Respiratory functional changes on intratracheal challenge of sensitized rats.

Inbred PVG/c rats were sensitized to DNP19-ovalbumin by intraperitoneal injection. Sensitized rats when challenged with antigen developed characteristic brief interruptions of expiratory flow ('expiratory notching'). The functional residual capacity fell in rats challenged with antigen or saline but the fall was greater in those sensitized rats challenged with antigen. No greater alterations in respiratory rate, minute volume, airways resistance or dynamic compliance occurred on antigen as compared with saline challenge of sensitized rats, suggesting that the expression of immediate respiratory hypersensitivity in the rat is different from the asthmatic response in humans. The expiratory notching was reduced if an additional airways resistance was added in series to the tracheostomy tube. This may be explained as a result of reduction in the dynamic compression which normally produced the expiratory notching.