- Respiratory complications are a leading cause of death post injury
- All patients with a spinal cord injury above L1 will have some form of lung dysfunction. The higher the level of injury the more severe the lung dysfunction will be
- As vital capacity is directly related to respiratory muscle strength, the higher the spinal cord injury the greater the decrease in vital capacity. A downward trend in vital capacity should be fully investigated as may lead to respiratory insufficiency
- Patients with tetraplegia with lesions at C5 and above have improved ventilation in supine position. Vital capacity is decreased in the sitting position due to increased effects of gravity on the abdominal contents, which leads to increased residual lung volume
- Atelectasis is the most common respiratory complication in patients with spinal cord injury and may lead to pneumonia, pleural effusion, and empyema
- Respiratory infections should be treated promptly with assisted coughing, physiotherapy, and antibiotics
- Patients with tetraplegia should be encouraged to perform daily routine inspiratory resistive training as this has been shown to improve strength and endurance of weak diaphragms and increase lung function
Atelectasis: Atelectasis is the most common respiratory complication of spinal cord injury. It refers to a collapsed lung segment due to retained secretions/decreased ventilation.
Bilevel Positive Airway Pressure (BiPAP): Bilevel Positive Airway Pressure delivers a preset inspiratory positive airway pressure (IPAP) followed by a preset expiratory positive airway pressure (EPAP).
Continuous Positive Airway Pressure (CPAP): Continuous Positive Airway Pressure is the use of continuous positive pressure to maintain a continuous level of positive airway pressure.
Forced Expiratory Volume in 1 second (FEV1): The FEV1 is the maximum volume of air that can be forcefully exhaled during one second.
Peak Expiratory Flow (PEF): The Peak Expiratory Flow is the maximum flow (speed of expiration) generated during maximum forceful expiration after a full inspiration.
Residual Volume: The volume of air remaining in the lungs after a maximal exhalation.
Vital Capacity (VC): Vital capacity is the maximum volume of air that can be expelled after a maximum inspiration.
All patients with a spinal cord injury above L1 will have some form of lung dysfunction. The higher the level of injury the more severe the lung dysfunction will be.
Respiratory complications are the leading cause of death in patients with spinal cord injury (37% in first year; 21% after) (Braddom, 2006).
50% of patients with complete cervical spinal cord injury will develop pneumonia in first month post injury.
Up to 40% of patients with spinal cord injury will have sleep apnea.
Pulmonary embolus is the third most common cause of death in the first year following spinal cord injury.
Braddom, R.L. (2006). Physical medicine and rehabilitation (3rd ed.). Philadelphia: Saunders.
Respiratory dysfunction resulting from cervical spinal cord injury depends on the level of injury and the extent of innervation. The higher level lesions result in denervation of progressively more of the expiratory and inspiratory muscles as illustrated in the image shown. Although the primary consequence of spinal cord injury is denervation of the respiratory pump, secondary consequences occur within the lungs because of the inability to effectively distend and inflate the lung to its full capacity. As a consequence, the compliance of the lungs diminishes with increasing time after spinal cord injury.
Complete paralysis of all muscles involved with respiration occurs when the lesion is above C3; this type of injury requires immediate and permanent ventilatory support in order to sustain life. The primary goal of ventilatory support is to ensure arterial blood gas homeostasis.
When the injury is between C3 to C5 (innervation of the diaphragm), respiratory insufficiency occurs via respiratory muscle dysfunction. Although primary and some accessory muscles of inspiration are fully innervated with injuries below cervical lesions, the ability to ventilate at higher levels is still compromised because the intercostals and other chest wall muscles do not provide the integrated expansion of the upper chest wall as the diaphragm descends during inspiration. Furthermore, ventilation during exercise can be greatly compromised. The expiratory muscles actively contract in healthy people whereas partial or fully denervated expiratory muscles in those with spinal cord injury will diminish exercise ventilation and ventilatory reserve.
Spinal cord injury at most levels affects innervation of the abdominal muscles (see image), which severely compromises the ability to generate cough and clear respiratory secretions. Cough generation is accomplished primarily by the expiratory intercostals muscles (thoracic roots) and the abdominal muscles (T4-L1). Cough is important as a defence mechanism to prevent respiratory tract infections and atelectasis. The respiratory system has other important roles such as speaking and posture-related activities which can also be negatively impacted by the spinal cord injury, especially with higher lesions.
(used with permission from www.scireproject.com)
Signs and symptoms
Atelactasis may present with:
- Change in respiratory rate
- Shortness of breath
- Increased heart rate
- Increased anxiety
- Increased volume or thickness of secretions
- Decrease in Vital Capacity (VC)
- Decrease in Peak Expiratory Flow (PEF)
- Decreased oxygen saturation
- Elevated temperature
Deep venous thrombosis/pulmonary embolus may present with:
- Swelling, redness, pain in the leg
- Shortness of breath, chest pain
- Unusual symptoms such as Autonomic Dysreflexia (AD), unexplained fever, or altered mental state
Risk factors for respiratory complications in patients with spinal cord injury:
- Higher level of complete neurological impairment
- Age >50 years
- Recent hospital admission
- Chronic lung disease (e.g., Chronic Obstructive Pulmonary Disease [COPD])
- Severe postural deformity
- Decrease in pulmonary function tests
Management and recommendations
Atelectasis needs to be recognised and treated to avoid further complications such as pneumonia, pleural effusion, and empyema.
Atelectasis is most commonly found in the left lower lobe so auscultation should be done either sitting up on lying on right side. Monitoring vital capacity is one of the best ways to detect early problems.
Treatment includes both lung expansion and mobilisation and clearing for secretions. This can be accomplished using different methods:
- Assisted coughing (using abdominal thrust or compression)
- Use of insufflator/exsufflator (device that delivers a deep breath then sucks the air out - video)
- Chest physiotherapy
- Placing patient in supine position (increases FEV1 and vital capacity)
- Bronchodilator (patients with spinal cord injury often have hyperactive airway due to unopposed cholinergic tone)
- Abdominal binder (helps reduce residual lung volume in sitting position)
- Continuous Positive Airway Pressure (CPAP) or Bilevel Positive Airway Pressure (BPAP)
- Increasing tidal volume on ventilator
Any signs or symptoms of pneumonia should be evaluated promptly with a chest x-ray and treated with assisted coughing, physiotherapy, and antibiotics.
- Closely monitor patients with an increased number of respiratory infections and/or hospital admissions for respiratory problems or refer to respirology
- Encourage patients with tetraplegia to perform routine daily inspiratory resistive training, which has been shown to improve strength and endurance of weak diaphragm and increase lung function
- Yearly Pulmonary Function Tests and/or respirology check-ups
- Smoking cessation
- Consider sleep study or nocturnal oximetry test to check for sleep apnea if there are signs and symptoms of sleep apnea
- Yearly influenza vaccination
- Pneumococcal vaccination, repeat once if first dose before age 65
- Encourage exercise (increases lung capacity)
There is level 4 evidence (based on 3 pre-post studies) (Almenoff et al., 1995; Spungen et al., 1993; Schilero et al., 2004) that ipratropium and metaproterenol have a positive effect on pulmonary function in subjects with tetraplegia.
There is level 1 evidence (based on 1 RCT) (Grimm et al., 2006) that salmeterol has a positive effect on pulmonary function in subjects with tetraplegia.
- Occurs in about 1 in 5 patients within the first week of spinal cord injury
- Can also occur later due to contributing factors:
- Post-traumatic syringomyelia (fluid filled cavity in spinal cord)
- Cervical spinal stenosis with compression
- Progressive scoliosis/kyphosis
- Loss of diaphragm motor fibres
- Signs of impending respiratory failure:
- Hypoxia with increase in respiratory rate
- Decrease in vital capacity to less than 15cc/kg ideal body weight
- Decrease negative inspiratory force to less than 20cm H2O
- Recognise early
- Requires intubation and mechanical ventilation
- If intubation necessary for more than 5 days consider tracheostomy
Almenoff, P.L., Alexander, L.R., Spungen, A.M., Lesser, M.D., & Bauman, W.A. (1995). Bronchodilatory effects of ipratropium bromide in patients with tetraplegia. Paraplegia, 33(5), 274-7.
Braddom, R.L. (2006). Physical medicine and rehabilitation (3rd ed.). Philadelphia: Saunders.
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