Introduction: 

Persistent symptoms following acute COVID-19 disease may cause significant disability, but few diagnostic tests have proved clinically useful. The forced oscillation technique allows the measurement of respiratory reactance and resistance which may be impaired following SARS-CoV-2 viral infection.

Aim: 

Evaluate the frequency and spectrum of oscillometry abnormalities among people with Long COVID.

Methods: 

Single centre cohort study. All adults aged over 16 years evaluated in the Long COVID clinic of St Vincent?s hospital, Sydney Australia. Oscillometry acquired using the forced ocillation technique (Tremoflo Pty Ltd) pre and post 400mcg inhaled salbutamol was collected per accepted standards (King et al 2020. ERJ, 55;2). Oscillometry values of R5, R5-20 and Ax were recorded and values below the lower limit normal reference values for age, height and gender were considered abnormal.

Results:

142 people with Long COVID underwent oscillometry testing between March and December 2022. Ages ranged between 17 and 89 years (mean SD) with 85 females and 57 males. The most common abnormality was an increased pre-bronchodilator R5-20 in 26.1% (37/142) and post bronchodilator R5-20 in 16.2% (23/142). Abnormal reactance (Ax) was found in 16.9% (24/142) pre-bronchodilator and 9.1% (13/142) post-bronchodilator.

Conclusion:

Abnormalities in resistance (R5-20) and reactance (Ax) were frequency observed amoungst ambulatory outpatients with Long COVID. Dysfunctional small airways may play a role in some symptoms of Long COVID.