, nasopharynx, and mask were determined. At least 96% of all mean pressure measurements were within 5 cm of H2O of the mean value for any horse. Peak pressure measurements were less repeatable, but at least 96% of all measurements were within 10 cm of H2O of the mean peak measurements for any horse. In 10 horses galloping at 14 m/s, the 95% confidence interval for peak tracheal and pharyngeal inspiratory pressures ranged from -40 to -50 cm of H2O and -20 to -26 cm of H2O, respectively. During expiration, the 95% confidence interval for peak tracheal and pharyngeal pressure at the same speed ranged from 15 to 28 cm of H2O and 10 to 24 cm of H2O respectively. During inspiration, horses with induced laryngeal hemiplegia had static pressure measurements generally outside that range. We conclude that determination of tracheal and pharyngeal pressures is a potentially useful adjunct for assessment of the proximal portion of the respiratory tract.