Prone position improves expiratory airway mechanics in severe chronic bronchitis

Abstract

Based on lung parenchyma-airways' interdependence, the present authors hypothesised that prone positioning may reduce airway resistance in severe chronic bronchitis. A total of 10 anaesthetised/mechanically ventilated patients were enrolled. Partitioned respiratory system (RS) mechanics during iso-flow experiments (flow=0.91 L·s-1, tidal volume (VT) varied within 0.2-1.2 L), haemodynamics, gas-exchange, expiratory airway resistance (Raw,exp), functional residual capacity (FRC), change in FRC (ΔFRC), end-expiratory lung volume (EELV), expiratory airway resistance at EELV (Raw,exp,EELV), intrinsic positive end-expiratory pressure (PEEPi), and mean end-expiratory flow were determined in baseline semirecumbent (SRBAS), prone, and post-prone semirecumbent (SRPP) postures. Pronation versus SRBAs resulted in significantly reduced Raw,exp (at VT ≥ 0.8 L), Raw,exp,EELV (18.3 ± 1.4 versus 31.6 ± 2.6 cm H2O·L-1·s-1), inspiratory airway resistance (at VT ≥ 1.0 L), static lung elastance (at VT ≤ 0.6 L), "additional" RS/lung resistance (at a range of VTS), ΔFRC (0.35 ± 0.03 versus 0.47 ± 0.03 L), EELV (4.92 ± 0.49 versus 5.65 ± 0.65 L), RS/lung PEEPi (6.7 ± 1.1/5.4 ± 0.6 versus 8.9 ± 1.7/7.8 ± 1.1 cm H2O), mean end-expiratory flow (63.9 ± 4.2 versus 47.9 ± 4.0 mL·s-1), and shunt fraction (0.16 ± 0.03 versus 0.21 ± 0.03); benefits were reversed in SRPP. In severe chronic bronchitis, prone positioning reduces airway resistance and dynamic hyperinflation. Copyright © ERS Journals Ltd 2005.