What are the treatment guidelines for respiratory distress in Motor Neuron Disease (MND)?

Treatment Guidelines for Respiratory Distress in Motor Neuron Disease

For patients with MND experiencing respiratory distress, initiate noninvasive ventilation (NIV) immediately when pulmonary function criteria are met or symptoms develop, using individualized pressure settings with ongoing optimization of secretion management, and do not delay intubation if NIV fails. 1

Monitoring and Early Detection

Perform pulmonary function testing every 6 months minimum to detect respiratory decline before crisis develops, measuring: 1

• Forced vital capacity (FVC) or slow vital capacity (SVC)
• Maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP), or sniff nasal inspiratory pressure (SNIP)
• Peak cough flow (PCF)

Recognize early symptoms of respiratory insufficiency that warrant immediate evaluation, even before acidosis develops: 1

• Morning headaches
• Fatigue and daytime somnolence
• Concentration or memory difficulties
• Orthopnea or shortness of breath
• Unrefreshing sleep with snoring, gasping, or witnessed apneas

Criteria for NIV Initiation

Initiate NIV when any of the following criteria are met: 1

Pulmonary Function Criteria:

• FVC <80% predicted WITH symptoms, or FVC <50% predicted without symptoms 1
• MIP <60 cm H₂O or MEP <40 cm H₂O 1
• PCF <270 L/min for age ≥12 years 1
• SNIP <70 cm H₂O in males or <60 cm H₂O in females for age ≥12 years 1

Overnight Oximetry/Blood Gas Criteria:

• SpO₂ ≤90% for ≥2% of sleep time 1
• PaCO₂ on arterial blood gas >45 mm Hg 1

Polysomnography Criteria (if performed):

• Apnea-hypopnea index ≥5 events/hour in adults 1
• SpO₂ ≤88% for at least 5 minutes continuously in adults 1

Critical caveat for MND specifically: Consider NIV in any breathless or acutely unwell MND patient even when normocapnic if vital capacity is <1 L and respiratory rate >20, as deterioration can be rapid. 1

NIV Settings and Optimization

Use controlled ventilation modes as triggering may be ineffective in MND, with initial pressure support typically 8-12 cm H₂O pressure difference (low pressures compared to other conditions). 1

Optimize NIV by adjusting: 1

• Mode of ventilation (no strong evidence favors one mode, but backup respiratory rate may improve patient-ventilator synchrony)
• Inspiratory time
• Inspiratory and expiratory pressures
• Set inspiratory/expiratory time ratio at 1:1 initially to allow adequate inspiration time 1

Monitor ongoing effectiveness through: 1

• Sleep quality assessment
• Digital ventilator downloads for leak detection
• Oximetry and capnography where available
• Patient comfort and tolerance

Special Considerations for Bulbar Dysfunction

Patients with bulbar impairment face significant challenges as they may not tolerate NIV or achieve adequate ventilation. 1, 2

For bulbar MND patients specifically: 2

• Trial NIV early but anticipate potential failure
• Use higher EPAP to overcome upper airway obstruction 1
• Place in HDU/ICU given higher failure risk and potential for rapid deterioration 2
• Do not delay intubation if NIV is failing 1, 2

Secretion Management (Critical in MND)

Implement aggressive secretion clearance strategies: 2

First-line:

• Oral anticholinergic medication for sialorrhea control 2
• Consider anticholinergic patch for longer-acting control 2

Second-line:

• Botulinum toxin injections to salivary glands if anticholinergics fail or cause intolerable side effects 2

Mechanical clearance:

• Lung volume recruitment (breath stacking) using handheld resuscitation bag or mouthpiece for patients with reduced cough effectiveness, requiring caregiver training 2
• Mechanical insufflation-exsufflation (MI-E) when alternative techniques cannot adequately improve cough effectiveness, essential when secretion clearance becomes inadequate 1, 2

Daytime Ventilatory Support

For patients with preserved bulbar function using nocturnal NIV, consider mouthpiece ventilation (MPV) for daytime ventilatory support as an adjunct. 1

Important limitation: Progressive bulbar symptoms in conditions like ALS may limit the use of MPV over time. 1

Transition to Invasive Mechanical Ventilation

Consider invasive home mechanical ventilation via tracheostomy when: 1, 2

• NIV fails or patient is intolerant of NIV (including extended daytime use)
• Worsening bulbar function develops
• Frequent aspiration occurs
• Insufficient cough persists despite adequate secretion management
• Episodes of chest infection recur despite optimal management
• Declining lung function continues

Start discussions about mechanical ventilation early in the disease course, including: 1, 2

• Goals of care
• Potential need for institutionalization
• Burden on caregivers
• Patient preferences and quality-of-life considerations
• Available resources (cost and care providers)

Oxygen Therapy

Use controlled oxygen therapy cautiously to achieve target saturations of 88-92%, as supplemental oxygen corrects hypoxemia without treating underlying hypoventilation or atelectasis and may impair central respiratory drive. 1, 2

Critical Pitfalls to Avoid

Do not wait for respiratory acidosis to develop before initiating NIV in MND patients—any elevation of PaCO₂ may herald an impending crisis due to reduced respiratory reserve. 1

Do not delay intubation if NIV is failing, unless escalation to invasive ventilation is not desired by the patient or deemed inappropriate, as extubation from invasive mechanical ventilation may be difficult in these patients. 1, 2

Polysomnography is not necessary for adult patients to initiate NIV—pulmonary function test criteria alone may be adequate, though sleep testing can be helpful when concern exists that PFT and clinical evaluation are not capturing complications. 1

Recognize that inability to clear secretions is a common cause of NIV failure, resulting from excessive volume of secretions or combination of limited inspiratory capacity, expiratory muscle weakness, and bulbar dysfunction. 1

Multidisciplinary Care Requirements

Ensure access to multidisciplinary team services including neurology, pulmonology, speech pathology, sleep medicine, and respiratory therapy, as this approach has been shown to improve quality of life and survival. 3

Senior/experienced input is essential in care planning, particularly when differences in opinion exist between medical staff and patient representatives. 1