A stable model of respiratory distress by small injections of oleic acid in pigs

Development of a stable model of respiratory distress in pigs with oleic acid, fulfilling clinical criteria of the adult respiratory distress syndrome (ARDS). Eight pigs (9.1±0.7 kg) were anesthetized with pentobarbital, paralyzed with tubocurarine and mechanically ventilated with an $F_{IO_2 } $ of 0.6, an I∶E ratio of 2∶3 and a PEEP of 0.2 kPa. Oleic acid (dissolved 1∶1 in 96% alcohol) was administered in a series of multiple injections of 0.1 ml until $P_{aO_2 } $ was lower than 8 kPa. Careful titration of the oleic acid injections on guidance of the $P_{aO_2 } $ established a reproducible respiratory distress ( $P_{aO_2 } $ =7.3±0.8 kPa), in which gas exchange and hemodynamic variables were stable for at least 4 h. The number of oleic acid injections (22±11, mean and SD) varied between the animals. With the use of multiple injections of oleic acid, a stable model of early respiratory distress in pigs can be achieved, in spite of individual differences in sensitivity. Such a stable model allows for a diversity of studies on early respiratory distress.