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Chapter 4: Your Child's Physical Needs
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PRESERVING RESPIRATORY FUNCTION

Most people, when they think of muscular dystrophy, think of wheelchairs and braces and the problems imposed by lack of mobility. But the most serious threat to health and life in DMD is impaired respiratory function, brought about by weakened respiratory muscles.

Respiratory function usually remains adequate until the boy with DMD is about 10 years old. Usually sometime between 10 and 14, respiratory muscle function starts to decline enough to produce changes in the way the lungs pull air in and push it out.

The diaphragm is a flat muscle that sits under the lungs. When we breathe in (inhale), the diaphragm goes down, pulling air into the lungs (like pulling back on the plunger of a syringe). When we breathe out (exhale), the diaphragm goes up, squeezing air out of the lungs.

In DMD, when the diaphragm becomes weakened and stiffened (with scar tissue), it's much less effective at its job, and breathing becomes difficult.

At the same time, other muscles, such as those between the ribs (the intercostal muscles) also weaken, so they can't help much either. The muscles that allow coughing also weaken.

When air exchange is no longer effective because the lungs aren't moving enough air in and out, the amount of oxygen in the blood gradually falls, and the amount of carbon dioxide builds up. (You may hear the term hypoxia, which means lack of oxygen, or occasionally hypercapnia, which means too much carbon dioxide.) Headaches, mental dullness, and difficulty concentrating or staying awake during the day are common signs of hypoxia and hypercapnia. People sometimes report nightmares, particularly involving drowning or suffocating, when they're not exchanging enough air during the night. Sometimes these symptoms are mistaken for depression or anxiety and treated with psychoactive drugs, when what's really needed is ventilatory support.

Sometimes oxygen is prescribed and, in some circumstances, it helps. However, the main problem for most boys with DMD is the inability to move enough air in and out of the lungs, and this is the primary problem that has to be addressed.

In addition to the poor gas exchange, weakness in the muscles of respiration and coughing set up conditions for infectious organisms to take root. The tiny air sacs (known as alveoli) in the lungs stay collapsed, sometimes trapping secretions. When secretions build up, they provide a good "soil" for bacteria and viruses to grow. To make matters worse, the boy with weakened respiratory muscles also has difficulty coughing, so the normal defenses people use to rid themselves of excess secretions aren't operating. A simple cold can quickly progress to pneumonia in a person with a lot of collapsed air sacs and an inadequate cough.

During infections, it's important to get prompt treatment before a respiratory emergency occurs. Many experts recommend the use of a coughing machine (the main brand is the Emerson In-exsufflator).

In addition, your doctor or physical or respiratory therapist can show you how to assist your child to cough up secretions with some manual maneuvers. These are known as assisted cough and percussion and postural drainage.

In general, as respiratory muscles and cough muscles weaken, it's important to start methods to keep the lungs and bronchial tree free from secretions. Assisted ventilation is often needed at this time, to correct the most important problem: insufficient air flow in and out of the lungs.

When the respiratory muscles get so weak that air can't be moved in and out of the lungs dependably, it becomes necessary to support these muscles, with either positive or negative pressure. It's at this point that assisted ventilation is often brought up as a new facet of the boy's therapy. It's useful to think of assisted ventilation as just another kind of brace, a "splint" for tired muscles -- in this case, the respiratory muscles. (It's important to remember that the modern approach to assisted ventilation is very different from that of decades ago, when choices about ventilation were considered "end-of-life" decisions and when ventilators meant being in an institution.)

photo: man using coughing machine
A man with muscular dystrophy uses a Cofflator®, an older style coughing machine.

Non-Invasive Ventilation

Non-invasive ventilation is so named to contrast it with invasive ventilation, the kind of ventilation that involves a tracheostomy, a surgically created hole in the throat (actually, in the trachea, which leads down to the lungs).

Non-invasive ventilation is done with devices external to the body. It can be used as needed during the day or night and can be easily removed when not needed. Often, it's used during the night and intermittently or not at all during the day, at least at first. Later, it may be needed all the time.

A simple way to deliver non-invasive ventilation is with a mask (see photos at left). The mask should fit snugly over the boy's face. The machine (ventilator) delivers a volume of air under pressure to the lungs. Modern ventilators come in many forms. Your doctors and respiratory therapists will help you decide what kind of ventilator to get and how to use it.

Experts in ventilation recommend a custom-designed mask, so that it fits very snugly but comfortably over the face. (Air leaks interfere with the pressure of air delivered to the lungs.) There are many kinds of masks available. You can also deliver assisted ventilation only through the nose or only through the mouth, using different kinds of devices. You may decide to use one type (for example, a mouth "pipe" mounted on the wheelchair) during the day and another (for example, a facial mask) during the night.

Another way to deliver ventilatory assistance is with negative pressure, which is done by creating lower pressure outside the lungs than inside them -- exactly what the diaphragm normally does. (This concept is derived from the old "iron lungs" of the 1940s and '50s.) As pressure decreases outside the lungs, the lungs naturally expand.

Today's negative pressure ventilators come in the form of jackets, vests and belts. These can be used only if the boy doesn't have a spinal curvature, however. Like the mask, they can be removed when not needed. There are updated versions of iron lungs, which a few patients prefer to other forms of ventilation. They're comfortable to sleep in. (The belt type of ventilatory assistance is actually a combination of positive and negative pressure. It pushes in with positive pressure to help with exhalation and pulls away, exerting negative pressure, to help with inhalation. It can only be used if the boy has a relatively straight spine.)

Many boys with DMD have found their general health and energy level much improved after they started using non-invasive ventilation during the night. One person commented that using nighttime ventilation felt like recharging his batteries. Energy for schoolwork, computers and friends can get a real boost after air exchange is improved.

photo: man using ventilation device while sleeping

photo: man sleeping with vent device
Non-invasive ventilation can be delivered during the night. The mask should fit snugly. (Top photo by Respironics Inc.)

Invasive (Tracheostomy) Ventilation

A tracheostomy is another way to deliver ventilatory assistance. Instead of pumping air into the nose or mouth, or applying negative pressure to the outside of the body, tracheostomy ventilation puts the air into a small tube inserted into the person's trachea in the throat.

Tracheostomy-delivered ventilation is sometimes preferred by physicians because it has a certain dependability. The air goes directly into the lungs (unless there's an obstruction in the tube), with no worries about a leaky mask or an ill-fitting negative pressure vest.

Many people associate tracheostomy ventilation with permanent ventilation. This is because, in many conditions where trachs are used, such as high spinal cord injury, there is no respiratory muscle activity and mechanical ventilation is needed all the time. However, in DMD, where there is usually some respiratory muscle control, trach-delivered ventilation doesn't have to be full time. The family can be taught to disconnect the trach for a certain amount of time during the day and then reconnect it (for example, overnight).

Another myth about trachs is that you can't talk with one. Most modern trachs are designed with valves to allow talking.

Tracheostomies aren't without their problems, however. Since humans aren't designed to have a plastic tube in the trachea, the presence of one is an unwelcome addition from the body's point of view. Frequent inflammations, infections and excess secretions are common with trachs. A tracheostomy is a sort of "open wound," necessitating careful attention and precautions. Some schools object to students with tracheostomies, citing insurance and liability problems.

Many people (for example, actor Christopher Reeve) have trachs and live well with them, but non-invasive ventilation in muscular dystrophy is a growing trend.

Get an Early Start on Respiratory Care

Many physicians now recommend a baseline respiratory function assessment at the time the child's DMD is first diagnosed, with re-evaluations at least yearly after that and more often if problems develop.

Careful monitoring of respiratory function, clearing of secretions with assisted coughing and other methods mentioned above, and prompt treatment of respiratory infections can help your child avoid the worst-case scenario: an emergency room visit that leads to medical interventions you haven't had time to plan for.

If a child with muscular dystrophy comes to a hospital emergency room in acute respiratory distress (for example, with an infection), the doctors are unlikely to be familiar with his condition and are likely to put a tube down his throat (intubate him) and start him on a ventilator. Intubation isn't a permanent solution, just an emergency measure, so after a few days, the next step has to be faced. In all likelihood, it will be a tracheostomy, because "weaning" from intubation to non-invasive ventilation in a boy with DMD takes special skill and experience.

photo: boys with traches
Tracheostomy ventilation puts air into a small tube in the throat.

Start talking to your doctor early about respiratory care, and think about your options. Get a referral to the pulmonology or respiratory therapy department of your hospital, and try to see therapists who are experienced with neuromuscular conditions. (Unfortunately, these are still a rarity.) Ask your doctor or therapist whether respiratory exercises or activities such as singing would be beneficial.

Start giving yourself some background in the subject. For some insight into different aspects of life with assisted ventilation, you may want to look at the I.V.U.N. News, the newsletter of the International Ventilator Users Network.

If your son is mature enough, involve him in the research and decision making before an emergency happens.

(Note: Traveling with a ventilator is entirely possible, but families should know that people with marginal respiratory function and low oxygen levels will have trouble at high altitudes.)

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