Resp Care
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Cough is an important component of airway clearance, particularly in individuals with intrinsic pulmonary disease, weakness of respiratory muscles, or central nervous system disease that impairs breathing. The use of assisted cough to enhance airway clearance in individuals with neuromuscular disease is essential to produce and maintain peak cough flow above a minimum and thereby avoid retained secretions that cause infection, inflammation, and respiratory failure. Periodic insufflation of the lung above a reduced vital capacity is also important, to maintain range of motion of the thoracic cage and avoid progressive respiratory disability. ⋯ Insufflation-exsufflation decreases episodes of respiratory failure, particularly during upper-respiratory-tract infection, and provides greater success in weaning from mechanical ventilation than do conventional methods. Alternatives to insufflation-exsufflation that can produce sufficient peak cough flow for airway clearance include (1) insufflation to maximum insufflation capacity (via breath-stacking with a bag and mask, a volume ventilator, or glossopharyngeal breathing) followed by a spontaneous cough, and (2) manually assisted cough with an abdominal thrust. The effectiveness of insufflation-exsufflation in patients with obstructive lung disease, such as chronic obstructive pulmonary disease or asthma, and in pediatric patients, is less clear.
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Respiratory compromise is the leading cause of morbidity and mortality in patients with neuromuscular and neurologic disease, and in elderly patients, who have a reduced pulmonary reserve from deterioration of the respiratory system associated with the normal aging process. Although the otherwise healthy older patient is normally asymptomatic, their pulmonary reserve is further compromised during stressful situations such as surgery, pneumonia, or exacerbation of a comorbid condition. The inability to effectively remove retained secretions and prevent aspiration contribute to this compromise. ⋯ Patients with neuromuscular disease often can not generate an effective cough to mobilize and evacuate secretions. Respiratory muscle training, manual cough assistance, mechanical cough assistance, high-frequency chest wall compression, and intrapulmonary percussive ventilation have each been suggested as having potential benefit in this population. Although strong evidence supporting the benefit of these therapies is lacking, clinicians must be guided as to whether there is a pathophysiologic rationale for applying the therapy, whether adverse effects are associated with the therapy, the cost of therapy, and whether the patient prefers a given therapy.
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The rationale for airway clearance therapy and basic principles of its application are identical for children and adults, but there are important differences in physiology (regarding airway mucus characteristics and airway mechanics) and pathological processes in children, as well as other considerations unique to the pediatric population. The major obstacle in reviewing the evidence for efficacy of airway clearance therapy in pediatrics is the lack of data from well-performed, adequately powered clinical trials. This problem is partially alleviated by the use of published meta-analyses. ⋯ Airway clearance therapy may be of benefit in preventing post-extubation atelectasis in neonates. Airway clearance therapy appears to be of minimal to no benefit in the treatment of children with acute asthma, bronchiolitis, hyaline membrane disease, and those on mechanical ventilation for respiratory failure in the pediatric intensive care unit, and it is not effective in preventing atelectasis in children immediately following surgery. All in all, however, given that these conclusions are based on very little data, future well-performed clinical trials might change the weight of evidence to contradict these current conclusions.
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In health, secretions produced in the respiratory tract are cleared by mucociliary transport, cephalad airflow bias, and cough. In disease, increased secretion viscosity and volume, dyskinesia of the cilia, and ineffective cough combine to reduce secretion clearance, leading to increased risk of infection. In obstructive lung disease these conditions are further complicated by early collapse of airways, due to airway compression, which traps both gas and secretions. ⋯ Directed cough, forced expiratory technique, active cycle of breathing, and autogenic drainage are all more effective than placebo and comparable in therapeutic effects to postural drainage; they require no special equipment or care-provider assistance for routine use. Researchers have suggested that standard chest physical therapy with active cycle of breathing and forced expiratory technique is more effective than chest physical therapy alone. Evidence-based reviews have suggested that, though successful adoption of techniques such as autogenic drainage may require greater control and training, patients with long-term secretion management problems should be taught as many of these techniques as they can master for adoption in their therapeutic routines.
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Pulmonary mucociliary clearance is an essential defense mechanism against bacteria and particulate matter. Mucociliary dysfunction is an important feature of obstructive lung diseases such as chronic obstructive pulmonary disease, asthma, cystic fibrosis, and bronchiectasis. ⋯ The involvement of the cholinergic and adrenergic neural pathways in the pathophysiology of mucus hypersecretion suggests the potential therapeutic role of bronchodilators as mucoactive agents. Although anticholinergics and adrenergic agonist bronchodilators have been routinely used, alone or in combination, to enhance mucociliary clearance in patients with obstructive lung disease, the existing evidence does not consistently show clinical effectiveness.