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Treatment of Pulmonary Disease Following Cervical Spinal Cord Injury

Summary

Evidence Report/Technology Assessment: Number 27

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Under its Evidence-based Practice Program, the Agency for Healthcare Research and Quality (AHRQ) is developing scientific information for other agencies and organizations on which to base clinical guidelines, performance measures, and other quality improvement tools. Contractor institutions review all relevant scientific literature on assigned clinical care topics and produce evidence reports and technology assessments, conduct research on methodologies and the effectiveness of their implementation, and participate in technical assistance activities.

Overview / Reporting the Evidence / Methodology / Findings / Future Research / Availability of the Full Report



Overview

The incidence of spinal cord injury (SCI) in the United States is approximately 10,000 new cases each year or 32 to 35 persons per million population. Because persons with SCI are surviving longer, the prevalence has been increasing and is now above 200,000 persons in the US. Despite being relatively uncommon, SCI is very expensive to treat incurring enormous costs for acute medical care, rehabilitation, medications and supplies, modification to home and vehicles, and personal assistance. SCI is the most expensive condition among all causes for hospitalization.

Injuries at the cervical level of the spinal cord, depending on the completeness of the lesion, can lead to tetraplegia, loss of sensory function, and paralysis of the respiratory muscles. Patients with paralyzed inspiratory muscles (principally the diaphragm) may not be able to breathe on their own and often must be placed on mechanical ventilators. Patients with weak or paralyzed expiratory muscles (principally the abdominal and intercostal muscles) may have impaired ability to cough and clear mucoid secretions. The accumulation of retained secretions can lead to atelectasis and pneumonia.

Respiratory failure is the most common cause of death for patients with cervical injuries (particularly high-cervical injuries) during the acute phase of hospitalization, and one of the three most common causes of death subsequently; 30 percent during acute hospitalization and 20 percent subsequently. The rate of respiratory complications is highest in the weeks immediately following SCI. Atelectasis and pneumonia are the most frequent respiratory complications.

This report assesses the evidence currently available on the prevention and treatment of pulmonary disease following traumatic cervical SCI. It focuses on empirical studies relating to two research questions:

  1. The management of ventilatory insufficiency in acute and chronic phases, including weaning from mechanical ventilation (MV), management of secretions, atelectasis, and pulmonary infection.
  2. The prevention of late respiratory failure in patients with traumatic cervical SCI.

Excluded from consideration were nonpulmonary complications of SCI and venous thromboembolism/pulmonary embolus. The report does not cover patients with SCIs occurring below the cervical level or respiratory muscle weakness caused by neuromuscular or other spinal cord diseases such as Guillain-Barré syndrome and polio.

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Reporting the Evidence

The key questions addressed in the report are:

  1. For persons with traumatic high cervical SCI who are at high risk of respiratory failure or require ventilator support, what are the best practices regarding ventilator management? Specifically:
    1. What characteristics predict need for initiation of mechanical ventilation?
    2. What characteristics predict success in weaning from mechanical ventilation?
    3. What ventilator management techniques improve the ability to wean from MV?
    4. What are safe and effective techniques for intubation and airway management?
    5. What are ventilator management techniques that can preserve lung compliance, prevent atelectasis, and reduce the risk of complications?
  2. For persons with traumatic cervical SCI who breathe on their own, what interventions—including medications (bronchodilators, mucolytics) and prophylactic respiratory therapy (noninvasive positive pressure ventilation [NPPV], assisted cough, postural drainage, humidification, spirometry, vital capacity [VC] assessment)—are effective to reduce the risk of late respiratory failure?

The report's focus is on patients with acute traumatic cervical SCI, regardless of the degree of completeness of injury. It also examines treatment in the days to months following acute injury and also the long-term followup over years.

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Methodology

Databases searched for literature were MEDLINE® (1966- Feb 2000), HealthSTAR (1975-Feb 2000), Cumulative Index to Nursing and Allied Health Literature (CINAHL®) (1983- Feb 2000), and EMBASE® (1980-Feb 2000). The search strategies combined an SCI concept (implemented using MeSH terms spinal cord injuries, paraplegia, and quadriplegia [exploded] and text words for tetraplegia, quadriplegia, and paraplegia) with a pulmonary disease concept. The search was limited to articles pertaining to humans and published in the English language.

Empirical studies or review articles were included after screening by the following criteria:

  1. The study population includes traumatic cervical SCI.
  2. Study question relates to the research questions described above.
  3. Study includes data on health outcomes, health services utilization or economic outcomes, or physiologic measures related to respiratory status.
  4. Study design is controlled trial, prospective trial with historical controls, prospective or retrospective cohort study, or medium- to large-sized (more than 20 subjects) case series.

Each article was independently reviewed by at least two investigators.

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Findings

Patients with cervical SCI are at significant risk for ventilatory failure, and this risk differs by the level and completeness of injury. Ventilatory support is needed for a majority of patients with C5 and higher injuries and virtually all patients with C3 and higher injuries in the acute phase. Patients with lower-cervical SCI are less likely to require mechanical ventilation (MV), as are those patients with greater forced vital capacity (FVC) on presentation. The amount of secretions and serious pulmonary infection (pneumonia) are associated with the need for MV. This finding suggests that treatments aimed at improving ventilation, cough, and secretion clearance may reduce the need for MV.

MV for ventilatory failure is usually performed using invasive (endotracheal or nasotracheal) intubation. However, NPPV can be successful for short- and long-term ventilatory assistance when used properly, particularly when patients have spontaneous FVC approaching 1 liter. In patients with C4 level of injury (LOI), weaning from MV is often a protracted process that is sometimes not successful. However, patients with C4-level SCI appear to have greater success when weaned by progressive ventilatory-free breathing than by synchronized intermittent mandatory ventilation techniques, which are more commonly used in patients with other causes for ventilatory failure. Furthermore, high ventilator volume (more than 20 cc/kg) is associated with less atelectasis and faster weaning.

Evidence is available on a variety of therapeutic and clinical assessment strategies among patients with traumatic tetraplegia, including the following:

  • Active respiratory muscle exercise with incentive spirometry, inspiratory resistance training, and abdominal weight training have all been associated with improvements in spontaneous vital capacity (VC) in prospective case series. However, in small randomized controlled trials (RCTs), these techniques have not been shown to improve ventilation, nor have the trials shown any difference between inspiratory resistance training and abdominal weight training.
  • Deflating cuffed tracheostomies or switching to cuffless tracheostomies is necessary to permit speech, but can cause hypocapnia as a result of increasing tidal volume to compensate for variable upper-airway leak. Adding dead space can increase pCO2 to near-normal levels, reducing hypocapnia during waking and sleeping periods. Speech valves are available to permit better speech.
  • Electrophrenic respiration has been successfully used for chronic ventilatory support, most often for part-time ventilatory support. Technologic advances in recent years appear to have improved the success of the technique, but reliability remains an important problem.
  • The pneumobelt may be used for part-time ventilatory support or as an adjunct to full-time noninvasive ventilatory support.
  • Noninvasive ventilation may reduce the risk of pneumonia compared with tracheostomy positive pressure ventilation for patients requiring chronic ventilatory support. This technique may also prevent the need for invasive ventilation for patients with acute ventilatory insufficiency.
  • Glossopharyngeal breathing training can allow patients ventilator-free breathing for short periods and improve the effectiveness of cough and audibility of their voices.
  • Cough is improved with manual assisted cough by 15 to 33 percent in two studies. Positive pressure insufflation can improve cough as well. These techniques used together provided near-normal cough peak flows. Although abdominal binding (corset) did not improve spontaneous cough when used alone, when used in conjunction with manual assisted cough, positive pressure insufflation, or both, a trend toward improvement was suggested by one study. It follows that cough can also be improved by mechanical insufflation-exsufflation, as this technique provides 10 liters/second of expiratory flow.
  • Rotating beds have been associated with lower rates of pulmonary complications compared with less frequent turning with a wedge turning device in patients with cervical SCI in retrospective case series.
  • Aggressive multi-modal respiratory therapy interventions (including frequent turning, suctioning [and bronchial lavage], chest percussion and assisted coughing, inhaled bronchodilator treatments, deep breathing, and incentive spirometry) have been associated with improvements in atelectasis in a small case series. The interventions have also been associated with reduced mortality, atelectasis, need for MV, and tracheostomy in a larger historical cohort comparison.
  • The reduction in VC associated with a change in position from supine to sitting is both statistically significant and clinically important. Hence, the seated position in which spirometric tests are usually performed is not optimal for patients with cervical SCI, in that FVC will be underestimated in this position.
  • Periodic chest roentgenography often discloses lesions for patients with tetraplegia, even in the absence of symptoms. Conversely, normal upright chest roentgenograms are not sensitive enough to exclude pulmonary abnormalities, particularly pleural effusions (which can be seen on lateral decubitus views).
  • In imaging the upper airway, tomography had better agreement with endoscopy for tracheal than glottic stenosis. Computed tomography was more accurate than tomography for diagnosing glottic stenosis, but was similarly accurate for grading the severity of tracheal stenosis.
  • Studies of bronchodilator effects suggest potential therapeutic benefit from long-term prophylactic therapy with inhaled beta-agonists to reduce symptoms of breathlessness associated with airway reactivity in persons with tetraplegia. However, none of these studies evaluated the long-term efficacy of bronchodilator or other drug treatments on symptoms, pulmonary function, or the incidence of pulmonary complications.
  • Very little data are available with which to describe the risk of late ventilatory failure or the potential effectiveness of treatments to delay or prevent it.
  • Despite the expectations of nondisabled persons, the long-term perceived quality of life and well-being are similar in ventilator-dependent and autonomously breathing patients with SCI.

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Future Research

Further research should be performed to answer important questions about the best care for patients with acute and chronic cervical SCI. The evidence base of clinical research on the management of pulmonary disease in this condition covers only a small number of many important management decisions. In addition, the amount and quality of the literature is relatively poor, with few studies using RCT or other designs to reduce bias. Clinical research on patients with cervical SCI has primarily been limited to observational studies, and primarily retrospective case series. Determining the influences of the interventions is problematic for several reasons, including imprecise characterization of treatments and lack of appropriate controls. Few of the extant studies have any type of comparison group. Case series can provide rates of outcome events (e.g., complications, successful weaning) that can be compared across series (benchmarks). However, case series provide biased and imprecise estimates of relative effectiveness and are less powerful than study designs that offer internal comparisons (e.g., RCTs, concurrent cohort comparisons, and historical cohort comparisons).

There is also a need for more precise and consistent characterization of the patients in terms of important prognostic features such as LOI, completeness, and time since injury. Most of the evidence comes from retrospective case series in which the intervention is difficult to characterize. In various studies, the method of clinical care is either not described or described individually for each patient in the series. In some studies that adequately describe the protocol for care, it is not possible to estimate the effects for individual components of care.

Finally, many of the clinical studies had small sample sizes. A small size limits the generalizability of a case series. For more well-designed studies, the small sample sizes limit the statistical power; for example, the few RCTs identified in this study were negative and lacked the statistical power to show clinically important differences. Future studies should seek to improve both the generalizability and the statistical power by including more patients. Because of the relative rarity of the condition, it will be necessary to aggregate patients through merging standardized data sets from many institutions or developing multi-site research networks.

The U.S. Model Spinal Cord Injury Systems Program is a network of 18 centers. They work together to maintain a national database, provide continuing education, and participate in independent and collaborative research relating to SCI. The "Model Systems" database has contributed greatly to our knowledge of the prevalence, natural history, cost, and sequelae of SCI. The data have clearly demonstrated improvement in survival of patients with SCI over the past few decades. Furthermore, the database, through measurement of incidence of complications, ventilator use at discharge, and other parameters, has been used to create benchmarks to guide the care of persons with SCI.

The Model Systems database currently does not include detailed clinical data of the type needed to examine how differences in clinical practice (e.g., ventilator settings, frequency and type of respiratory therapy) might influence clinical outcomes such as weaning success, time on MV, incidence of atelectasis, or mortality. Agreeing on specific detailed clinical data to collect on day-to-day management practices for persons with SCI, and expanding the Model Systems database to include such data, would make it possible to correlate clinical practices with the health outcomes already obtained in Model Systems data. This would seem a natural extension of the current effort and would facilitate inter-site collaboration in the design and conduct of prospective clinical trials, which would be necessary to definitively answer questions of clinical management.

The Department of Veterans Affairs (VA) network of 23 designated SCI centers handles approximately two-thirds of VA in-patient visits for persons with SCI. The Department has recently developed a national registry of veterans with spinal cord dysfunction to allow more effective planning and administration for SCI care, both in the specialized centers and throughout the network of VA hospitals and clinics. The clinical database, obtained by linking data from the Department's patient treatment file, is, like the Model Systems database, insufficiently detailed for effective outcomes research.

Further queries of the Model Systems and VA databases are warranted to describe the occurrence of respiratory illnesses and complications in the course of care following SCI. Few of the currently available reports of Model Systems data have focused primarily on respiratory complications. Despite the lack of detailed data on treatment, the database does provide an opportunity to better describe the epidemiology of respiratory illness and complications. This more-detailed information could be useful for estimating the burden of illness, for modeling, or for cost-effectiveness analysis. These types of data, in turn, will provide motivation for funders to support collaborative clinical research efforts.

An active clinical research network would offer the opportunity to implement protocols across multiple institutions, and to test for differences in outcomes associated with different protocols. A variety of management algorithms have been either described in the literature or put to use within systems or single institutions. Not one of these guidelines was developed using an explicit evidence-based process or has been rigorously tested in clinical practice. The evidence compiled in this report will be used by the Consortium for Spinal Cord Medicine in their efforts to develop a new guideline using a more explicit process linking recommendations to evidence. Much of the justification for the current respiratory care of patients with tetraplegia comes from data on or experience with patients with other illnesses; thus, guidelines on this topic will need to be based to a large extent on interpretation of these data. Explicit methods are needed for integrating data on related populations with our understanding of the pathophysiology of cervical SCI and other diseases. The Consortium for Spinal Cord Medicine, professional associations and similar groups, after examining the current state of research in this area, would be in a good position to outline an agenda for future research by prioritizing questions that would be most useful in guiding clinical care.

Most of the published research on pulmonary disease in SCI focuses on care of acutely injured subjects. As acute SCI is the most expensive condition among all causes for hospitalization, the acute management phase should be a high priority for research. However, as long-term SCI survival has increased, the prevalence of patients with chronic SCI grows ever larger; and pulmonary complications of chronic SCI will become of greater clinical importance. Currently, little data are available regarding the incidence of late respiratory failure, and even fewer data are available on the effectiveness of therapies that may be effective to prevent it. In this instance, venues such as the VA spinal cord injury centers and the Model Systems institutions (in which cohorts of patients with chronic cervical SCI are followed) might decide that the systematic collection of data about their patients' clinical care could be valuable.

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Availability of the Full Report

The full evidence report from which this summary was derived was prepared by the Agency for Healthcare Research and Quality by the dukeepc.htm">Duke Evidence-based Practice Center under contract No. 290-97-0014. Printed copies may be obtained free of charge from the AHRQ Publications Clearinghouse by calling 1-800-358-9295. Requestors should ask for Evidence Report/Technology Assessment No. 27, Treatment of Pulmonary Disease Following Cervical Spinal Cord Injury (AHRQ Publication No. 01-E014).

The Evidence Report is also online on the National Library of Medicine Bookshelf.

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AHRQ Publication Number 01-E013
Current as of June 2001

 

The information on this page is archived and provided for reference purposes only.

 

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