Changes in arterial oxygen saturation in patients with hyperreactive airways during a histamine inhalation test

The arterial oxygen saturation (SaO2) of 55 adult patients with hyperreactive airways was monitored with an eight-wavelength ear oximeter during a histamine inhalation test. The post-challenge fall (mean +/- s.d.) in peak expiratory flow was 38 +/- 15% of the baseline value; it was accompanied by a fall in SaO2 of 1.1 +/- 1.8 per cent, from 96.6 +/- 1.8 to 95.5 +/- 2.3%. It is concluded that, in the histamine inhalation test used in this study, even the development of marked bronchoconstriction usually causes only slight changes in SaO2.