Effect of Disease Severity on Respiratory Impedance in Parkinson's Disease

Background: Parkinson's disease (PD) is a progressive neurodegenerative disorder. PD has been traditionally perceived as a motor disorder. However, it is frequently associated with pulmonary dysfunction which has been assessed by Spirometry, an effort-dependent technique.

Purpose: To evaluate in patients with PD the effect of disease severity on respiratory impedance using Impulse Oscillometry (IOS) and to correlate with Spirometry.

Methods: The study was conducted on 30 patients diagnosed with PD. Pulmonary function was assessed by IOS and spirometer. IOS is an effort-independent technique that uses sound waves of different frequencies to measure airway resistance. Spirometer measures the lung volume and generates flow-volume and volume-time relationship.

Results: The mean age of patients was 60.1±9.45. Resistance at 5 Hz (R5) was found to be negatively correlated with forced expiratory volume in the first second of the FVC manoeuver (FEV₁) (r = -0.628, P = .002), FEV₁/FVC (forced vital capacity) (r = -0.487, P = .025), and PEF (r = -0.599, P = .004), and resistance at 20 Hz (R20) with FEV₁ (r = -0.474,P = .029) and PEF (r = -0.522, P = .015). There was significant increase in R5 (0.32(0.36-0.28) vs 0.47(0.60-0.36); P = .04) and R20 (0.25(0.28-0.20) vs 0.30(0.40-0.25); P = .04) in stage II as compared to stage I of Hoehn-Yahr scale.

Conclusion: IOS might be a promising tool for diagnosis of respiratory dysfunction in addition to Spirometry, especially in cases where patients are not able to perform forced manoeuvers.