SPINAL CORD INJURY AND BREATHING

Jul
27
2011

Posted by: admin in Categories: Cardio & Blood- Сholesterol.

Spinal cord injury can have profound effects on breathing. Some individuals must rely on a mechanical ventilator for the long term, and this need for a ventilator twenty-four hours a day can be a tremendous burden, because the ventilator must be kept available and in working order at all times.Some people have sufficient strength in their breathing muscles to manage without the ventilator for short periods of time, and other devices can sometimes be used to extend this period off the ventilator. One such device is the implantable phrenic nerve stimulator. If the phrenic nerve is undamaged, stimulating the nerve electrically causes the diaphragm to contract. By careful control of the stimulation, the diaphragm can contract with enough strength to fill the lungs with air, as in normal breathing.An electrical stimulator can sometimes be implanted in the body surgically. Its stimulation of the phrenic nerves then produces artificial breathing. This technique has several problems, however. First, it can be used only with certain types of spinal cord injury. Second, it rarely works full-time; rather, it provides part-time relief from the mechanical ventilator. Third, its effectiveness may be only temporary, slowly decreasing over several years as scarring develops around the nerve, making it resistant to stimulation. Fourth, the device may fail unexpectedly, so a mechanical ventilator must be available in case of emergency. This greatly reduces the benefit of the phrenic nerve stimulator: a primary reason for developing this device was to avoid the inconvenience of keeping a mechanical ventilator available at all times. Still, the potential benefits of artificial breathing are great, and several laboratories are working on methods to increase the effectiveness and reliability of the electrical stimulator.An additional problem with breathing after spinal cord injury is weakness of the muscles of expiration (breathing out). The key muscles of expiration are the abdominal and chest muscles, which get their nerve supply from the thoracic levels of the spinal cord. Anyone with a spinal cord lesion above T2 is likely to have some weakness of expiration, even if the diaphragm is working well. Breathing is certainly possible without expiratory muscles, but we need these muscles to exhale forcefully, to shout, and most importantly, to cough. Coughing is essential for keeping the lungs clear and preventing infection, especially pneumonia. Patients with cervical spinal cord injury are highly vulnerable to respiratory tract infections because they cannot cough.”Quad coughing” is a very effective method of clearing the lungs, but it requires another individual’s assistance. Although no method is yet available for a person with quadriplegia to cough effectively without assistance, researchers are working on several methods for independent artificial coughing. The first is a mechanical method, such as a specially made body jacket that squeezes the abdomen and chest to help generate a cough. The second method is electrical stimulation of the expiratory muscles, causing muscle contraction and forcing air out of the chest. These methods for independent artificial coughing are not yet available for clinical use.Another method for artificial coughing uses a mechanical device that has air pumps for exsufflation and insufflation. The device first blows air into the lungs (exsufflation), and then forcefully sucks it out of the lungs (insufflation) at high velocity. Some patients can learn to use this device for independent artificial coughing. Further research is needed to determine whether this is more effective at clearing the lungs than routine quad coughing.
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