Abstract
BackgroundReal-time bedside information on regional ventilation and perfusion during mechanical ventilation (MV) may help to elucidate the physiological and pathophysiological effects of MV settings in healthy and injured lungs. We aimed to study the effects of positive end-expiratory pressure (PEEP) and tidal volume (VT) on the distributions of regional ventilation and perfusion by electrical impedance tomography (EIT) in healthy and injured lungs.MethodsOne-hit acute lung injury model was established in 6 piglets by repeated lung lavages (injured group). Four ventilated piglets served as the control group. A randomized sequence of any possible combination of three VT (7, 10, and 15 ml/kg) and four levels of PEEP (5, 8, 10, and 12 cmH2O) was performed in all animals. Ventilation and perfusion distributions were computed by EIT within three regions-of-interest (ROIs): nondependent, middle, dependent. A mixed design with one between-subjects factor (group: intervention or control), and two within-subjects factors (PEEP and VT) was used, with a three-way mixed analysis of variance (ANOVA).ResultsTwo-way interactions between PEEP and group, and VT and group, were observed for the dependent ROI (p = 0.035 and 0.012, respectively), indicating that the increase in the dependent ROI ventilation was greater at higher PEEP and VT in the injured group than in the control group. A two-way interaction between PEEP and VT was observed for perfusion distribution in each ROI: nondependent (p = 0.030), middle (p = 0.006), and dependent (p = 0.001); no interaction was observed between injured and control groups.ConclusionsLarge PEEP and VT levels were associated with greater pulmonary ventilation of the dependent lung region in experimental lung injury, whereas they affected pulmonary perfusion of all lung regions both in the control and in the experimental lung injury groups.
Highlights
Real-time information on regional ventilation and perfusion, and their changes, during mechanical ventilation (MV) may help elucidate the physiological and pathophysiological effects of MV settings in healthy and injured lungs.Borges et al Intensive Care Medicine ExperimentalA single-compartment model of the healthy lung can describe aeration and its changes associated with a homogeneous distribution of airway pressures, expansion, and stretching across the lung parenchyma [1]
Investigational protocol We studied the effects of combinations of positive end-expiratory pressure (PEEP) and Tidal volume (VT) on regional ventilation and perfusion by electrical impedance tomography (EIT) in volume-controlled mode
During the measurements of these cardiopulmonary parameters, mechanical ventilation was set in volume-controlled mode, with Fraction of inspired oxygen (FIO2) 0.3–0.4 for the control animals and 0.7–0.8 for those with lung injury, respiratory rate (RR) 25, PEEP 5, and a VT of 10 ml/kg
Summary
Real-time information on regional ventilation and perfusion, and their changes, during mechanical ventilation (MV) may help elucidate the physiological and pathophysiological effects of MV settings in healthy and injured lungs.Borges et al Intensive Care Medicine ExperimentalA single-compartment model of the healthy lung can describe aeration and its changes associated with a homogeneous distribution of airway pressures, expansion, and stretching across the lung parenchyma [1]. Real-time information on regional ventilation and perfusion, and their changes, during mechanical ventilation (MV) may help elucidate the physiological and pathophysiological effects of MV settings in healthy and injured lungs. Electrical impedance tomography (EIT) has emerged as a new functional-imaging method potentially meeting many clinical needs It is a non-invasive, radiation-free tool to monitor, in real-time and at the bedside, the distribution of pulmonary ventilation [3,4,5,6,7,8,9,10,11]. We aimed to study the effects of positive end-expiratory pressure (PEEP) and tidal volume (VT) on the distributions of regional ventilation and perfusion by electrical impedance tomography (EIT) in healthy and injured lungs
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