Intrinsic PEEP and Arterial P_CO2in Stable Patients with Chronic Obstructive Pulmonary Disease

Abstract

Dynamic pulmonary hyperinflation and intrinsic PEEP (PEEPi) are known to play an important role in causing acute respiratory failure in COPD patients. In the present study, we have explored (1) the prevalence and magnitude of PEEPi in stable COPD patients, and (2) the correlation of PEEPi with respiratory mechanics and PaCO2. In 96 stable COPD patients with varying degrees of airway obstruction, we measured pulmonary flow resistance (RL), dynamic lung compliance (CLdyn), breathing pattern, arterial blood gases, and dynamic PEEPi. Dynamic PEEPi was determined as a negative deflection in esophageal pressure from the start of inspiratory effort to the onset of inspiratory flow. A significant correlation was found between dynamic PEEPi and FEVi (% predicted; r = -0.56, p less than 0.001), between PEEPi and RL (r = 0.69, p less than 0.001), and between PaCO2 and PEEPi (r = 0.6, p less than 0.001). These results indicate that increased severity of airway obstruction promotes PEEPi and concomitant dynamic hyperinflation. This implies increased inspiratory work in the face of decreased effectiveness of the inspiratory muscles as pressure generators. The present results suggest that dynamic hyperinflation may play a role in causing chronic hypoventilation in COPD patients.

Respiratory mechanics in patients with tense cirrhotic ascites

“…1). This negative deflection in Ppl will be referred to as intrinsic positive end-expiratory pressure (PEEPi) for consistency with previous investigations [15,16].…”

“…Total lung resistance was obtained using the isovolume method of FRANK et al [14]. Dynamic lung elastance was determined by dividing the difference in Ppl between points of zero flow by VT. To evaluate end-expiratory alveolar pressure, we used the indirect method recently described by HALUSZKA et al [15] and DAL VECCHIO et al [16], rather than the direct method of airway occlusion. This was because awake subjects react to airway occlusion in an unpredictable fashion, so that no reliable measurements of alveolar pressure can be obtained.…”

Expiratory muscle pressure and breathing mechanics in chronic obstructive pulmonary disease

“…Indeed, using an expiratory negative pressure technique, ELTAYARA et al [6] confirmed the presence of expiratory airflow limitation during quiet breathing in~60% of patients with stable COPD. HALUSZKA et al [7] reported the presence of dynamic hyperinflation at rest in over two-thirds of patients with stable COPD. These observations suggest that expiratory airflow limitation is quite common in stable COPD patients at rest.…”

“…Because of chronic airflow obstruction, many stable COPD patients have expiratory airflow limitation [6] and dynamic hyperinflation at rest [3,4,7,8]. This makes it unlikely for expiratory muscle recruitment in such COPD patients to be effective in lowering the end-expiratory lung volume.…”

Long-term oxygen therapy in COPD patients with moderate hypoxaemia: does it add years to life?

“…It is worth noting that among the ANTADIR patients, a sig-nificant proportion presented with a clinical picture of emphysema. The lungs of such patients are usually hyperinflated with intrinsic positive end-expiratory pressure (PEEP) [13,14]. The work of breathing is increased [15,16].…”