What is normal breathing?
We talk a lot about abnormal breathing on websites like this. I thought it would be neat to write a post of what it is like to breathe normal. After all, this is the goal of any asthma treatment program, to control and prevent asthma. Here is a picture of what it looks like when you are breathing normal.
Eupnea: This is the term for normal respiration, or normal breathing. According to Dictionary.com, it is the free and easy respiration when at rest. (1, 2)
Atmospheric Air (Room Air): It contains a mixture of about 21% oxygen (O2), 0.04% carbon dioxide (CO2), and a combination of other gases. O2 and CO2 are the only gases you need to know about for our purposes.
Regulation of Breathing: If you think about it, you can make a conscious effort to breathe. But, even when you get busy, even when you’re sleeping, you will continue to breathe. This is because normal breathing subconscious, regulated by a system that begins with chemoreceptors.
Chemoreceptors: They are groups of nerve cells located at the base of the brain and the arch of your aorta. They recognize changes inside your body signaling that it’s time for a breath. They send signals via nerves to the respiratory center.
Respiratory Center: It is located in your brainstem, and includes the medulla oblongata and pons. It sends signals via nerves to the the muscles of inspiration to initiate a breath.
Muscles of Inspiration: These include intercostal muscles and your diaphragm. The intercostal muscles contract to lift your ribcage up and out. Your diaphragm contracts and moves downward, pushing your stomach out.
Inspiration: These actions create a negative pressure inside your chest to draw atmospheric air into your lungs.
Nose: As you inhale, air enters through your nose. Here it is filtered as it passes through small hairs. It is humidified and heated to body temperature as it passes the turbinates. This is why it’s a good idea to breathe through your nose, even though you might be tempted, for various reasons (like sinusitis or polyps), to be a mouth breather.
Upper Airway: Air then passes through your pharynx, where both food and air travel. It then passes past the epiglottis, which closes during exhalation to prevent food from entering the larynx and lower airway. From here it passes through a large opening called the glottis, which is where your vocal cords are located. Air then passes through the larynx (voice box), trachea, and then to the corina, where it travels to either to right or left lung.
Right lung:It has three lobes, the upper, middle, and lower.
Left lung: It has two lobes, the upper and lower, mainly because the heart occupies some of this space.
Lower Airways: After the carina, in either the left or right lung, air passes through the bronchus, which are your larger airways. Like a tree, these divide into smaller and smaller airways, called bronchioles. Air travels along these all the way to alveoli, and this is where ventilation takes place.
Ventilation: This is when oxygen enters the bloodstream and carbon dioxide enters the lungs.
Cellular respiration: Oxygen travels via the bloodstream to the various cells of the body, where it is used to make energy. This energy allows the cell to perform a specific function. Each tissue of your body, including your heart, liver, brain, and lungs, are made up of many cells, each of which perform a job necessary to keep that organ healthy and functioning.
Carbon dioxide: This is a waste product of cellular respiration. When oxygen enters a cell, it leaves the cell and enters the bloodstream. When oxygen leaves the alveoli and enters the bloodstream, carbon dioxide enters the alveoli. It then travels through your air passages and is exhaled into the atmosphere.
Expiration: Normal expiration is passive, meaning that no effort is needed for it to occur. As soon as the muscles of inspiration relax, natural recoil of the chest occurs, creating a positive pressure inside your chest, forcing air out of your lungs. You can, however, make a conscious effort to exhale when you need to, such as to force a cough to remove phlegm from your airway.
Breathing Pattern: During normal breathing, your stomach goes out, and there is minimal movement of your chest and shoulders. Muscles wrapped around your airways are fully relaxed, allowing airways to be fully dilated. This allows the clear and easy passage of air through them. A typical person breaths at a rate of 12-20 times per minute.
Conclusion: So you can see that normal breathing is spontaneous, and it allows for the free and easy passage of air into and out of your lungs. This is how your breathing should be between asthma episodes. The goal of any asthma treatment program is to keep you breathing normal, and to prolong the intervals between attacks, preferably forever. For further reading, check out “Understanding the Respiratory System,” by Kathi MacNaughton.