by David Miedinger, Anja Jochmann, Lucia Schoenenberger, Prashant N. Chhajed, Jörg D. Leuppi
There is conflicting evidence about resting carbon dioxide levels in asthmatic individuals. We wanted to determine if transcutaneously measured carbon dioxide levels prior and during bronchial provocation testing differ according to asthma status reflecting dysfunctional breathing. Methods
We investigated active firefighters and policemen by means of a validated questionnaire on respiratory symptoms, spirometry, bronchial challenge testing with methacholine (MCT) and measurement of transcutaneous blood carbon dioxide partial pressure (PtcCO2) at rest prior performing spirometry, one minute and five minutes after termination of MCT. A respiratory physician blinded to the PtcCO2 results assigned a diagnosis of asthma after reviewing the available study data and the files of the workers medical screening program. Results
The study sample consisted of 128 male and 10 female individuals. Fifteen individuals (11%) had physician-diagnosed asthma. There was no clinically important difference in median PtcCO2 at rest, one and five minutes after recovery from MCT in asthmatics compared to non-asthmatics (35.6 vs 35.7 mmHg, p?=?0.466; 34.7 vs 33.4 mmHg, p?=?0.245 and 37.4 vs 36.4 mmHg, p?=?0.732). The median drop in PtcCO2 during MCT and the increase after MCT was lower in asthmatics compared to non-asthmatics (0.1 vs 3.2 mmHg, p?=?0.014 and 1.9 vs 2.9 mmHg, p?=?0.025). Conclusions
PtcCO2 levels at rest prior and during recovery after MCT do not differ in individuals with or without physician diagnosed asthma. The fall and subsequent increase in PtcCO2 levels are higher in non-asthmatics than in asthmatics and seems to be related with increased number of respiratory maneuvers during MCT.