Respiratory physiologic changes following spinal cord injury
- Eric Garshick, MD, MOH
Eric Garshick, MD, MOH
- Professor of Medicine
- Harvard Medical School
- Section Editor
- Michael J Aminoff, MD, DSc
Michael J Aminoff, MD, DSc
- Editor-in-Chief — Neurology
- Section Editor — Medical Neurology
- Professor of Neurology
- University of California, San Francisco School of Medicine
- Deputy Editors
- Geraldine Finlay, MD
Geraldine Finlay, MD
- Deputy Editor — Pulmonary, Critical Care, and Sleep Medicine
- Associate Professor
- Tufts University School of Medicine
- Janet L Wilterdink, MD
Janet L Wilterdink, MD
- Senior Deputy Editor — UpToDate
- Deputy Editor — Neurology
- Associate Professor
- Brown University School of Medicine
The annual incidence of spinal cord injury (SCI) in the United States is estimated to be 54 cases per million population or approximately 16,965 new cases in 2012 . Since 2010, the most frequent neurologic category of SCI at discharge has been incomplete quadriplegia (also known as tetraplegia) at 45 percent, followed by incomplete paraplegia at 21 percent, complete paraplegia at 20 percent, and complete quadriplegia at 14 percent .
The majority of causes of traumatic SCI in 2012 included vehicular accidents (31 percent), falls (40.4 percent), and firearm injuries (5.4 percent) . The percentage of SCI associated with falls increased significantly from 28 percent in 1997 through 2000 to 66 percent in 2010 through 2012 in persons aged 65 or older. Causes of nontraumatic SCI include tumor, vascular disease, demyelinating spinal cord diseases, and spinal stenosis . Respiratory failure is common after SCI and respiratory complications are among the most common causes of death [4,5], particularly in the years following acute injury  and in patients who have required mechanical ventilation [7,8].
SCI results in physiologic changes that affect many organ systems. The changes in pulmonary physiology that occur following SCI will be reviewed here. The diagnosis and management of acute and chronic SCI and the management of the respiratory complications of SCI are discussed separately. (See "Acute traumatic spinal cord injury" and "Evaluation and acute management of cervical spinal column injuries in adults" and "Chronic complications of spinal cord injury and disease" and "Disorders affecting the spinal cord" and "Respiratory complications in the adult patient with chronic spinal cord injury" and "Spinal column injuries in adults: Definitions, mechanisms, and radiographs".)
ASSESSMENT OF LEVEL AND COMPLETENESS OF SCI
Pulmonary physiologic changes due to spinal cord injury (SCI) are related to the extent of neurological impairment. The American Spinal Injury Association Impairment Scale (AIS) is used to classify the degree of impairment that is based on strength in key muscles and on a sensory exam (table 1) . An exam guide and worksheet for assessing SCI is available through the American Spinal Cord Injury Association. (See "Acute traumatic spinal cord injury", section on 'Clinical presentation'.)
The patient’s strength in key muscle groups is assessed and graded. A muscle grade of 5/5 is normal, and a grade of 3/5 means the muscle can be moved against gravity. The motor level is defined as the most caudal key muscle that is graded 3/5 or 4/5 with the segment cephalad to that level graded 5/5. The sensory level is defined as the most caudal dermatome to have normal sensation for both pinprick and light touch. For areas that lack key muscles to test, such as between T2 and L1, sensory findings are used to estimate motor levels.
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- ASSESSMENT OF LEVEL AND COMPLETENESS OF SCI
- PULMONARY PHYSIOLOGIC CHANGES
- Timing of changes in ventilatory function
- Impairment of ventilatory muscle function
- - Muscles of respiration
- - Injury above C3
- - Injury at C3 through C5
- - Injury at C6 through C8
- - Injuries of the thoracic spinal cord
- Changes in lung and chest wall compliance
- Airflow limitation and bronchial hyperresponsiveness
- Changes in ventilatory control
- ASSESSMENT OF PULMONARY FUNCTION
- Technical considerations in measuring pulmonary function
- - Measurement of height
- - Use of modified ATS standards
- - Mouthpiece for pressure measurements
- Effect of posture
- Expected values for spirometry
- Expected values for lung volumes
- Longitudinal assessment of pulmonary function
- Maximal inspiratory and expiratory pressures
- Bronchial hyperresponsiveness and bronchodilator response
- Other etiologies of PFT abnormalities
- SUMMARY AND RECOMMENDATIONS