Chapter 4: Respiratory dysfunction and cardiovascular conditioning

Breathing issues and respiratory dysfunction are a common issue within the Parkinson’s population. They are at risk of complications for a couple of reasons; underlying disease pathology and the side effects of medication. The degeneration of the substantia nigra and loss of dopaminergenic neurons can cause changes in ventilatory parameters. Overtreatment with levodopa can cause respiratory dyskinesia which can be difficult to differentiate from complications of the disease itself. Therapy using ergo derivatives may cause pleuropulmonary fibrosis. Pneumonia resulting from respiratory issues remains a leading cause of morbidity in the Parkinson’s population. (Shill H, 2002)

In the following text, we will learn more about respiratory dysfunction from two experts in the neurology world, Dr. Ingrid Estrada-Belleman and Dr. Fernando Carrera. Let’s have a look at these insights they have so generously provided.

By Dr. Ingrid Estrada-Belleman and Dr. Fernando Carrera

Introduction

Parkinson’s disease has been associated with respiratory dysfunction since its discovery by James Parkinson. It is known to be an important cause of morbidity and mortality. Parkinson’s disease is characterized by cardinal symptoms such as: rigidness, tremor, slowness in movement (bradykinesia), and postural instability in late stages of the disease.

Clinical manifestations

There are a variety of respiratory symptoms such as dyspnea (defined as a feeling of difficult breathing), which depends on the severity of the disease and daytime somnolence secondary to a daytime lack of oxygen. Despite having different lung alterations, most patients remain asymptomatic because of their functional disability and the considerable effort needed for performing tasks.

There are different mechanisms and factors that affect breathing and can influence the degree of respiratory dysfunction. There are restrictive patterns that are secondary to an increase in the stiffness of the thorax and airflow obstruction. Some individuals can present abnormalities of the diaphragm, another important respiratory muscle.

The severity of Parkinson’s disease can be measured with the Hoehn and Yahr scale, which consists of five stages. Patients with more severe disease are confined to a wheelchair or are bedridden. In mild and moderate disease, patients are able to perform respiratory efforts without a problem, but there could be difficulty to perform repetitive “breathing tasks” due to respiratory muscle fatigue, a factor that has been related with ventilatory deterioration. Patients with Parkinson’s disease have greater respiratory effort and are less capable of completing a respiratory cycle.

Respiratory Physiology

Upper Airway Obstruction

The upper airway is the space that extends from the mouth to the main bronchi and includes the nasopharynx, larynx and trachea. The lower airway extends from the lobar bronchi to the alveolus, which is the functional unit of the lung. Air flow in the upper airway comprises atmospheric pressure (atmP) and intratracheal pressure (ItrP). In a forced inspiration, AtmP is greater than ItrP, leading to a tendency for trachea collapse. On the contrary, in a forced expiration, ItrP is greater than AtmP with a tendency to trachea expansion. When there is an obstruction, air flow is affected. Upper airway obstruction has been reported in up to 33% of patients with Parkinson’s disease. The main manifestation is a decrease in voice intensity which is the result of involvement of the arytenoid muscle and an increase in muscle fatigability, an alteration that affects 70% of patients with Parkinson’s. There are two types of airway obstruction in Parkinson’s: the first is called respiratory flutter. This is caused by oscillations of supraglottic structures and the vocal cords. The frequency of the oscillations corresponds to the tremor at rest seen in Parkinson’s. The second type of obstruction is the change in air lung volume due to neuromuscular disorders of the rib cage, which prolongs expiration. It is important to bear in mind that studies done in patients with Parkinson’s disease were performed under levodopa treatment and therefore they reported less obstruction in the respiratory tract.

Pulmonary Restrictive Pattern

Before the widespread use of levodopa, there were more severe grades of Parkinson’s with noticeable comorbidity. This is thought to be the cause of pulmonary restriction and may be secondary to kyphoscoliosis (abnormal curvature of the spine) in patients with a thorax deformity or secondary to the disease because of decreased lung elasticity caused by prolonged stiffness or dyskinesia (involuntary movements) in late stages of the disease. The intercostal muscles can develop tremor which contributes to a decrease in breathing coordination. Dopaminergics are not very effective and they have not been shown to decrease the degree of pulmonary restriction. Likewise, levodopa and dopamine agonists derived from ergotamine can develop dyskinesias in the diaphragm generating respiratory distress.

Central Ventilatory Control

Dyspnea can occur centrally, which corresponds to the central nervous system impulse that controls breathing; and peripherally, which corresponds to the abnormalities of the rib cage. Symptoms may arise from both mechanisms. The more the disease progresses, the more intolerance to exercise. This leads to the abandonment of physical activity and a rapid progression of the disease. On the other hand, patients also present an alteration in the perception of dyspnea, which tends to decrease after taking levodopa.

Complications

Two types of complications can occur, one secondary to the adverse effects of the drugs, and the other caused by the aforementioned abnormalities.

Most dopamine agonists derived from ergotamine produce lung fibrosis in 2-5% of patients. This relationship has not been shown with agents such as pramipexole, rotigotine, and ropirinole. The most frequent symptoms are a dry cough and chest pain. There may also be lung infiltrates and fluid collections on chest x-ray. This usually resolves when medication is stopped and could be due to inflammation due to serotonergic stimulation.

In the late stages of the disease, motor and non-motor symptoms may coexist – motor symptoms such as alteration in language, writing, swallowing, walking, and balance exist; also, non-motor symptoms such as cognitive alteration, psychosis, hallucinations, anxiety, depression, sleep problems, and fatigue sensation. One of the most reported complications is aspiration pneumonia caused by an alteration in the mechanisms of swallowing, mastication and cough reflex. This allows aspiration of secretions into the airway. Due to pulmonary compression, patients with restrictive patterns develop atelectasis (pulmonary collapse) which also increases the risk of infection.

Rehabilitation

Rehabilitation has been studied extensively in Parkinson’s disease. Different types of interventions have reported short-term improvement (3 months). Motor symptoms are most prevalent. Due to the inability to coordinate breathing with locomotion, more effort and energy are required.

Certain respiratory patterns have been defined depending on the predominance of symptoms and although most patients in early stages are asymptomatic, respiratory disorders have also been associated with an increase in functional disability.

Several rehabilitation methods have been tested in studies that included people with severe disease: walking, treadmill use, dancing (Waltz, foxtrot, tango), physiotherapy, and martial arts (Tai Chi or Qingong). Average duration was 30 to 60 minutes for a minimum of 3 months with the aim of creating movement strategies in the arms and legs, improving exercise resistance, balance and posture. An important increase in walking speed, improvement in walking distance of two and six minutes, mobility and functional status (Timed Up & Go Test), improvement in the Unified Parkinson’s Disease Rating Scale (UPDRS) in general, and in activities of daily life were seen. Rehabilitation can be a viable option because it has had good results.

We know that at the beginning of the disease the first respiratory disability is rapid fatigability when performing repetitive breathing tasks. Taking into account the risk of a sedentary lifestyle, it would be appropriate to perform rehabilitation models depending on the respiratory status.

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