What is the recommended treatment for a cough in a patient with Duchenne muscular dystrophy (DMD)?

Management of Cough in Duchenne Muscular Dystrophy

Patients with DMD and impaired cough (peak cough flow <270 L/min or maximal expiratory pressure <60 cm H2O) should use mechanical insufflation-exsufflation (MI-E) devices combined with manually assisted cough techniques to prevent respiratory complications and hospitalization. 1

Assessment of Cough Effectiveness

Before initiating treatment, measure the following parameters to determine cough impairment:

• Peak cough flow (PCF): Values <270 L/min indicate need for assisted cough technologies 1
• Maximal expiratory pressure (MEP): Values <60 cm H2O correlate with ineffective cough 1
• Vital capacity and maximum insufflation capacity: Track progressive respiratory muscle weakness 1
• Home pulse oximetry: Monitor effectiveness of airway clearance during respiratory illnesses 1

Critical thresholds exist where cough becomes completely ineffective—PCF around 160 L/min is associated with inability to clear secretions and increased risk of hospitalization, particularly when scoliosis prevents optimal manual assistance 1

Primary Treatment Approach: Mechanical Insufflation-Exsufflation

The American Thoracic Society strongly supports MI-E as the preferred method for cough augmentation in DMD patients. 1

Why MI-E is Superior

• Generates higher peak cough flows than breath stacking or manual assistance alone 1
• Prevents hospitalization and need for tracheostomy when PCF falls to 160 L/min 1
• Clears secretions from peripheral airways (unlike traditional suctioning) 1
• Can be used through endotracheal tubes in intubated patients 1
• Avoids mucosal trauma and improves patient comfort compared to direct tracheal suctioning 1

MI-E Technique

The device provides positive pressure breath (insufflation) followed by negative pressure exsufflation to simulate an effective cough 1. Use postoperatively or during respiratory infections when pain or weakness prevents spontaneous coughing 1.

Reported Complications (Generally Mild)

• Transient nausea and abdominal distention 1
• Bradycardia and tachycardia 1

Complementary Manual Techniques

Combine MI-E with manually assisted cough maneuvers for optimal results 1:

Inspiratory Assistance Methods

• Air stacking: Taking serial tidal breaths without exhaling between them improves maximum insufflation capacity 1
• Glossopharyngeal breathing: Forcing air into lungs using mouth muscles 1
• Bag-mask ventilation: Using self-inflating bag with positive pressure 1

Expiratory Augmentation

Push on upper abdomen or chest wall synchronized with the patient's cough effort to augment forced exhalation 1

When to Initiate Assisted Cough

Start teaching airway clearance strategies early and employ them aggressively at the first sign of difficulty. 1

Specific indications include:

• Clinical history suggesting difficulty with airway clearance 1
• PCF <270 L/min in teenage or adult patients 1
• MEP <60 cm H2O 1
• During any respiratory infection (baseline measurements don't guarantee adequate clearance when respiratory muscle function deteriorates acutely) 1

Postoperative Management

After general anesthesia or procedures, particularly spine/chest/abdomen surgery 1:

• Use MI-E in all DMD patients with impaired cough (PCF <270 L/min or MEP <60 cm H2O) 1
• Benefits include cough augmentation and deep-lung insufflation to treat/prevent atelectasis 1
• MI-E is especially useful when pain prevents spontaneous coughing 1

Critical Pitfall: Oxygen Therapy

Use supplemental oxygen cautiously—it can mask hypoventilation and atelectasis without treating the underlying cause. 1

• Monitor SpO2 continuously but also assess carbon dioxide levels via blood gas or capnography 1
• Determine if hypoxemia is due to hypoventilation, atelectasis, or airway secretions 1
• Treat the underlying cause rather than simply correcting hypoxemia 1
• Oxygen may impair central respiratory drive 1

Alternative Techniques (Limited Evidence)

Mucus Mobilization Devices

• Intrapulmonary percussive ventilation: May resolve persistent consolidations refractory to conventional therapies, but limited data in DMD 1
• High-frequency chest wall oscillation: Used in neuromuscular weakness but no published data to support recommendation 1

Important caveat: Any airway clearance device requiring normal cough is less effective in DMD without concurrent assisted cough 1

Bronchoscopy

Reserve bronchoscopy only for persistent atelectasis after all noninvasive techniques have failed and a mucus plug is suspected. 1 It has not proven beneficial as routine therapy 1.

Monitoring During Respiratory Illness

• Prescribe home pulse oximetry when maximum assisted cough PCF falls below 300 L/min 2
• Use oximetry to identify when to intensify airway clearance 1
• Increase MI-E frequency during intercurrent respiratory infections 2
• Return SpO2 to ≥95% using continuous NIV and mechanically assisted cough as needed 2

Integration with Ventilatory Support

Patients requiring noninvasive positive pressure ventilation (NPPV) should continue assisted cough techniques 1. Consider extubating directly to NPPV in patients with FVC <50% predicted, delaying extubation until respiratory secretions are well controlled 1.