PubMed:18596639 JSONTXT

{"project":"PubMed_Structured_Abstracts","denotations":[{"id":"T1","span":{"begin":110,"end":557},"obj":"OBJECTIVE"},{"id":"T2","span":{"begin":566,"end":585},"obj":"METHODS"},{"id":"T3","span":{"begin":595,"end":640},"obj":"METHODS"},{"id":"T4","span":{"begin":651,"end":670},"obj":"METHODS"},{"id":"T5","span":{"begin":686,"end":868},"obj":"METHODS"},{"id":"T6","span":{"begin":900,"end":2427},"obj":"RESULTS"},{"id":"T7","span":{"begin":2441,"end":2626},"obj":"CONCLUSIONS"}],"text":"Effects of prone position and positive end-expiratory pressure on lung perfusion and ventilation.\nOBJECTIVES: Prone positioning is frequently used during acute respiratory distress syndrome. However, mechanisms by which it improves oxygenation are poorly understood, as well as its interaction with positive end-expiratory pressure. This study was conducted to decipher the respective effects of positive end-expiratory pressure and posture during lung injury on regional lung ventilation, perfusion and recruitment assessed by positron emission tomography.\nDESIGN: Experimental study.\nSETTING: Research laboratory of a university hospital.\nSUBJECTS: Six female piglets.\nINTERVENTIONS: After oleic acid-induced lung injury, all animals were studied in supine and prone position at both positive end-expiratory pressure 0 and positive end-expiratory pressure 10 cm H2O.\nMEASUREMENTS AND MAIN RESULTS: In each experimental condition, regional lung perfusion and ventilation were assessed with positron emission tomograph using intravenous 15O-labeled water and inhaled nitrogen-13. Nonaerated lung weight was assessed with positron emission tomograph, and alveolar recruitment was defined as the difference of nonaerated lung weight between conditions. Positive end-expiratory pressure was associated with significant alveolar recruitment (130 +/- 85 and 65 +/- 29 g of lung in supine and prone position, respectively [p \u003c 0.05 vs. 0]), whereas recruitment induced by posture was not statistically significant (77 +/- 97 g with positive end-expiratory pressure 0 and 13 +/- 19 g with positive end-expiratory pressure 10 [p \u003e 0.05 vs. 0]). Regardless the posture, positive end-expiratory pressure redistributed both perfusion and ventilation toward dependent regions. Recruitment by positive end-expiratory pressure was restricted to dorsal regions in supine position, but extended diffusely along the ventral-to-dorsal dimension in prone position. Prone position was associated with recruitment in dorsal regions with concomitant derecruitment in ventral regions, magnitude of this being reduced by positive end-expiratory pressure. Prone position redistributed ventilation toward dorsal and ventral regions at positive end-expiratory pressure 0 and positive end-expiratory pressure, respectively. Finally, prone position redistributed perfusion toward ventral regions, to an extent amplified by positive end-expiratory pressure.\nCONCLUSIONS: Positive end-expiratory pressure and posture act synergistically by redistributing lung regional perfusion toward ventral regions, but have antagonistic effects on regional ventilation."}