ABSTRACT
After electrical stimulation of the phrenic nerve,the function of the diaphragm was assessed by measurement of the transdiaphragmatic pressure (PDi),establishment of the Pdi-sti-mulating frequency (F) curve,and analysis of the power spectrum on the diaphragmatic elec-tromyogram (EMGdi) at spontaneous breathing.Hypercapnia of the dogs was induced by forcing the animals to inhale a mixture of CO2 and air.The findings were as follows:(1) After acute hypercapnia,PDi rapidly and progressively decreased.The power spectrum of EMGdi was also reduced.The PDi-F curve was shifted to right.These findings suggest that the function of the diaphragm was severely damaged.(2) The decrease of pH value was the important cause of diaphragmatic fatigue.(3) The diaphragm in a static condition could reduce the damage of hypercapnia.(4) Cedi-lanid exerted certain effects on the prevention of diaphragmatic fatigue created by acute hypercapnia.
ABSTRACT
The study on the functions of the diaphragm has been carried on for 5 years.It consisted of the studies on the relationship of the tension and endurance of inspiratory muscles with pulmonary functions,the changes of diaphragmatic electromyogram in maximal ventilation volume test in normal subjects and patients with chronic obstructive pulmonary disease(COPD),the functional changes of the diaphragm in dogs with RDS and the therapeutic effects of aminophylline.the changes of diaphragmatic electromyogram in dogs with hypoxemia and hy-percapnia,determination of transdiaphragmatic pressure,the relationship of the stimulation frequency on the phrenic nerve with diaphragmtic fatigue,etc.It was found that there existed di-aphragmtic fatigue in dogs with RDS,in dogs with hypoxemia and hypercapnia,and in patients with COPD,and aminophylline,digoxin,salbutomal ?-receptor excitory agents can minimize or prevent diaphragmatic fatigue.