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 was evaluated in 18 boys and 8 girls 7-18 years of age, with bronchial asthma, during bronchial provocation with histamine-HCl. Transcutaneous oxygen tension (tcPO2), carbon dioxide tension (tcPCO2) and the breathing pattern assessed by the transthoracic impedance technique were continuously monitored during the provocation. At reaction, when the fall in the forced expiratory volume in 1 s (FEV1) was 20% or more, the tcPO2 fell by 15% or more below the baseline in 22/26 and by 20% or more in 14/26 children. In some children, a marked fall in the tcPO2 was already noted after the saline inhalation and the first histamine dose steps without simultaneous changes in the FEV1. This early fall in the tcPO2 correlated to changes in the breathing pattern and was interpreted as a sign of compensatory hypoventilation secondary to the hyperventilation observed during the inhalations. We conclude that transcutaneous oxygen tension can be used as an indicator of a bronchial 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 oxygen tension.