Understanding Breathing


Why Is Breathing Essential?

We need to breathe to bring oxygen into our bodies and push carbon dioxide out of our bodies. Oxygen is needed by our bodies to turn sugar (glucose) into energy that the body needs in order to do work. The by-product of this conversion is carbon dioxide. Oxygen in our lungs is bound to red blood cells, and when we breathe, our blood stream transports oxygen to cells around our body. The body has large spare stores of sugar, but not of oxygen. Therefore if our breathing stops, oxygen is not available to tissue, energy cannot be made, and tissue injury can occur very quickly.

How Does Breathing Work?


The mechanics of breathing involves the processes of inhalation and exhalation. During inhalation air flows through the airway (nose, throat, windpipe and the bronchial trees) and into small “spongy” sacs (alveoli) which make up the lungs. Oxygen in inspired air is passed from the lungs to red blood cells for transportation around the body. During exhalation carbon dioxide moves from the blood into the lungs and then flows through the airway to the external environment. This is an exchange process: oxygen is exchanged for carbon dioxide.

Breathing is regulated or controlled by the brain. Our brains send regular messages, in response to blood gas and pH signals, along our spinal cords and peripheral nerves to our breathing muscles. Our muscles respond to these messages and increase their activity.

How is Ventilation Controlled?


Neural sensors monitor the amounts of oxygen and carbon dioxide in the blood. Carbon dioxide levels in our body drive respiration. When our body has too much carbon dioxide, such as during exercise or when we have a temperature, our respiratory drive will increase the rate and depth of breathing. This removes carbon dioxide from the body, while adding oxygen. In CCHS the central respiratory drive mechanism is impaired.

The amount of air that is inhaled with each breath is called Tidal Volume (TV). The Respiratory Rate (RR) and the Tidal Volume determine the Minute Ventilation (MV) or how much air is moved in a minute.

How Does Breathing Change with Age?

While people are still growing, they have a relatively high demand for fuel and oxygen. Therefore, MV rates are automatically adjusted throughout our lifespan to provide us with the oxygen we need. Therefore, MV rates, under normal circumstances, can range from around 40 breaths per minute in the newborn period, to a rate of 12-18 breaths per minute in adulthood. In contrast, tidal volumes remain relatively constant over time. Patients with CCHS can have inadequate rates and/or tidal volume values.

What Are Hypoxia and Hypercapnia?

If MV is inadequate this can lead to decreased levels of oxygen (hypoxia), and increased levels of carbon dioxide in the blood (hypercapnia or hypercarbia). This imbalance can be damaging to the brain, heart and lungs, especially in babies and young children whose organs are still developing.