A C5-C6 spinal cord injury can absolutely cause breathing problems, and the risk is higher than many people expect. The diaphragm, your primary breathing muscle, is controlled by the phrenic nerve, which originates from spinal cord segments C3 through C5. Because a C5-C6 injury sits right at the lower edge of that critical zone, it can partially disrupt the nerve signals that keep the diaphragm working at full strength. The result is a spectrum of respiratory difficulties ranging from mild shortness of breath during exertion to serious complications like pneumonia and, in some cases, the need for temporary ventilator support.
Why the C5-C6 Level Matters for Breathing
The phrenic nerve is the main nerve responsible for contracting your diaphragm, which does roughly 70 to 80 percent of the work during a normal breath. The nerve fibers that form the phrenic nerve exit the spinal cord at C3, C4, and C5. An injury at C5-C6 can damage or compress the lowest phrenic motor neurons, those at the C5 segment, while leaving the higher fibers at C3 and C4 partially or fully intact. This is why a C5-C6 injury typically does not stop someone from breathing altogether the way a C1 or C2 injury might, but it can weaken the diaphragm on one or both sides.
Research in animal models of cervical contusion injuries targeting the C4-C5 level has shown that phrenic motor neuron loss leads to degeneration of phrenic nerve fibers and denervation at the junction where the nerve meets the diaphragm muscle, producing a persistent reduction in diaphragm function on the injured side.1PubMed Central. Degeneration of phrenic motor neurons induces long-term diaphragm deficits following mid-cervical spinal contusion in mice In practical terms, this means even an “incomplete” C5-C6 injury can leave someone with a diaphragm that contracts less forcefully than it should, reducing the volume of air they can move with each breath.
How Breathing Mechanics Change
Beyond the diaphragm itself, a C5-C6 injury disrupts the intercostal muscles between the ribs and the abdominal muscles, both of which receive nerve signals from thoracic segments well below the injury. Losing intercostal muscle function means the rib cage can no longer expand properly during inhalation. Instead, the chest wall often pulls inward when a person tries to breathe in, a pattern called paradoxical chest wall movement.2Thorax. Contribution of the rib cage to breathing in tetraplegia This wastes energy: the diaphragm is pulling air in while the chest wall is collapsing, so a portion of each breath accomplishes nothing useful.
People with tetraplegia also develop decreased lung and chest wall compliance alongside increased rib cage stiffness, all of which raise the effort required for every breath.3PubMed. Pulmonary function and spinal cord injury You can think of it like trying to inflate a balloon inside a rigid box: the lungs want to fill, but the container around them resists. Over time, the stiffer chest wall also reduces the amount of air the lungs can hold at rest, lowering what clinicians call vital capacity.
The Cough Problem
Breathing in is only half the equation. Breathing out forcefully, which is what you need for an effective cough, depends heavily on the abdominal muscles. Those muscles are innervated by thoracic and lumbar nerve segments, so a cervical injury essentially paralyzes them. The result is a dramatically weakened cough. Respiratory impairment after spinal cord injury is characterized by low lung volumes and a weak cough secondary to respiratory muscle weakness, with more severe impairment in higher cervical injuries.4PubMed Central. Respiratory problems and management in people with spinal cord injury
A weak cough is not just an inconvenience. It means mucus, bacteria, and debris that would normally be expelled from the airways stay put. Secretion retention sets the stage for lung infections and collapsed lung segments. In one study of acute spinal cord injury patients, half developed atelectasis or pneumonia within the first 30 days, and the rate was significantly higher in those with higher-level injuries, reaching about three-quarters of that group.5PubMed. Atelectasis and pneumonia in acute spinal cord injury Interestingly, left-sided lung involvement was four times more common than right-sided, likely because the anatomy of the left bronchus makes it harder to clear secretions from that lung even under normal circumstances.
Respiratory Complications in the Acute Phase
The first weeks after a cervical spinal cord injury are the most dangerous period for the lungs. A study of patients with acute traumatic cervical spinal cord injury found that roughly 40 percent developed respiratory complications, with pneumonia being the most common, followed by the need for intubation and tracheostomy.6PubMed Central. Risk factors and the surgery affection of respiratory complication and its mortality after acute traumatic cervical spinal cord injury Several factors increased the odds of respiratory trouble: a more complete injury (meaning greater loss of function below the injury level), a higher injury location within the cervical spine, a history of smoking, and the use of high-dose steroids.
For people with C5-C6 injuries specifically, the picture depends heavily on whether the injury is complete or incomplete. Complete injuries, where no motor or sensory function is preserved below the injury, carry a far higher complication rate. One study found that complete spinal cord injury at C5-C7 raised the risk of needing a tracheostomy dramatically compared to incomplete injuries at the same level.7PubMed Central. Characterizing the need for tracheostomy placement and decannulation after cervical spinal cord injury The encouraging finding from that same study was that most patients who received a tracheostomy were eventually decannulated, meaning the tube was removed and they returned to breathing independently. Even among patients with high cervical complete injuries, those who regained enough motor function to shrug their shoulders within three weeks tended to be successfully weaned off the tracheostomy later.
Bronchospasm and Airway Sensitivity
There is an underappreciated respiratory problem that affects people with cervical spinal cord injuries and has nothing to do with muscle weakness. The sympathetic nervous system, which normally helps keep your airways relaxed and open, runs through the thoracic spinal cord. A cervical injury cuts off the brain’s ability to send those “relax the airways” signals. Meanwhile, the parasympathetic system, which runs through the vagus nerve and tends to constrict the airways, remains fully intact because the vagus nerve exits directly from the brainstem, above any cervical injury.
This imbalance creates a situation where the airways are hypersensitive and prone to constriction. A study of cervical spinal cord injury patients found that all subjects demonstrated airway hyperresponsiveness to methacholine challenge testing, and this hyperreactivity was completely blocked by an inhaled anticholinergic medication (ipratropium bromide).8PubMed. Bronchial hyperresponsiveness after cervical spinal cord injury In plain language, the twitchy airways are caused by unopposed parasympathetic tone, and they can be treated the same way asthma-like symptoms are treated: with inhalers that block the constriction. This is worth knowing because many people with cervical injuries experience wheezing or chest tightness and may not realize it has a treatable cause distinct from their muscle weakness.
Sleep-Disordered Breathing
Breathing problems in cervical spinal cord injury do not take a break at night. Sleep-disordered breathing, including both obstructive and central sleep apnea, is strikingly common. A systematic review found that rates of sleep-disordered breathing approach 60 percent in people with motor-complete tetraplegia, and central apnea (where the brain intermittently fails to send the signal to breathe, rather than the airway being physically blocked) is more common in people with tetraplegia than in those with lower-level injuries.9PubMed Central. Sleep disordered breathing in spinal cord injury: A systematic review
A population-based study looking specifically at men with spinal cord injuries found that about 15 percent of all tetraplegic patients had a diagnosed sleep apnea condition, compared to under 4 percent of paraplegic patients. Among tetraplegic patients, those with more rostral (higher) injury levels and obesity were at greater risk.10Spinal Cord. Factors associated with sleep apnea in men with spinal cord injury: a population-based case-control study Fewer than half of those diagnosed were receiving any treatment, which suggests sleep apnea is significantly under-managed in this population. For someone with a C5-C6 injury, unrecognized sleep apnea can compound daytime fatigue, worsen cognitive function, and even raise cardiovascular risk over time.
Why Sitting Up Can Make It Worse
One of the more counterintuitive aspects of breathing after a cervical spinal cord injury is that sitting upright can actually make it harder to breathe, the opposite of what happens in people without spinal cord injury. When you sit up, gravity pulls the abdominal contents downward and away from the diaphragm. Normally, your abdominal muscles tighten to support the diaphragm from below, giving it something to push against. Without functioning abdominal muscles, the diaphragm essentially sags, losing the mechanical advantage it needs to contract efficiently.
Studies have shown that moving tetraplegic patients from lying flat to a 70-degree tilt or seated position reduces both diaphragm pressure generation and vital capacity.11PubMed Central. Effect of abdominal binders on breathing in tetraplegic patients Abdominal binders, which are essentially elastic wraps around the midsection, help compensate by pushing the abdominal contents back up against the diaphragm. Research has found that wearing a girdle or binder while seated improves vital capacity and inspiratory capacity while also reducing the subjective sensation of breathlessness.12PubMed. Respiratory effects of combined truncal and abdominal support in patients with spinal cord injury For people with C5-C6 injuries who notice they breathe better lying flat than sitting in a wheelchair, an abdominal binder is often one of the first and simplest interventions offered.
Techniques for Improving Cough and Clearing Secretions
Because a weak cough drives so many of the respiratory complications after cervical spinal cord injury, a significant amount of clinical effort goes into finding ways to augment it. Two main approaches exist: assisted coughing techniques performed manually, and mechanical devices that simulate a cough.
A study of 15 inpatients with complete tetraplegia at C4-C6 tested several combinations of air stacking (using a manual resuscitation bag to fill the lungs beyond what the person can inhale independently) and abdominal compression (a caregiver pushing on the abdomen during a cough attempt). Spontaneous cough produced peak cough flows that were well below the threshold considered effective for clearing secretions. But combining air stacking with abdominal compression roughly doubled peak cough flow, bringing it close to normal values.13Spinal Cord. Use of air stacking and abdominal compression for cough assistance in people with complete tetraplegia This combined technique is low-cost, requires no special equipment beyond a resuscitation bag, and can be taught to caregivers or family members.
Mechanical insufflation-exsufflation devices, which deliver a deep breath followed by a rapid suction to simulate a cough, represent another option. A retrospective evaluation of patients with acute cervical spinal cord injury found that none of those who received prophylactic mechanical insufflation-exsufflation developed respiratory complications during the study period, though the sample was too small for the difference to reach statistical significance.14Physiotherapy in Respiratory Care. Mechanical insufflation-exsufflation for the prevention and treatment of respiratory complications in acute cervical spinal cord injury: A retrospective service evaluation
Respiratory Muscle Training
Just as you can strengthen limb muscles through exercise, the respiratory muscles that remain functional after a C5-C6 injury can be trained to work harder. Respiratory muscle training typically involves breathing against a resistance, either during inhalation or exhalation, for repeated sets. A small study of people with cervical spinal cord injury found that active inspiratory and expiratory muscle training improved maximal breathing pressures, vital capacity, and peak expiratory flow in all participants who completed the training protocol.15Spinal Cord Series and Cases. Respiratory muscle training may improve respiratory function and obstructive sleep apnoea in people with cervical spinal cord injury The study also noted potential improvements in sleep apnea severity, which makes sense given that stronger upper airway and respiratory muscles may help keep the airway open during sleep.
Rehabilitation programs for cervical spinal cord injury patients increasingly incorporate respiratory training as a standard component alongside mobility and strength work. The evidence base is still growing, but the principle is straightforward: whatever muscle function remains can be pushed to do more.
Ventilator Weaning and Long-Term Independence
Some people with C5-C6 injuries require mechanical ventilation in the immediate aftermath, especially if the injury is complete or if there are associated injuries like chest trauma. The question that matters most to patients and families is whether they will get off the ventilator. The answer, for C5-C6 level injuries, is usually yes. A study of ventilated spinal cord injury patients found that about three-quarters were successfully extubated by the time of discharge, with lower injury levels and higher initial consciousness scores both predicting successful weaning.16Journal of Trauma and Acute Care Surgery. Spinal Cord Injury: Outcomes of Ventilatory Weaning and Extubation Since C5-C6 is a relatively lower cervical level compared to C1-C4, the odds of weaning are better, particularly in incomplete injuries where some phrenic nerve function is preserved.
For the smaller number of patients with very high or very complete injuries who cannot be fully weaned from mechanical ventilation, diaphragm pacing systems offer an alternative. These devices electrically stimulate the phrenic nerve to make the diaphragm contract, allowing periods off the ventilator. A European study of patients with high spinal cord injuries found that among those implanted with diaphragm pacing systems who had at least a year of follow-up, about 38 percent achieved complete ventilator independence, using the pacer around the clock. The median use across all implanted patients was 15 hours per day.17PubMed Central. Diaphragm Pacing in Patients with Spinal Cord Injury: A European Experience While diaphragm pacing is more commonly applied in injuries above C5, it illustrates the range of options available when respiratory support is needed long term.
What Happens to Lung Function Over the Years
The long-term trajectory of lung function after cervical spinal cord injury is not entirely reassuring. A cross-sectional survey of 222 outpatients with chronic spinal cord injury found that vital capacity and the volume of air that can be forcefully exhaled in one second were normal in people with low-level paraplegia who had never smoked but declined with higher injury levels, dropping more sharply in those with tetraplegia. In middle-aged people with tetraplegia, a longer duration of injury was associated with greater loss of lung function, independent of age itself.18PubMed. Pulmonary function in chronic spinal cord injury: a cross-sectional survey of 222 southern California adult outpatients This suggests that living with a cervical spinal cord injury imposes a progressive burden on the respiratory system, likely due to a combination of muscle deconditioning, chronic low-level secretion retention, repeated infections, and changes in chest wall mechanics over time.
The practical implication is that respiratory monitoring and proactive management should not stop after the acute rehabilitation phase. Ongoing respiratory muscle training, vigilance for sleep apnea, prompt treatment of chest infections, and attention to posture and abdominal support remain relevant for years and decades after the original injury. For someone with a C5-C6 injury, the respiratory picture is generally more manageable than for someone injured at C3 or C4, but it is not something that simply resolves once the initial hospitalization is over.
Incomplete Versus Complete Injuries
The single biggest variable in how much a C5-C6 injury affects breathing is whether the injury is complete or incomplete. A complete injury at C5 means the spinal cord is fully disrupted at that level, cutting off virtually all signals below it. An incomplete injury preserves some pathways, and even a small number of intact nerve fibers to the diaphragm can make an outsized difference in breathing capacity. Many people with incomplete C5-C6 injuries have only mildly reduced lung function and never require ventilatory support, while those with complete injuries at the same level face substantially higher risks of pneumonia, tracheostomy, and prolonged hospitalization.
The completeness distinction also affects recovery potential. In the tracheostomy study mentioned earlier, complete cervical spinal cord injury was overwhelmingly the strongest predictor of needing a tracheostomy, dwarfing the effect of injury level alone.7PubMed Central. Characterizing the need for tracheostomy placement and decannulation after cervical spinal cord injury Conversely, any early sign of motor recovery below the injury level, such as shoulder shrugging within the first few weeks, was a strong signal that the patient would eventually breathe independently. This is one reason clinicians closely monitor neurological recovery in the early weeks after injury: even small gains in motor function can translate into meaningful improvements in respiratory independence.
Smoking, Obesity, and Other Modifiable Risks
Certain factors that are modifiable amplify the respiratory impact of a C5-C6 injury. Smoking history increases the odds of respiratory complications after acute traumatic cervical spinal cord injury, with one study calculating roughly triple the risk for smokers compared to nonsmokers.6PubMed Central. Risk factors and the surgery affection of respiratory complication and its mortality after acute traumatic cervical spinal cord injury Obesity is a significant risk factor for sleep apnea in this population, as it is in the general population, but its effects are compounded by reduced respiratory muscle strength.10Spinal Cord. Factors associated with sleep apnea in men with spinal cord injury: a population-based case-control study Body weight is also a practical concern because excess abdominal weight pushes the diaphragm upward and further reduces lung volumes, especially in the supine position where many spinal cord injury patients spend significant time.
For someone living with a C5-C6 injury, quitting smoking and managing weight are among the most impactful things they can do to protect their breathing long term. These interventions do not restore lost nerve function, but they reduce the additional load on a respiratory system that is already working with a significant disadvantage.