Effect of lung stress index on titration of positive end-expiratory pressure at post-recruitment in three canine acute respiratory distress syndrome models / 中华外科杂志

<p><b>OBJECTIVE</b>To investigate the relationship of lung stress index and positive end-expiratory pressure (PEEP) at post-recruitment in different canine acute respiratory distress syndrome (ARDS) models.</p><p><b>METHODS</b>The ARDS models were induced by intravenous oleic acid, saline lavage and hydrochloric acid aspiration in anesthetized dogs. During volume control ventilation with constant inspiratory flow, PEEP was set to obtain a b (stress index) value between 0.9 and 1.1 (b = 1) before and post recruitment maneuver (RM). PEEP was changed to obtain b < 1 (0.6 < b < 0.8) and b > 1 (1.1 < b < 1.3). Meanwhile, the recruited volume (RV) was measured and pulmonary mechanics and gas exchange were observed.</p><p><b>RESULTS</b>At b = 1 after RM, PEEP were (10.8 +/- 2.3), (12.8 +/- 1.8) and (9.2 +/- 1.8) cm H2O in the oleic acid, saline-lavaged and hydrochloric acid aspiration groups, respectively. PEEP in saline-lavaged group was higher than that in hydrochloric acid aspiration group (P < 0.05). The ratio of partial arterial oxygen tension and fraction of inspiratory oxygen (PaO(2)/FiO(2)) at b = 1 without RM was lower than those post-RM in all three groups (P < 0.05). In oleic acid group, PaO(2)/FiO(2) at b = 1 post-RM was (399 +/- 61) mm Hg, which was higher than that at b < 1 [(307 +/- 71) mm Hg], but there was no difference between those at b = 1 and b > 1. At b = 1 after RM, PaO(2)/FiO(2) in the saline-lavaged group was higher than that in acid aspiration group, but no difference between saline-lavaged group and oleic acid group was found. At b = 1 post-RM, RV were higher than that at b = 1 before RM in all three groups (P < 0.01), but there was no significant difference among three groups. At b = 1 post-RM in three groups, pulmonary compliance were higher than those at b > 1, but airway plateau pressure were lower than those at b > 1.</p><p><b>CONCLUSIONS</b>Lung stress index could be a good indicator for PEEP titration at post-RM.</p>

Assessment of stroke volume variation and intrathoracic blood volume index on the responsiveness to volume loading in mechanically ventilated canine with hemorrhagic shock / 中华外科杂志

<p><b>OBJECTIVE</b>To assess the significance of stroke volume variation (SVV) and intrathoracic blood volume index (ITBI) on the responsiveness to volume loading in mechanically ventilated canine with hemorrhagic shock.</p><p><b>METHODS</b>Hemorrhagic shock canine model was established with the modified Wiggers' method. The heart rate (HR), mean artery pressure (MAP), central venous pressure (CVP), pulmonary artery wedge pressure (PAWP), intrathoracic blood volume index (ITBI) and stroke volume variation (SVV) were investigated by Swan-Ganz catheter or PiCCO monitor. Graded volume loading (VL) was performed. Successive responsive VLs were performed (increase in SV > 5% after VL) until continuous change in SV < 5% (unresponsive) was reached.</p><p><b>RESULTS</b>Fourteen canines were studied and a total of 134 VLs were performed. In 94 VLs, an increase in SV of more than 5% was reached. In the other 40 VLs, increase in SV was less than 5%. The change of HR, MAP, ITBI, SVV in responsive were more than those of unresponsive after VL. The change of CVP, PAWP in responsive were less than those of unresponsive. Significant correlation was found between DeltaSV after VL and the baseline values of ITBI, SVV. No correlation was found between DeltaSV and HR, MAP, CVP, PAWP. Significant correlations were also found between DeltaSV and DeltaCVP, DeltaPAWP, DeltaITBI, DeltaSVV after fluid loading. No correlation was found between DeltaSV and DeltaHR, DeltaMAP. By using receiver operating characteristic analysis, the area under the curve were 0.872 for SVV and 0.689 for ITBI, more than those of HR, MAP, CVP, PAWP statistically. As SVV value of 9.5% or more will predict an increase in the SV of at least 5% in response to a VL with a sensitivity of 92.6% and a specificity of 82.5%.</p><p><b>CONCLUSIONS</b>SVV and ITBI were more useful indicators than CVP and PAWP on the assessment of responsiveness to volume loading. SVV as a functional preload parameter and for on-line monitoring may help to improve the hemodynamic management.</p>