| Objective: A implanted diaphragm pacemaker (IDP) was researched and developed to treat the patients with deficiency of respiration and need of long-term assistant ventilation. A animal model of diaphragm pacing (DP) was set up to ascertain that the influence of different electrical parameters is the important premise for DP. A study was performed in Zelanian rabbits to discuss the effects of different pulse amplitudes on the diaphragm muscle with IDP controlled by program.Methods: Part one -The signal of microsecond stimulation ( PWM pulse, lowpass, magnification and modification of signal) controlled by singlechip was produced. The appropriate pulse and frequency of the stimulation signal in the DP was selected and applied to pace the phrenic nerve. Part two -the changes of breathing after blocking the different regions in the medulla of rabbit were observed; the breathing was perpetually ceased by electrical damage of medulla; the phrenic nerve in the back of neck was exposed, and the bipolar electrode (acted as recording and pacing electrode)was embed to pace the diaphragm for two hours. Part three -the effects in the diaphragm muscle of the Zelanian rabbits after DP with different pulse amplitudes were as follows: 1 24 Rabbits were divided into four groups including: operated but not diaphragm paced (ONDP) pulse amplitude increasing (PAIC) pulse amplitude invariable (PAIV) and pulse amplitude decreasing (PADC). Each of them was paced for two hours. 2 thechanges of electromyogram of the diaphragm were observed during the process. 3 The diaphragm muscle was immediately collected , put into the liquid nitrogen pot and kept frozen at -80 C when the experiment was finished. And then following steps were respectively done: (1)the concentration of free adenine nucleotides was measured by high performance liquid chromatography (HPLC). (2)the amount of superoxide dismutase (SOD), malondialdehyde(MDA) and the total resist oxide capacity (T-ROC) was assayed. 4 the ultrastructure of diaphragm muscle was observed when the experinent was finished.Results: Part one-The instrument was successfully manufactured: 1 it was detected by the oscillograph; 2 The amplitude of phrenic nerve compound action potential didn't significantly decline after DP for 8 hours; 3 The demyelination of phrenic nerve can't be observed by the electron microscope. Part two - The breathing was reversibly ceased by symmetrically blocking the internal region of the nucleus retrofacialis ,and abidingly ceased by the electrical damage of the section . Thus, the animal model of diaphragm pacing in rabbit was established successfully. Part three - 1 The content of ATP decreased , while that of ADP and AMP increased to some extent in the groups of DP(PAIC, PAIV, PADC) compared with the groups of ONDP (P>0.05) .But it was meaningless to statistical research (P>0.05) . When paced by different pulse amplitudes, the content of ATP in diaphragm muscle declined with difference. It decreased the least in PAIC, and PAIV in the next place. 2, The amount of MDA in PAIC, PAIV and PADC was higher than that in ONDP while the activity of SOD and T-ROC lower (P>0.05) after DP for two hours. The amount of MDA in PAIC was lower compared with that in PAIV and PADC, SOD activity and T-ROC higher accordingly after DP for two hours. There were no considerable differences in the content ofMDA, activity of SOD and T-ROC between PAIC and ONDP (P>0.05 ) . The amount of MDA in PATV and PADC was more than that in PAIC while SOD and T-ROC less (P<0.05) after DP for two hours. 3 There was no difference in electromyogram in these groups after DP for 60 min and 120 min. 4 The pathologic observation of diaphragm muscle in these groups was showed as follows: Under the electron microscope, the diaphragm muscle fibres formed in order, Z-lines clear, mitochondrias round, elliptical or bacilliform distributing averagely between the muscle fibrils. The number of glycogen was considerable. Mitochondrias crista was clear. And no change of vacuolar degeneration or electron density alterat...
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