A Primary Care Provider’s Guide to Managing Respiratory Health in Subacute and Chronic Spinal Cord Injury

Mr. A is 30 years old with C4 American Spinal Injury Association Impairment Scale (AIS) A tetraplegia from a motor vehicle crash 6 months ago. He initially required tracheostomy and mechanical ventilation. He was successfully weaned and decannulated 3 months ago. His forced vital capacity is 1 liter. He is assisted with respiratory exercises and mechanical insufflation–exsufflation or manual assisted cough to optimize respiratory health and secretion management. He uses CPAP at home for sleep-disordered breathing. This winter, he was admitted to the hospital with influenza and required a short period of reintubation, oxygen, and a course of antiviral therapy. During his hospitalization, he received scheduled nebulizers, mucolytics, percussive therapy, and mechanical insufflation–exsufflation every 4 hours and as needed to manage his secretions. He gradually improved over the next 2 weeks and successfully discharged home.

Spinal cord injury (SCI) alters respiratory physiology, heightening the risk for multiple complications such as atelectasis, bronchitis, pneumonia, and sleep-disordered breathing. Respiratory diseases including pneumonia remain the leading cause of death after SCI, causing or contributing to ~24% of deaths in Veterans with SCI.¹  It remains one of the top reasons for rehospitalization in the first year following SCI, prolongs hospitalization, and negatively impacts quality of life.^2–5  Pneumonia in people with SCI carries higher morbidity and mortality versus the population without SCI. The high incidence of respiratory complications after SCI and their associated mortality underscore the importance of prevention, timely diagnosis, and appropriate treatment. Primary care providers along with consumers with SCI, a physiatrist, and a knowledgeable pulmonologist are key team members in optimizing respiratory health after SCI.

The diaphragm is the primary muscle of inspiration, contributing 70% of the inhaled tidal volume (TV). In quiet inspiration, the diaphragm descends in contraction while the external intercostal muscles work synergistically to expand the rib cage.⁶  During labored breathing, accessory inspiratory muscles (the sternocleidomastoids and upper trapezius, innervated by cranial nerve XI; the scalenes, innervated by C2–C7) are recruited to elevate the upper ribs and sternum.⁷ 

While quiet expiration is passive, forceful expiration and coughing require recruitment of the thoracically innervated rectus abdominis, internal intercostals, and the external and internal obliques.

Higher levels and completeness of injury correlate with the degree of ventilatory dysfunction and risk for complications.⁸  Ventilatory restriction after SCI is characterized by decreased forced vital capacity (VC), 1 second forced expiratory volume (FEV1), inspiratory capacity, and total lung capacity (TLC) but increased residual volume.^8,10  The degree of diaphragmatic involvement determines the ability to wean from ventilatory support, but this varies even with each SCI level. The injury level may also evolve over time. In general, permanent ventilator assistance is usually required for complete SCI at C1 and C2 due to diaphragmatic paralysis.⁸  Initial temporary ventilation with subsequent weaning can be variably achieved with complete SCI at C3. In the absence of other factors that would prevent ventilatory weaning, complete injuries at C4 and below and incomplete higher level SCIs are usually associated with successful weaning.⁹  Neuromuscular changes due to SCI lead to poor abdominal wall stabilization, paradoxical motion of the chest with inspiration, and impaired ability to recruit accessory musculature in high tetraplegia. Reversible obstruction due to bronchial hyperresponsiveness¹⁰  and parasympathetically mediated bronchial mucus hypersecretion¹¹  also occur. If present, a tracheostomy tube further contributes to secretion formation. The combination of restrictive ventilation, weak cough, bronchoconstriction, and hypersecretion are all risk factors for atelectasis, poor secretion clearance, and pulmonary infections.

Respiratory muscle training (RMT) shares the same principles as peripheral muscle training, with the goal of increasing strength and endurance. A training session consists of breathing a set number of times or a specified duration of time. RMT can be inspiratory, expiratory (in low thoracic SCI and below), or both. Handheld devices are used for several possible training regimens (resistive, threshold, and normocapnic hyperpnea) singly or in combination. There are no data identifying which RMT is optimal in SCI. Studies of RMT in tetraplegia demonstrated that it is safely used in acute SCI and increases VC, strength (maximal inspiratory and expiratory pressures), and endurance during the training period.^12–14  Although more research is needed, RMT is currently a widely utilized, safe, and relatively inexpensive training modality. Perhaps if RMT was approached similarly to limb training, with an ongoing maintenance program, the decline in maximum inspiratory pressure/maximum expiratory pressure (MIP/MEP) may be obviated. Precautions include avoiding use in the setting of unstable asthma, pneumothorax, or other barotrauma.

Glossopharyngeal breathing (GPB) is a long-established technique of breath stacking to improve cough and maintain ventilation. Speech therapists are principally involved in training. The patient inspires air to TLC then uses mouth and throat muscles to repeatedly gulp or piston air into the lungs as many times as possible, thus exceeding TLC. This is followed by passive exhalation. GPB improves VC and peak cough flow (PCF),^15,16  with possible improvement in lung compliance and vocal quality. The exercise can be done independently, requires no equipment, and has no contraindications. GPB practice should not only be encouraged but also actively implemented and supported by the rehabilitation team. Note that learning and use of GPB can be less efficient in the presence of a tracheostomy, particularly with an inflated cuff, due to airflow obstruction.

Tetraplegic or high paraplegic SCI reduces VC in an upright position due to flattening and shortening of the diaphragm after loss of abdominal muscle support. Elastic abdominal binders increase abdominal pressure support to position the diaphragm in a higher, more optimal point on its length-tension curve, improving VC and decreasing functional residual capacity.¹⁷  Use cautious introduction and attention to proper positioning to avoid negative impact on breathing and eating. Monitor for increased dyspnea, fatigue, atelectasis, and hypoxemia with abdominal binder use.

Mobilizing secretions is the cornerstone of prevention and treatment of atelectasis and respiratory infections. Although tracheal suctioning and bronchoscopy may sometimes be necessary, the strategies below are often preferred and effective, either alone or in combination.

Mechanical insufflation–exsufflation (MIE) is a commonly used and highly effective therapy for acute and chronic SCI to promote secretion clearance and augment VC. The device simulates a cough by delivering high flow positive inspiratory air via face mask, mouthpiece, or tracheostomy, followed by negative expiratory pressure. Assistance is usually required for device use. It is preferred by patients and caregivers and can be used by ventilated and nonventilated persons. MIE may aid in the clearance of microatelectasis, prevents re-intubation,¹⁸  and improves lung compliance. Avoid use with concurrent pneumothorax/pneumomediastinum and bullous emphysema.

Manually assisted coughing (MAC or quad cough) requires assistance, but it can increase PCF without need for equipment. The patient maximally inhales, then coughs. The caregiver times an upward abdominal thrust below the diaphragm with the cough. Assess tolerability, and watch for nausea and vomiting. Avoid use, if possible, in the setting of an IVC filter or recent chest/abdominal trauma.

Chest wall percussion therapy uses vibration administered via a handheld device, manual chest therapy, or a percussive vest to loosen secretions for expectoration. Postural drainage, with or without percussive therapy, often generates secretion mobilization. Consider handheld continuous or oscillating positive expiratory pressure devices.

Ensure sufficient hydration to keep secretions thin. This may include the use of heat moisture exchanger (HME) adaptors to tracheostomies or the use of misted air. Saline use with MIE is often helpful.

Pharmacologic secretion management consists of the use of mucoactive agents designed to either decrease mucous hypersecretion or increase the ability to expectorate the mucous.¹⁹  Consider bronchodilators to improve FEV1, especially with an obstructive respiratory impairment.^10,17  Medication selection should be based on specific clinical presentation.

Conventional SCI clinical practice guidelines support the use of high TV ventilation of up to 15 to 25 mL/kg ideal body weight (IBW) while maintaining peak pressures under 40 cm H₂O to decrease the time required for ventilator liberation and the frequency of atelectasis.^20,21  The current intensive care unit practice of using low TV ventilation to improve outcomes from acute lung injury (ALI) may lead to atelectasis, mucous plugging, and decreased surfactant production. Because patients with SCI have a predilection for atelectasis and retained secretions, this population may not benefit from lower TV settings beyond the high-risk period for ALI.

The most successful method of ventilator weaning for patients with SCI is progressive ventilator-free breathing, allowing systematic conditioning of respiratory muscles to extend ventilator-free periods.²⁰  Prevention of atelectasis and respiratory infections is critical during weaning.

Slightly over half of the population with high-level tetraplegia will require long-term mechanical ventilation (MV). With chronic tracheostomy for MV, it is important to work towards cuffless or deflated cuff tracheostomy use to improve speech and swallow function. Patients can be adequately, safely ventilated with cuffless tracheostomy tubes and have fewer complications ^22,23  Adjust the ventilator settings when using a cuffless tracheostomy to offset air leaks and optimize speech.

Diaphragm pacing or phrenic nerve stimulators utilize negative rather than positive pressure to replace or decrease mechanical ventilation. Intact phrenic nerve function is required. This alternative offers a more natural negative pressure breath, improved sense of smell, decreased secretions/suctioning, and increased sense of freedom and independence.²⁴ 

Venous thromboembolic disease (VTE) risk in chronic SCI is considerably lower than in the acute period. But previous VTE, medical illness, surgery, prolonged immobilization with illness, and fractures increase this risk. Resumption of prophylaxis is recommended when not contraindicated.²⁵ 

Community-acquired pneumonia, hospital/ventilator-associated pneumonia, and aspiration pneumonia present great risk to people with SCI (Table 1). Pneumonia occurs in half of patients with acute SCI and is the most common cause of mortality in both acute and chronic SCI.^8,26–28  The rate of fatal pneumonia among people with complete tetraplegia is significantly greater than in the non-SCI population.^29,30  Individuals with tetraplegia are particularly at risk. Altered perception of fatigue and dyspnea can lead to a less predictable clinical course than in persons without SCI.

The risk for dysphagia and consequent aspiration pneumonia is elevated in patients with cervical SCI.³¹  Pharyngeal phase dysphagia is most common. The presence of a tracheostomy triples the dysphagia risk.

Given the higher morbidity and mortality from pneumonia, SCI-specific care recommendations include vigilant prevention via appropriate influenza and pneumococcal vaccination, regular respiratory exercises to prevent mucus plugging, and aspiration prevention. Early identification and treatment of pneumonia, intensive use of secretion management strategies, close clinical monitoring, and early remobilization are critical. Temporary MV may be required by individuals with cervical injuries. Co-management with a pulmonologist specializing in neuromuscular care is advised.

The overall prevalence of sleep-disordered breathing (SDB) among people with SCI peaks at 74% to 83% in the first 6 to 20 weeks post SCI and improves to 40% to 60% in chronic SCI. This rate is much higher than in the general population (9%–24%).^32–36 

SDB is more common in tetraplegia versus paraplegia^33,34,37  and in complete versus incomplete SCI.³⁶  Obstructive sleep apnea (OSA) is far more common than central or mixed sleep apnea,^34–38  but central sleep apnea occurs more frequently in tetraplegia.³³ 

Factors associated with SDB in the general population, such as higher body mass index (BMI), neck circumference, and older age, have been similarly reported post SCI, with variable association with use of sedating medications.^32,39  Lower CPAP pressure requirements in subjects with SCI suggest factors beyond upper airway collapse.³⁴ 

Diagnosis of SDB in the setting of SCI presents unique challenges. Neurocognitive changes and snoring have been reported by patients with tetraplegia and OSA.^32,40  However, few report daytime somnolence, confounding clinical detection by symptom screening.⁴¹  The higher prevalence of asymptomatic OSA in SCI has led some authors to recommend performance of a baseline formal sleep study.^33,35  Home sleep apnea testing with transcutaneous capnography is emerging as a potential option, but there are limitations to this study with no comparative study to formal polysomnography.³⁹ 

CPAP is the primary treatment. People with tetraplegia and sleep apnea require assistance to don, remove, and adjust the interface. Nonadherence is common and has been attributed to inability to fall asleep, mask discomfort, and claustrophobia.⁴² 

Health care providers should maintain a high index of suspicion for SDB after SCI, particularly in complete tetraplegia. If feasible, polysomnography will help detect the presence of sleep apnea.

Lung function, including FEV1, naturally declines with age at approximately the same rate in the general and SCI populations. Decline in FVC and FEV1 with aging and SCI is associated with persistent wheezing and is accelerated by an increase in BMI in persons who are overweight or obese and by persistent smoking. It is not predicted by level or severity of injury.^8,43 

Some targeted preventive health measures such as immunization, counseling, and resources for smoking cessation and weight management are similar to the general population. As of 2015, the high-risk population for influenza vaccination includes persons with SCI, and annual immunization should be strongly encouraged.⁴⁴  To our knowledge, there are no guidelines directing pneumococcal vaccination in the setting of SCI. The Centers for Disease Control and Prevention recommends PCV13 for all adults aged 65 and older, with PPSV23 administration at least 1 year later. High-risk groups are also offered PPSV23 once before age 65, while some experts recommend vaccination with both PCV13 and PPSV23 before 65.⁴⁵  Even though SCI is not yet formally included in the high-risk group, some systems of care include them in practice, given the markedly increased risk for pneumonia-related morbidity and mortality. Additional attention is needed to identify and treat comorbid SDB.

Mr. A saw his primary care provider for a follow-up visit 2 weeks after discharge. He was close to his respiratory baseline and still needed scheduled MIE. He was afebrile and off O2 and mucolytics. His primary care provider reviewed Mr. A’s respiratory care regimen and encouraged continued use of MIE or MAC, and CPAP for his SDB. Preventive strategies were reviewed, including regular RMT and GPB exercises, immunizations, weight management, and tobacco abstinence.

Even though the risk of death within the first year after SCI has been declining, long-term respiratory complications remain the principal cause of mortality and one of the leading causes for the high rate of rehospitalization after SCI. A higher level and severity of SCI correlates with the degree of ventilatory dysfunction, complication profile, and risk.

The heightened morbidity and mortality from pneumonia support regular influenza vaccination for all with SCI, along with respiratory exercises to enhance inspiratory and expiratory strength for effective secretion management. Early identification and aggressive treatment of pneumonia, with secretion management as the cornerstone, and monitoring for SDB and for respiratory decline with age are essential to SCI care.

Primary care providers, in collaboration with consumers and rehabilitation and pulmonary providers, play a key role in prevention, targeted surveillance, education, and specialized management of respiratory disease over the lifetime of a person with SCI.

More high-quality and longitudinal research is needed to define the functional benefits of many of the respiratory interventions used in SCI and to improve understanding of the combined impact of aging and SCI. These data will enhance prevention and treatment practices for SCI respiratory complications and inform the development of recommendations for monitoring and optimizing pulmonary function for healthy living after SCI.

The authors report no conflicts of interest.