### Evidence Report/Technology Assessment: Number 27

# Treatment of Pulmonary Disease Following Cervical Spinal Cord Injury

## Summary

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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

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## Overview

The incidence of spinal cord injury (SCI) inthe United States is approximately 10,000 newcases each year or 32 to 35 persons per millionpopulation. Because persons with SCI aresurviving longer, the prevalence has beenincreasing and is now above 200,000 persons inthe US. Despite being relatively uncommon,SCI is very expensive to treat incurring enormouscosts for acute medical care, rehabilitation,medications and supplies, modification to homeand vehicles, and personal assistance. SCI is themost expensive condition among all causes forhospitalization.

Injuries at the cervical level of the spinal cord,depending on the completeness of the lesion, canlead to tetraplegia, loss of sensory function, andparalysis of the respiratory muscles. Patients withparalyzed inspiratory muscles (principally thediaphragm) may not be able to breathe on theirown and often must be placed on mechanicalventilators. Patients with weak or paralyzedexpiratory muscles (principally the abdominal andintercostal muscles) may have impaired ability tocough and clear mucoid secretions. Theaccumulation of retained secretions can lead toatelectasis and pneumonia.

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

This report assesses the evidence currentlyavailable on the prevention and treatment ofpulmonary disease following traumatic cervicalSCI. It focuses on empirical studies relating totwo research questions:

- The managementof ventilatory insufficiency in acute and chronicphases, including weaning from mechanicalventilation (MV), management of secretions,atelectasis, and pulmonary infection.
- The prevention of late respiratory failure in patientswith traumatic cervical SCI. 

Excluded from consideration were nonpulmonary complicationsof SCI and venous thromboembolism/pulmonaryembolus. The report does not cover patients withSCIs occurring below the cervical level orrespiratory muscle weakness caused byneuromuscular or other spinal cord diseases suchas Guillain-Barré syndrome and polio.

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## Reporting the Evidence

The key questions addressed in the report are:

- For persons with traumatic high cervical SCIwho are at high risk of respiratory failure orrequire ventilator support, what are the bestpractices regarding ventilator management?Specifically:   - What characteristics predict need forinitiation of mechanical ventilation?
  - What characteristics predict success inweaning from mechanical ventilation?
  - What ventilator management techniquesimprove the ability to wean from MV?
  - What are safe and effective techniquesfor intubation and airway management?
  - What are ventilator managementtechniques that can preserve lungcompliance, prevent atelectasis, and reducethe risk of complications?
- For persons with traumatic cervical SCI whobreathe on their own, what interventions—including medications (bronchodilators,mucolytics) and prophylactic respiratorytherapy (noninvasive positive pressureventilation [NPPV], assisted cough, posturaldrainage, humidification, spirometry, vitalcapacity [VC] assessment)—are effective to reduce therisk of late respiratory failure?

The report's focus is on patients with acute traumaticcervical SCI, regardless of the degree of completeness of injury.It also examines treatment in the days to months followingacute 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 Indexto Nursing and Allied Health Literature (CINAHL®) (1983-Feb 2000), and EMBASE® (1980-Feb 2000). The searchstrategies combined an SCI concept (implemented usingMeSH terms spinal cord injuries, paraplegia, and quadriplegia[exploded] and text words for tetraplegia, quadriplegia, andparaplegia) with a pulmonary disease concept. The search waslimited to articles pertaining to humans and published in theEnglish language.

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

- The study population includes traumatic cervical SCI.
- Study question relates to the research questions describedabove.
- Study includes data on health outcomes, health servicesutilization or economic outcomes, or physiologicmeasures related to respiratory status.
- Study design is controlled trial, prospective trial withhistorical controls, prospective or retrospective cohortstudy, or medium- to large-sized (more than 20 subjects)case series.

Each article was independently reviewed by at least twoinvestigators.

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## Findings

Patients with cervical SCI are at significant risk forventilatory failure, and this risk differs by the level andcompleteness of injury. Ventilatory support is needed for amajority of patients with C5 and higher injuries and virtuallyall patients with C3 and higher injuries in the acute phase.Patients with lower-cervical SCI are less likely to requiremechanical ventilation (MV), as are those patients with greaterforced vital capacity (FVC) on presentation. The amount ofsecretions and serious pulmonary infection (pneumonia) areassociated with the need for MV. This finding suggests thattreatments aimed at improving ventilation, cough, andsecretion clearance may reduce the need for MV.

MV for ventilatory failure is usually performed usinginvasive (endotracheal or nasotracheal) intubation. However,NPPV can be successful for short- and long-term ventilatoryassistance when used properly, particularly when patients havespontaneous FVC approaching 1 liter. In patients with C4level of injury (LOI), weaning from MV is often a protractedprocess that is sometimes not successful. However, patientswith C4-level SCI appear to have greater success when weanedby progressive ventilatory-free breathing than by synchronizedintermittent mandatory ventilation techniques, which aremore commonly used in patients with other causes forventilatory failure. Furthermore, high ventilator volume (morethan 20 cc/kg) is associated with less atelectasis and fasterweaning.

Evidence is available on a variety of therapeutic and clinicalassessment strategies among patients with traumatictetraplegia, including the following:

- Active respiratory muscle exercise with incentivespirometry, inspiratory resistance training, and abdominalweight training have all been associated withimprovements in spontaneous vital capacity (VC) inprospective case series. However, in small randomizedcontrolled trials (RCTs), these techniques have not beenshown to improve ventilation, nor have the trials shownany difference between inspiratory resistance training andabdominal weight training.
- Deflating cuffed tracheostomies or switching to cufflesstracheostomies is necessary to permit speech, but cancause hypocapnia as a result of increasing tidal volume tocompensate for variable upper-airway leak. Adding deadspace can increase pCO2 to near-normal levels, reducinghypocapnia during waking and sleeping periods. Speechvalves are available to permit better speech.
- Electrophrenic respiration has been successfully used forchronic ventilatory support, most often for part-timeventilatory support. Technologic advances in recent yearsappear to have improved the success of the technique, butreliability remains an important problem.
- The pneumobelt may be used for part-time ventilatorysupport or as an adjunct to full-time noninvasiveventilatory support.
- Noninvasive ventilation may reduce the risk ofpneumonia compared with tracheostomy positive pressureventilation for patients requiring chronic ventilatorysupport. This technique may also prevent the need forinvasive ventilation for patients with acute ventilatoryinsufficiency.
- Glossopharyngeal breathing training can allow patientsventilator-free breathing for short periods and improvethe effectiveness of cough and audibility of their voices.
- Cough is improved with manual assisted cough by 15 to33 percent in two studies. Positive pressure insufflationcan improve cough as well. These techniques usedtogether provided near-normal cough peak flows.Although abdominal binding (corset) did not improvespontaneous cough when used alone, when used inconjunction with manual assisted cough, positive pressureinsufflation, or both, a trend toward improvement wassuggested by one study. It follows that cough can also be improved by mechanical insufflation-exsufflation, as thistechnique provides 10 liters/second of expiratory flow.
- Rotating beds have been associated with lower rates ofpulmonary complications compared with less frequentturning with a wedge turning device in patients withcervical SCI in retrospective case series.
- Aggressive multi-modal respiratory therapy interventions(including frequent turning, suctioning [and bronchiallavage], chest percussion and assisted coughing, inhaledbronchodilator treatments, deep breathing, and incentivespirometry) have been associated with improvements inatelectasis in a small case series. The interventions havealso been associated with reduced mortality, atelectasis,need for MV, and tracheostomy in a larger historicalcohort comparison.
- The reduction in VC associated with a change in positionfrom supine to sitting is both statistically significant andclinically important. Hence, the seated position in whichspirometric tests are usually performed is not optimal forpatients with cervical SCI, in that FVC will beunderestimated in this position.
- Periodic chest roentgenography often discloses lesions forpatients with tetraplegia, even in the absence ofsymptoms. Conversely, normal upright chestroentgenograms are not sensitive enough to excludepulmonary abnormalities, particularly pleural effusions(which can be seen on lateral decubitus views).
- In imaging the upper airway, tomography had betteragreement with endoscopy for tracheal than glotticstenosis. Computed tomography was more accurate thantomography for diagnosing glottic stenosis, but wassimilarly accurate for grading the severity of trachealstenosis.
- Studies of bronchodilator effects suggest potentialtherapeutic benefit from long-term prophylactic therapywith inhaled beta-agonists to reduce symptoms ofbreathlessness associated with airway reactivity in personswith tetraplegia. However, none of these studiesevaluated the long-term efficacy of bronchodilator orother drug treatments on symptoms, pulmonary function,or the incidence of pulmonary complications.
- Very little data are available with which to describe therisk of late ventilatory failure or the potential effectivenessof treatments to delay or prevent it.
- Despite the expectations of nondisabled persons, thelong-term perceived quality of life and well-being aresimilar in ventilator-dependent and autonomouslybreathing patients with SCI.

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## Future Research

Further research should be performed to answer importantquestions about the best care for patients with acute andchronic cervical SCI. The evidence base of clinical research onthe management of pulmonary disease in this condition coversonly a small number of many important managementdecisions. In addition, the amount and quality of theliterature is relatively poor, with few studies using RCT orother designs to reduce bias. Clinical research on patients withcervical SCI has primarily been limited to observationalstudies, and primarily retrospective case series. Determiningthe influences of the interventions is problematic for severalreasons, including imprecise characterization of treatments andlack of appropriate controls. Few of the extant studies haveany type of comparison group. Case series can provide rates ofoutcome events (e.g., complications, successful weaning) thatcan be compared across series (benchmarks). However, caseseries provide biased and imprecise estimates of relativeeffectiveness and are less powerful than study designs that offerinternal comparisons (e.g., RCTs, concurrent cohortcomparisons, and historical cohort comparisons).

There is also a need for more precise and consistentcharacterization of the patients in terms of importantprognostic features such as LOI, completeness, and time sinceinjury. Most of the evidence comes from retrospective caseseries in which the intervention is difficult to characterize. Invarious studies, the method of clinical care is either notdescribed or described individually for each patient in theseries. In some studies that adequately describe the protocolfor care, it is not possible to estimate the effects for individualcomponents of care.

Finally, many of the clinical studies had small sample sizes.A small size limits the generalizability of a case series. Formore well-designed studies, the small sample sizes limit thestatistical power; for example, the few RCTs identified in thisstudy were negative and lacked the statistical power to showclinically important differences. Future studies should seek toimprove both the generalizability and the statistical power byincluding more patients. Because of the relative rarity of thecondition, it will be necessary to aggregate patients throughmerging standardized data sets from many institutions ordeveloping multi-site research networks.

The U.S. Model Spinal Cord Injury Systems Program is anetwork of 18 centers. They work together to maintain anational database, provide continuing education, andparticipate in independent and collaborative research relatingto SCI. The "Model Systems" database has contributed greatlyto our knowledge of the prevalence, natural history, cost, andsequelae of SCI. The data have clearly demonstratedimprovement in survival of patients with SCI over the past fewdecades. Furthermore, the database, through measurement ofincidence of complications, ventilator use at discharge, andother parameters, has been used to create benchmarks to guidethe care of persons with SCI.

The Model Systems database currently does not includedetailed clinical data of the type needed to examine howdifferences in clinical practice (e.g., ventilator settings,frequency and type of respiratory therapy) might influenceclinical outcomes such as weaning success, time on MV,incidence of atelectasis, or mortality. Agreeing on specificdetailed clinical data to collect on day-to-day managementpractices for persons with SCI, and expanding the ModelSystems database to include such data, would make it possibleto correlate clinical practices with the health outcomes alreadyobtained in Model Systems data. This would seem a naturalextension of the current effort and would facilitate inter-sitecollaboration in the design and conduct of prospective clinicaltrials, which would be necessary to definitively answerquestions of clinical management.

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

Further queries of the Model Systems and VA databases arewarranted to describe the occurrence of respiratory illnessesand complications in the course of care following SCI. Few ofthe currently available reports of Model Systems data havefocused primarily on respiratory complications. Despite thelack of detailed data on treatment, the database does providean opportunity to better describe the epidemiology ofrespiratory illness and complications. This more-detailedinformation could be useful for estimating the burden ofillness, for modeling, or for cost-effectiveness analysis. Thesetypes of data, in turn, will provide motivation for funders tosupport collaborative clinical research efforts.

An active clinical research network would offer theopportunity to implement protocols across multipleinstitutions, and to test for differences in outcomes associatedwith different protocols. A variety of management algorithmshave been either described in the literature or put to usewithin systems or single institutions. Not one of theseguidelines was developed using an explicit evidence-basedprocess or has been rigorously tested in clinical practice. Theevidence compiled in this report will be used by theConsortium for Spinal Cord Medicine in their efforts todevelop a new guideline using a more explicit process linkingrecommendations to evidence. Much of the justification forthe current respiratory care of patients with tetraplegia comesfrom data on or experience with patients with other illnesses;thus, guidelines on this topic will need to be based to a largeextent on interpretation of these data. Explicit methods areneeded for integrating data on related populations with ourunderstanding of the pathophysiology of cervical SCI andother diseases. The Consortium for Spinal Cord Medicine,professional associations and similar groups, after examiningthe current state of research in this area, would be in a goodposition to outline an agenda for future research byprioritizing questions that would be most useful in guidingclinical care.

Most of the published research on pulmonary disease inSCI focuses on care of acutely injured subjects. As acute SCIis the most expensive condition among all causes forhospitalization, the acute management phase should be a highpriority for research. However, as long-term SCI survival hasincreased, the prevalence of patients with chronic SCI growsever larger; and pulmonary complications of chronic SCI willbecome of greater clinical importance. Currently, little dataare available regarding the incidence of late respiratory failure,and even fewer data are available on the effectiveness oftherapies that may be effective to prevent it. In this instance,venues such as the VA spinal cord injury centers and theModel Systems institutions (in which cohorts of patients withchronic cervical SCI are followed) might decide that thesystematic collection of data about their patients' clinical carecould be valuable.

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## Availability of the Full Report

The full evidence report from which this summary wasderived was prepared by the Agency for Healthcare Researchand Quality by the Duke Evidence-based Practice Centerunder contract  No. 290-97-0014. Printed copies may be obtained free of chargefrom the AHRQ Publications Clearinghouse by calling 1-800-358-9295. Requestors should ask for EvidenceReport/Technology Assessment  No. 27, *Treatment ofPulmonary Disease Following Cervical Spinal Cord Injury* (AHRQ Publication  No. 01-E014).

The Evidence Report is also online on the National Library of Medicine Bookshelf, or can be downloaded as a zipped file.

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*AHRQ Publication Number 01-E013Current as of June 2001*

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**Internet Citation:**

*Treatment of Pulmonary Disease Following Cervical Spinal Cord Injury*. Summary, Evidence Report/Technology Assessment: Number 27. AHRQ Publication  No. 01-E013, June 2001. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/epcsums/spinalsum.htm

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