Possibilities of pulse oscillometry in the diagnosis of small airway dysfunction in patients with bronchial asthma

Abstract

Small airway dysfunction (SAD) is associated with poorly controlled asthma and frequent exacerbations. Objective. To assess the prevalence of SAD in asthmatics using spirometry, body plethysmography, and impulse oscillometry (IOS).

Materials and methods. The observational cross-sectional study of 61 patients with asthma was performed. Conclusion available SAD was made on the basis of identifying one of the criteria or their combination: 1) slow vital capacity (SVC) — forced vital capacity (FVC) >10% according spirometry; 2) "air trapping" according body plethysmography; 3) presence of pathological frequency dependence of the resistance (R) at 5 and 20 Hz (R5 – R2 0 >0,07 kPa*sec/I) according IOS.

Results. The analysis was performed for the entire group as well as for patients with FEV1 >80%pred. and FEV1/SVC<0.7 (group 1) and patients with FEV1>80%pred. and normal FEV1/SVC (group 2). SAD was most often diagnosed using IOS and the selected criterion R5 – R20>0.07 kPa*sec/I since 75% of patients had this deviation in the entire group, 65% of patients in group 1 and 55% of patients in group 2 whereas only in 48% and 24% of cases in the entire group according body plethysmography and spirometry, respectively.

Conclusion: SAD is definitely observed in patients with asthma. IOS is a more effective method of diagnosing SAD compared to spirometry and body plethysmography and can serve as a supplement functional method, especially in cases of normal parameters of spirometry and body plethysmography in asthmatics.