Validation of masks for determination of V̇O2 max in horses exercising at high intensity.

This research aims to validate the use of specially designed masks for accurate field measurement of maximal oxygen consumption (V̇O₂ max) in horses. The study focused on designing and testing two variations of a facemask and its electronic control module (ECM) that allow breath-by-breath measurement of airflows and oxygen content while also accommodating the horse’s needs, such as unrestricted ventilation and the ability to wear a bit.

Mask and Its Function

• Two versions of masks were designed along with an Electronic Control Module (ECM). These were aimed at making possible the breath-by-breath measurement of airflow through two 7.8 cm pneumatic tubes located 7.5 cm in front of each horse’s nostril.
• One mask variation (Mask B) covered the lower jaw, whereas the other (Mask R) left the jaw free, making it possible for the horse to wear a bit if it is being ridden.
• The ECM included an analogue-to-digital converter, a lithium-ion battery that provided power and signal filtering to the pneumotachometers (devices that measure the rate of airflow), and an oxygen-sensing cell. It also powered a pump connected to gas sampling ports placed between the horse’s nostrils and the pneumotachometers.

Measurements and Results

• Inspired and expired gases’ airflows and oxygen contents were recorded through the ECM and transferred electronically to a notebook. The data was used to determine the V̇O₂ using a customised software program.
• Measurements of V̇O₂ max and arterial blood gases were performed on six horses during multiple treadmill tests. Each horse wore each mask twice and the results were compared to those gathered from an already established open flow-through system.
• The study found that the blood gases and V̇O₂ max (151.9±7.0 [mean±s.d.; O], 151.5±9.6 [B], 149.5±7.5 [R] ml/[kg.min]) were not significantly different between masks. This indicates that the readings were reproducible for each mask variant, affirming the efficacy and consistency of the masks.
• An intraclass correlation coefficient, a statistical measure to assess the rating reliability amongst raters, was used to evaluate the system utility and it was found to be 0.99 – suggesting a highly reliable system.

Conclusion and Potential Application

• It was concluded that despite some rebreathing of expired air from the mask’s dead space, the masks developed are capable of accurately measuring V̇O₂ max during treadmill exercise.
• The Mask R, which allows the horse to wear a bit, was found to have potential for application in measuring V̇O₂ max under actual field conditions – making it an exciting innovation for improving horse training and monitoring.