Physiologic and Radiologic Studies

Much attention has been paid to ventilatory manuevers that can recruit and maintain lung volume in acute lung injury. In a canine lung injury model, using saline lavage, Downie and colleagues used small-volume tidal pressure–volume loops to examine this issue. Recruitment was found only if the peak pressure exceeded the pressure at which compliance increased (i.e., the Pflex) on a pressure–volume curve. Compliance was relatively constant at various PEEP levels after inflation from functional residual capacity. However, compliance peaked at moderate PEEP after deflation from total lung capacity. These results indicate that Pflex is the pressure threshold for recruitment, but do not suggest that quasi-static pressure–volume curves are useful in predicting steady-state lung volumes.

Albaiceta and colleagues used a tomographic method (computed tomography scan) to measure lung aeration (increase in normally aerated lung) and recruitment (decrease in nonaerated lung) in 12 patients with early acute lung injury in whom a pressure–volume curve was used to identify the inflection point on the pressure–volume curve. Aeration at the inflection point was similar in lung injury from pulmonary or extrapulmonary origin. There were no significant changes in the hyperinflated lung tissue. The results support the use of the deflation limb of the pressure–volume curve for adjusting PEEP in patients with acute lung injury. However, there is no direct evidence in this study that adjusting the level of PEEP in this way will improve clinical outcomes.

Citations 1-2 of 2 total displayed.

Tomographic Study of the Inflection Points of the Pressure–Volume Curve in Acute Lung Injury

Guillermo M. Albaiceta, Francisco Taboada, Diego Parra, Luis H. Luyando, Juan Calvo, Rafael Menendez, and Jesús Otero
Am. J. Respir. Crit. Care Med. 170: 1066 -1072. First published online as doi:10.1164/rccm.200312-1644OC [Abstract] [Full text]

Pressure–Volume Curve Does Not Predict Steady-State Lung Volume in Canine Lavage Lung Injury

John M. Downie, Arthur J. Nam, and Brett A. Simon
Am. J. Respir. Crit. Care Med. 169: 957 -962. First published online as doi:10.1164/rccm.200305-614OC [Abstract] [Full text]

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