Management of Neuromuscular Respiratory Failure





Patients with neuromuscular disease presenting with severe weakness require close monitoring of their respiratory status, as progression to respiratory failure can occur relatively suddenly. As the fundamental problem is one of ventilation as opposed to oxygenation, patients may continue to have normal oxygen saturation despite progressively worsening respiratory function. Similarly, hypercarbia represents a late manifestation of neuromuscular respiratory insufficiency and indicates impending respiratory failure; ventilatory support should start before hypercarbia is present. It is therefore critical to monitor ventilatory capacity frequently in these patients, typically with bedside measures of vital capacity and negative inspiratory force (NIF).



  • A.

    For patients with myasthenia gravis or Guillain-Barré syndrome, preparation and planning for starting plasmapheresis or intravenous immunoglobulin therapy should begin as soon as respiratory concerns are identified.


  • B.

    Respiratory status should be assessed a minimum of every 4 hours. The goal is to gauge whether the patient requires ventilatory support. Forced vital capacity (FVC) and NIF are both measurements of a patient’s respiratory muscle strength and also correlate with the ability to cough and clear secretions. A simple bedside maneuver to roughly estimate FVC is to have the patient count as high as they can in a single breath; each number counted is equivalent to approximately 100 mL of FVC. For example, if a patient is able to count to 25, her FVC is about 2500 mL. The “20/30” rule is a good rule of thumb—if the FVC drops below 20 mL/kg, the NIF below 30 cm H 2 O, or the patient is more than mildly dyspneic, ventilatory support should be started. A drop of 30% or more in either FVC or NIF should also prompt consideration of elective ventilatory support. The presence of facial weakness can sometimes confound measurement of FVC and NIF in the nonintubated patient, due to an inability to maintain a tight seal on the measurement device. This should be taken into consideration when these parameters are interpreted.


  • C.

    If the cause of weakness is Guillain-Barré syndrome, intubation and invasive mechanical ventilator support should be started, as these patients typically have progressive worsening over days before improvement starts to occur, even with immunotherapy.


  • D.

    If the patient is oxygenating well on room air, one can assume the patient is not markedly hypercapnic and does not have significant consolidation; noninvasive positive pressure ventilation in the biphasic positive airway pressure (BiPAP) mode can be started.


  • E.

    If supplemental oxygen is required, arterial blood gas (ABG) and chest radiograph (CXR) should be checked. If hypercapnia is present or CXR shows consolidation concerning for aspiration pneumonia or pneumonitis, BiPAP is not appropriate and intubation should be undertaken.


  • F.

    If inspiratory pressures (IPAP) greater than 20 cm H 2 O are required, there is a risk of overcoming the lower esophageal sphincter tone and insufflating the stomach, and intubation should be pursued.


  • G.

    An increasing oxygen requirement or increasing IPAP are signs the patient may be failing BiPAP. An ABG should check for hypercapnia and CXR for signs of consolidation and aspiration. If present, intubation should be pursued.


  • H.

    When intubating a patient with neuromuscular disease, special attention should be paid to the choice of paralytic agent. If possible, intubation of patients with myasthenia gravis or Guillain-Barré syndrome should be performed without a neuromuscular blocking agent; when necessary, one-third to one-half the usual intubating dose of a nondepolarizing agent should be used. Depolarizing agents such as succinylcholine should be avoided given the unpredictable response in myasthenia and the risk of hyperkalemia in Guillain-Barré syndrome. Be prepared for a prolonged effect, and sedate and monitor the patient appropriately.


  • I.

    As muscle weakness begins to improve, daily spontaneous breathing trials (SBTs) with FVC and NIF measurements should occur. When the patient passes the SBT, FVC is > 10 cc/kg, and NIF > 20 cm H 2 O, a trial of extubation should be considered. BiPAP ventilation can be used as a bridge immediately following extubation as needed.




Algorithm 60.1


Flowchart for the treatment of a patient with neuromuscular respiratory failure. BiPAP, Biphasic positive airway pressure; IPAP, inspiratory pressure; IVIg, intravenous immune globulin; NIF , negative inspiratory force.

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May 3, 2021 | Posted by in NEUROLOGY | Comments Off on Management of Neuromuscular Respiratory Failure

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