Published ahead of print on August 18, 2004, doi:10.1164/rccm.200312-1644OC Am. J. Respir. Crit. Care Med., Volume 170, Number 10, November 2004, 1066-1072 A more recent version of this article appeared on November 15, 2004
Submitted on December 2, 2003 Tomographic Study of the Inflection Points of the Pressure-Volume Curve in Acute Lung InjuryGuillermo M Albaiceta1*,1 Department of Intensive Medicine, Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain, 2 Department of Radiology, Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain * To whom correspondence should be addressed. E-mail: guillermo.muniz{at}sespa.princast.es.
The inflection points of the pressure-volume curve have been used for setting mechanical ventilation in patients with acute lung injury. However, the lung status at these points has never been specifically addressed. In 12 patients with early lung injury we traced both limbs of the pressure-volume curve by means of a stepwise change in airway pressure, and a CT scan slice was obtained for every pressure level. Although aeration (increase in normally-aerated lung) and recruitment (decrease in non-aerated lung) were parallel and continuous along the pressure axis during inflation, loss of aeration and derecruitment were only significant at pressures below the point of maximum curvature on the deflation limb of the pressure-volume curve. This point was related to a higher amount of normally-aerated tissue and a lower amount of poorly and non-aerated tissue when compared to the lower inflection point on both limbs of the curve. Aeration at the inflection points was similar in lung injury from pulmonary or extrapulmonary origin. There were no significant changes in hyperinflated lung tissue. These results support the use of the deflation limb of the pressure-volume curve for positive end-expiratory pressure setting in patients with acute lung injury. Key words: Acute lung injury, mechanical ventilation, alveolar recruitment, positive end-expiratory pressure, computed tomography
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