Effect of CPAP on Respiratory Load in COPD

State Key Laboratory of Respiratory Disease19 enrolled

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.

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.

Study Type

INTERVENTIONAL

Allocation

Purpose

TREATMENT

Masking

NONE

Enrollment

Conditions

Chronic Obstructive Pulmonary Disease

Interventions

Continuous Positive Airway PressureDEVICE

Patients with COPD were recruited to breath under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O).

Eligibility

Sex: ALLMin age: 40 YearsMax age: 80 Years

Medical Language ↔ Plain English

Inclusion Criteria: 1. Willing to participate after informed consent 2. Males and females, any race and aged 40-80 years 3. GOLD II-IV COPD (post-bronchodilator FEV1 \< 80 % of the predicted normal, and a post-bronchodilator FEV1/FVC \< 0.70) Exclusion Criteria: 1. Patients recovering from acute exacerbation less than 4 weeks. 2. Patients with concomitant pulmonary disease (e.g. lung fibrosis, interstitial lung disorder).

Locations (1)

Guangzhou Medical University

Guangzhou, Guangdong, China

Outcomes

Primary Outcomes

Diaphragm EMG

assessment of the electrical activity of the diaphragm (EMG-di)

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Lung volume

measurement of end inspiratory lung volume (EILV)

Time frame: 1-3 minutes after each CPAP level (0, 4, 6, 8 and 10 cm H2O)

Intrinsic positive end expiratory pressure (PEEPi)

PEEPi was calculated from the negative deflection in Pes from the onset of inspiratory effort to the point of zero flow during spontaneous breathing.

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Inspiratory pressure

assessment of esophageal pressure and transdiaphragmatic pressure by caculating tidal variations in Pes (∆Pes) and Pdi (∆Pdi) relatived to initiation of effort.

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Inspiratory work

the pressure-time product of the respiratory muscles (PTPes/min) and of the diaphragm (PTPdi/min) were calculated under the Pes and Pdi versus time curve and expressed per minute.

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Sensation of breathing effort

Using questionnaire to assess the sensation of breathing effort. Sensation of breath effort of CPAP use was divided into three types corresponding to -1, 0, 1 score respectively, 0 refers to the same sensation as the feeling of breathing at the atmosphere without CPAP; 1 refers to the more difficult sensation to breath at the CPAP condition than at the atmosphere.; -1 refers to the easier sensation to breath at the CPAP condition than at the atmosphere.

Data from ClinicalTrials.gov

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Secondary Outcomes

Respiratory rate (RR)

assessment of respiratory rate (RR)

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Tidal volume (Vt)

assessment of tidal volume

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Minute ventilation (VE)

assessment of minute ventilation

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Peak inspiratory flow rate

assessment of peak inspiratory flow rate

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Expiratory muscle EMG

assessment of the electrical activity of the internal oblique muscle (EMG-obl) and the rectus muscle (EMG-rec)

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.

Expiratory pressure

The change in Pga resulting from the contraction of the abdominal muscles during expiration was analyzed

Time frame: Around 5 minutes signals under the atmosphere pressure and different levels of CPAP (4, 6, 8 and 10 cm H2O) were recorded.