REPEATED MEASUREMENT OF RESPIRATORY-FUNCTION AND BRONCHOCONSTRICTION IN UNANESTHETIZED MICE

A noninvasive forced oscillation technique was used to determine respi ratory function in unanesthetized and spontaneously breathing mice. Ps eudorandom noise pressure variations in a frequency range of 16-208 Hz were applied to the body surface, and the flow response was measured at the nose. From the pressure-flow relationship, respiratory transfer impedance was calculated. Study of intra-animal variability on a shor t- and a long-term basis revealed that the real part of respiratory tr ansfer impedance was reproducible within 9%. The imaginary part appear ed less reproducible (within 22%). Furthermore, bronchoconstrictive re sponses were investigated and analyzed by evaluation of respiratory re sistance as measured at 16 Hz (Rrs(16)). During the first 15 min after ovalbumin challenge in ovalbumin-sensitized mice, Rrs(16) was signifi cantly increased [49 +/- 7% (SE)]. Inhalation of methacholine in untre ated mice induced an increase in Rrs(16) of 75 +/- 16% (SE). In saline -challenged animals, no significant changes were observed. This method enables evaluation of long-term respiratory function in mice and appe ared to be a sensitive measure for bronchoconstriction.