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

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.

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

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.

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.

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.