Resp Care
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Although life-saving, mechanical ventilation is associated with numerous complications. These include pneumonia, cardiovascular compromise, barotrauma, and ventilator-induced lung injury. Recent data from animal studies suggest that controlled mechanical ventilation can cause dysfunction of the diaphragm, decreasing its force-generating capacity--a condition referred to as ventilator-induced diaphragmatic dysfunction (VIDD). ⋯ Whether the decrease in diaphragmatic contractility observed during controlled ventilation contributes to failure to wean from the ventilator is difficult to ascertain. Weaning-failure patients have reasons other than VIDD for respiratory-muscle weakness. Until we have further data, it seems prudent to avoid the use of controlled mechanical ventilation in patients with acute respiratory failure.
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Motor weakness in a patient in the intensive care unit (ICU) may be related to (1) pre-existing neuromuscular disorder that leads to ICU admission, (2) new-onset or previously undiagnosed neurological disorder, or (3) complications of non-neuromuscular critical illness. Neuromuscular syndromes related to ICU treatment consist of critical illness polyneuropathy, critical illness myopathy, and prolonged neuromuscular blockade, and are now recognized as a frequent cause of newly acquired weakness in ICU patients. Clinical features include quadriparesis, muscle wasting, and difficulty weaning from the ventilator. ⋯ A subgroup of patients with myasthenia gravis with muscle-specific tyrosine kinase antibody is noted to present as respiratory crisis. Muscle biopsy in ICU paralysis syndromes may be helpful in arriving at a specific diagnosis or to classify the type of critical illness myopathy. Nerve biopsy is only rarely indicated.
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Neuromuscular abnormalities culminating in skeletal-muscle weakness occur very commonly in critically ill patients. Intensive-care-unit (ICU) acquired neuromuscular abnormalities are typically divided into 2 discrete classes: polyneuropathy and myopathy. However, it is likely that these 2 entities commonly coexist, with myopathy being the most common cause of weakness. ⋯ The only intervention proven to reduce the incidence of ICU-acquired neuromuscular abnormalities is intensive insulin therapy. Additional research is necessary to better delineate the causes and pathogenesis of these disorders and to identify potential preventive and therapeutic strategies. In addition, consensus guidelines for its classification and diagnosis are needed.
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Neuromuscular diseases that affect the respiratory system are a major cause of morbidity and mortality in both acute and long-term settings. This conference examined the pathophysiology and management of neuromuscular diseases in both settings. ⋯ This summary of the conference briefly describes the main points of each presentation and highlights areas that need addressing in the future. Major topics covered include the basic respiratory pathophysiology of neuromuscular disease; respiratory complications and management of amyotrophic lateral sclerosis; techniques of noninvasive ventilation and secretion removal; and evaluation and management of neuromuscular-induced respiratory failure in the acute-care setting, including Guillain-Barré syndrome, myasthenic crisis, and critical-illness myoneuropathy.
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Most children with neuromuscular disease eventually require assistance with airway clearance and with breathing, especially during sleep. Techniques and devices for airway clearance and noninvasive ventilation that are commonly used in adults have been successfully adapted for use in infants and young children. Both physiological differences and small size of young patients with neuromuscular disease, however, can limit the applicability of such interventions or require special consideration. ⋯ The paucity of nasal interfaces and headgear commercially made for small patients can reduce patient tolerance of noninvasive ventilation and exacerbate patient-ventilator dyssynchrony. Despite these issues, a greater number of children with neuromuscular diseases are living well past their second decade. Strategies to transition these patients to appropriate adult-care providers, to secure cost-effective health care for them, and to help integrate them into adult society must be developed.