A demand diaphragm pacemaker.

A PACO2 feedback control system (demand diaphragm pacemaker) was developed in this laboratory to maintain homeostasis during diaphragm pacing, thus avoiding hypo- or hyperventilation. Application of this system to the research animal made it possible to maintain blood gases and pH within normal limits for up to 15 hrs. Oscillation between maximal tidal volume and apnea that occurred with the amplitude feedback control was eliminated by using a rate feedback control. A possible additional benefit of a feedback control system is the reduction of current applied to the nerve as compared to that in asynchronous pacing, thereby minimizing the fatigue phenomenon.