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Transcript of Chapter 29 Neuromuscular and Other Diseases of the Chest Wall Copyright © 2013, 2009, 2003, 1999,...
Chapter 29
Neuromuscular and Other Diseases of the Chest Wall
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 2
Learning Objectives
List the potential respiratory complications associated with neuromuscular disease.
Identify the clinical signs and symptoms associated with respiratory muscle weakness.
Copyright © 2013, 2009, 2003, 1999, 1995, 1990, 1982, 1977, 1973, 1969 by Mosby, an imprint of Elsevier Inc. 3
Learning Objectives (cont.)
Describe techniques for monitoring the patient with respiratory muscle weakness.
Describe the general respiratory care management of patients with respiratory muscle weakness.
Learning Objectives (cont.)
Describe the clinical findings and treatment for each of the following neuromuscular disorders: Duchennes muscular dystrophy, Myotonic dystrophy, Polymyositis , Myasthenia gravis, Lambert-Eaton syndrome, Guillain-Barre syndrome, Unilateral diaphragmatic paralysis, Amyotrophic lateral sclerosis, Critical illness myopathy and polyneuropathy, Spinal cord injury, Stroke, Traumatic brain injury, Kyphoscoliosis, Flail chest
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Introduction
Pulmonary consequences of NMD may include: Hyperventilation Central apnea Atelectasis leading to hypoxemia Hypertension
Introduction (cont.)
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All of the following are consequences of Neuromuscular disorder, except:
A. Atelactasis leading to hypoxemia
B. Hypertension
C. Central Apnea
D. Stroke
Principles of Neuromuscular Weakness of Ventilatory Muscles
Pathophysiology & pulmonary function testing Monitoring & assessing patients for
respiratory insufficiency Management of respiratory muscle weakness
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Pathophysiology & PFTs
NMD normal lung parenchyma reveals restrictive defect Decreased VC, FEV1, TLC
Normal or increased RV & diffusing capacity corrected for VA
Positional changes suggest diaphragmatic weakness Seated to supine: >20% decline in FEV1 & VC
Decreased PImax & Pemax
ABG: PaO⇓ 2, PaCO⇓ 2, but deterioration leads to PaCO⇑ 2
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. .
Pathophysiology & PFTs (cont.)
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All of the following reveal a restrictive lung defect, except:
A. Increased RV
B. Decreased FVC
C. Decreased FEV1
D. Decreased TLC
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Monitoring & Assessing Patients for Respiratory Insufficiency
Respiratory muscle weakness leads to fatigue & respiratory failure May necessitate MV, so monitor carefully to
determine when to initiate Monitoring involves serial measurements of
PImax, VC, & ABG values May monitor maximal nasal sniff inspiratory
force & nocturnal oximetry Close monitoring of all respiratory function is
important
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Management of Respiratory Muscle Weakness
Weakness leads to respiratory insufficiency & retained secretions
Consider NIV or MV via tracheostomy Augmentation of secretion clearance & assist with
cough NIV increasingly used for short-term & intermittent
ventilatory support i.e., Pneumonia or surgical event
Diaphragmatic pacing for spinal injuries FDA approved May be useful to treat NMD as well
Specific Neuromuscular Diseases
Disorders of muscle: Duchenne Muscular Dystrophy Myotinic Dystrophy Polymyositis
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Duchenne Muscular Dystrohpy
Genetic muscle-wasting disorder Manifests early by waddling gait, lordosis,
frequent falls Most affected children are wheelchair dependent
by age 12 Point of significant respiratory function decline Adapt rapid shallow breathing pattern Progression leads to PPV, initially only nocturnal
Death occurs by age 20, usually result of declining respiratory muscle strength & subsequent infection
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Myotonic Dystrophy
Most common MD in adults Respiratory dysfunction is common
Respiratory muscle weakness OSA & CSA , very common even at early age Bulbar muscle dysfunction Aspiration
Tend to be sensitive to anesthesia & respiratory depressants so prolonged postoperative monitoring is required
Nocturnal NIV for oxygen & ventilation issues, while central hypoventilation requires tracheostomy & MV
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Polymyositis
Inflammatory myopathy of unknown cause Ventilatory insufficiency & failure are usual
If occurs, parallel progression of limb weakness Corticosteroids are mainstay of initial
management 10–30% develop interstitial lung disease, with
diffuse infiltrates predominantly in bases
Disorders of the Neuromuscular Junction
Myasthenia gravis (MG) Lambert-Eaton syndrome (LES)
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Disorders of the Neuromuscular Junction
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Myasthenia Gravis
Characterized by intermittent muscle weakness Worsens with repetition Improves with anticholinesterase medications
Caused by antibodies that inactivate ACh-R, blocking electrical impulse transmission
Neoplastic growth within the thymus gland is common
Typically occurs earlier in life in women & later in men
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Myasthenia Gravis (cont.)
Characterized by progressive loss of muscle function often starting with eye muscles Vary through day or progress, especially with
repetitive use Diagnosis is by presence of anti–ACh-R
antibodies & improvement with use of edrophonium
Treatment includes Thymectomy & anticholinesterase drugs Plasmapheresis to remove anti–ACh-R antibodies
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Myasthenia Gravis (cont.)
Pulmonary complications depend on affected muscles Upper airway obstruction Exertional dyspnea Ventilatory failure
Typically display Decreased TLC, VC, PImax, PEmax
• Sensitive markers of early respiratory muscle weakness Myasthenic crisis is acute respiratory
insufficiency caused by infection, surgery or excess anticholinesterase inhibitors
Myasthenia Gravis (cont.)
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Myasthenia Gravis (cont.)
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Lambert-Eaton Syndrome
More than fifty percent of cases associated with cancer, most of those with small cell carcinoma of lung
Autoantibodies interfere with release of ACh Presence is supported by nerve conduction
studies Increasing strength with repetition differentiates LES
from MG Respiratory failure is rare
Disorders of the Nerves
Guillain-Barre Syndrome (GBS) Phrenic Nerve & Diaphragmatic Paralysis
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Disorders of the Nerves (cont.)
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Guillain-Barre Syndrome
Most common peripheral neuropathy Characterized by paralysis & hyporeflexia, self-
limiting Thought to be caused by antimyelin antibodies Diagnosis: High CSF protein levels & slow
impulse transmission
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Patient has a sigh mechanism compromised with Atelactasis ,mild hypoxemia and VC of 30 mL/kg. Which would be most appropriate?
A. Chest physical therapy
B. Incentive Spirometry
C. Positive pressure ventilation
D. Full ventilation
Phrenic Nerve Damage & Diaphragmatic Paralysis
Phrenic nerve arises from C3 to C5 Damage to one phrenic nerve affects one
hemidiaphragm Bilateral interruption in high cervical injuries
results in complete diaphragmatic paralysis Reversible unilateral paralysis can occur due
to pneumonia Typically asymptomatic, diagnosed by radiography
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Phrenic Nerve Damage & Diaphragmatic Paralysis
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Which of the following does the phrenic nerve arise from?:
A. C1 to C3
B. C3 to C5
C. T1 to T3
D. T3 to T5
Disorders of the Spinal Cord
Amytrophic Lateral Sclerosis (ALS): Lou Gehrig Disease
Spinal Cord Trauma
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Amyotrophic Lateral Sclerosis (ALS): Lou Gehrig Disease
Characterized by progressive deterioration of upper & lower motor neurons
Male-to-female ratio for ALS is approximately 1.2:1
80% of patients have died by 5 years Medical treatment is essentially ineffective
Riluzole: trials shown extended life 4.2 months
Amyotrophic Lateral Sclerosis (ALS): Lou Gehrig Disease (cont.)
Supportive therapy central theme in managing ALS Key strategies: Prevent respiratory complications
& assess need for MV If PEmax <40 cm H2O patient has ineffective
cough• Treat with assisted cough, postural drainage
Consider instituting MV if:• PImax <60 cm H2O, PaCO2 >45 mm Hg, VC <20 ml/kg,
or NSIF >–40 cm H2O• Many patients opt not to prolong life with MV
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All of the following would lead to initiation mechanical ventilation in ALS patients, except:
A. VC >20 ml/kg
B. PaCO2 >45 mm Hg
C. PImax <60 cm H2O
D. NSIF >–40 cm H2O
Spinal Cord Trauma
Respiratory impact of spinal injury depends on level of injury & if complete or partial
High cervical injuries (C1-2) result in complete paralysis & death unless immediate MV is instituted
Middle-low cervical injury (C3-C8): though diaphragm is impacted at C3-C5, many can come off MV Adapt rapid shallow breathing pattern by use of
accessory muscles
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Disorders of the Brain
Trauma, stroke, hemorrhage, & infection can all impact respiration by: Abnormalities in lungs themselves, such as
neurogenic pulmonary edema
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Stroke
Interruption of blood flow to portion of brain, which results in persistent dysfunction
Could be thrombotic, embolic or hemorrhagic Impairment related to which structures were
damaged Treatment
Early (3–4.5 hours) use of thrombolytic agents after thrombotic event improves survival & function
Physical & occupational therapy Speech therapy if indicated
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Stroke (cont.)
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Traumatic Brain Injury
Blunt or penetrating injury resulting in brain lesions May cause direct trauma to respiratory centers Cause neurogenic pulmonary edema,
hypersecretion of mucus, leading to respiratory failure
Disorders of the Thoracic Cage
Kyphoscoliosis Flail chest
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Kyphoscoliosis
Posterior angulation of thorax (kyphosis) & lateral curature of spine (scoliosis) occur together
Kyphoscoliosis may result in hypoventilation, hypercapnia, & pulmonary HTN Decreased compliance seen with these patients
• Result in TLC & VC & restrictive disorder⇓• May have impaired diaphragmatic function
Spinal fixation may improve compliance, prevent further pulmonary dysfunction, preexisting conditions will not be reversed
Kyphoscoliosis (cont.)
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Kyphoscoliosis (cont.)
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Flail Chest
Multiple rib fractures result in portion of chest wall becoming free-floating, moving in paradoxic motion during respiratory cycle Bows out during expiration, in during inspiration
Often accompanied by pneumothorax, pulmonary contusion, hemothorax, which require emergent care