INFLUENCE OF BREATHING PATTERN ON TRANSCUTANEOUS OXYGEN AND CARBON-DIOXIDE TENSION DURING HISTAMINE PROVOCATION IN CHILDREN WITH BRONCHIAL-ASTHMA

The influence of the breathing pattern on transcutaneous blood gases w as evaluated in 18 boys and 8 girls 7-18 years of age, with bronchial asthma, during bronchial provocation with histamine-HCl. Transcutaneou s oxygen tension (tcPO(2)), carbon dioxide tension (tcPCO(2)) and the breathing pattern assessed by the transthoracic impedance technique we re continuously monitored during the provocation. At reaction, when th e fall in the forced expiratory volume in 1 s (FEV(1)) was 20% or more , the tcPO(2) fell by 15% or more below the baseline in 22/26 and by 2 0% or more in 14/26 children. In some children, a marked fall in the t cPO(2) was already noted after the saline inhalation and the first his tamine dose steps without simultaneous changes in the FEV(1). This ear ly fall in the tcPO(2) correlated to changes in the breathing pattern and was interpreted as a sign of compensatory hypoventilation secondar y to the hyperventilation observed during the inhalations. We conclude that transcutaneous oxygen tension can be used as an indicator of a b ronchial reaction during bronchial provocation tests in children only if one takes account of the fact that the breathing pattern during the inhalation of the challenge compound per se has an effect on the oxyg en tension.