[Comparison of the effect of 2 methods of histamine administration on the bronchomotor response in asthmatics]

Bronchial provocation tests are useful for the detection of subclinical bronchial hyper-reactivity. Their standardisation is vital, in particular the method of administration of the bronchoconstrictor agent. Our study compares two systems of histamine delivery: an aerosol propellant with freons and a jet nebuliser linked to a dosimeter. Ten allergic asthmatics underwent bronchial provocation by each of these two systems at 8 days interval. The forced expired volume in one second FEV1 (VEMS) and specific conductance (sGAW) were measured during both tests. The dose of histamine inducing a reduction of VEMS of 20% (PD VEMS) or of sGAW of 40% (PD sGAW) was calculated. The comparison of the two methods showed a lower threshold of sensitivity when histamine was administered by dosimetry whether it was in terms of PD 20 VEMS (p less than 0.01) or PD 40 sGAW (p less than 0.05). The threshold of sensitivity expressed as PD 20 VEMS and PD 40 sGAW are superimposable by the dosimetric technique but on the other hand, using the aerosol dosage method, the threshold of sensitivity expressed in PD 40 sGAW is significantly lower than that for PD 20 VEMS (p less than 0.02). The 2 differences of bronchial response as a function of the method of administration of histamine could be explained by a better bronchial penetration, accompanied by a more central depot of the drug when histamine is administered by dosimetry.