title: 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 x 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 (DeltaFRC), 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 > or =0.8 L), Raw,exp,EELV (18.3+/-1.4 versus 31.6+/-2.6 cm H2O x L(-1) x s(-1)), inspiratory airway resistance (at VT > or =1.0 L), static lung elastance (at VT < or =0.6 L), "additional" RS/lung resistance (at a range of VTs), DeltaFRC (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 x 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.
authors.affiliation: University of Athens Medical School, Dept of Intensive Care Medicine, Attikon University Hospital, Athens, Greece.
authors.forename: S D
authors.initials: SD
authors.lastname: Mentzelopoulos
authors.forename: C
authors.initials: C
authors.lastname: Roussos
authors.forename: S G
authors.initials: SG
authors.lastname: Zakynthinos
mesh_terms: D000368:Aged; D000403:Airway Resistance / Q000502:physiology; D000704:Analysis of Variance; D029481:Bronchitis, Chronic / Q000503:physiopathology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016684:Prone Position / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*