A cough involves bringing air in and forcing it out of the lungs. As respiratory muscles weaken, someone with DMD may not be able to cough or breathe well. In addition, infections and complications can last longer. A strong cough involves three phases:
Deep breath in
Forcefully breathe out, at first, with the vocal cords closed for a second to build up pressure
The vocal cords open and there’s a large flow of air outwards
Since the respiratory muscles allow a person to breathe in or out, as the muscles weaken so do the strength and effectiveness of the cough.
When a cough isn’t working as well as it should to clear the airways, it needs assistance. The goal in all these options is to maximize a person's ability to cough and clear his airways effectively.
There is a way of measuring the effectiveness of a cough using something called Peak Cough Flow (PCF), sometimes referred to as Cough Peak Flow (CPF). PCF measures how fast you can breathe air out when you cough. The PCF score is an indication of how well mucus and other secretions are being removed from the airways. Scores will vary so patients should talk to their doctor to see what a healthy score is for them.
This technique involves another person helping a patient cough. Someone trained in this technique presses on the patient’s abdomen while the patient coughs to make the cough more forceful.
The idea here is to stack one small breath on top of another small breath until the lungs are filled. A doctor might also refer to breath stacking as lung volume recruitment (LVR).
Breath stacking involves a mouthpiece or facemask and a manual resuscitator bag (also known as an Ambu® Bag). The manual resuscitator is an inflatable air bag that looks a little like a balloon. Squeezing the air bag sends air to the lungs.
The boy or his caregiver squeezes the bag several times in a row, while the boy holds his breath between each squeeze until his lungs are full. Then he can cough more forcefully.
These devices mechanically simulate a natural cough by inflating then helping to pull air out of the lungs. They create a greater speed in a cough than the manual assisted cough method.
When a person breathes in, the machine delivers air to the lungs to help inflate them (called positive pressure). When it’s time to breathe out, the machine helps pull air out of the lungs (called negative pressure). This changing of pressure from positive to negative helps create a more effective cough.
Boys might start with manual techniques and when those become less effective, move to mechanical devices. A doctor can help you decide which technique is best, when to initiate it, and how often to use it.
Measuring lung capacity while they’re still able to walk helps boys become familiar with how to do the test so future tests will be easier to do. By practicing the tests, they become a reliable indicator and can be performed effectively. The measurements also establish a baseline level of respiratory muscle strength. Having this history can help guide future treatment decisions. It can also help detect and manage any potential problems early.
After losing the ability to walk, it could take a while before the signs of respiratory loss become obvious. Evaluating respiratory function before problems arise lets doctors monitor progress, detect the first signs of respiratory muscle weakness, and plan the best treatment options to help keep the lungs working as well as possible.
Doctors check respiratory function because it can help signal trouble breathing now or in the future. The results can also indicate respiratory muscle strength and help measure disease progression.
Spirometry is one of the most common ways to learn how well the respiratory muscles are working. A spirometry test can gauge how DMD is progressing and influence treatment decisions. FVC, FEV1 and PEF are all measured by spirometry.
MEP (Maximal Expiratory Pressure) and MIP (Maximal Inspiratory Pressure) are indications of respiratory muscle strength. Together they measure pressure created when you inhale or exhale into a device that creates a certain amount of resistance to inhaling or exhaling. MIP measures how strongly you can breathe in, MEP measures how strongly you can breathe out.
Imagine it this way: say you have a straw in a very, very thick milkshake. You’d use all your might to inhale through your mouth and draw the milkshake up the straw. That’s the kind of pressure MIP measures—the pressure you create by trying to breathe in against a somewhat blocked tube. MEP measures the opposite—the amount of pressure you create trying to exhale against a somewhat blocked tube, like blowing the milkshake out of the straw.
Read about ways you can help maintain respiratory airway clearance.
There are ways you may be able to prevent future problems.
When the respiratory muscles weaken, complications can happen such as not being able to cough or breathe strongly. This can lead to pneumonia and other serious breathing problems. These complications may be preventable by monitoring respiratory function and talking to a doctor right away when complications happen.
As the respiratory muscles weaken, it’s harder for the body to clear the airways of secretions and mucus. This buildup can cause an infection to quickly develop into something more serious or prolong the infection. Even something that seems minor like a cold, can become serious quickly in those with DMD. So, it’s important to closely monitor any medical issues that come up.
Your respiratory system is divided into two sections: the lower and upper respiratory tracts. Each can get different types of infection.
The upper respiratory tract includes the nose, nasal cavity, and the throat.
The most frequent infection in the upper respiratory tract is the common cold, which is usually caused by a virus. A cold can quickly escalate into sinusitis or become more serious and move into the lower respiratory tract. Always watch a cold carefully, and if it starts getting worse or won't go away, talk to your doctor.
Getting a flu vaccine every year can help prevent the flu. The CDC recommends flu vaccination once a year, for people over 6 months of age, as soon as the vaccine becomes available.
The lower respiratory tract includes the windpipe that leads to the lungs as well as air sacs in the lungs that are involved in getting oxygen into the blood.
Treatment for pneumonia involves antibiotics for bacterial pneumonia and in some cases antiviral medication for viral pneumonia. There’s also a vaccine that helps protect against bacterial pneumonia. Talk to your doctor to see if vaccination is appropriate.
Learn more about what you can do to fight off illness with flu shots and vaccines.
Sometimes the first signs of respiratory muscles weakening happen at night. Tests can be done while a boy is sleeping to gauge how well his respiratory muscles are working to help a doctor determine care options.
When a person stays overnight at a special sleep center, trained experts can measure how well the breathing muscles and lungs can bring oxygen into the body and remove carbon dioxide.
In addition, when this is measured during deep sleep (REM or dream sleep when the body relaxes completely), it can pick up the early stages of respiratory failure. This would prompt using a breathing machine called a ventilator.
There is also a test that a person can do in his own bed. How does it work?
A doctor uses oxygen saturation levels to see if there’s enough oxygen in the blood at night; this is known as an oximetry test.
This at-home test is not as extensive as the test in the sleep facility, so there is some debate about its accuracy. Your care team can help you decide which test is best for you.
Read about ventilation devices to help nighttime breathing.
Typically, boys with DMD first need help breathing at night. As DMD progresses, they may also need help breathing during the day. Specially designed machines can support breathing and improve a boy’s quality of life.
There are two types of ventilation: noninvasive and invasive. Choosing which type to use is a very personal decision; what’s right for one boy may not be right for another. By talking to your care team, you can decide what type of ventilation is best for your situation.
Noninvasive devices deliver breaths into a patient via:
There’s no surgery, nothing breaks the skin, or is permanently attached to the body.
Potential benefits of noninvasive ventilation support:
Bi-level ventilation provides 2 levels of pressure. One level to push air into the lungs, then a second, lower level to allow breathing out. You may also see these named BiPAP™ machines (for bi-level positive airway pressure ventilators).
How they work:
Unlike BiPAP machines, CPAP (continuous positive airway pressure) machines deliver the same level of pressure to breathe in and out. Typically those with DMD use BiPAP because weakened respiratory muscles need extra support. The dual pressure levels of BiPAP give greater assistance to the muscles that control breathing in and little or no resistance to breathing out. CPAP machines can’t do that because they provide only one level of pressure. CPAP machines are typically for sleep apnea caused by an obstruction in the airway.
As the respiratory muscles weaken, those with DMD may need even more ventilation support.
Volume cycled ventilators deliver a specific volume of air to the lungs instead of providing pressure like a BiPAP ventilator machine does. So, volume cycled ventilators may provide more breathing support than bi-level ventilators. That’s why some doctors recommend volume cycled ventilators as DMD progresses and the respiratory muscles continue to lose strength.
Invasive ventilation involves inserting a tube in the throat to serve as an airway. Usually it’s an option considered once other noninvasive options have been explored.
Advantages of invasive ventilation:
Disdvantages of invasive ventilation:
Performing a Tracheostomy
A tracheostomy is invasive ventilation because it involves a surgical procedure. An incision is made in the neck and through the trachea (windpipe) and a tube is inserted. Air now goes in and out of the tube and not through the nose and mouth.
Having multiple experts on the team allows for cross-specialty coordination and communication. The goal is to provide broader care and support.
Specializes in caring for the heart
Explains diagnosis, how DMD is inherited, and orders and interprets genetic tests.
Manages and treats neurological conditions including DMD. Your neurologist is central to your care team.
Manages non-DMD-related health conditions.
Develops treatment techniques to improve movement.
Specializes in caring for the lungs
Registered Dietician Nutritionist (RDN)
Expert in dietary needs.
Helps DMD families find medical resources and advocates for them in the school and community.
Physical Medicine and Rehabilitation: physicians who help maximize your muscles’ ability to move
Respiratory Therapist: assesses lung function and helps develop treatment plan
Speech Language Pathologist: evaluates speech and swallowing skills and develops treatment plan
Those with DMD should see a doctor who specializes in respiratory care (a pulmonologist):