• Huibert R van Genderingen, Adrianus J van Vught, and Jos R C Jansen.
• Department of Clinical Physics and Informatics, Vrije Universiteit Medical Center, PO Box 7057, 1007 MB, Amsterdam, The Netherlands. hr.genderingen@vumc.nl
• Intensive Care Med. 2003 Feb 1;29(2):233-40.

ObjectiveTo assess the degree of linearity between lung volume and impedance change by electrical impedance tomography (EIT) in pigs with acute lung injury and to investigate regional impedance changes during a pressure-volume maneuver.Design And SettingExperimental animal study in a university research laboratory.Patients And ParticipantsNine pigs with lung injury induced by lung lavage.InterventionsThe lungs were insufflated to four different lung volumes. Next the lungs were inflated in steps up to 40 cm H(2)O and then in steps deflated.Measurements And ResultsEIT measurements were performed. Impedance was highly linear with lung volume ( r(2)=0.97). From the pressure-volume maneuver regional pressure-impedance (P-I) curves were obtained in the upper half (ventral) and lower half (dorsal) of the thoracic cross-section. Excellent fit was found of the regional P-I curves with a predefined sigmoid equation ( r(2)=0.998). The P-I curves after lavage were markedly different than before lavage. The P-I curves recorded after lavage displayed a strong heterogeneity on the inflation limb: Lower corner pressure (traditionally lower inflection point) was significantly higher in the dorsal (28.3+/-4.1 cm H(2)O) than in the ventral region (17.5+/-4.3 cm H(2)O). The deflation limb displayed a more homogeneous pattern. Upper corner pressure and true inflection point, where the curve slope is maximal, in the dorsal region were only slightly higher than in the ventral region (1-2 cm H(2)O).ConclusionsEIT and automated curve fitting provide information on regional lung inflation and deflation which may be of clinical use for optimizing ventilator settings.

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