Abstract
Objective: The last half-century has seen substantial changes in asthma treatment and care. We investigated whether arterial blood gas parameters in acute and non-acute asthma have changed historically. Methods: We performed a systematic search of the literature for studies reporting ,
and forced expiratory volume in 1 s, percentage of predicted (FEV1%). For each of the blood gas parameters, meta-regression analyses examined its association with four background variables: the publication year, mean FEV1%, mean age and female fraction in the respective studies. Results: After screening, we included 43 articles comprising 61 datasets published between 1967 and 2013. In studies of habitual-state asthma, mean
was positively associated with the publication year (p = 0.001) and negatively with mean age (p < 0.01). Mean
showed a positive association with publication year (p = 0.001) and a negative association with female fraction (p < 0.05). In acute asthma studies, blood gas levels were unassociated with publication year and mean age, mean
was positively associated with FEV1% (p < 0.05) whereas mean
showed a negative association with FEV1% (p < 0.05) for studies with mean FEV1% <40. In neither acute nor habitual-state studies was mean arterial pH associated with any of the predictor variables. Conclusions: In studies of habitual-state asthma, mean reported
and
levels were found to have increased since 1967. In acute asthma studies, mean
and
were associated with mean FEV1% but not with either publication year or patient age.
Notes
1The content values were with few exceptions not reported by the original authors but were computed by the authors of this article by using established algorithms (see Appendix for details)