Water aerosols and cough.

Area of Science:

• Respiratory Physiology
• Neuroscience
• Clinical Medicine

Background:

• Ultrasonically nebulized water (fog) inhalation is a known cough stimulant.
• The specific sensory receptors and neural pathways mediating the cough reflex are not fully elucidated.
• Patients with Parkinson's disease and laryngectomized individuals are susceptible to chest infections, suggesting potential respiratory control deficits.

Purpose of the Study:

• To investigate the sensory and motor components of the cough reflex induced by fog inhalation.
• To evaluate cough responses in patients with Parkinson's disease and laryngectomized patients.
• To explore the role of airway rapidly adapting receptors in fog-induced cough and ventilatory responses.

Main Methods:

• Assessing cough threshold and motor response intensity (flow variables, abdominal muscle EMG) to increasing fog concentrations in humans.
• Comparing cough responses in normal subjects, patients with Parkinson's disease, and laryngectomized patients.
• Investigating the effects of nedocromil sodium on cough threshold and ventilatory parameters.

Main Results:

• Parkinson's disease patients exhibited normal cough thresholds but reduced expiratory muscle force during reflex coughing.
• Laryngectomized patients also showed normal cough thresholds but diminished muscle force for threshold stimuli, though voluntary cough was preserved.
• In normal subjects, fog inhalation increased respiratory drive and ventilation, suggesting activation of airway rapidly adapting receptors; nedocromil sodium attenuated these effects.

Conclusions:

• Impaired central motor control of expiratory muscles may contribute to inefficient airway clearing in Parkinson's disease patients.
• Preserved voluntary cough in laryngectomized patients offers a potential strategy for mucus clearance.
• Quantifying sensory and motor aspects of cough provides valuable insights for human cough research.