ACD 06/11/2014

JORGE JO KAMIMOTO MD PGY-1 IM

Neuromuscular disorders and respiratory failureLEARNING POINTS

3 mechanisms 1. Weakness of the upper airway

Partial airway obstruction

2. Weakness of the inspiratory and inspiratory muscles Inspiratory

Initially hypoxemia with compensatory tachypnea due to V/Q mismatch

Then exhaustion , hypercapnia and respiratory acidosis

Expiratory

Impaired cough and clearance of secretion

Atelectasis and pneumonia

3. Concomitant cardiopulmonary disease Pneumonia, Atelectasis, DVT/PE

What clues do you look for to decide if this patient needs ICU monitoring or ventilator support

Why is it important? Emergency intubation carries higher risk of complications vs elective

intubation

Clinical features Bulbar dysfunction – Aspiration risk

Respiratory muscle strength testing

ABG

Crit Care Med 2003 Vol. 31, No. 1

• Identified 6 independent factors for Endotracheal Mechanical Ventilation• Time from onset to admission < 7 days• Inability to lift elbows above bed • Inability to lift the head• Ineffective cough • Increased liver enzymes • Inability to stand

• If patient has at least one of this criteria ICU monitoring is recommended

Respiratory muscle strength testing

How often?

Every 6-12 hours

FVC

Normal 60-70 ml/Kg

Expressed as % of predicted

NIF

Ability to maintain alveolar ventilation

PEF

Ability to cough and clear airways

Remember the 20/30/40 rule:

FVC < 20ml/Kg, NIF < 30 cm H2O, PEF < 40cmH2O

ABG

Obtain ABG with any suspicion of evolving respiratory failure

Consider intubation with PaO2 < 60mmHg or PaCO2 > 50 mmHg

Arch Neurol. 2001;58(6):893-898. doi:10.1001/archneur.58.6.893

Early use of BIPAP in MG Lesser need for intubation and mechanical ventilation

 However, patients in whom BIPAP fails Higher rate of pulmonary complications

Need for prolonged ventilation >10 days

PCO2 > 45mmHg strong predictor of BIPAP failure

Crucial to start BIPAP before Hypercapnia develops.

Remember :

The most important factor in intubation either elective or emergent is clinical bedside clinical judgment.

References

Rezania K1, Goldenberg FD, White S. Neuromuscular disorders and acute respiratory failure: diagnosis and management. Neurol Clin. 2012 Feb;30(1):161-85, viii. doi: 10.1016/j.ncl.2011.09.010.

Seneviratne J, Mandrekar J, Wijdicks EM, Rabinstein AA. Noninvasive Ventilation in Myasthenic Crisis. Arch Neurol.2008;65(1):54-58. doi:10.1001/archneurol.2007.1.

Lawn ND, Fletcher DD, Henderson RD, Wolter TD, Wijdicks EM. Anticipating Mechanical Ventilation in Guillain-Barré Syndrome. Arch Neurol. 2001;58(6):893-898. doi:10.1001/archneur.58.6.893.

Sharshar T1, Chevret S, Bourdain F, Raphaël JC; French Cooperative Group on Plasma Exchange in Guillain-Barré Syndrome. Early predictors of mechanical ventilation in Guillain-Barré syndrome. Crit Care Med. 2003 Jan;31(1):278-83.