Type I are slow twitch and fatigue resistant Type II are fast twitch but easily fatigued Therefore, type 1 are spared in mm of DMD patients and the degen occurs in type II fast twitch fibers
Dystrophic muscle= one with dystrophy, with less dystrophin protein
Tight IT bands Walking with weak paraspinals: sagging pelvis as the foot is raised, so waddling gait, tilting of the body to one side
Neuromuscular Disorders Respiratory Complications and Assessment
Approach to Respiratory
Consultant IM &Pulmonary
• Most prevalent childhood muscular dystrophy,
every 1 in 3000-6000 male births
• X-linked recessive ,Deficiency of the muscle
• Shortened lifespan due to progressive muscle
weakness and complications- mean age is 19
without intervention, mid-to-late twenties with
• Provides mechanical reinforcement
to the sarcolemmal membrane of
muscle fibers; protects muscle fibers
from being damaged while stressed
during muscle contraction.
• Progressive weakness of hip and
shoulder girdle musculature
• Weakness in paraspinals make
• Leads to:
• Waddling gait
• Lumbar lordosis
• Forward thrusting of the
• Scapular winging
• AP scoliotic curve
• Joint contractures
• Respiratory impairment
• Weight gain
1. Insufficient ventilation : dyspnea, orthopnea, rapid shallow
breathing ,hypercapnia, or hypoxemia.
2. Nocturnal hypoventilation may induce choking, insomnia,
daytime hypersomnolence, morning headaches, fatigue, or
3. Bulbar dysfunction dysarthria, dysphagia, weak
mastication, facial weakness, nasal speech, or a protruding
4. Ineffective cough aspiration, retention of secretions, or
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
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
•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
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
• MIP and MEP –
1.MIP < -30 cm H2O a high risk for hypercapnia
2.MEP <40 cm H2O inadequate cough strength and risk for
3.VC < 20 mL/kg, 60%, or 1 L*. Or 30 - 50 % compared to a prior
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
Assess need for ventilatory
• 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.
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
2.Intermittent MV for a long duration (ie, years), such as
patients with nocturnal hypoventilation or early chronic
The likelihood that NPPV will be
unsuccessful or cause a complication is
increased when any of the following exist:
2.Upper airway obstruction
3.Retention of respiratory secretions
• 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.
Should be initiated early for the following reasons:
•Intubation itself has risks that are best managed in a controlled
dysautonomia increases the risk of severe hypotension and
•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
• 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
preintubation to pre-
Predictors of failed extubation
• Advanced age
were associated with
Factors predicting extubation success in patients with Guillain Barrésyndrome. Nguyen TN,
Badjatia N, Malhotra A, Gibbons FK, Qureshi MM, Greenberg SA Neurocrit Care.
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
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.
•Correct electrolyte abnormalities
•Avoid neuromuscular blocking agents, aminoglycosides, and
•Nutritional status should be maintained
•Prophylaxis for DVT and stress gastric ulcers should be provided
•The head of the bed should be elevated by 45º to decrease the
risk for ventilator-associated pneumonia .
• 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].