With age, the respiratory muscles of patients with Duchenne muscular dystrophy (DMD) become progressively weaker, but a proper pulmonary care program can prevent, address and manage respiratory complications.
DMD is a genetic disorder characterized by progressive muscle degeneration and weakness. This almost exclusively male syndrome stems from a lack of dystrophin, a protein that helps keep muscle cells intact. Patients are typically diagnosed as they become symptomatic between the ages of 3 and 5.
According to Daniel W. Sheehan, PhD, MD, who manages the respiratory care of patients with neuromuscular diseases including spinal muscle atrophy, DMD, and other muscular dystrophies, a proactive anticipatory approach is best.
“It’s important to follow the patient’s respiratory muscle strength over time because red flags will appear throughout the process,” said Sheehan, who is a UBMD pediatric pulmonologist at Women and Children’s Hospital of Buffalo, and clinical associate professor of pediatrics at the Jacobs School of Medicine and Biomedical Sciences at the University at Buffalo, The State University of New York.
For optimal care delivery, Sheehan recommends a team philosophy, comprising physicians and respiratory therapists with expertise in non-invasive neuromuscular respiratory care.
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Progression of Respiratory Muscle Weakness
The vital capacity of DMD patients typically falls or plateaus after loss of ambulation. Without a trained professional who knows what to look for or pulmonary function testing, this significant change in respiratory health could be overlooked. “Because the patient isn’t walking, he’s not getting short of breath,” Sheehan explained.
“After a patient loses ambulation, it’s important to have two yearly pulmonary function evaluations, because some won’t show signs of hypoventilation,” Sheehan told ADVANCE. This methodical care model is addressed in the CDC’s 2010 DMD Care Considerations guidelines.
In the mid-to-late teenage years, the cough of a patient with DMD will become significantly weak. “For some individuals with neuromuscular weakness, throat clearing is the extent of their cough because they aren’t able to take a deep breath in and are not able to use chest and abdominal muscles to produce a forceful cough,” Sheehan qualified.
Also in the mid-to-late-teenage years, patients begin to hypoventilate while sleeping. “When we breathe in, we bring oxygen in and blow out carbon dioxide,” explained Sheehan. “When we don’t breathe deep enough during sleep, then the body’s oxygen level goes down and the body’s carbon dioxide goes up.” Patients who have progressed to this level of respiratory deterioration may suffer from restless sleep, nightmares, morning headaches, mood changes, snoring or night sweats. “We also watch for changes in school performance for high school or college students,” Sheehan shared.
In the late teens and 20s, some individuals will start to hypoventilate while they are awake as well. As a result, these patients will have a lower body oxygen number (oxyhemoglobin saturation </= 95%) and higher carbon dioxide level. Patients who hypoventilate when awake may have a general shortness of breath, soft voice and may exhibit signs of anxiety. When 24-hour ventilation support becomes necessary, ventilation can continue non-invasively with a nasal mask, nasal pillows or a sip-mouthpiece.
Emergency and Hospital Care
Sheehan and his team prepare families for emergency events with information about emergency protocols and encourage them to bring their respiratory assist devices to the emergency department. His colleague, Lisa Flattery-Walsh, RRT, Women and Children’s Hospital of Buffalo, also stressed that “these patients may need oxygen in the emergency room, but more importantly, they need to get secretions out of their lungs and have ventilation supported. If a patient is just given oxygen, then it masks the real problem.”
According to Flattery-Walsh, the goal is breathing room air. “It’s not like an asthma patient needing oxygen,” she qualified. “DMD patients need ventilation supported and need cough assist therapy.”
With respect to care in the intensive care unit (ICU), Sheehan relayed, “a young adult with DMD who is intubated can present challenges for a healthcare provider (HCP) who is not familiar with the diagnosis. The HCP might assume that since the patient has minimal use of their arms or legs that they are not extubatable; this can result in unneeded tracheostomies. For the past 10 years, when a patient is intubated because of respiratory distress, we follow a protocol that maximizes airway clearance before extubation to noninvasive ventilation.”
Sheehan pointed out that education and home follow-up are also incredibly important to care plans. “Home care companies deliver devices to the patients and instruct on their use, but also provide valuable information back to the team,” he said.
What Needs to be Done?
The CDC-funded Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet) collects critical information about care services received by individuals with Duchenne and Becker Muscular Dystrophies. Working with MD STARnet, Sheehan and others have discovered great variability monitoring of lung function despite the 2004 ATS consensus statement. “We hope to uncover barriers that prevent guidelines from being implemented,” he said.
Sheehan also suggested that there is a shortage of RTs and pulmonologists trained in noninvasive neuromuscular care. “Additional training is needed for this generation of pulmonologists as well as the next generation of pulmonologists caring for this population,” he observed.
The American Thoracic Society and American Academy of Chest Physicians offers short courses in neuromuscular respiratory care, but they are not always offered annually. Sheehan strongly feels greater training needs to occur in adult and pediatric pulmonology fellowships.
Finally, Sheehan called for a greater partnership between pulmonologists, respiratory therapists and neuromuscular clinics. “Although there is a complexity in having multidisciplinary clinics that approach specific diseases, inter-professional teams deliver the highest quality and safest care,” he concluded.
Rebecca Mayer Knutsen is a staff writer at ADVANCE.
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