Summary
Evidence Report/Technology Assessment: Number 27
Please Note: The evidence report this summary was derived from has not been updated within the past 5 years and is therefore no longer considered current. It is maintained for archival purposes only.
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:
- The management
of ventilatory insufficiency in acute and chronic
phases, including weaning from mechanical
ventilation (MV), management of secretions,
atelectasis, and pulmonary infection.
- 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:
- 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:
- What characteristics predict need for
initiation of mechanical ventilation?
- What characteristics predict success in
weaning from mechanical ventilation?
- What ventilator management techniques
improve the ability to wean from MV?
- What are safe and effective techniques
for intubation and airway management?
- What are ventilator management
techniques that can preserve lung
compliance, prevent atelectasis, and reduce
the risk of complications?
- 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:
- The study population includes traumatic cervical SCI.
- Study question relates to the research questions described
above.
- Study includes data on health outcomes, health services
utilization or economic outcomes, or physiologic
measures related to respiratory status.
- 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 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
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