Abstract
Background: The use of commercialised forced oscillation techniques to assess impedance in obstructive diseases such as asthma has gained popularity. However, it has yet to be fully established whether resistance and reactance measurements are comparable across different FOT devices. Methods: We compared two commercially available FOT devices: Impulse Oscillometry System (IOS) and TremoFlo FOT (Thorasys) in a) clinical adult population of healthy controls (n=14), asymptomatic smokers (n=17) and individuals with asthma (n=73) and b) a 3D printed CT-based airway model resistance, as well as a 3 litre standardised volume reactance. Results: Resistance measurements were higher with FOT compared to IOS, however there was no evidence of systematic bias. In contrast, significant bias was demonstrated with reactance (primarily elastance) measurements across the devices. The TremoFlo device recorded smaller (more negative) reactances at 5Hz and 20Hz (numerically smaller) when compared to IOS. The printed airway resistance and standardised volume reactance confirmed the observations in patients. Discussion: We have demonstrated that the impulse oscillation system and Tremoflo FOT generate comparable measurements of airways resistance. In contrast, FOT appeared to be more sensitive at probing airway elastance properties when compared to IOS. Our results highlight the need for further standardisation across FOT measurement devices.
Highlights
A number of studies have evaluated the utility of FOT, most commonly IOS in both adults and children
Age differed numerically across groups (p = 0.018, one way ANOVA), statistically significant differences were not seen between groups
The asthmatic individuals were primarily Global Initiative for Asthma (GINA8) treatment steps II to IV, with sub optimal control of symptoms, Asthma Control Questionnaire [ACQ-6: 1.07, 1.05)]. Both Forced Expiratory Volume in the first second (FEV1) (L) and FEV1 standardised residual (SR) were significantly different across the three groups, with significantly more expiratory flow limitation in the asthmatic group when compared with healthy controls
Summary
A number of studies have evaluated the utility of FOT, most commonly IOS in both adults and children. The purpose of this study was to evaluate and compare the impedance (resistance and reactance) between these two commercial devices using (i) a clinical population study of adults with asthma, aged matched healthy volunteers and asymptomatic smokers and (ii) using a three dimensional printed airway resistance phantom and standardised volume (reactance only) phantoms. We hypothesised that both devices would yield comparable resistance and reactance without evidence of systematic measurement bias between the two devices
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