Parameterisation of Respiratory Impedance in Lung Cancer Patients From Forced Oscillation Lung Function Test

Objective: This study aims to analyze the contribution and application of forced oscillation technique (FOT) devices in lung cancer assessment. Two devices and corresponding methods can be feasible to distinguish among various degrees of lung tissue heterogeneity. Methods: The outcome respiratory impedance Z(rs) (in terms of resistance R-rs and reactance X-rs) is calculated for FOT and is interpreted in physiological terms by being fitted with a fractional-order impedance mathematical model (FOIM). The non-parametric data obtained from the measured signals of pressure and flow is correlated with an analogous electrical model to the respiratory system resistance, compliance, and elastance. The mechanical properties of the lung can be captured through Gr to define the damping properties and H-r to describe the elastance of the lung tissue, their ratio representing tissue heterogeneity eta(r). Results: We validated our hypotheses and methods in 17 lung cancer patients where we showed that FOT is suitable for non-invasively measuring their respiratory impedance. FOIM models are efficient in capturing frequency-dependent impedance value variations. Increased heterogeneity and structural changes in the lungs have been observed. The results present inter- and intra-patient variability for the performed measurements. Conclusion: The proposed methods and assessment of the respiratory impedance with FOT have been demonstrated useful for characterizing mechanical properties in lung cancer patients. Significance: This correlation analysis between the measured clinical data motivates the use of the FOT devices in lung cancer patients for diagnosis of lung properties and follow-up of the respiratory function modified due to the applied radiotherapy treatment.