Respiratory system impedance with impulse oscillometry in Parkinson's disease: Relation with disease severity

Abstract

Introduction: Parkinson9s disease (PD) is progressive neurodegenerative disorder. Pulmonary dysfunction in these patients is traditionally assessed using Spirometry is difficult to perform in patients with advanced disease. Aim: To evaluate airway mechanics in patients with Parkinson9s disease using Impulse Oscillometry System (IOS) and to relate with disease severity. Methods: Study was conducted on 30 patients with PD. Pulmonary function was assessed using IOS and Spirometery. IOS measures respiratory impedance (R20, R5, X20, X5) using sound waves with different frequencies, superimposed on the patient9s tidal volume. Spirometer measures lung --volume and provides flow-volume and volume–time relationship. Results: R5 (0.40±0.14 vs 0.27±0.02 p=0.0001), R20 (0.30±0.08 vs 0.25±0.02 p=0.002), resonant frequency (18.4±5.05 vs 15.7±1.2 p=0.005) and total impedance (0.43±0.15 vs 0.32±0.03 p=0.0006) were elevated as compared to control values. R5 (p=0.0413), R20 (p=0.0453), ΔX5 (p=0.0113), Mean R5-R20 ( p=0.0312) increased with increase in disease severity. Nine patients could not perform spirometry. R5 inversely correlated with FEV1 (r= -0.628, p=0.002), FEV1/FVC (r= -0.487, p=0.025) and PEF (r= -0.599, p=0.004) and R20 with FEV1 (r=-0.474, p=0.029) and PEF (r= -0.522, p=0.015). Conclusion: Characteristic changes in IOS were found in PD patients with increase in disease severity. R5 and R20 correlated with FEV1, FEV1/FVC and PEF, conventionally used to diagnose pulmonary dysfunction. IOS being effort independent technique, is thus more suitable for assessment of lung functions in patients with motor symptoms e.g. PD where patients are unable to perform forced manoeuvre.