[Effect of lung strain on breathing mechanics in dogs with acute respiratory distress syndrome]

To explore the effect of lung strain on breathing mechanics in dogs with acute respiratory distress syndrome (ARDS).Twenty-four healthy male Beagle dogs were recruited to reproduce medium ARDS models with venous injection of 0.18 mL/kg oleic acid, and they were randomly assigned to five groups with random numbers table method. In lung protective ventilation (LPV) group (n = 4), the ventilation was supported for 24 hours with tidal volume (VT) at 6-8 mL/kg, and in lung strain 1.0, 1.5, 2.0, 2.5 groups (S1.0, S1.5, S2.0, S2.5 groups), the VT was calculated from lung strain, the volume recruitment by positive end expiratory pressure (VThe VT of group LPV was (7.1±0.5) mL/kg. With the increase of lung strain, VT was gradually increased. VT of group S1.0 [(7.3±1.8) mL/kg] was similar to group LPV. VT of groups S1.5, S2.0, S2.5 was significantly higher than that of group LPV (mL/kg: 13.3±5.5, 18.7±5.4, 20.1±7.4 vs. 7.1±0.5, all P0.05). Moreover, under the same lung strain, the difference in VT among individuals was large. The Cst of each group was decreased significantly at the end of the experiment as compared with that before model reproduction. With the increase of lung strain, the rate of Cst descending was increased, Cst dropped more significantly in groups S2.0 and S2.5 than that in groups S1.0 and S1.5 [(48.0±15.0)%, (54.4±9.5)% vs. (25.9±13.7)%, (38.6±8.1)%, all P0.05]. Pplat and pulmonary stress at model reproduction in all groups were significantly higher than those before model reproduction, and they increased with the prolongation of ventilation time. Pplat and lung stress at 4 hours of ventilation in group S1.5 were significantly higher than those in group LPV [Pplat (cmHIn animal ARDS models, the larger the lung strain, the higher the Pplat and lung stress during mechanical ventilation, VT originated for lung strain 2.0 and 2.5 may further reduce Cst in ARDS models, when lung strain over 1.5, Pplat and lung stress increased significantly, which exceeded the safe range of LPV (35 cmH