Pulmonary function in Parkinson's disease

Pulmonary function was investigated in 31 consecutive patients with relatively severe Parkinson's disease. Clinical disability was assessed by Hoehn and Yahr scale, Northwestern University Disability Scale and Websterscore. All patients were on levodopa substitution therapy and used anticholinergics. Pulmonary function was investigated by spirography, determination of a maximal inspiratory and expiratory flow-volume curve and, when possible, maximal static mouth pressures were determined. Peak inspiratory and expiratory flow, maximal expiratory flow at 50% and maximal static mouth pressures were significantly below normal values. Vital capacity, forced inspiratory volume in 1 s and the ratio of forced expiratory volume in 1 s and vital capacity were relatively normal. Nine patients had upper airway obstruction (UAO) as judged by abnormal values for peak inspiratory flow, the ratio of forced expiratory volume in 1 s and peak expiratory flow and the ratio of maximal expiratory and inspiratory flow at 50%. Flow-volume curves were normal in eight patients; four patients demonstrated flow decelerations and accelerations (type A) and 16 had a rounded off flow-volume curve (type B). Type A can be explained by UAO and type B by a combination of decreased effective muscle strength and possible UAO. Overall results of pulmonary function tests in patients without any clinical signs or symptoms of pulmonary disease point to subclinical upper airway obstruction and decreased effective muscle strength in a significant proportion of patients.