Effects of CPAP Level on Respiratory Mechanics and Central Drive in Patients With COPD
Effects of CPAP Level on Respiratory Mechanics and Central Drive in Patients With COPD
Chronic Obstructive Pulmonary Disease (COPD) is a common respiratory disease characterized by
 airflow limitation that is progressive and not fully reversible. Expiratory flow limitation
 (EFL) is the main mechanism leading to dynamic pulmonary hyperinflation (DPH) and intrinsic
 positive end-expiratory pressure (PEEPi). DPH and PEEPi lead to increased inspiratory muscle
 efforts and impaired central drive mechanical and ventilation coupling, which is an important
 mechanism of dyspnea. Appropriate setting of extrinsic PEEP (PEEPe) can decrease inspiratory
 efforts and work of breathing, improve patient-ventilator synchrony in severe COPD patients
 with PEEPi and treated with mechanical ventilation. Nevertheless, the effects of CPAP/PEEPe
 level on respiratory mechanics, especially on central drive mechanical and ventilation
 coupling, still need further investigations.

 In the present study, about 40 patients with COPD will be recruited as research subjects. And
 the investigators aim to observe the changes in respiratory mechanics, central drive
 mechanics, central drive mechanical and ventilation coupling at different levels of CPAP.
 Contrast analysis will be conducted to evaluate the effects of CPAP level on respiratory
 mechanics and central drive during DPH, which may provide a reasonable basis for the clinical
 application of CPAP to COPD patients and the exploration of a new reasonable CPAP setting
 method.
Patients with COPD are divided into two groups: moderate group and severe group, both of
 which are intervented by CPAP level. The static pressure volume curves of the lung and chest
 wall (Campbell diagram) were established with slow deep respiratory manoeuvre. Before using
 CPAP level, we will measure the relevant parameters of lung volume, respiratory flow,
 diaphragm electromyogram, central drive mechanical and ventilation coupling. Then incremental
 CPAP level will be applied to investigate the effects of CPAP level on the above mentioned
 respiratory mechanics parameters.
Inclusion Criteria:

 -  Patients from Zhu jiang Hospital,Southern Medical University

 -  Patients aged 40-70 years old

 -  Patients with pulmonary function test of forced expiratory volume at one second
 (FEV1)/forced vital capacity(FVC) < 70% and 30% ≤ FEV1%pred < 80%

 -  Patients in a clinically stable state

 -  Patients who signed informed consent.

 Exclusion Criteria:

 -  Patients with signs of an airway infection

 -  Patients with an acute exacerbation during the previous 4 weeks

 -  Patients with giant bulla(≥3cm in diameter)

 -  Patients with recent upper abdominal surgery

 -  Patients with one or more of the following diseases: esophageal cancer, reflux
 esophagitis, severe obstructive sleep apnea (apnea hypopnea index>15/hr),
 neuromuscular disease, or significant heart failure

 -  Patients with poor compliance.