The Clinical Utility of Respiratory Oscillometry in Asthma Management

BACKGROUND: Oscillometry provides complementary information to spirometry, but is not a routine lung function test, partly due to paucity of real-world studies and non-standardised methodology and interpretation. AIMS: To facilitate adoption of oscillometry as a standard lung function test by demonstrating clinical utility in asthma: (i) correlating oscillometry with symptom control scores, (ii) phenotyping fixed airflow obstruction (FAO), (iii) longitudinal monitoring, and (iv) proposing a quality control pathway with grading criteria to improve operator competency. METHODS: Adults with asthma attending clinical review completed the Asthma Control Test, fraction exhaled nitric oxide, oscillometry then spirometry before and after salbutamol. Relationship between lung function parameters and symptom control, ability of cut-offs to identify abnormal lung function and poor asthma control, and limits of agreement during stability were determined. RESULTS: Oscillometry identified bronchodilator response (BDR) and abnormal lung function more frequently and with greater sensitivity than spirometry. Reactance measured by oscillometry was consistently associated with poor asthma control. Oscillometry and spirometry had moderate concordance in identifying significant longitudinal change, and both lacked concordance with symptom control. Limits of agreement between visits in stable asthma were at least twofold published oscillometry values in health. CONCLUSION: Reactance was more sensitive in identifying poor asthma control than spirometry. There was moderate longitudinal concordance between oscillometry and spirometry, not observed with asthma symptoms. Proposed oscillometry cut-offs for BDR and FAO and limits of agreement will assist clinical interpretation. The quality control framework with grading criteria will assist objective assessment of quality and competency facilitating adoption of oscillometry as a standard clinical test