Investigation of the effects of histamine inhalation on the tracheobronchial tree of calves by the forced oscillation technique

Gustin, P., Dhem, A.R., Lekeux, P., Lomba, F., Lándsér, F.J. & Van de Woestijne, K.P. Investigation of the effects of histamine inhalation on the tracheobronchial tree of calves by the forced oscillation technique. J. vet. Pharmacol. Therap. 11 , 374–380.
Effects of histamine inhalation were investigated with two different techniques in nine conscious, healthy calves. The oesophageal balloon technique was used to measure the dynamic respiratory compliance (C_dyn) and the pulmonary resistance (RL). The reactance (X_rs) and the resistance (R_rs) of the respiratory system were measured at high frequencies by the forced oscillation technique. These parameters were recorded before and after histamine inhalation. Three histamine dihydrochloride solution concentrations were used (16 mg/ml; 32 mg/ml; 64 mg/ml). Histamine inhalation induced a decrease in Cd_yn and X_rs an increase in R_rs, RL and of the resonant frequency and a negative frequency dependence of R_rs. Some of these changes were satisfactorily correlated with the histamine solution concentrations. The resonant frequency was well correlated with C_dvn. It was concluded that histamine inhalation induces a decrease of the calibre of small and large airways and a non-homogeneous behaviour of the pulmonary ventilation in awake calves. The forced oscillation technique can be used to perform an inhalation provocation test in unsedated animals.