Respiratory Care in Neuromuscular Disorders

Diagnostic Evaluation

• The American Thoracic Society recommends respiratory muscle strength assessment through maximum inspiratory and expiratory pressures (MIP/MEP) or sniff nasal inspiratory pressure (SNIP) to evaluate respiratory function in patients with neuromuscular disorders 1
• Peak cough flow measurement is used to assess cough effectiveness, with values less than 270 L/min indicating ineffective cough 1
• Body plethysmography is the preferred method for measuring total lung capacity (TLC) when available, providing accurate measurements of lung volume, as recommended by the European Respiratory Society guidelines 2, 3
• Helium dilution technique is an alternative for measuring TLC when plethysmography is not feasible, especially for patients with mobility limitations, as recommended by the European Respiratory Society 4
• High-resolution CT (HRCT) of the chest is essential for identifying parenchymal abnormalities, as suggested by the American Thoracic Society 2
• Diffusing capacity (DLCO) measurement is necessary to assess gas exchange, as recommended by the European Respiratory Society 4
• The following table summarizes the key diagnostic considerations:

5, 3, 6, 7, 8, 9

• Regular spirometry (FVC, FEV1) should be performed every 3-6 months initially to monitor respiratory function, as recommended by the American College of Chest Physicians 2
• Pulse oximetry should be used to assess for hypoxemia, and arterial blood gas analysis should be considered if hypercapnia is suspected, as suggested by the American Thoracic Society 10
• Respiratory muscle strength should be assessed through maximum inspiratory and expiratory pressures, as recommended by the American Association for Respiratory Care 10
• Peak cough flow measurement (<270 L/min indicates ineffective cough) should be performed to evaluate cough effectiveness, as suggested by the American Thoracic Society 10

Ventilatory Support

• The American College of Chest Physicians recommends considering non-invasive ventilation (NIV) in patients with evidence of sleep-disordered breathing or hypoventilation on polysomnography, abnormal pulmonary function tests, or overnight oximetry showing desaturation 1
• NIV settings should be individualized to achieve ventilation goals by adjusting mode of ventilation, inspiratory time, and inspiratory and expiratory pressures, according to the American College of Chest Physicians 1
• For patients with preserved bulbar function using NIV, the American College of Chest Physicians suggests considering mouthpiece ventilation (MPV) for daytime support 1
• The American Thoracic Society recommends using controlled oxygen therapy to achieve a target saturation of 88-92% if hypoxemia is present, with a strength of evidence based on moderate-quality evidence 11

Pharmacological Interventions

• The American College of Chest Physicians recommends considering anticholinergic medications for sialorrhea in patients with neuromuscular disorders 1
• For progressive pulmonary fibrosis, antifibrotic agents (nintedanib, pirfenidone) should be considered, as recommended by the American Thoracic Society 2
• Avoid high-dose systemic corticosteroids for long-term management, as they have not been shown to improve lung function in many chronic lung diseases and are associated with numerous adverse effects, as stated in the European Respiratory Journal 12
• The American College of Chest Physicians recommends a trial of bronchodilator therapy (LABA/LAMA) given the significant obstructive component, and the American College of Physicians suggests considering adding inhaled corticosteroids if features suggest asthma or significant bronchodilator response 13, 14

Advanced Care Planning

• The American College of Chest Physicians suggests starting discussions regarding the use of mechanical ventilation early in the course of illness, including goals of care, potential need for institutionalization, and caregiver burden 1
• The American Thoracic Society recommends not attempting to "wean" patients with chronic neuromuscular causes of restrictive ventilatory impairment from ventilatory support, as this is not a realistic goal, based on high-quality evidence 15
• A multidisciplinary approach, including collaboration between pulmonologists, rheumatologists, and radiologists, is essential for complex cases, especially connective tissue disease-related interstitial lung disease (ILD), as recommended by the European Respiratory Society 2

Monitoring and Treatment

• Serial spirometry is essential to assess progression and treatment response, with FEV1 being the primary measurement for monitoring obstructive disease and FVC for monitoring the restrictive component, as recommended by the American Thoracic Society 5
• Obstructive lung disease is characterized by a reduced FEV1/FVC ratio (<5th percentile of predicted), reduced FEV1, and increased FRC, RV, TLC, and RV/TLC due to air trapping, as noted by the European Respiratory Society 3
• Restrictive lung disease is characterized by a normal or increased FEV1/FVC ratio, reduced TLC, and reduced VC, as noted by the European Respiratory Society 3
• Mixed defects are characterized by both FEV1/FVC and TLC below the 5th percentiles of predicted values, as noted by the European Respiratory Society 3
• Obstructive disease severity can be graded based on FEV1 % predicted, with mild (FEV1 ≥70% predicted), moderate (FEV1 50-69% predicted), and severe (FEV1 <50% predicted) categories, as recommended by the European Respiratory Society 16
• Airway clearance techniques should be used for patients with ineffective cough, as suggested by the American Association for Respiratory Care 10
• For the restrictive component, treatment depends on the underlying cause identified through additional testing, and if interstitial lung disease is found, referral to a specialist for consideration of specific therapies is recommended, according to the European Respiratory Review 17