A servo-controlled respiration system for inhalation studies in anesthetized animals.

To facilitate aerosol deposition experiments and aerosol exposures in anesthetized animals, a servo-controlled respiration system was developed and tested. The system induces ventilation by varying extrathoracic pressure in a whole body respiratory in which an intubated animal is placed. The pressure inside the whole body respirator is varied with a three-way servo-controlled spool valve connected to sources of positive and negative pressure. A computer-based system detects respiratory flow and computes the controlling signal for the valve by using a proportional-integral-derivative algorithm, to achieve desired patterns of flow and volume vs. time. The system was used with dogs and found to accurately induce various single-breath breathing patterns involving constant-flow inspirations and expirations as well as breath-hold periods. A similar system was used to induced repeated breaths with desired parameters for continuous exposure to particles and for ventilation of animals between experiments.