Objective To investigate the effects of mechanical ventilation( MV) via different tidal volume ( VT) in combination with positive end expiratory pressure( PEEP) on dogs with acute lung injury( ALI) . Methods Dog model of oleic acid-induced ALI was established. And after that animals were randomized into different MV groups ( included low VT group, VT =6 mL/kg; and high VT group, VT =20 mL/kg) and ventilated for 6 h with a PEEP of 10 cmH2O. Arterial blood gas wasmeasured before, during and after ALI model was established ( at 1 h,2 h, 4 h and 6 h during MV) . The albumin concentration in BALF and pathological change of the lung tissue were evaluated in order to determine the lung injury while animals were sacrificed after 6 h MV. Results ALI model was successfully established ( 2. 50 ±0. 80) hours after oleic acid injection. Arterial pH decreased much severer in the low VT group than the high VT group( P lt;0. 01) . PaO2 and SaO2 in ventilation groups decreased after modeling but increased after MV, and PaO2 and SaO2 were significantly higher in the low VT group than the high VT group after 6 h MV( P lt;0. 05) . PaCO2 fluctuated less in the high VT group, while it increased significantly in the low VT group after MV( P lt; 0. 01) . Oxygenation index( PaO2 /FiO2 ) was lowered after modeling( P lt; 0. 01) , decreased to about 190 mm Hg after 1 h MV. And PaO2 /FiO2 in low VT group was significantly higher than the high VT group after 6 h MV( P lt; 0. 05) . BALF albumin concentration and the lung injury score in the low VT group were both significantly lower than the high VT group( both P lt; 0. 05) . Conclusions Ventilation with PEEP could improve the oxygenation of ALI dogs, and low VT ventilation improves the oxygenation better than high VT. Otherwise, low VT could induce hypercapnia and ameliorate lung injury caused by high VT MV.
Objective To study the influence of low-tidal volume and positive end expiratory pressure (PEEP) protective ventilation on cardiac output volume in elderly patients under general anesthesia. Methods From August 2012 to July 2014, 60 elderly patients undergoing selective surgery were divided into three groups with 20 patients in each. Group A was treated with conventional ventilation: tidal volume at 8 mL/kg, PEEP at 0 cm H2O (1 cm H2O=0.098 kPa); group B was treated with a tidal volume of 6 mL/kg and a PEEP of 5 cm H2O; group C was treated with a tidal volume of 6 mL/kg and a PEEP of 8 cm H2O. We then observed and analyzed the blood pressure, heart rate, cardiac output, arterial blood gas and airway mean pressure before induction of anesthesia (T0), 15 minutes of mechanical ventilation after the induction of anesthesia (T1), 60 minutes after anesthesia induction (T2), and 15 minutes after tracheal extubation (T3). Results In all the three groups, the mean arterial pressure and cardiac output were stable. In group B and C, central venous pressure increased significantly, the mean airway pressure and lung compliance increased, and the arterial oxygen branch pressure also increased significantly (P < 0.05). Conclusion Low-tidal volume combined with 5-cm H2O or 8-cm H2O positive end expiratory pressure lung-protective ventilation had a small influence on the cardiac output of elderly patients under anesthesia, which can be safely used.