Abstract
Introduction: Immediately after a deep inspiration there is a response in the airway resistance. In patients with asthma the response to deep inspiration (DI) is impaired compared with healthy subjects.
Aim: We want to investigate the airway resistance response after DI changes when subjects are exposed to a bronchoconstrictor.
Methods: All subjects were symptomatic asthmatics. They all preformed a tidal breathing challenge test (Mch) with methacholinebromide from 0.039–39.6 mg/ml in doubling doses. After each inhalation the airway resistance was measured by impulse oscillometry (IOS/PFT, Care Fusion, Würzburg) during 60-80 seconds with a DI at 30s. At 90s FEV1 was measured. P-values >0.05 were assumed to be significant.
Results: We analyzed 24 tests. One patient was excluded because of spirometric induced asthma. In 12 cases we found a PC20 <16 mg/ml. In 11 patients there was no PC20 or a PC20 >16.
We found a significant difference in ΔR5 between baseline and the highest concentration both in cases and non cases (resp. p=0.024 and p=0.022).
Conclusion: When PC20 is reached there is still an overall decrease in airway resistance after DI. Compared to those who didn't reach PC20 <16 the decrease is not significant but both groups had a high SE. The response to DI is highly variable in asthmatics.
- © 2011 ERS