TY - JOUR
T1 - Differences in regional pulmonary pressure-impedance curves before and after lung injury assessed with a novel algorithm
AU - Grychtol, Bartłomiej
AU - Wolf, Gerhard K.
AU - Arnold, John H.
PY - 2009/6
Y1 - 2009/6
N2 - Global pressure-volume (PV) curves are an adjunct measure to describe lung characteristics in patients with acute respiratory distress syndrome (ARDS). There is convincing evidence that high peak inspiratory pressures (PIP) cause barotrauma, while optimized positive end-expiratory pressure (PEEP) helps avoid mechanical injury to the lungs by preventing repeated alveolar opening and closing. The optimal values of PIP and PEEP are deduced from the shape of the PV curve by the identification of so-called lower and upper inflection points. However, it has been demonstrated using electrical impedance tomography (EIT) that the inflection points vary across the lung. This study employs a simple curve-fitting technique to automatically define inflection points on both pressure-volume (PV) and pressure-impedance (PI) curves to asses the differences between global PV and regional PI estimates in animals before and after induced lung injury. The results demonstrate a clear increase in lower inflection point (LIP) along the gravitational axis both before and after lung injury. Moreover, it is clear from comparison of the local EIT-derived LIPs with those derived from global PV curves that a ventilation strategy based on the PV curve alone may leave dependent areas of the lung collapsed. EIT-based PI curve analysis may help choosing an optimal ventilation strategy.
AB - Global pressure-volume (PV) curves are an adjunct measure to describe lung characteristics in patients with acute respiratory distress syndrome (ARDS). There is convincing evidence that high peak inspiratory pressures (PIP) cause barotrauma, while optimized positive end-expiratory pressure (PEEP) helps avoid mechanical injury to the lungs by preventing repeated alveolar opening and closing. The optimal values of PIP and PEEP are deduced from the shape of the PV curve by the identification of so-called lower and upper inflection points. However, it has been demonstrated using electrical impedance tomography (EIT) that the inflection points vary across the lung. This study employs a simple curve-fitting technique to automatically define inflection points on both pressure-volume (PV) and pressure-impedance (PI) curves to asses the differences between global PV and regional PI estimates in animals before and after induced lung injury. The results demonstrate a clear increase in lower inflection point (LIP) along the gravitational axis both before and after lung injury. Moreover, it is clear from comparison of the local EIT-derived LIPs with those derived from global PV curves that a ventilation strategy based on the PV curve alone may leave dependent areas of the lung collapsed. EIT-based PI curve analysis may help choosing an optimal ventilation strategy.
KW - EIT
KW - pressure-volume curve
KW - inflection points
KW - optimal ventilation strategy
UR - http://dx.doi.org/10.1088/0967-3334/30/6/S09
U2 - 10.1088/0967-3334/30/6/S09
DO - 10.1088/0967-3334/30/6/S09
M3 - Article
SN - 0967-3334
VL - 30
SP - S137-S148
JO - Physiological Measurement
JF - Physiological Measurement
IS - 6
ER -