Objective: To explore the value of vibration response imaging (VRI) system in evaluating airway resistance of asthmatics.
Methods: The asthmatic group had 64 patients with a FEV1 of (56 +/- 18)% predicted before bronchodilator, and a FEV1 of (69 +/- 18)% predicted after bronchodilator. The control group had 20 patients with COPD with a FEV1 of (64 +/- 17)% predicted before bronchodilator, and a FEV1 of (66 +/- 19)% predicted after bronchodilator. All patients underwent VRI examination in close proximity of each spirometric recording before and after bronchodilator. VRI outcomes were evaluated to determine whether the VRI technology could detect changes in airway resistance in asthmatics. The statistical analysis in comparison between VRI outcomes before and after bronchodilator was performed using a matched pairs signed rank test. Linear regression was used to describe the relation between the improvements of VRI parameters and the increase in FEV1. ROC curve was used to evaluate the accuracy of this examination.
Results: After bronchodilator, VRI outcomes including flow graph characteristics, dynamic appearance, shape of the maximal energy frame and rale counts had significant improvements after bronchodilator (M = 7.5, 14.5, 12.5, 7.5, respectively, all P<0.05). Outcomes in the control group showed no significant improvements (M = 0.5, 2.0, 0.5, 1.0, respectively, all P>0.05). y = 0.12784 + 0.06767x1 + 0.04723x2 + 0.04919x3 + 0.00391x4 was the model of the linear regression between improvements of VRI parameters (x1, x2, x3, x4) and the observed changes in FEV1 (y), F = 10.16, P<0.01. According to the bronchodilation test, the sensitivity was 81.3%, and the specificity was 55.0%. The area under the ROC curve was 0.704.
Conclusion: VRI outcomes including graph characteristics, dynamic appearance, shape of the MEF and rale counts may be a promising method to evaluate changes of airway resistance in asthmatics.