Possibilities of pulse oscillometry in the diagnosis of small airway dysfunction in patients with bronchial asthma
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-R20 > 0,07 kPa•sec/l) 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/l 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.