Abnormal Lung Function Found in Patients With Early-Stage Parkinson Disease

Results of a study on patients with early-stage Parkinson disease (PD) add to the evidence showing an association between PD and pulmonary function and point to the potential use of respiratory center drive to identify early PD.

Prior research has shown that impaired pulmonary function is a nonmotor symptom of PD that increases disability in patients with PD, and respiratory complications are associated with greater mortality. However, most of the studies involved patients with advanced-stage PD. The researchers of the current study set out to investigate the link between pulmonary function and early-stage idiopathic PD, as well as the role of respiratory center drive, which is measured by airway occlusion pressure and is associated with the level of muscular activity when breathing in.

The study, published in Frontiers in Neurology, enrolled 43 patients with idiopathic PD (ie, PD with unknown cause) and 41 healthy controls from the hospital at Tianjin Medical University in China. The patients had a mean (SD) disease duration of 1.67 (1.14) years, and their mean (SD) total levodopa equivalent dose was 313.18 (206.50) mg. The control participants were matched to the patients on age, sex, and body mass index.

All study participants underwent pulmonary function tests administered by a respiratory physician to measure indicators of ventilation function, respiratory muscle strength (measured by percentage of predicted values of maximal inspiratory pressure [PImax] and maximal expiratory pressure [PEmax]), and respiratory drive (measured by percentage of the predicted value of airway occlusion pressure [P0.1]). The patients with PD also completed several neuropsychological examinations.

There were no significant differences in ventilation function between the patients and the healthy controls, which the authors wrote was expected due to the patients being in an early clinical stage of the disease. However, the patients did have significantly reduced respiratory muscle strength in both PImax (P = .001) and PEmax (P = .002) compared with healthy controls. These differences remained significant when comparing male patients and female patients with controls of their same gender.

Additionally, the patients with PD showed significant increases in respiratory drive compared with the controls (mean [SD] P0.1 = 156.78 [63.24] vs 82.40 [13.14], respectively; P <.001). Again, the results were still significant when comparing patients and controls within genders. There was very little overlap between the values for most male and female patients and those of the controls, indicating separation.

The researchers did not find any significant correlations between the neurological assessment results and either ventilation function, respiratory muscle strength, or respiratory drive.

In addition to finding evidence of significantly lower respiratory muscle strength and higher respiratory drive in patients with early idiopathic IPD than in controls, the researchers noted the “remarkable separation” between the P0.1 values of patients and controls. This separation indicates that the measurement could potentially be used in diagnosis of early-stage PD.

“The early diagnosis of PD will greatly help optimize therapeutic strategies, especially in cases with very mild or atypical motor and nonmotor symptoms,” the study authors concluded. “Therefore, our data strongly supports P0.1 as a safe, noninvasive, and convenient measurement for early-stage [idiopathic PD] in clinical practice.”

Reference

Zhang W, Zhang L, Zhou N, et al. Dysregulation of respiratory center drive (P0.1) and muscle strength in patients with early stage idiopathic Parkinson’s disease. Front Neurol. 2019;10:724. doi: 10.3389/fneur.2019.00724.