A mouthpiece face mask for the exercising dog.

To develop a rebreathing method for lung volumes, cardiac output with acetylene, and CO diffusing capacity in awake exercising dogs, we have modified and adapted the low-dead-space mask of Montefusco et al. (Angiology 34: 340-354, 1983). We have simplified the fabrication procedure, allowing the physiologist to make the device from parts that can be prefabricated before each dog is custom fitted with the mouthpiece. This decreases the anesthesia time required to custom fit the mouthpiece to each dog. We have also reduced the weight of the mask, making it more tolerable during exercise. We have validated that the mask is leak-free by having the dog rebreathe an inert insoluble gas, He, until equilibration is achieved between the bag and lung. Preliminary measurements of lung volume, cardiac output with acetylene, and CO diffusing capacity have been made during exercise.