The purpose of this study is to assess the Respiratory Muscle Function and Neural Respiratory Drive in Interstitial Lung Disease patients.

In total, 50 patients with interstitial lung disease (ILD) are going to recruited.The patients are studied at the afternoon in a semirecumbent position. After the application of topical anaesthesia (2% xylocaine), the patient will be asked to swallow two balloon-tipped catheters and the multi-pair esophageal electrode catheter through the nose into the their right position.

At the first period, the stable signals of unassisted spontaneous breathing (about 10min) were chosen to be recorded. The Esophageal and gastric balloon-catheters are used to detect the intra-thoracic and abdominal pressure.The diaphragm electromyogram (EMGdi) will be recorded from a multipair esophageal electrode.The baseline data of the respiratory muscle activity will be detected by these catheters and electrode.p0.1 (the negative airway pressure generated during the first 100 ms of an occluded inspiration) will be also meassured.

After the first period, the nonvolitional tests on respiratory muscle function and strength (twitch mouth and transdiaphragmatic pressure during bilateral magnetic phrenic nerve stimulation (TwPmo and TwPdi) will be done.

After the second period,the patients will be ask to perform different maneuvers, including maximal inspiration against a closed valve ,maximal inspiration to total lung capacity (TLC),maximalexpiration at the total lung capacity (TLC) against a closed valve and maximal sniff from functional residual capacity(FRC).Each maneuver will repeated more than three times with an interval of 30 s or more. Inspiratory capacity(IC),global maximal inspiratory pressure (PImax), maximal sniff nasal pressure (SnPna) and maximalexpiratory pressure will be meassured with the balloon-catheters.The maximal value of the diaphragm electromyogram (EMGdi) will be recorded during these maneuvers.

Inclusion Criteria:

• Interstitial lung disease patient meet the diagnose criteria of interstitial lung disease

Exclusion Criteria:

1. Severe Cardiovascular disease
2. Pneumonia
3. Neuromuscular and chest wall deformity
4. Respiratory arrest
5. Cardiovascular instability (hypotension, arrhythmias, myocardial infarction)
6. Change in mental status; uncooperative patient

Interstitial Lung Disease patients