Frequency-dependent compliance in the rabbit before and after sarin administration

¹ Chemical Defense Experimental Establishment, Porton Down, Wiltshire, England

Static and dynamic pulmonary compliance have been studied in 16 rabbits anesthetized with sodium pentobarbital, and ventilated by intermittent positive pressure pump. Functional residual volume increased at inflation rates of 56/min and above, and compliance decreased at rates greater than 60–70/min. These changes are interpreted as a distention of lung units with a long time constant. Following inhalation of sarin (isopropyl methylphosphonofluoridate) 12–120 µg/kg, the static compliance was slightly decreased, but there was no indication of an increase of gas trapping unless the dose of sarin was sufficient to cause death. Sarin accentuated the effects of increasing inflation rate by increasing the time constant of all lung units.