The Respiratory System


The Respiratory System Following a Spinal Cord Injury

The respiratory system of a person suffering a spinal cord injury may be impaired due to paralysis of the chest muscles, abdominal muscles or diaphragm. The degree of impairment will vary depending on the level of spinal cord injury.

Overview of the Respiratory System

The tube which carries the air from the mouth is called the trachea or windpipe, this later divides into two at which point it becomes the bronchi and divides the air equally to each lung. Once the air enters the lungs it passes through a fine spongy structure which contains an extensive network of blood vessels, these vessels bring carbon dioxide into the lungs for removal, and take oxygen from the lungs to the body.

The process of breathing is controlled subconsciously, and involves muscles in the ribcage, between the ribs called intracostal muscles, and another muscle called the diaphragm. These muscles work together, and to breath in, the intracostal muscles lift the ribs up and forward whilst the diaphragm moves downwards, thus expanding the lungs and resulting in an inward breath. To breath out, the intercostal muscles and the diaphragm are relaxed, resulting in an outward breath.

The lining of the bronchi is very sensitive and is covered in a layer of mucus which helps protect the delicate structure of the lungs and moisten the air, it also helps to filter out dust and bacteria from reaching the lungs. If bacteria does reach the lungs, it can form into a chest infection, or if dust is inhaled, it can cause a reaction of coughing. Coughing is induced by a rapid contraction of the abdominal muscles to expel air at force from the lungs, and for the spinally injured, only a low level spinal cord injury will leave the cough reflex in tact.

Effects of a Spinal Cord Injury

The effects on the respiratory system from a spinal cord injury will vary from person to person, however, several generalisations can be made with regards to the level of injury and how it affects the breathing process.

With a spinal cord injury of C4 and higher all the muscles which control breathing will be paralysed. These muscles are the intracostal muscles, the diaphragm and the abdominal muscles. For a person with a high spinal cord injury to breath, the person will need a machine called a ventilator to breath for them, this machine forces air in and out of the lungs to re-oxygenate the blood. In order to cough, the person will need help by way of a carer performing an assisted cough procedure. An alternative to a ventilator is a diaphragm pacemaker. Pulses are sent down electrodes from the pacemaker implanted under the skin in either the neck or upper chest to the phrenic nerves in the neck, causing the diaphragm to contract. This contraction causes inhalation of air. When the pulses stop, the diaphragms relax and exhalation occurs. Repetition of this series of pulses produces a normal breathing pattern. A breathing pacemaker can provide ventilatory support for patients with chronic respiratory insufficiency whose diaphragm, lungs, and phrenic nerves have residual function.

Injuries between C4 and T6 will leave the person able to breath on their own, however, because the intracostal muscles may be weakened or paralysed depending on the level of injury, breathing may be mainly done in patients with a cervical injury solely by the diaphragm. Again, coughing may also be a problem, quadriplegics may need help in coughing, whilst paraplegics may have enough abdominal movement to innervate sufficient pressure to clear their airways on their own.

Injuries between T6 and T12 do not normally affect breathing, however the ability to cough will be impaired. It is only with injuries below T12 that normal breathing and cough reflexes are preserved.

Respiratory Infections

The inability to cough is of major importance to a person with a spinal cord injury, as failure to remove dust, mucus or saliva from the lungs can lead to infection. The most common infections are common colds, bronchitis (inflammation of the bronchus), bronchiolitis (inflammation of the bronchioles) and pneumonia. If an infection does occur in the lungs it may be necessary to take a course of antibiotics to help clear the chest.

With all infections of the chest, it may be necessary to clear the lungs with an assisted cough. This procedure is done by applying firm, even pressure just below the ribcage by a carer, while the person breathes out or tries to cough. Careful control of the pressure used by the carer is critical, to avoid causing injury and to help give the most effective 'cough'.

A way to help keep the fine structures of the lungs clear is to do deep breathing exercises, and one of the best deep breathing exercises is to do physical exercise.

Smoking Following a Spinal Cord Injury

It goes without saying that those people who continue to smoke following a spinal cord injury, are at an even higher risk of developing a chest infection, and pneumonia, than a non smoker.

In short, if you are a paraplegic or quadriplegic, GIVE UP SMOKING !

  • The respiratory system following a spinal cord injury.

    The respiratory system following a spinal cord injury.