Intrinsic Dynamic Positive End-Expiratory Pressure in Stable Patients with Chronic Obstructive Pulmonary Disease

Background: Assessment of intrinsic dynamic positive end-expiratory pressure (PEEPi,dyn) may be clinically important in stable patients with chronic obstructive pulmonary disease (COPD), but epidemiological data are scant. Objectives: The aim of our study was (i) to assess the PEEPi,dyn in a large population of stable patients with COPD and (ii) to evaluate the correlations with some noninvasive measurements routinely assessed. Method: Retrospective analysis of lung mechanics, dynamic volumes, arterial blood gases, dyspnoea by means of the Medical Research Council (MRC) scale, the COPD Assessment Test score, and maximal inspiratory/expiratory pressures in 87 hypercapnic and 62 normocapnic patients. Results: The mean PEEPi,dyn was significantly higher in hypercapnic than normocapnic patients (2.8 +/- 2.2 vs. 1.9 +/- 1.6 cm H2O, respectively, p = 0.0094). PEEPi,dyn did not differ according to Global Initiative for Chronic Obstructive Lung Disease stage, MRC score, or use or not of long-term oxygen therapy. There were significant although weak correlations between PEEPi,dyn and airway obstruction, hyperinflation, respiratory muscle function, arterial CO2 tension, and number of exacerbations/year. The transdiaphragmatic pressure was the strongest variable associated to PEEPi,dyn (R = 0.5713, p = 0.001). Conclusion: In stable patients with COPD, PEEPi,dyn is higher in hypercapnic patients and weakly correlated to noninvasive measures of lung and respiratory muscle function.

Automated summary

The study found that in stable COPD patients, hypercapnic patients had significantly higher intrinsic dynamic positive end-expiratory pressure (PEEPi,dyn) compared to normocapnic patients. There were weak correlations between PEEPi,dyn and various noninvasive measurements of lung and respiratory muscle function. Transdiaphragmatic pressure was identified as the strongest variable associated with PEEPi,dyn.