Ergometer within a whole-body plethysmograph to evaluate performance of guinea pigs under toxic atmospheres

A guinea pig ergometer was constructed within an enclosure, with inlet and outlet ports for continuous ventilation, designed so that the enclosure would work as a whole-body plethysmograph as well as an inhalation exposure chamber. This system provided continuous measurement of tidal volume, respiratory frequency, oxygen uptake, and carbon dioxide output which enabled an evaluation of performance in terms of distance traveled over time with the animals running at a known speed and constant oxygen uptake. The effects of CO or HCl in running versus sedentary animals were investigated using this apparatus. For CO, exercise increased the rapidity of the onset of incapacitation as would be predicted by the increase in metabolic rate. HCl produced a more severe incapacitating effect in exercising animals that was out of proportion with the increase in minute volume induced by exercise.