title: Prone position improves lung mechanical behavior and enhances gas exchange efficiency in mechanically ventilated chronic obstructive pulmonary disease patients.
abstract: Pronation might favorably affect respiratory system (rs) mechanics and function in volume-controlled, mode-ventilated chronic obstructive pulmonary disease (COPD) patients. We studied 10 COPD patients, initially positioned supine (baseline supine [supine(BAS)]) and then randomly and consecutively changed to protocol supine (supine(PROT)), semirecumbent, and prone positions. Rs mechanics and inspiratory work (W(I)) were assessed at baseline (0.6 L) (all postures) and sigh (1.2 L) (supine(BAS) excluded) tidal volume (V(T)) with rapid airway occlusion during constant-flow inflation. Hemodynamics and gas exchange were assessed in all postures. There were no complications. Prone positioning resulted in (a) increased dynamic-static chest wall (cw) elastance (at both V(Ts)) and improved oxygenation versus supine(BAS), supine(PROT), and semirecumbent, (b) decreased additional lung (L) resistance-elastance versus supine(PROT) and semirecumbent at sigh V(T), (c) decreased L-static elastance (at both V(Ts)) and improved CO(2) elimination versus supine(BAS) and supine(PROT), and (d) improved oxygenation versus all other postures. Semirecumbent positioning increased mainly additional cw-resistance versus supine(BAS) and supine(PROT) at baseline. V(T) W(I)-sub-component changes were consistent with changes in rs, cw, and L mechanical properties. Total rs-W(I) and hemodynamics were unaffected by posture change. After pronation, five patients were repositioned supine (supine(POSTPRO)). In supine(POSTPRO), static rs-L elastance were lower, and oxygenation was still improved versus supine(BAS). Pronation of mechanically ventilated COPD patients exhibits applicability and effectiveness and improves oxygenation and sigh-L mechanics versus semirecumbent ("gold standard") positioning.
  
  
  CONCLUSIONS
  By assessing respiratory mechanics, inspiratory work, hemodynamics, and gas exchange, we showed that prone positioning of mechanically ventilated chronic obstructed pulmonary disease patients improves oxygenation and lung mechanics during sigh versus semirecumbent positioning. Furthermore, certain pronation-related benefits versus preprone-supine positioning (reduced lung elastance and improved oxygenation) are maintained in the postprone supine position.
authors.affiliation: Department of Intensive Care Medicine, Henry Dunant General Hospital; and Evangelismos General Hospital, Athens, Greece.
authors.forename: Spyros D
authors.initials: SD
authors.lastname: Mentzelopoulos
authors.forename: Spyros G
authors.initials: SG
authors.lastname: Zakynthinos
authors.forename: Charris
authors.initials: C
authors.lastname: Roussos
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Tzoufi
authors.forename: Argyris S
authors.initials: AS
authors.lastname: Michalopoulos
mesh_terms: D018806:APACHE; D000368:Aged; D000403:Airway Resistance / Q000502:physiology; D000465:Algorithms; D003422:Critical Care; D005260:Female; D005540:Forced Expiratory Flow Rates; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008168:Lung / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D016684:Prone Position / Q000502:physiology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology* / Q000628:therapy*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012121:Respiration, Artificial; D015656:Respiratory Mechanics / Q000502:physiology*; D012907:Smoking / Q000503:physiopathology; D016683:Supine Position / Q000502:physiology; D014797:Vital Capacity