Respiratory Care in Spinal Muscular Atrophy: Airway Clearance

Weakness in the respiratory system is a common and serious complication of spinal muscular atrophy (SMA),¹ and pulmonary disease is the primary cause of morbidity and mortality in SMA type 1 and SMA type 2 patients.² Muscle atrophy and hypotonia are directly related to the severity of respiratory complications. Indeed, severe muscle weakness and the amount of time these SMA patients spend lying down contribute to their inability to remove secretions from their lower respiratory tract and to the development of recurrent infections. These infections exacerbate muscle weakness, creating a problematic negative feedback loop.³

In SMA type 1, also known as acute SMA, or Werdnig-Hoffman disease, children cough and have a weak cry. They usually lose their ability to swallow before they reach the age of one. The weakness in their trunk and limbs spreads to intercostal muscles, preventing the development of a normal respiratory cycle.² Those who have SMA type 1 are likely to develop a host of respiratory issues before respiratory failure leads to death by the age of two. Among these complications are hypoventilation, dysphagia, pulmonary aspiration, and recurrent lower respiratory tract infections.⁴ 

For those with SMA type 2, respiratory insufficiency is the primary cause of morbidity and mortality. Ineffective cough with decreased airway clearance, insufficient development of the lungs and chest, nocturnal hypoventilation, and heightened risk for pulmonary infection are among the most common respiratory complications in this group of patients.⁵ Patients with SMA type 3 are less likely than those with SMA type 2 to have problems with swallowing, coughing, or nocturnal hypoventilation, and those with SMA type 4 do not experience respiratory problems.²

Improving airway clearance is an important part of respiratory care for many SMA patients, but there are also specific times when airways clearance is particularly important. For instance, it is critical for the successful preoperative and postoperative management of SMA patients.¹ Understanding patients’ need for airway clearance during sleep is also vital. Indeed, the medical community has begun to appreciate the importance of identifying sleep-disordered breathing when managing respiratory complications in SMA patients.¹

 Research on bronchiolar clearance in SMA suggests that continuous positive airway pressure (CPAP) may have clinical significance for those with SMA and that mechanical force could be one strategy for clearing the airway.⁷ Newer technologies offer noninvasive forms of ventilation that can help with this airway clearance. Even pulmonary physiotherapy and postural drainage can be effective in helping to move secretions out of the airway.² 

Whereas there has been some disagreement as to the best way to manage respiratory care for SMA type 1 patients – with clinicians offering these infants everything from no intervention to tracheostomy and long-term invasive ventilation⁶ – basic respiratory care in patients with forms of SMA less severe than type 1 can delay the progression of SMA and prolong patients’ lives.² Having rapid access to clinical interventions when needed can be critical for the respiratory health of these patients. The respiratory support offered could range from noninvasive ventilation to tracheostomy and mechanical ventilation. Because they are prone to lower respiratory infections, having quick access to antibiotics and staying up-to-date on vaccinations, including those against agents that can lead to severe pulmonary infections, is also important for SMA patients.²

References

1. Iannaccone ST. Modern management of spinal muscular atrophy. J Child Neurol. 2007;22(8):974-978. doi:10.1177/0883073807305670

2. Baioni MTC, Ambiel CR. Spinal muscular atrophy: diagnosis, treatment and future prospects. J Pediatr (Rio J). 2010;86(4):261-270. doi:doi:10.2223/JPED.1988

3. Wang CH, Finkel RS, Bertini ES, et al. Consensus statement for standard of care in spinal muscular atrophy. J Child Neurol. 2007;22(8):1027-1049. doi:10.1177/0883073807305788

4. Fitzgerald DA, Doumit M, Abel F. Changing respiratory expectations with the new disease trajectory of nusinersen treated spinal muscular atrophy [SMA] type 1. Paediatr Respir Rev. July 2018. doi:10.1016/j.prrv.2018.07.002

5. Gormley MC. Respiratory management of spinal muscular atrophy type 2. J Neurosci Nurs. 2014;46(6):E33-41. doi:10.1097/JNN.0000000000000080

6. Bush A, Fraser J, Jardine E, Paton J, Simonds A, Wallis C. Respiratory management of the infant with type 1 spinal muscular atrophy. Arch Dis Child. 2005;90(7):709-711. doi:10.1136/adc.2004.065961

7. Klefbeck B, Svartengren K, Camner P, et al. Lung clearance in children with Duchenne muscular dystrophy or spinal muscular atrophy with and without CPAP (continuous positive airway pressure). Exp Lung Res. 2001;27(6):469-484.