Shortness of breath is a serious and relatively common non-motor symptom experienced by individuals with Parkinson’s disease (PD). This sensation of difficult or uncomfortable breathing is often overlooked or misattributed to other conditions, yet it significantly affects quality of life. The pathology of PD, involving the loss of dopamine-producing neurons, impacts the complex system controlling respiration. This neurodegenerative process affects the respiratory system in several distinct ways: the mechanics of breathing, the upper airway, and the central control of ventilation.
Impact of Motor Symptoms on Respiratory Mechanics
The cardinal motor symptoms of Parkinson’s disease directly compromise the ability of the chest and lungs to fully expand, leading to a restrictive pattern of lung dysfunction. Rigidity, the persistent stiffness of muscles, affects the intercostal muscles between the ribs and the diaphragm. This rigidity restricts chest wall movement and prevents the full excursion of the diaphragm, resulting in shallower breaths.
Bradykinesia, the slowness and smallness of movement, causes hypokinesia of the respiratory muscles, meaning they move less than required. This leads to a reduced tidal volume, the amount of air inhaled and exhaled with each breath. The cumulative effect of muscle rigidity and hypokinesia is a progressive weakening of the respiratory muscles, resulting in reduced maximal inspiratory and expiratory pressures.
The characteristic flexed posture (kyphosis) that develops in advanced PD physically limits lung capacity by compressing the chest cavity. Stiffness in the thoracic spine and rib cage reduces overall chest compliance, making it harder to take a deep breath. These restrictive changes in lung function are strongly correlated with the severity of both bradykinesia and rigidity.
Airway Obstruction and Aspiration Risks
Upper airway issues, separate from chest wall mechanics, can also cause feelings of breathlessness in Parkinson’s disease. The muscles controlling the vocal cords and the throat are affected by the disease, leading to laryngeal dysfunction. This may manifest as dystonia, causing the vocal cords to spasm or become immobile, which physically narrows the airway.
This narrowing can produce stridor, a high-pitched, harsh breathing sound indicating significant upper airway obstruction. Many people with PD also experience dysphagia, or difficulty swallowing, which is a major factor in acute respiratory distress. Swallowing requires precise coordination between the respiratory and pharyngeal muscles to protect the windpipe.
Impaired coordination or reduced sensation can lead to aspiration, where food, liquid, or saliva enters the lungs instead of the stomach. Aspiration is a major risk factor for aspiration pneumonia, a frequent and life-threatening cause of acute shortness of breath and mortality in PD patients. This risk is often present even in those who are asymptomatic for swallowing difficulties.
Autonomic and Central Nervous System Involvement
Beyond the physical motor symptoms, neurodegeneration in Parkinson’s disease affects the central control systems that regulate involuntary breathing. The brainstem contains nuclei responsible for setting the automatic rate, rhythm, and depth of breathing. Early involvement of the brainstem can lead to dysfunction in the medullary respiratory centers.
This central failure can disrupt the normal ventilatory drive, leading to central hypoventilation, where the brain’s signal to breathe is impaired. An abnormal response to changes in blood carbon dioxide levels suggests a problem with the central chemoreflexes that monitor blood gas levels. Autonomic nervous system dysfunction common in PD can also contribute to increased airway resistance.
Dopaminergic medications used to treat PD motor symptoms can also complicate respiratory function. For instance, levodopa can induce respiratory dyskinesia, an irregular and rapid breathing pattern that typically occurs when the medication is at its peak effect. This involuntary movement of the respiratory muscles can cause subjective feelings of shortness of breath.
Managing Respiratory Symptoms in Parkinson’s Disease
Addressing shortness of breath requires a comprehensive medical evaluation to distinguish PD-related symptoms from other common causes, such as heart disease or standard lung infections. Identifying and treating non-PD causes is an essential component of management. Once other conditions are ruled out, treatment focuses on PD-specific interventions.
Medication Optimization
Optimizing anti-Parkinsonian medication timing and dosage is an effective strategy, especially to manage “wearing off” symptoms that cause increased rigidity or the presence of respiratory dyskinesia. Adjusting medication helps ensure consistent control over the motor symptoms that restrict chest movement. Advanced treatments like deep brain stimulation (DBS) can also be considered to improve motor fluctuations that negatively impact breathing.
Physical and Respiratory Therapy
Physical therapy focuses on respiratory muscle strength training (RMST) to improve both inspiratory and expiratory muscle function. Expiratory muscle strength training (EMST) specifically improves cough effectiveness and reduces the risk of aspiration. Postural training and aerobic exercise are encouraged to improve lung expansion and overall respiratory endurance.
Managing Swallowing Issues
Speech-language pathologists play a significant role in managing dysphagia, a major risk factor for acute respiratory issues. They provide swallowing safety techniques and recommend dietary modifications to prevent aspiration. Early diagnosis and intervention for swallowing problems are important steps in preventing aspiration pneumonia.