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Defective motor control of coughing in Parkinson's disease
G A Fontana1, T Pantaleo, F Lavorini
1Dipartimento di Fisiopatologia Clinica, Sezione di Fisiopatologia Respiratoria, Università di Firenze, and U. O. di Geriatria, Ospedale I.N.R.C.A., "I Fraticini," Florence, Italy. g.fontana@dfc.unifi.it
Abstract:
The high incidence of serious chest infections in patients with Parkinson's disease is unexplained, but an impairment in cough reflex may have a role. Maximal voluntary cough (MVC) and reflex cough (RC) to inhalation of ultrasonically nebulized distilled water were analyzed in patients with Parkinson's disease and age-matched control subjects by monitoring the integrated electromyographic activity (IEMG) of abdominal muscles. The peak amplitude of IEMG activity (IEMGP) was expressed as a fraction of the highest IEMGP value observed during MVC corrected to account for possible losses in abdominal muscle force due to reduced central muscle activation. Cough intensity was indexed in terms of both the IEMGP and the ratio of IEMGP to the duration of the expiratory ramp (TEC), i.e., the rate of rise of IEMG activity. Cough threshold was slightly higher in patients than in control subjects, but the difference failed to reach statistical significance. Compared with control subjects, patients displayed a lower IEMGP during maximal expiratory pressure maneuvers (PEmax), MVC, and RC (p always < 0.01); TEC during RC was longer (p < 0.01) than in controls. Consequently, the rate of rise of IEMG activity during cough was always lower in patients (p < 0. 01), especially during RC. Finally, PEmax, and both the peak and rate of rise of IEMG activity during RC were inversely related to the level of clinical disability (Spearman rank correlation coefficient, rs = -0.88, -0.86, and -0.85, respectively, p always < 0.01). The results indicate that the central neural mechanisms subserving the recruitment of motor units and/or the increase in their frequency of discharge during voluntary and, even more markedly, RC are impaired in patients with Parkinson's disease.
Insights
Patients with Parkinson's disease have impaired cough reflexes, leading to reduced cough intensity and a higher risk of chest infections. This study quanties the neural deficits in voluntary and reflex cough mechanisms in Parkinson's patients.
Area of Science:
- Neurology
- Respiratory Medicine
- Physiology
Background:
- Patients with Parkinson's disease (PD) exhibit a high incidence of serious chest infections, the cause of which remains unclear.
- A potential contributing factor is an impairment in the cough reflex, a critical protective mechanism for the airways.
Purpose of the Study:
- To investigate the functional integrity of voluntary cough (MVC) and reflex cough (RC) mechanisms in patients with PD.
- To quantify the neural deficits in motor unit recruitment and frequency modulation during cough in PD patients.
Main Methods:
- Maximal voluntary cough (MVC) and reflex cough (RC) were induced by ultrasonically nebulized distilled water.
- Integrated electromyographic activity (IEMG) of abdominal muscles was monitored to assess cough intensity and timing.
- Peak IEMG amplitude (IEMGP) and the ratio of IEMGP to expiratory duration (TEC) were analyzed, with IEMGP corrected for maximal expiratory pressure (PEmax).
Main Results:
- Patients with PD showed significantly lower IEMGP during PEmax, MVC, and RC compared to controls (p < 0.01).
- Reflex cough duration (TEC) was longer in PD patients (p < 0.01), resulting in a lower rate of rise of IEMG activity.
- Impaired cough function, including PEmax and RC parameters, correlated inversely with the severity of clinical disability in PD patients (r = -0.85 to -0.88, p < 0.01).
Conclusions:
- Central neural mechanisms responsible for motor unit recruitment and frequency modulation during voluntary and reflex cough are impaired in Parkinson's disease.
- These deficits in cough reflex function likely contribute to the increased susceptibility to chest infections observed in PD patients.
- The findings highlight the importance of addressing respiratory muscle dysfunction in the management of Parkinson's disease.