Children with uncontrolled asthma and significant reversibility might show hypoxaemia

Asthmatic children free of exacerbation with airway obstruction may have low partial pressure of oxygen (PaO2) which can be a marker for future risk, but PaO2 is scarcely measured during pulmonary function testing. We prospectively included asthmatic children with airway obstruction referred for pulmonary function testing, including blood gas analysis (n = 51). Hypoxaemia, defined as a value lower than − 2 z-score, was present in 15 (29%) children, and 37 (72%) children had a significant reversibility after bronchodilator administration. The multivariable model showed a positive influence of baseline forced expiratory volume in 1 s (FEV1) on PaO2 (β coefficient 0.69, [95% CI: 0.07; 1.30]; P = 0.03), whereas uncontrolled asthma and FEV1 reversibility negatively influenced it (β coefficient − 1.59 [95% CI: − 2.74; − 0.44]; P = 0.01; and − 0.07 [95% CI: − 0.13; − 0.02]; P = 0.01, respectively). As a consequence, children with uncontrolled symptoms of asthma and FEV1 reversibility ≥ 12% were significantly more at risk of having hypoxaemia compared to children with well/partly controlled asthma or no significant reversibility of FEV1. Conclusion: Among obstructive asthmatic children without current exacerbation, hypoxaemia is more likely to be seen in children with uncontrolled asthma and a significant post-bronchodilator FEV1 reversibility, in favour of different pathophysiology and treatment requirements of their airway obstruction.