Disorders of Ventilation: Weakness, Stiffness, and Mobilization

The number of children who require chronic mechanical ventilation has grown with improvements in care, assistive technologies, and philosophical approaches to some progressive diseases. The causes of chronic respiratory failure include respiratory pump dysfunction, abnormal respiratory drive, and airway, parenchymal, or pulmonary vascular disorders. The goals of chronic mechanical ventilatory support, however, are independent of the etiology of respiratory failure. Children considered for chronic mechanical ventilation at home must be medically stable, have a family committed to learning all aspects of the child's care, and adequate funding to support the cost of equipment, supplies, and skilled care. Technological improvements in equipment have broadened options to improve patient-ventilator synchrony and comfort. Outcomes of ventilator-assisted children depend in part on the etiology of their underlying illness, with those diseases likely to improve over time also being the most likely to permit liberation from chronic ventilatory support. Underlying disease impacts survival as well, although some children with chronic respiratory failure die of complications from other comorbidities or from tracheostomy-related accidents. Ventilator-assisted childrens' quality of life is generally good, but their care is stressful for their families. Challenges in developing better equipment for very young patients, and in supporting patients and their families to gain better access to public resources like school, transportation, and housing as well as services to avoid caregiver fatigue, take on increased importance as this population continues to grow. Health care systems must also develop transition programs for older ventilator-dependent children as they reach adulthood.

Spinal muscular atrophy [SMA] is the most common genetic cause of childhood mortality, primarily from the most severe form SMA type 1. It is a severe, progressive motor neurone disease, affecting the lower brainstem nuclei and the spinal cord. There is a graded level of severity with SMA children from a practical viewpoint described as “Non-sitters”, “Sitters” and less commonly, “Ambulant” correlating with SMA Type 0/Type 1, Type 2 and Type 3 respectively. Children with SMA Type 0 have a severe neonatal form whilst those with SMA Type 1 develop hypoventilation, pulmonary aspiration, recurrent lower respiratory tract infections, dysphagia and failure to thrive before usually succumbing to respiratory failure and death before the age of 2 years. The recent introduction of the antisense oligonucleotide nusinersen into clinical practice in certain countries, following limited trials of less than two years duration, has altered the treatment landscape and improved the outlook considerably for SMN1 related SMA. Approximately 70% of infants appear to have a clinically significant response to nusinersen with improved motor function. It appears the earlier the treatment is initiated the better the response. There are other rarer genetic forms of SMA that are not treated with nusinersen. Clinical expectations will change although it is unclear as yet what the extent of response will mean in terms of screening initiatives [e.g., newborn screening], “preventative strategies” to maintain respiratory wellbeing, timing of introduction of respiratory supports, and prolonged life expectancy for the subcategory of children with treated SMA type 1. This article provides a review of the strategies available for supporting children with respiratory complications of SMA, with a particular emphasis on SMA Type 1.