The roles of impulse oscillometry in detection of poorly controlled asthma in adults with normal spirometry

Abstract

Background

Impulse oscillometry (IOS) has been introduced as a method of assessing asthma control. However, the cutoff IOS values for the detection of asthma control in adults are still unclear.

Objective

To assess the diagnostic ability of IOS for distinguishing between poorly controlled and well controlled adult asthmatic subjects with normal spirometry.

Methods

This cross-sectional study was conducted at the Lung Health Center, Chiang Mai, Thailand, between July 2019 and June 2020. IOS and spirometry were performed in all adult asthmatic subjects but only subjects with normal spirometry were enrolled. Poorly controlled asthma was defined in accordance with the Global Initiative for Asthma (GINA) plus an asthma control test (ACT) score ≤19. A Receiver Operating Characteristic (ROC) curve was plotted to detect poorly controlled asthma using the area under the ROC (AuROC) and 95%CI.

Results

One hundred and forty-two adult asthmatic subjects registering normal spirometry with a mean age of 53.4 ± 15.8 years were enrolled. Eighty-nine (62.7%) subjects were female. IOS parameters including heterogeneity of resistance at 5 Hz and resistance at 20 Hz (R5–R20) and area under reactance (AX) demonstrated excellent detection of poorly controlled asthma with an AuROC of 0.911 and 0.904, respectively. The z-score or absolute value of R5–R20 ≥ 0 and 1 cmH₂O/L/s, respectively, represented the highest AuROC of 0.86, with a sensitivity and a specificity of ≥80.0% for the detection of poorly controlled asthma.

Conclusion

IOS is a valuable tool for the detection of poorly controlled asthma in adults with normal spirometry.

Keywords:

• Asthma
• lung function
• impulse oscillometry
• asthma control
• adult
• airway resistance

Acknowledgments

The authors would like to thank all subjects who participated in this study. The authors also wish to acknowledge the contribution of the staff of the Division of Pulmonary, Critical Care and Allergy, Department of Internal Medicine, Faculty of Medicine, Chiang Mai University to this trial. We thank the Faculty of Medicine Graduate Student Scholarship, Chiang Mai University for the financial support. The authors would like to thank Mrs. Joan Elizabeth Peagam, Research administration section, Faculty of Medicine, Chiang Mai University for native English proofreading.

Author contributions

Conceptualization, W.C., S.N., C.L., and C.P.; Methodology, W.C., S.N., C.L.; C.P. Software: W.C.; Validation, W.C., S.N., C.L., and C.P.; Formal Analysis, W.C., S.N.; Investigation, W.C., C.L., and C.P.; Resources, W.C., C.L., and C.P.; Data Curation, W.C. and C.P.; Writing – Original Draft Preparation, W.C.; Writing – Review and Editing, W.C., S.N., C.L., and C.P.; Visualization, W.C., S.N., C.L., and C.P.; Supervision, S.N., C.L., and C.P.; Project Administration, W.C., and C.P.; Funding Acquisition, W.C., S.N., and C.P. All authors have read and agreed to the published version of the manuscript.

Disclosure statement

The authors have no conflict of interest in connection with this work.

Additional information

Funding

This study is funded by the Faculty of Medicine, Chiang Mai University Research Fund under Grant No. 037/2563.