Management of airway clearance in neuromuscular disease

The clearance of airway secretions from the lungs is normally supported by the mucociliary escalator and by cough. These protective mechanisms provide an effective means of pulmonary-hygiene maintenance in healthy individuals. Patients with neuromuscular disease that affects the respiratory pump (the muscles of breathing) can experience mild to profound limitation in both ventilation and cough. Neuromuscular respiratory insufficiency, when left untreated, can substantially impact quality of life and life expectancy. In most cases of neuromuscular disease, respiratory failure and pneumonia are the primary causes of death. Invasive mechanical ventilation and tracheal suctioning have been successfully used when needed to support respiratory insufficiency in this population. These modalities, though supportive, have been associated with substantial morbidity when used in patients with neuromuscular disease. The advent of noninvasive ventilation as a means of supporting chronic neuromuscular respiratory insufficiency has spurred the development of noninvasive cough-augmentation therapy to support airway clearance. Unfortunately, the need to support cough clearance is not always addressed, and few guidelines for the management of cough insufficiency have existed until relatively recently. An understanding of neuromuscular respiratory pathophysiology and the modes of effective noninvasive cough support are key in the evaluation and management of neuromuscular diseases. This review is meant to provide a basic understanding of cough mechanics, and the pathophysiology and management of neuromuscular cough insufficiency.     

Clinical review: Long-term noninvasive ventilation

Noninvasive positive ventilation has undergone a remarkable evolution over the past decades and is assuming an important role in the management of both acute and chronic respiratory failure. Long-term ventilatory support should be considered a standard of care to treat selected patients following an intensive care unit (ICU) stay. In this setting, appropriate use of noninvasive ventilation can be expected to improve patient outcomes, reduce ICU admission, enhance patient comfort, and increase the efficiency of health care resource utilization. Current literature indicates that noninvasive ventilation improves and stabilizes the clinical course of many patients with chronic ventilatory failure. Noninvasive ventilation also permits long-term mechanical ventilation to be an acceptable option for patients who otherwise would not have been treated if tracheostomy were the only alternative. Nevertheless, these results appear to be better in patients with neuromuscular/-parietal disorders than in chronic obstructive pulmonary disease. This clinical review will address the use of noninvasive ventilation (not including continuous positive airway pressure) mainly in diseases responsible for chronic hypoventilation (that is, restrictive disorders, including neuromuscular disease and lung disease) and incidentally in others such as obstructive sleep apnea or problems of central drive.     

High-frequency chest-wall oscillation in a noninvasive-ventilation-dependent patient with type 1 spinal muscular atrophy

With the recent increased use of noninvasive ventilation, the prognoses of children with neuromuscular disease has improved significantly. However, children with muscle weakness remain at risk for recurrent respiratory infection and atelectasis. We report the case of a young girl with type 1 spinal muscular atrophy who was dependent on noninvasive ventilation, and in whom conventional secretion-clearance physiotherapy became insufficient to clear secretions. We initiated high-frequency chest-wall oscillation (HFCWO) as a rescue therapy, and she had improved self-ventilation time. This is the first case report of HFCWO for secretion clearance in a severely weak child with type 1 spinal muscular atrophy. In a patient with neuromuscular disease and severe respiratory infection and compromise, HFCWO can be used safely in combination with conventional secretion-clearance physiotherapy.     

Pneumothorax associated with mechanical insufflation-exsufflation and related factors

Impaired cough that results in ineffective airway secretion clearance is an important contributor to pulmonary complications in patients with neuromuscular weakness including spinal cord injury. Mechanical insufflation-exsufflation (MI-E) is a respiratory aid used by patients with weak respiratory muscles to increase cough peak flows and improve cough effectiveness. Relative contraindications to MI-E are said to include susceptibility to pneumothorax, but the association of pneumothorax with MI-E use has never before been described. We report two cases of pneumothorax in patients with respiratory muscle weakness associated with daily use of MI-E: one was a 58-yr-old male with C4 ASIA C tetraplegia, and the other was a 26-yr-old male with Duchenne muscular dystrophy. Both patients also used positive-pressure ventilatory assistance. Although seemingly rare in this patient population, ventilator users also using MI-E who have increasing dyspnea or who require increasing positive inspiratory pressures when using noninvasive ventilation should be evaluated for pneumothorax.     

Ventilator weaning by lung expansion and decannulation

This case series of ventilator-dependent patients with neuromuscular disease who had no ventilator-free breathing ability demonstrates that decannulation and switching to continuous noninvasive intermittent positive-pressure ventilation combined with regular lung expansion therapy can result in improvements in pulmonary function and at least partial ventilator weaning. These six patients were also managed using mechanical insufflation-exsufflation for regular lung expansion and cough assistance. Thus, some ventilator users with neuromuscular disease can benefit from tracheostomy tube decannulation and transition to noninvasive intermittent positive-pressure ventilation and assisted coughing for ventilator weaning to predominantly nocturnal-only use.     

Care of the chronic tracheostomy

A minority of patients with neuromuscular disease require placement of a tracheostomy, usually for the purpose of providing mechanical ventilation. Often the tracheostomy is performed during a hospital admission for an acute illness. The debate about the appropriate timing of tracheostomy in critically ill patients has not been resolved; however, the weight of evidence now favors performing a tracheostomy early (within 7 d of translaryngeal intubation) if the period of mechanical ventilation is likely to be prolonged beyond 3 weeks. For patients with chronic progressive weakness who develop respiratory difficulty, the consensus of opinion is that tracheostomy should be performed in patients with severe bulbar involvement, inability to effectively cough up secretions despite mechanical aids for secretion clearance, or for those who are unable to tolerate or fail noninvasive ventilation. The decision to perform tracheostomy in patients with chronic neuromuscular weakness involves consideration of several factors, including complications, resources, quality of life, ethical issues, cosmetic issues, and cost. Complications from tracheostomy and physician-perceived poor quality of life often lead to a negative bias, such that some patients may be denied this life-saving procedure. Special training is needed to provide long-term tracheostomy care, and an organized approach should be followed to decannulate patients who recover from their acute illness. Appropriate and skilled care could significantly improve the longevity and quality of life of those patients with neuromuscular disease who have a tracheostomy for long-term ventilation.     

Dysfonction hémodynamique au cours du sepsis : approche expérimentale

Long-term noninvasive ventilation (NIV) is increasingly used in children. It requires the delivery of a ventilatory assistance by an interface that connects the patient??s airways, such as a nasal or facial mask, or rarely a nasal canula. NIV is indicated in diseases causing chronic alveolar hypoventilation, including neuromuscular disorders, maxillo-facial or upper airway abnormalities, thoracic deformities, some lung diseases, and disorders of respiratory control. In these diseases, NIV is the first-line treatment when chronic respiratory failure occurs because it is noninvasive and can be applied on demand, preferentially during sleep. The increasing use of NIV in children is explained by the improvement of the diagnosis of chronic alveolar hypoventilation, the availability of pediatric interfaces, and the increasing performance of home ventilators.     

The growing role of noninvasive ventilation in patients requiring prolonged mechanical ventilation

For many patients with chronic respiratory failure requiring ventilator support, noninvasive ventilation (NIV) is preferable to invasive support by tracheostomy. Currently available evidence does not support the use of nocturnal NIV in unselected patients with stable COPD. Several European studies have reported benefit for high intensity NIV, in which setting of inspiratory pressure and respiratory rate are selected to achieve normocapnia. There have also been studies reporting benefit for the use of NIV as an adjunct to exercise training. NIV may be useful as an adjunct to airway clearance techniques in patients with cystic fibrosis. Accumulating evidence supports the use of NIV in patients with obesity hypoventilation syndrome. There is considerable observational evidence supporting the use of NIV in patients with chronic respiratory failure related to neuromuscular disease, and one randomized controlled trial reported that the use of NIV was life-prolonging in patients with amyotrophic lateral sclerosis. A variety of interfaces can be used to provide NIV in patients with stable chronic respiratory failure. The mouthpiece is an interface that is unique in this patient population, and has been used with success in patients with neuromuscular disease. Bi-level pressure ventilators are commonly used for NIV, although there are now a new generation of intermediate ventilators that are portable, have a long battery life, and can be used for NIV and invasive applications. Pressure support ventilation, pressure controlled ventilation, and volume controlled ventilation have been used successfully for chronic applications of NIV. New modes have recently become available, but their benefits await evidence to support their widespread use. The success of NIV in a given patient population depends on selection of an appropriate patient, selection of an appropriate interface, selection of an appropriate ventilator and ventilator settings, the skills of the clinician, the motivation of the patient, and the support of the family.     

Noninvasive ventilation

Noninvasive positive-pressure ventilation (NPPV) is the delivery of mechanical-assisted breathing without placement of an artificial airway such as an endotracheal tube or tracheostomy. During the first half of 20th century, negative-pressure ventilation (iron lung) provided mechanical ventilatory assistance. By the 1960s, however, invasive (ie, by means of an endotracheal tube) positive-pressure ventilation superseded negative-pressure ventilation as the primarily mode of support for ICU patients because of its superior delivery of support and better airway protection. Over the past decade, the use of NPPV has been integrated into the treatment of many medical diseases, largely because the development of nasal ventilation. Nasal ventilation has the potential benefit of providing ventilatory assistance with greater convenience, comfort, safety, and less cost than invasive ventilation. NPPV is delivered by a tightly fitted mask or helmet that covers the nares, face, or head. NPPV is used in various clinical settings and is beneficial in many acute medical situations. This article explores the trends regarding the use of noninvasive ventilation. It also provides a current perspective on applications in patients with acute and chronic respiratory failure, neuromuscular disease, congestive heart failure, and sleep apnea. Additionally, it discusses the general guidelines for application, monitoring, and avoidance of complications for NPPV.     

Alternatives to endotracheal intubation for patients with neuromuscular diseases

OBJECTIVE: To evaluate the usefulness of continuous noninvasive mechanical ventilation and mechanical coughing aids to avoid endotracheal intubation and tracheostomy during episodes of acute respiratory failure in patients with neuromuscular disease. DESIGN: We conducted a prospective cohort study at the respiratory medicine ward of a university hospital to study the success rate of the use of continuous noninvasive mechanical ventilation and manually and mechanically (CoughAssist) assisted coughing to avert endotracheal intubation in 24 consecutive episodes of acute respiratory failure for 17 patients with neuromuscular disease. The noninvasive mechanical ventilation and coughing aids were used to reverse decreases in oxyhemoglobin saturation and relieve respiratory distress that occurred despite oxygen therapy and appropriate medication. Noninvasive mechanical ventilation was delivered by volume ventilators (Breas PV 501) alternating nasal/oronasal and oral interfaces. RESULTS: Noninvasive management was successful in averting death and endotracheal intubation in 79.2% of the acute episodes. There were no significant differences in respiratory function between the successfully treated and unsuccessfully treated groups before the current episode. Bulbar dysfunction was the independent risk factor for failure of noninvasive treatment (P < 0.05; odds ratio, 35.99%; 95% confidence interval, 1.71-757.68). CONCLUSIONS: Intubation can be avoided for some patients with neuromuscular disease in acute respiratory failure by some combination of noninvasive mechanical ventilation and mechanically assisted coughing. Severe bulbar involvement can limit the effectiveness of noninvasive management.     

Noninvasive ventilation in neuromuscular disease: equipment and application

Noninvasive support of ventilation is commonly needed in patients with neuromuscular disease. Body ventilators, which are used rarely, function by applying intermittent negative pressure to the thorax or abdomen. More commonly, noninvasive positive-pressure ventilation (NPPV) is used. This therapy can be applied with a variety of interfaces, ventilators, and ventilator settings. The patient interface has a major impact on comfort during NPPV. The most commonly used interfaces are nasal masks and oronasal masks. Other interfaces include nasal pillows, total face masks, helmets, and mouthpieces. Theoretically, any ventilator can be attached to a mask rather than an artificial airway. Portable pressure ventilators (bi-level positive airway pressure) are available specifically to provide NPPV and are commonly used to provide this therapy. Selection of NPPV settings in patients with neuromuscular disease is often done empirically and is symptom-based. Selection of settings can also be based on the results of physiologic studies or sleep studies. The use of NPPV in this patient population is likely to expand, particularly with increasing evidence that it is life-prolonging in patients with diseases such as amyotrophic lateral sclerosis. Appropriate selection of equipment and settings for NPPV is paramount to the success of this therapy.     

What does airway resistance tell us about lung function?

Spirometry is considered the primary method to detect the air flow limitation associated with obstructive lung disease. However, air flow limitation is the end-result of many factors that contribute to obstructive lung disease. One of these factors is increased airway resistance. Airway resistance is traditionally measured by relating air flow and driving pressure using body plethysmography, thus deriving airway resistance (R(aw)), specific airway resistance (sR(aw)), and specific airway conductance (sG(aw)). Other methods to measure airway resistance include the forced oscillation technique (FOT), which allows calculation of respiratory system resistance (R(RS)) and reactance (X(RS)), and the interrupter technique, which allows calculation of interrupter resistance (R(int)). An advantage of these other methods is that they may be easier to perform than spirometry, making them particularly suited to patients who cannot perform spirometry, such as young children, patients with neuromuscular disorders, or patients on mechanical ventilation. Since spirometry also requires a deep inhalation, which can alter airway resistance, these alternative methods may provide more sensitive measures of airway resistance. Furthermore, the FOT provides unique information about lung mechanics that is not available from analysis using spirometry, body plethysmography, or the interrupter technique. However, it is unclear whether any of these measures of airway resistance contribute clinically important information to the traditional measures derived from spirometry (FEV(1), FVC, and FEV(1)/FVC). The purpose of this paper is to review the physiology and methodology of these measures of airway resistance, and then focus on their clinical utility in relation to each other and to spirometry.     

Noninvasive ventilation in chronic obstructive lung disease

Noninvasive mechanical ventilation is provided without establishing an endotracheal airway. In acute respiratory failure due to chronic obstructive lung disease, noninvasive positive-pressure ventilation delivered through a nasal or face mask may eliminate the need for intubation and related complications, reduce the duration of hospitalisation and improve survival compared to assisted ventilation through an endotracheal tube. In chronic respiratory failure related to neuromuscular diseases and thoracic deformities, the advent of noninvasive intermittent longterm ventilation is well established. However, it is not clear, whether addition of noninvasive ventilation to standard treatment with medication and longterm oxygen improves symptoms and survival in chronic respiratory failure due to chronic obstructive lung disease. During introduction of noninvasive ventilation, patients must be monitored closely. Patient selection and information, meticulous optimization of the ventilator settings and delivery system, education and experience of the personnel have an important impact on the success of this novel way of providing mechanical ventilatory support.     

Forced expiratory technique, directed cough, and autogenic drainage

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. Techniques have been developed to optimize expiratory flow and promote airway clearance. 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.     

Mechanical insufflation-exsufflation for airway mucus clearance

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. Mechanical insufflation-exsufflation is a therapy in which the device (the CoughAssist In-Exsufflator is the only currently marketed insufflation-exsufflation device) gradually inflates the lungs (insufflation), followed by an immediate and abrupt change to negative pressure, which produces a rapid exhalation (exsufflation), which simulates a cough and thus moves secretions cephalad. Mechanical insufflation-exsufflation is used with patients with neuromuscular disease and muscle weakness due to central nervous system injury. 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.     

Treatment of tracheal and bronchial tumors and tracheal and bronchial stent placement

Tumors of and trauma to the trachea and bronchi can result in loss of integrity of the airway and death. Once treated primarily with thoracic surgery, these conditions are increasingly being managed with interventional pulmonary procedures outside the operating room but requiring the assistance of anesthetists. These interventional procedures require airway instrumentation, necessitating anesthesia care for ventilation and obtundation of airway reflexes. A thorough preoperative assessment and consultation with the pulmonologist or surgeon performing the procedure are essential for successful completion of the tumor and scar reduction and subsequent stent placement. In addition, anesthetists may care for patients undergoing nonpulmonary surgery who have an existing bronchial or tracheal stent or patients requiring correction of displaced stents. A discussion on the preferred methods for caring for patients in these situations is included.     

Airway clearance applications in infants and children

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. A review of pediatric studies suggests that airway clearance therapy is of clear and proven benefit in the routine care of cystic fibrosis, and that no specific airway-clearance technique is clearly superior, but for any individual patient the technique that is most likely to maximize patient adherence to treatment is preferred. Airway clearance therapy appears likely to be of benefit in the routine care of children with neuromuscular disease and cerebral palsy, and is probably of benefit in treating atelectasis in children on mechanical ventilation. 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.     

New approaches in the rehabilitation of the traumatic high level quadriplegic

The use of noninvasive alternatives to tracheostomy for ventilatory support have been described in the patient management of various neuromuscular disorders. The use of these techniques for patients with traumatic high level quadriplegia, however, is hampered by the resort to tracheostomy in the acute hospital setting. Twenty traumatic high level quadriplegic patients on intermittent positive pressure ventilation (IPPV) via tracheostomy with little or no ability for unassisted breathing were converted to noninvasive ventilatory support methods and had their tracheostomy sites closed. Four additional patients were ventilated by noninvasive methods without tracheostomy. These methods included the use of body ventilators and the noninvasive intermittent positive airway pressure alternatives of IPPV via the mouth, nose, or custom acrylic strapless oral-nasal interface (SONI). Overnight end-tidal pCO2 studies and monitoring of oxyhemoglobin saturation (SaO2) were used to adjust ventilator volumes and to document effective ventilation during sleep. No significant complications have resulted from the use of these methods over a period of 45 patient-years. Elimination of the tracheostomy permitted significant free time by glossopharyngeal breathing for four patients, two of whom had no measurable vital capacity. We conclude that noninvasive ventilatory support alternatives can be effective and deserve further study in this patient population.     

Noninvasive ventilation for acute respiratory failure

PURPOSE OF REVIEW: This review critically examines recent literature related to applications of noninvasive ventilation in the acute setting. RECENT FINDINGS: Recent articles have strengthened the evidence supporting the use of noninvasive ventilation for patients with cardiogenic pulmonary edema and exacerbation of severe chronic pulmonary obstructive disease. In the former, however, it remains unclear whether noninvasive ventilation offers any significant advantages over continuous positive airway pressure. The rate of myocardial infarction seems to be no higher when patients with cardiogenic pulmonary edema are treated with noninvasive ventilation rather than continuous positive airway pressure, although caution is still advised in patients with acute coronary syndromes. Noninvasive ventilation also does not seem to increase the risk of dissemination of severe acute respiratory syndrome to health care workers as long as strict isolation procedures are used. Noninvasive ventilation facilitates weaning in patients with chronic obstructive pulmonary disease but should not be used routinely to treat extubation failure, and necessary intubation should not be delayed. Guidelines for the use of noninvasive ventilation can alter caregivers' behavior but have not been clearly shown to improve outcomes. Outcomes do seem to improve, however, as caregivers acquire experience with the technique. SUMMARY: The recent literature has refined some of the current indications for noninvasive ventilation in the acute-care setting, including chronic pulmonary obstructive disease and cardiogenic pulmonary edema. Guidelines for use are now being developed, and outcomes seem to be improving, partly as a consequence of greater caregiver experience and possibly related to technologic advances.     

Neuromuscular disease causing acute respiratory failure

In the developed world, Guillain-Barré syndrome and myasthenia gravis account for the majority of cases of acute respiratory failure associated with neuromuscular disease. The 4 components that contribute to respiratory failure are upper-airway dysfunction, inspiratory-muscle weakness, expiratory-muscle weakness, and the pulmonary complications associated with these conditions. Careful observation and objective monitoring are essential to determine the appropriate timing of intubation and mechanical ventilation. Pulmonary function tests that can help predict the need for mechanical ventilation include vital capacity, peak inspiratory pressure, and peak expiratory pressure. The morbidity and mortality of patients who require mechanical ventilation are not insubstantial. This paper will review the mechanisms underlying acute respiratory failure, the clinical assessment of patients, the predictors of the need for mechanical ventilation, and the intensive-care-unit morbidity and mortality of patients with Guillain-Barré syndrome or myasthenia gravis.