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- Title
Pattern of lung emptying and expiratory resistance in mechanically ventilated patients with chronic obstructive pulmonary disease.
- Authors
Kondili, Eumorfia; Alexopoulou, Christina; Prinianakis, George; Xirouchaki, Nectaria; Georgopoulos, Dimitris
- Abstract
<bold>Objectives: </bold>To study the pattern of lung emptying and expiratory resistance in mechanically ventilated patients with chronic obstructive pulmonary disease (COPD).<bold>Design: </bold>A prospective physiological study.<bold>Setting: </bold>A 12-bed Intensive Care Unit.<bold>Patients: </bold>Ten patients with acute exacerbation of COPD.<bold>Interventions: </bold>At three levels of positive end-expiratory pressure (PEEP, 0, 5 and 10 cm H(2)O) tracheal (Ptr) and airway pressures, flow (V') and volume (V) were continuously recorded during volume control ventilation and airway occlusions at different time of expiration.<bold>Measurements and Results: </bold>V-V' curves during passive expiration were obtained, expired volume was divided into five equal volume slices and the time constant (tau) and dynamic deflation compliance (Crs(dyn)) of each slice was calculated by regression analysis of V-V' and post-occlusion V-Ptr relationships, respectively. In each volume slice the existence or not of flow limitation was examined by comparing V-V' curves with and without decreasing Ptr. For a given slice total expiratory resistance was calculated as tau/Crs(dyn), whereas expiratory resistance (Rrs) and time constant (tau(rs)) of the respiratory system were subsequently estimated taken into consideration the presence of flow limitation. At zero PEEP, tau(rs) increased significantly toward the end of expiration due to an increase in Rrs. PEEP significantly decreased Rrs at the end of expiration and resulted in a faster and relatively constant rate of lung emptying.<bold>Conclusions: </bold>Patients with COPD exhibit a decrease in the rate of lung emptying toward the end of expiration due to an increase in Rrs. PEEP decreases Rrs, resulting in a faster and uniform rate of lung emptying.
- Subjects
OBSTRUCTIVE lung diseases; CRITICAL care medicine; MULTIVARIATE analysis; AIR ducts; LUNG physiology; INTENSIVE care units; AIRWAY (Anatomy); OBSTRUCTIVE lung disease treatment; ADULT respiratory distress syndrome treatment; ARTIFICIAL respiration; CLINICAL trials; COMPARATIVE studies; LONGITUDINAL method; RESEARCH methodology; MEDICAL cooperation; RESEARCH; RESPIRATORY measurements; ADULT respiratory distress syndrome; TIME; EVALUATION research; POSITIVE end-expiratory pressure; PHYSIOLOGY
- Publication
Intensive Care Medicine, 2004, Vol 30, Issue 7, p1311
- ISSN
0342-4642
- Publication type
journal article
- DOI
10.1007/s00134-004-2255-z