Validation of masks for determination of VO 2 max in horses exercising at high intensity

Summary Background The need for a horse to be ridden while wearing a measurement device that allows unrestricted ventilation and gas exchange has hampered accurate measurement of its maximal oxygen consumption (V̇O 2 max) under field conditions. Objectives Design and validate a facemask with the potential to measure V̇O 2 max accurately in the field. Study design Experiment with 6 × 6 Latin square design. Methods Two variations of a mask and associated electronic control module ( ECM ) were designed to enable breath‐by‐breath measurement of airflows through two 7.8 cm diameter pneumotachometers located 7.5 cm in front of each narus. The ECM was comprised of an analogue‐to‐digital converter and a lithium‐ion battery that provided power and signal filtering to the pneumotachometers and an oxygen sensing cell, and powered a pump connected to gas sampling ports between the nares and pneumotachometers. Airflow and oxygen content of inspired and expired gases were recorded through the ECM and electronically transferred to a notebook. V̇O 2 was determined from these recordings using a customised software program. Mask B encased the lower jaw. Mask R left the jaw free so the horse could wear a bit if ridden. V̇O 2 max and arterial blood gases were measured in 6 horses during multiple treadmill tests. Each mask was worn twice and results compared to those from an established open flow‐through system (O) by ANOVA ‐ RM (P<0.05). System utility was evaluated using the intraclass correlation coefficient of 4 independent raters. Results Blood gases and V̇O 2 max (151.9±7.0 [mean±s.d.; O], 151.5±9.6 [B], 149.5±7.5 [R] ml/[kg.min]) were not different between masks. V̇O 2 max measures were reproducible for each mask. Intraclass correlation coefficient between raters = 0.99. Main limitations Some rebreathing of expired air from mask dead space. Conclusion Masks capable of measuring V̇O 2 max during treadmill exercise were developed, tested and found to be accurate. Mask R has potential application to measurement of V̇O 2 max under field conditions.