Abstract
For a controlled study of respiratory failure, a model of the disease is necessary. In order to establish a method to develop graded respiratory failure in animals, paraquat (10mg/kg) was administrated intraperitonealy to 20 rats once a week 6 times.
The growth rates of the rats were much slower than those of the control rats. One rat died from respiratory distress on the 30th day after the first injection of paraquat. The others were subjected to blood gas analysis and histological study 2 weeks after the last injection.
The rats were lightly anesthetized with intraperitoneal pentobarbital and blood gas samples were taken from the abdominal aorta through a laparotomy incision. Respiratory depression due to general anesthesia was ruled out with a low PaCO2, but rats had a PaO2 of 72.0±3.0 torr, which was lower than those of the control.
The light- and electron-microscopic examination revealed destruction of the pneumocytes, an increase of alveolar macrophages, perivascular and peribronchiolar cell infiltration, a thickening of the alveolar septa, an increase of fibrocytes, plasmacytes and lymphocytes in the interstitium.
The rats, with a significant retarded growth rate and a low PaO2, consistently had a correlated degree of pathological changes specific to the lung. Though repeated blood gas sampling from a small animal is impractical, an observation of the growth rate is easy. The slower growth rate of rats treated with paraquat certainly predicts the development of respiratory failure in these animals.
This method of induction and prediction of respiratory failure promises to be a useful model for the study of respiratory failure.
