Breathing pattern and its variability in the early Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder in which respiratory disturbances may occur even in the early stages of the disease. Current pathogenetic models suggest that neurodegeneration also affects neural structures involved in the control of ventilation, potentially leading to alterations in breathing pattern. In addition to these central mechanisms, peripheral factors such as respiratory muscle weakness and chest wall rigidity may also contribute to these changes. However, evidence on breathing pattern alterations in patients with early-stage PD remains limited, and breathing pattern variability has not yet been investigated in this population. This study therefore aimed to characterize the spontaneous breathing pattern and its variability in patients with early-stage PD. We examined 17 patients with PD and 17 sex and age matched controls. We assessed a breath-to-breath respiratory measures - tidal volume, inspiratory and expiratory times - recorded using respiratory inductive plethysmography for each phase of the examination protocol (supine rest, head-up tilt, supine recovery). Further we calculated following parameters: respiratory cycle duration (Ttot), respiratory rate (fR), minute ventilation (MV), the duty cycle (Ti/Ttot), mean inspiratory flow (Vt/Ti) and a measure of rapid shallow breathing (fR/Vt). In our study, patients with PD exhibited an increased respiratory rate (fR) accompanied by a preserved ratio of inspiratory and expiratory phases duration. The increase in fR, together with non-significant changes in tidal volume (Vt), resulted in elevated minute ventilation (MV). Analysis of breathing pattern variability revealed more unstable respiratory cycle duration in PD patients, manifested as increased variability of respiratory rate. We conclude that patients with early-stage PD exhibit subtle alterations in spontaneous breathing pattern and its variability, which may be detectable before the onset of clinically manifest respiratory dysfunction.