| Budget Amount *help |
¥7,800,000 (Direct Cost: ¥7,800,000)
Fiscal Year 1997: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1996: ¥6,200,000 (Direct Cost: ¥6,200,000)
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| Research Abstract |
We compared the diaphragmatic fatigue produced by bilateral phrenic nerve stimulation, which is synchronized to inspiratory and expiratory phase fo mechanical ventilation, to investigate the effect of mechanichal ventilatory suport on the diaphragmatic fatigue in mongrel dogs.
[METHOD] Phrenic nerves were exposed and stimulated at neck region (tetanus stimulation for 1 sec at 40Hz), and bilateral diaphragmatic muscle tensions were measured through transducers attached to infradiaphragmatic surface. Two balooon-catheters were placed at esophgus and stomach, then pressure differences (Pdi) were measured. Diaphragmatic muscle fatigue was induced by tetanic phrenic stimulation (tetanic stimuli for 1sec at a rate of 12/min) for 30min synchronized to inspiratory phase (Insp.group, n=9) and expiratory phase (Exp.group, n=9) of mechanical ventilation. Muscle twitchs and Pdi were measured before induction of fatigue, immediately after fatigue, 30min and 60min after fatigue. Fatigue was assesed by the profile of muscle twitches at tetanic frequencies of 10,20,30,40,50 and lOOHz.
[RESULT] Muscle twitches and Pdi in both group were reduced after induction of fatigue, where the higher the frequency of stimuli was, the smaller the depressions of muscle twitch and Pdi were. The depression in muscle twitch and Pdi did not differ significantly between two groups. The depression in Pdi were lesser than that in muscle twitch at some frequencies.
[DISCUSSION] Inspiratory synchronization failed to relieve the diaphragmatic fatigue. This might be due to the low inspiratory flow, which was not enough to lessen the work of diaphragmatic muscle. In our study, we adopted the supramaximal stimulation to induce the muscle fatigue, and this might in part be a cause not to relieve the fatigue.
[CONCLUSIONS] In clinical setting, the reduction of the actual inspiratory effort is more important than the synchronization to respiratory phase.
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