Effect Of Different Intensity Of Threshold Inspiratory Muscle Training Load On Respiratory Physiology In Patients With Stable Chronic Obstructive Pulmonary Disease

[Background]Chronic obstructive pulmonary disease(COPD)is a systemic inflammatory disease,often with skeletal muscle and respiratory muscle disfunction,leading to increased symptoms of dyspnea,decreased daily activity.In response to the decline in inspiratory muscle function,inspiratory muscle training has become an important part of pulmonary rehabilitation.However,there is no uniform standard for the setting of the intensity of inspiratory muscle training(IMT)load.Previous studies have explored the appropriate intensity of inspiratory muscle training load by comparing the improvement of clinical outcomes of pulmonary rehabilitation under different inspiratory muscle training load,but most studies didn’t evaluate the improvement of respiratory physiology.And as the subjects often lack effective supervision and guidance during the training,it’s still defective to determine the appropriate intensity of inspiratory muscle training load only by the pulmonary rehabilitation effect.[Objective]In this study,the classical respiratory mechanics and electromyography method was used to investigate the changes of respiratory physiology response of COPDpatients with inspiratory muscle weakness in stable phase under different intensity of threshold inspiratory muscle training,and provide respiratory physiology basis for selecting appropriate intensity of inspiratory muscle training load.[Methods]This study included patients with COPD who were in clinically stable phase and grouped subjects using a 6×6 Latin square design.Subjects were divided into six groups and subjected to a different sequence of threshold IMT.Basic data were collected prior to the experiment:name,age,gender,pulmonary function,Maximal Inspiratory Pressure(MIP)and Maximum Expiratory Pressure(MEP),6-minute walk test(6MWT),modified Medical Research Council(mMRC),St George’s Respiratory Questionnaire(SGRQ),COPD Assessment Test(CAT),Hospital Anxiety and Depression Scale(HADS).Respiratory physiological parameter was recorded during the experiment:respiratory rate(RR),inspiratory time(Ti),expiratory time(Te),respiratory cycle(Ttot),inspiratory time/total breath cycle duration(Ti/Ttot),tidal volume(VT),average inspiration flow rate(VT/Ti),mean expiratory flow rate(VT/Te),minute ventilation(VE),oral pressure(Pmo),intra-oesophageal pressure(Pes),intragastric pressure(Pgas),transdiaphragmatic pressure,the diaphragmatic muscle tension time index(TTdi),diaphragm pressure time product(PTPdi),diaphragmatic myoelectricity(RMSdi),corrected diaphragmatic myoelectricity(RMSdi/RMSdimax),and ventilation central decoupling(VE/RMSdi).[Results]A total of 12 stable COPD subjects successfully completed the entire experiment.RR during training was significantly reduced compared with that before and after training,along with the increases of Ti,Ti/Ttot and Ttot before and after training.VT,VE,VT/Ti,VT/Te after training were significantly increased than before training.There were significant increases in absolute value of Pdi and Pmo,Pes,PTPdi,TTdi,RMSdi and RMSdi/RMSdimax during training than before and after training,moreover increased with the raise of the threshold load.Under the threshold load of 50%MIP and 60%MIP,the TTdi after training increased significantly than beforetraining.VE/RMSdi during training was significantly reduced compared with that before and after training,and gradually decreased with the increase of threshold load.VE/RMSdi after training was larger than before training.There were no significant differences in the changes of respiratory time parameters such as RR,Ti,Te,Ti/Ttot,Ttot and respiratory flow capacity parameters such as VT,VE,VT/Ti,VT/Te under different intensity of threshold inspiratory muscle training loads.The absolute value of Pmo and Pes increased significantly with the raise of threshold load.Pga,Pdi also increased,but no remarkable difference.PTPdi at the threshold load of 60%MIP was significantly increased,but no changes had been found in the changes of TTdi,RMSdi,VE/RMSdi.[Conclusion]1.By using the mixed linear model for overall analysis(before,during,and after training),patients with COPD may not show a significant increase in respiratory muscle work when the threshold load of IMT at 60%MIP or less,and the degree of diaphragm fatigue may not increase significantly.2.In COPD patients,at the load of 50%MIP and 60%MIP,and the diaphragm fatigue after training was significantly increased than before training.3.COPD patients during different intensity of threshold IMT can cause an increased in respiratory center drive,respiratory muscle work,diaphragm fatigue,and ventilation efficiency.4.COPD patients can temporarily improve the ventilation index and ventilation efficiency after the different intensity of threshold IMT.