A Functional and Morphologic Analysis of Pressure-Controlled Inverse Ratio Ventilation in Oleic Acid-Induced Lung Injury: Methods

The experimental protocol was approved by the local animal ethics committee.
Twelve pigs weighing 25 ±4 kg were used. After preanesthetic medication with ketamine hydrochloride (10 mg/kg IM), a venous line was inserted into a peripheral vessel and pentobarbital (10 mg/kg) and fentanyl (0.1 mg) were administered. An endotracheal tube (6.5-mm internal diameter) was placed in the trachea through a tracheostomy. The animal was placed in the supine position and the lungs were mechanically ventilated at a respiratory frequency of 15 breaths per minute using a constant inspired oxygen concentration of 60 percent (Siemens Elema Servoventilator 900 C). Minute ventilation was adjusted to obtain normoventilation during baseline recordings prior to lung injury, and was then kept essentially constant throughout the experiment. Anesthesia was maintained by repeated intravenous injections of fentanyl (0.1 to 0.2 mg) and diazepam (0.2 mg/kg) as required. Pancuronium bromide (0.03 mg/kg) in iterated doses was used for muscle relaxation. Throughout the experiment, physiologic saline solution was infused IV at a rate of 100 ml/h other canadianfamilypharmacy.
An arterial catheter was placed in the abdominal aorta through a femoral cut-down and used for pressure monitoring and sampling of arterial blood gases. A Swan-Ganz catheter (7 F, Edwards Laboratories) was introduced through the femoral vein and advanced into the pulmonary artery.
Adequate positioning of the catheter tip in a branch of the pulmonary artery was confirmed by pressure registration during balloon inflation, thus providing a pulmonary artery wedge pressure (PAWP) reading. A catheter was surgically placed in the urinary bladder, and urine output was collected.
The lung injury model used has been described in detail by others and only a short description is given herein. Oleic acid (0.15 to 0.2 ml/kg) was dissolved in an equal volume of absolute ethanol and infused by a motor syringe during a 30-min period. To counteract circulatory instability caused by oleic acid, 15 ml/kg of dextran 70 was infused over 30 min prior to the administration of oleic acid. Lung injury was usually evident after 60 to 90 min. At the end of each experiment, the animal was killed by an intracardiac injection of potassium chloride.

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