The Respiratory Physiology Variation of COPD Patients in Inspiratory Muscle Training

Subjects:

COPD group ( experimental group ) Ten subjects with moderate COPD were will be recruited from the investigators outpatient clinic for the study. According to the criteria of the American Thoracic Society (ATS), COPD is defined as postbronchodilator forced expiratory volume in 1 second (FEV1) of 30% to 79% of the predicted value and a ratio of FEV1 to forced vital capacity (FVC) ,70%.

Inclusion criteria:(1)Severe and very severe COPD (postbronchodilator FEV1/FVC under 70% and FEV1 under 50% of the predicted value;(2)Inspiratory muscle weakness（Maximal Inspiratory Pressure under 60cmH2O（centimeter water column）.(3) bronchial dilation test(BDT) negative.(4) Exclusion of other cardiopulmonary diseases.

Exclusion criterion:(1)Suffer from acute exacerbation less than 4 weeks.(2) Intravenous or oral corticosteroids in 4 weeks.(3) With other heart, lung and brain disorders.(4) With poor compliance.

Healthy volunteers group (control group ) Inclusion criteria:(1) Normal lung function(FEV1/FVC above 70% and FEV1 above 50% of the predicted value); (2)Without inspiratory muscle weakness（Maximal Inspiratory Pressure above 60cmH2O）(3) without nervous system and respiratory diseases.

Experimental methods : prospective randomized controlled trial（RCT）

1. record the information of the subjects: sexuality, age ( years ), height ( cm), weight ( kg ), BMI ;
2. Pulmonary function tests:forced expiratory volume in 1 second（FEV1）, FEV1 of the predicted value (FEV1/Pred%), forced vital capacity (FVC), FVC of the predicted value (FVC/Pred%), a ratio of FEV1 to forced vital capacity (FEV1/FVC%).
3. Synchronous record:mouth pressure ( Pm ), esophageal pressure ( Peso ), intragastric pressure ( Pgas ),transdiaphragmatic pressure ( Pdi ), flow ( flow ), tidal volume ( volume ), Five lead diaphragmatic electromyography of the esophagus ( electromyography diaphragm （EMGdi1, EMGdi2, EMGdi3, EMGdi4, EMGdi5 )）.
4. Measure the maximal inspiratory pressure, records of maximum transdiaphragmatic pressure and maximum diaphragmatic electromyography simultaneously.

Subjects suffer from different level of threshold load generated by threshold loading device. Detecting the pressure and electrical while adjust the load to 30%,40%,50%,60%,70%,80% of the MIP respectively. The change from baseline in transdiaphragmatic pressure will be detect in each level of load.