The possibilities of impulse oscillometry in the diagnosis of the lung function disorders after COVID-19

Background. Impulse oscillometry (IOS) is an effort independent method of studying lung mechanics.Aim. To study the diagnostic significance of IOS in assessing lung mechanics after COVID-19.Materials and methods. Spirometry, body plethysmography, diffusion test (DLCO), IOS parameters were analyzed in 315 patients (the median age 48 years), the median period from the beginning of COVID-19 to the study was 50 days. Statistical analysis included descriptive statistics, correlation analysis and one-dimensional logistic regression analysis with an assessment of odds ratios.Results. In general group, spirometry and body plethysmography parameters were in normal values, while DLCO was reduced in 61% of patients. Parameters of IOS were analyzed in the general group and between the groups, depending on the value of DLCO and total lung capacity (TLC): normal or reduced. In general group, reactance area (AX), hererogeneity of resistance Rrs5-Rrs20, resistance at 5 Hz (Rrs5), reactance at 5 Hz (Delta Xrs5) were increased in 29.8, 17.8, 6, 4.8% of patients, respectively, and were statistically significantly higher in the group with reduced TLC, whereas in the group with reduced DLCO AX, Rrs5-Rrs20 were statistically significantly higher. Logistic regression analysis showed that patients with Rrs5-Rrs20>0.07 kPaxs/l or AX>0.32 kPa/l had a 1.99-fold and 2.24-fold increased risk for decrease DLCO, respectively, while the risk of decrease in TLC was 2.25-fold (p=0.012) and 3.16-fold (p<0.001) higher, respectively.Conclusion. IOS allow to detect both dysfunction of small airways (if AX or Rrs5-Rrs20 are increased) and the risk of restrictive pattern and lung diffusion impairment after COVID-19.