Overview
Both intrinsic positive end expiratory pressure (PEEPi) and dynamic hyperinflation are considered as inspiratory loads which increase work of breathing in patients with COPD. The application of extrinsic positive end expiratory pressure (PEEPe) supplied by CPAP has been claimed to reduce inspiratory load based on change in esophageal pressure which could be significantly affected by change in lung volume and airflow. The investigator hypothesized that CPAP could increase respiratory load because it increases lung volume.
Description
Objective: To assess the effect of CPAP on respiratory load and lung volume in stable COPD. Methods: Patients with COPD were recruited to breath under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O). Diaphragm EMG, esophageal pressure (Pes) and transdiaphragmatic pressure (Pdi) were recorded using balloon esophageal electrode catheter (Yinghui, Guangzhou, China). End inspiratory lung volume (EILV) was measured directly from a pneumotachograph combined with a three way valve under the different CPAP levels. Sensation of breathing difficulty was also assessed. In an additional study, the effect of airflow on pressure was investigated by a physical mode.
Eligibility
Inclusion Criteria:
- Willing to participate after informed consent
- Males and females, any race and aged 40-80 years
- GOLD II-IV COPD (post-bronchodilator FEV1 < 80 % of the predicted normal, and a post-bronchodilator FEV1/FVC < 0.70)
Exclusion Criteria:
- Patients recovering from acute exacerbation less than 4 weeks.
- Patients with concomitant pulmonary disease (e.g. lung fibrosis, interstitial lung disorder).