A NEW OPEN AND CLOSED RESPIRATION CHAMBER

¹ United States Army Institute of Surgical Research, Brooke Army Medical Center, Fort Sam Houston, TX 78234, U.S.A.

A new, fully automated, open and closed respiration chamber has been constructed, which is large enough to accommodate man or comparable sized animals. Metabolic rate is calculated from measured changes in respiratory gas volumes while the system is hermetically sealed. When CO₂ concentration reaches a prescribed level, large ports are opened and the chamber is ventilated. By repeating this process, a series of metabolic determinations can be conducted over an extended period. Temperature, humidity and air velocity are fixed, but chamber volume and pressure vary with changes in the respiratory exchange of the animal and/or barometric pressure. Small, rapid changes in gas volumes are monitored by a low-resistance spirometer and large changes accommodated in a second, high-volume, motorized spirometer. Chamber operations, data aquisition and metabolic calculations are performed by a small computer. System calibration with methanol combustion indicates that estimates of respiratory gas exchange are highly accurate over a temperature range from 10-40°C.