The breathing muscles are supplied by nerves that emerge from the spinal cord in various locations, from the Cervical through the Lumbar levels. “Even the abdominal muscles are involved in breathing,” said Joshua O. Benditt, MD, Assistant Professor of Medicine, Pulmonary Division. Injury to the spinal cord at or above these levels therefore affects the ability to breathe. “The higher up the Lesion is, the more serious the effect on the breathing system. In fact, you can almost predict from the injury level the degree of breathing function a patient will have,” Benditt said.
“What that means is that if you have a (complete) high-level cord lesion, C3 or above, you will be on a Ventilator.” A ventilator is a pumping device that takes over the role of the breathing muscles, delivering air to the lungs. “If your lesion is between C3 and C5, you may be on a ventilator, and if it is below C5, there’s a good chance that you may get off a mechanical ventilator,” Benditt said. In patients with incomplete injuries, predicting the eventual level of function is very difficult.
During the acute-care phase immediately following injury, many patients with cervical lesions and even some with high Thoracic lesions use a ventilator at some point. Some need ventilator support only for a short time, while others require it on a long-term basis. Which category they will belong to is a key issue for patients and their caregivers, Benditt said, “because of the expenditure, the effect on the patient, the effect on the family” of long-term ventilator support. “It means a whole different level of care.”
Unfortunately, the only way to tell for certain whether a patient will be able to stop using a ventilator is to simply wait and see what happens. Making the transition to independent breathing can take several months, and often there are setbacks during that period. “A lot will depend on the age of the patient,” Benditt said. Younger patients are able to breathe on their own more readily than older patients with the same sorts of injuries, because “lung function in all of us tends to deteriorate over time”. Smoking history will also have an effect.
Types of Ventilator
There are two basic types of mechanical ventilator. Negative pressure ventilators, such as the well-known “iron lung”, create a vacuum around the outside of the chest, causing the chest to expand and suck air into the lungs. Positive pressure ventilators, which have been available since the 1940s, work on the opposite principle, pushing air into the lungs. “Until maybe the last five to 10 years, if you had a positive pressure ventilator, that meant you had a Tracheostomy–a hole in the throat with a small plastic tube to which a ventilator can be attached,” Benditt said.
Now, however, a small face mask can be used over the nose and/or the mouth for positive pressure ventilation. Some ventilators use a cone-shaped device that is held over the nose with straps (see photo); others use a small mask that covers the lower part of the face. For patients who need breathing assistance only part of the time, such non-invasive means offer a way to avoid the complications associated with tracheostomies.
Most patients who use a ventilator part of the time do so at night. They may be able to breathe but unable to take large breaths, which over time can cause the lungs to partially collapse (a process called Atelectasis) and allow secretions to build up, which can lead to pneumonia. This process can be avoided by nightly use of a ventilator to fully inflate the lungs.
Another technique for overcoming paralysis of the breathing muscles involves the implantation of an electronic device in the chest to stimulate the phrenic nerve and send a regular signal to the diaphragm, causing it to contract and fill the lungs with air. Phrenic nerve pacers have been available since the late 1950s, but are extremely expensive (hundreds of thousands of dollars by the time all associated costs are figured in) and are therefore rarely used.
Complications
As stated above, atelectasis and the buildup of secretions, if left unchecked, can progress to pneumonia, a potentially fatal complication. This is of particular concern in the acute setting, Benditt said, “and a lot of our efforts are aimed at trying to prevent it.”
“People with spinal cord injury in general have a problem coughing, and that’s particularly problematic with a tracheostomy tube.” Most of the muscles used in exhaling, and also in coughing, are located in the abdominal wall, and thus are affected even with lower thoracic injuries. Also, a tracheostomy tube partially blocks the airway, making it difficult to cough out secretions.
For this reason, ventilator users with tracheostomies need to have secretions suctioned from their lungs on a regular basis. Depending on the patient, this may be needed anywhere from every half hour to only once a day. The patient can generally tell when suction is needed, either by feeling secretions in the chest or hearing a change in the sound of his or her own breathing. In general, Benditt said, suction is needed less often as time passes after the injury.
Another way to help a patient clear secretions is the so-called “Quad cough”, a manually assisted cough in which a helper pushes down, suddenly and repeatedly, on the upper abdomen of a reclining patient, helping to produce the sudden exhalations necessary to clear the lungs.
“Early detection of problems is always critical,” Benditt said. Ventilator users who develop symptoms such as a cough, a change in the color of respiratory secretions to yellow or green, or fever should get medical attention and appropriate antibiotic therapy early on if they appear to have a respiratory infection.
There are many potential complications related to tracheostomy tubes, including the inability to speak or swallow normally. “In order to speak, you need to get air to the vocal cords,” Benditt said. Tracheostomy openings are located below the vocal cords, so the air bypasses the larynx entirely unless the tracheostomy tube is specifically designed to direct air upward during exhalation and thus permit speech during regular, periodic intervals. This type of device was used by actor Christopher Reeves in his televised interview last year, Benditt said.
The muscles used for swallowing are located on the inside of the neck, and a tracheostomy tube can interfere with swallowing function and even cause the patient to aspirate or inhale food into the lungs. In cases where these problems are severe, a feeding tube may be inserted through the skin into the stomach, bypassing the throat.
Another tracheostomy-associated complication is infection. The tube is a foreign body in the neck, and has the potential of introducing organisms that would ordinarily be stopped by natural defense mechanisms in the nose and mouth. Care of the tracheostomy site, which requires cleaning and dressing on a daily basis, is an important preventive measure. Finally, Benditt said, whenever air is blown into the lung, there is some possibility of rupturing the lung. However, this is a very rare occurrence in patients with SCI.
Any mechanical device can fail, but power outages and malfunctions do not necessarily spell doom for full-time ventilator users. There is a backup breathing technique called Glossopharyngeal breathing or “frog breathing”, which involves forcing air into the trachea with the muscles of the neck, or basically swallowing air into the lungs. “If they’re off the ventilator, they can keep themselves breathing for many hours like that,” Benditt said.
Providing ventilatory care for someone with a high spinal cord injury involves a “fair amount” of work, Benditt said. “You’re going to have to do suction, you’re going to have to do tracheostomy care, you’re going to have to deal with the ventilator itself, attaching it, unattaching it.” At home, this care might be provided by attendants, family members, or a combination of both. However, insurance coverage for home attendant care has been decreasing in recent years. “Unfortunately, someone who is very wealthy might be able to afford full-time attendant care at home, while others have to live in a chronic care facility,” Benditt said.
An organization called the International Ventilator Users Network (IVUN) exists to link ventilator users with each other and with health care professionals interested in home mechanical ventilation. The IVUN puts out a newsletter twice a year, and can be contacted at 5100 Oakland Avenue #206, St. Louis MO 63110-1406 (314-534-0475, or FAX 314-534-5070).
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