Spinal cord injury and its impact on breathing

As we all know breathing is mandatory for life’s development. A spinal cord injury alters the breathing capacity and causes some of the problems mentioned in this post.

How breathing works

The oxygen that we breathe in comes from our lungs which are located in the chest. There is a membrane called visceral pleura  between our chest and lungs. This is a very important membrane for breathing since it enwraps both lungs and the inside of the thoracic cage (parietal pleura).

Let’s imagine our lung as if it was a balloon.  When the chest expands, the lung becomes larger due to the air that we breathe in through our mouth. When we close our mouth and do not let any more air in, the chest stops expanding.

The muscles controlling the chest movement regulate the air that is inhaled and exhaled from our lungs. The diaphragm can be found among these muscles and moves down towards our tummy and increases abdominal pressure. When we breathe out, the diaphragm loosens.

After reading that our diaphragm is able to breathe by its own we may wonder what the other muscles moving the chest are for. Depending on the breathing stage we are in, some muscles are involved and others are not:

• Breathe-in stage: the muscles involved in the stage are external intercostal muscles, the scalene muscles and the sternocleidomastoid muscle.
• Breathe-out stage: the muscles involved here are the internal intercostal muscles.

Nerves that move  the breathing muscles

The phrenic nerve is in charge of moving the diaphragm. This nerve originates in the spinal cord (C3 and C4) to go down the chest to reach the diaphragm.  Cervical spinal cord injuries occur at C5-C6 level and it is likely that the diaphragm is not affected. The higher the injury is, the more intercostal muscles could be affected.

Respiratory impairments depending on the severity of the spinal cord injury

Thanks to this brief summary, and depending on the type of spinal cord injury, we are going to know which respiratory impairments may occur:

• Injuries above C4: patients suffer from bad functioning of their respiratory muscles and need using a life-support machine.
• Injuries under C4: these patients may be able to breathe by their own to some extent since their diaphragm functions correctly.
• Injuries above T7: these patients have not preserved core muscles and are not able to cough correctly which makes it difficult for them to clear their lungs and increase their risk of pulmonary infection.