RESPIRATORY RESISTANCE AND TRANSCUTANEOUS PO2 DURING HISTAMINE PROVOCATION IN CHILDREN WITH BRONCHIAL-ASTHMA

Bronchial reactivity was assessed in 66 children with bronchial asthma (aged 8-15 years) by provocation with histamine-HCl during a symptom-free period. A significant bronchial reaction to histamine was defined as a 50% increase in the resistance of the respiratory system (R(rs)) determined by the forced oscillation technique. The provocative dose causing a 50% increase in the R(rs) (PD50R(rs)) was interpolated from the log dose-response curve. The mean PD50R(rs) was significantly lower in children with asthma (0.22 mg/mL) compared with a group of healthy children in the same age range (1.55 mg/mL) (P < 0.001). In children with clinically severe asthma, the mean PD50R(rs) was lower (0.13 mg/mL) than in children with mild asthma (0.34 mg/mL) (P < 0.001). Transcutaneous P(O2) (Ptc(O2)) was monitored in 25 of the children with asthma. In this group the proportion of mild and severe asthma, the baseline lung function variables, and the PD50R(rs) were not significantly different from those of the whole group of children. During the reaction, the Ptc(O2) fell on average by 29% of the baseline value (P < 0.001); in 88% of the children, the fall in Ptc(O2) was 20% or more of the baseline value. We conclude that histamine provocation tests using the forced oscillation technique and transcutaneous P(O2) to assess a bronchial reaction have a good discriminatory capacity tor different degrees of clinical severity of asthma in children.