Altered Respiratory Response to Baroreceptor Stimulation in Patients With Parkinson’s Disease

Parkinson's disease (PD) causes significant cardiovascular and respiratory dysregulation, negatively impacting quality of life. This dysregulation may involve disruptions in baroreceptor-respiratory reflexes, essential for the complex interplay between the cardiovascular and respiratory systems; however, this possibility still requires further investigation. Considering that prior studies have demonstrated reduced baroreflex gain and impaired chemoreceptor responses in PD, the present study tested the hypothesis that patients with PD exhibit blunted respiratory responses to baroreflex stimulation compared to healthy controls. To test this, all subjects underwent baroreflex unloading and reloading using intravenous bolus injection of sodium nitroprusside (65–100μg) followed by 65–100μg phenylephrine hydrochloride 1 min afterwards, aimed at inducing an extensive range of the reflex arc by eliciting rapid changes in blood pressure (BP, modified-Oxford technique) during supine rest. Beat-to-beat heart rate (electrocardiography) and blood pressure (BP, finger photoplethysmography), as well as respiration rate, and estimated tidal volume, minute ventilation (VE, estimated from a pneumobelt) were measured both at rest and during the sequential boluses of vasoactive drugs. Results indicated that, compared to rest, patients with PD exhibited a significantly increase in ventilatory response to baroreflex unloading (VE: Δ+11±3%, P=0.024), and this response was preserved when compared to controls (VE: Δ+9±2%). However, decreases in VE during baroreflex reloading are exaggerated in patients with PD in comparison to controls (PD: Δ-22±3% vs. Δ-10±4% in controls, P=0.020). Estimated tidal volume similarly increased in both groups during baroreflex unloading; however, during reloading, the inhibitory response was significantly more pronounced in PD patients (PD: Δ-20±4% vs. Δ-8±5% in controls, P=0.034). Notably, respiration rate remained stable throughout the experiments, and there were no significant differences in the magnitude of BP fluctuations between groups. In conclusion, these findings demonstrate that patients with PD exhibit altered baroreceptor-respiratory reflex responses compared to healthy controls, characterized by an exaggerated inhibitory effect on respiratory drive during baroreflex loading. Understanding the mechanisms underlying these changes could lead to targeted therapies and interventions to improve patient outcomes. CNPq, FAPDF and CAPES. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.