Muscular dystrophy is a group of conditions characterized by progressive muscle weakness. In addition to affecting muscles used for movement, the disease can cause weakness in muscles needed for respiration, which can result in breathing problems.
Trouble breathing means that the body isn’t getting enough oxygen. Common respiratory symptoms in muscular dystrophy include shortness of breath, wheezing, or abnormally fast and shallow breaths. Breathing problems also can cause sleep disturbances if the person isn’t getting enough oxygen while asleep.
Causes of breathing problems
One of the most important respiratory muscles is the diaphragm, which sits just below the lungs and helps in the process of inhalation to supply oxygen to the lungs. The weakening of the diaphragm in people with muscular dystrophy results in reduced oxygen intake and decreased lung function.
Different muscles are involved in exhalation to remove carbon dioxide from the body. In patients, the excessive workload on the lungs, due to poor diaphragm function and the weakening of abdominal muscles, hinders the elimination of carbon dioxide.
Weakness in the muscles of the upper respiratory tract — the nose, mouth, throat, and voice box — can cause difficulty breathing, particularly during sleep. This makes muscular dystrophy patients prone to breathing problems such as sleep apnea, when a person temporarily stops breathing during sleep.
Respiratory muscles also support coughing, and their breakdown makes coughing difficult. Difficulty coughing, in turn, can make it harder to clear mucus and other substances from the lungs and airways.
Postural problems such as scoliosis (the abnormal sideways curvature of the spine) affects the structure of the chest wall, and can also contribute to breathing problems.
Testing the lungs
To track and manage breathing problems, muscular dystrophy patients should have their lung function evaluated regularly starting in childhood. Generally, lung testing is done annually while patients are able to walk, and every six months if they are no longer able to.
The most common lung function test is called spirometry, which basically involves measuring how much air a person can breathe out in a forced breath. This is used to calculate the forced expiratory volume, the amount of air that can be exhaled in a specific amount of time, and the forced vital capacity, or the total air exhaled.
Other tests may be used to measure how much pressure the lungs can exert while breathing in or out — referred to as maximal inspiratory pressure and maximal expiratory pressure, respectively — or the strength of a person’s cough, often measured with peak cough flow.
Pulse oximetry is a simple test to measure how much oxygen is in the blood, an indicator of lung function. Sleep studies may be helpful for identifying breathing problems that occur during sleep.
Treatment and management
Treatment to address breathing problems in people with muscular dystrophy is tailored based on their breathing symptoms.
Children with muscular dystrophy are prone to respiratory infections such as pneumonia so a pneumonia vaccination is recommended as a preventive measure. Annual vaccines against the seasonal flu are also recommended for people with muscular dystrophy.
A number of medications may help alleviate respiratory symptoms, including bronchodilators (to widen airways), mucolytics (to help break down mucus), and/or decongestants, which help to decrease swelling and inflammation.
For acute respiratory infections, antibiotics are prescribed to kill disease-causing bacteria.
Physiotherapy can also help manage scoliosis. Surgery may be required for more severe cases of scoliosis to relieve the pressure on respiratory muscles and ease breathing.
Ventilation can help patients with respiratory failure or hypoventilation (excessively slow breathing) to breathe normally using non-invasive as well as invasive means. Non-invasive ventilation involves using a face mask, whereas invasive ventilation involves inserting a tube into the windpipe, either through the patient’s mouth or nose.
Last updated: Jan. 13, 2022, by Marisa Wexler MS
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