Respiratory measurements of unsedated small laboratory mammals using nonrebreathing valves

The respiratory frequency, tidal volume, minute volume, oxygen uptake and carbon dioxide output of unsedated hamsters, rats, guinea pigs and rabbits were measured to obtain comparative data and to evaluate the performance of those species as unsedated subjects. The animals were trained to remain stationary and breathe through nonrebreathing valves while expired gas was collected and respiratory frequency was monitored. Measurements of dogs also were conducted to obtained comparative data by similar methods. Hamsters were readily trained and performed reliably during repeated trials. Rats and guinea pigs were more difficult to train and performed erratically. The rabbits' performance was intermediate between that of hamsters and the other species. The back pressures caused by the small animal nonrebreathing valves at estimated peak flow rates were either similar to or less than those encountered by dogs. Measured respiratory values were compared to values predicted by published equations based on body weight. Data from this study generally reflected species differences related to body weight and metabolic rate similar to those predicted by the equations, but values from the four smaller species also may have reflected differences related to behavior.