Approach to Respiratory Complications with Neuromuscular Disorders

Nahid SherbiniConsultant IM &PulmonaryKFH Medina

DMD

• Most prevalent childhood muscular dystrophy, every 1 in 3000-6000 male births

• X-linked recessive ,Deficiency of the muscle protein Dystrophin

• Shortened lifespan due to progressive muscle weakness and complications- mean age is 19 without intervention, mid-to-late twenties with proper care.

Dystrophin

• Provides mechanical reinforcement to the sarcolemmal membrane of muscle fibers; protects muscle fibers from being damaged while stressed during muscle contraction.

Associated Pathologies: Weakness

• Progressive weakness of hip and shoulder girdle musculature

• Weakness in paraspinals make walking difficult

• Leads to:• Waddling gait• Lumbar lordosis• Forward thrusting of the

abdomen • Scapular winging • AP scoliotic curve• Joint contractures• Respiratory impairment• Weight gain

CLINICAL MANIFESTATIONS 1. Insufficient ventilation : dyspnea, orthopnea, rapid shallow

breathing ,hypercapnia, or hypoxemia.

2. Nocturnal hypoventilation may induce choking, insomnia, daytime hypersomnolence, morning headaches, fatigue, or impaired cognition.

3. Bulbar dysfunction dysarthria, dysphagia, weak mastication, facial weakness, nasal speech, or a protruding tongue.

4. Ineffective cough aspiration, retention of secretions, or pneumonia.

EVALUATION

1. Confirm respiratory muscle weakness

2. Assess cough

3. Assess need for ventilatory support

Degree of respiratory muscle weakness cannot be predicted by the degree of peripheral muscle weakness. *

-->tests of respiratory muscle function are essential to identify the patient who is at risk for respiratory failure.

*Respiratory muscle weakness in peripheral neuropathies Burakgazi AZ, Höke A J Peripher Nerv Syst. 2010 Dec;15(4):307-13

Confirm respiratory muscle weakness

by PFT - No single abnormality is diagnostic of respiratory muscle weakness*; Typical abnormalities include:1.A Restrictive pattern

2.Expiratory muscle weakness increased (RV)

3.FVC measured in the supine position is >10 % lower than in the upright position.

4.MVV is reduced

5.DLCO is normal

*The value of multiple tests of respiratory muscle strength. Steier J, Kaul S, Seymour J, Jolley C, Rafferty G, Man W, Luo YM, Roughton M, Polkey MI, Moxham J Thorax. 2007;62(11):975.

1. Confirm respiratory muscle weakness

•Maximal inspiratory pressure (MIP) or maximal expiratory pressure (MEP) is reduced.

The MIP reflects the strength of the diaphragm and other inspiratory muscles, while

the MEP reflects the strength of the abdominal muscles and other expiratory muscles.

•IN bulbar dysfunction the sniff nasal inspiratory pressure (SNIP)

2-Assess cough 1. Peak cough flow — The peak cough flow (PCF) is measured by.

A PCF l< 160 L/min =an ineffective cough ,between 160 -- 270 L/min are at risk for respiratory tract infections, which can further reduce muscle strength .

2. MEP — <60 cm H2O suggests

3. Expiratory cough flow tracings — The absence of transient increases in expiratory flow above the maximal flow-volume loop (ie, cough spikes)

3-Assess need for ventilatory support • MIP and MEP –

1.MIP < -30 cm H2O a high risk for hypercapnia

2.MEP <40 cm H2O inadequate cough strength and risk for secretion retention.

3.VC < 20 mL/kg, 60%, or 1 L*. Or 30 - 50 % compared to a prior measurement.

The repeated measurement of vital capacity is a poor predictor of the need for mechanical ventilation in myasthenia gravis. Rieder P, Louis M, Jolliet P, Chevrolet JC Intensive Care Med. 1995;21(8):663.

Assess need for ventilatory support

• A "20-30-40 rule" has been proposed .

The rule advocates the initiation of ventilatory support when

VC < 20 mL/kg,

MIP < -30 cm H2O

or MEP < 40 cm H2O.

MECHANICAL VENTILATION NPPV may benefit patients who require:

1.Continuous MV for a short duration (ie, days), such as patients with an acute neuromuscular disease (eg, Guillain-Barré syndrome)

2.Intermittent MV for a long duration (ie, years), such as patients with nocturnal hypoventilation or early chronic respiratory failure.

The likelihood that NPPV will be unsuccessful or cause a complication is increased when any of the following exist:

1.Bulbar dysfunction

2.Upper airway obstruction

3.Retention of respiratory secretions

4.Poor cooperation

5.Inadequate cough.

• An observational study compared 14 patients with neuromuscular disease who received NPPV for acute respiratory failure to 14 historical controls who received invasive MV .

The NPPV group lower mortality

a shorter length of ICU stay

& decrease needing invasive MV.*

Non-invasive ventilatory approach to treatment of acute respiratory failure in neuromuscular disorders. A comparison with endotracheal intubation. Vianello A, Bevilacqua M, Arcaro G, Gallan F, Serra E Intensive Care Med. 2000;26(4):384.

Invasive MVShould be initiated early for the following reasons:

•Intubation itself has risks that are best managed in a controlled setting

dysautonomia increases the risk of severe hypotension and bradycardia .

•decrease the risk of early-onset pneumonia*.

Prognosis and risk factors of early onset pneumonia in ventilated patients with Guillain-Barrésyndrome.Orlikowski D, Sharshar T, Porcher R, Annane D, Raphael JC, Clair B Intensive Care Med. 2006;32(12):1962.

PROGNOSIS• Among intubated patients with GBS

mortality UP 20 %

median duration of MV is UP 29 days *.

• Among intubated patients with myasthenia gravis,

mortality is UP 8 %

duration of is 14 days .

• Among intubated patients admitted to ICU, diaphragmatic dysfunction 64 % . Mortality (26 %) .

Long-term outcome in patients with Guillain-Barrésyndrome requiring mechanical ventilation. Fletcher DD, Lawn ND, Wolter TD, Wijdicks EF Neurology. 2000;54(12):2311.

Predictors of successful Extubation

• (MIP) more negative than -50 cm H2O

• Improvement VC by > 4 mL/kg from preintubation to pre-extubation.

Predictors of failed extubation

• dysautonomia

• Advanced age

• pulmonary complications (pneumonia, atelectasis) were associated with extubation failure

Factors predicting extubation success in patients with Guillain Barrésyndrome. Nguyen TN, Badjatia N, Malhotra A, Gibbons FK, Qureshi MM, Greenberg SA Neurocrit Care. 2006;5(3):230.

COUGH ASSISTANCE

1.Mechanical insufflation-exsufflation APPLY PRESSURE

2.Manually-assisted coughing ABD TRUST

3.Hyperinflation maneuvers Inc TV by Glossopharyngeal breathing (ie, repetitive air gulping) ,Delivery of stacked breaths and Mechanical inspiration using a mechanical insufflator or a volume cycled ventilator

4.Secretion mobilization techniques.

By High frequency chest-wall oscillation and Intrapulmonary percussive ventilation.

TRACHEOSTOMY

1. Difficulty clearing their secretions.

2. Intermittent long-term mechanical ventilation, but in whom NPPV is contraindicated (eg, severe bulbar dysfunction).

3. Intermittent long-term NPPV is no longer sufficient.

4. Fail to wean from invasive MV.

GENERAL CARE•Correct electrolyte abnormalities

•Avoid neuromuscular blocking agents, aminoglycosides, and glucocorticoids.

•Nutritional status should be maintained

•Prophylaxis for DVT and stress gastric ulcers should be provided when indicated.

•The head of the bed should be elevated by 45º to decrease the risk for ventilator-associated pneumonia .

GENERAL CARE

• Decisions regarding long-term support.

Progressive neuromuscular diseases of childhood, such as spinal muscular atrophy and Duchenne muscular dystrophy present different challenges, as parents are often the main decision makers. [ long-term ventilatory support is more common and often associated with good quality of life].