Agreement of airway resistance measurements by two different techniques of body-plethysmography and impulse oscillometry in asthmatic patients

Background: Airway resistance can be measured by different techniques of body-plethysmography and impulse oscillometry (IOS). So far there has been no systematic study comparing validity of these techniques in relation to clinical condition of the patients reported. Aims and objectives: We investigated correlation between these techniques in assessment of airway resistance and asthma control test. Methods: In 92 patients with asthma selected on the basis of ATS criteria for diagnosis of asthma and GINA asthma control test (ACT) questionnaire completed. Pulmonary function tests including body-plethysmography with airway resistance measurement and impulse oscillometry measuring total airway resistance at 5 Hz and 20Hz was done using IOS. Results: ACT score has a significant correlation with a r value of - 0.34 with total airway resistance measured by body-plethysmography (p=0.003) and also significant correlation with r value of - 0.31 (p=0.002) with airway resistance measured by IOS at 5Hz but no significant correlation with airway resistance measured by IOS at 20 Hz. There is a significant correlation between airway resistance measured by body plethysmography and airway resistance measured by IOS at 5 Hz and at 20 Hz. Conclusion: These finding indicates a good correlation of total airway resistance measured by body plethysmography and by IOS at 5 Hz as well as 20 Hz, which is stronger with the first, Also significant negative correlation between ACT score and airway resistance centered in peripheral airways measured by IOS at 5 Hz but not with the resistance at central airways measured mainly by IOS at 20Hz.