Normal Respiratory Function

Normal Respiratory Function

To recognize when something isn’t working right, you need to know what it looks like when working perfectly.  therefore, let’s do a lesson on normal respiratory function.  Don’t worry; it won’t be painful.

Overview of the Normal Respiratory Function

The purpose of the normal respiratory function is to breathe oxygen from the atmosphere and supply it to the body’s organs—the oxygen and carbon dioxide, a waste gas in the lung, exchange. The gas waste product is then eliminated from the body into the atmosphere completing the breathing cycle.

The Respiratory System Has Two Tracts

The entire respiratory system has two tracts—an upper and a lower. Together they perform the normal respiratory function or exchange oxygen and carbon dioxide between the body and the air.

  • Upper Respiratory Tract – As you would guess, this is the area in the head behind the nose.
    • The nasal cavity directly behind the nose breathes air into the body.
      • It has cilia, little tiny hairs that trap dirt and help keep them out of the lungs.
    • The sinuses are air spaces located around your nose and in front of the skull and forehead.
      • Sinuses help regulate air temperate as you breathe.
    • Also, air enters your mouth, down your pharynx (throat), past your larynx (voice box), and into your lungs.
  • Lower Respiratory Tract – Once something passes the voice box and gets as far as the Trachea (windpipe), you’re in lower respiratory tract territory.
    • Trachea -The windpipe is very rigid and looks like a series of multiple rings.
      • The trachea is where most people choke to death if an object obstructs the airway.
    • Lungs – The trachea branches into two bronchi (tubes) that each lead to a lung.
      • Bronchi branch into bronchioles that look like tree branches and end in alveoli (air sacs).
      • Alveoli are responsible for exchanging oxygen and carbon dioxide.
Gas Exchange

The oxygen and carbon dioxide exchange happen in the smallest spaces of the lung, the alveoli. Here’s how:

  1. The heart pumps the carbon dioxide-filled blood to the lungs in the veins.
  2. Once there, the blood releases the CO2 into the alveoli, and the alveoli exchange it for oxygen.
  3. The blood now leaving the lungs has become filled with oxygen goes into the heart with fresh new oxygenated blood to be sent around to all the organs.
Common Terms to Know
  1. Gas volume for an average adult after maximum inspiration (breathing in) is 6-8 liters. The inspiration is called Total Lung Capacity (TLC). TLS increases in patients with chronic obstructive pulmonary disease (COPD) and decreases in conditions like fibrosis and restrictive disorders.
  2. Even after breathing out all you can breathe, some air is left in the lung to keep the lung from collapsing. This left-over air is called residual volume (RV) and is usually around 2-2.5 liters.
  3. For most healthy adults, the typical amount breathed in and out (inspired and exhaled) is called vital capacity (VC), and that is around 4-6 liters. This amount of VC is decreased in restrictive and obstructive lung diseases because trapped air occurs in both situations.
  4. After a normal expiration, the lungs’ volume (not when they ask you to breathe out as much as you can; just a normal breath) is called functional residual capacity (FRC). That amount is usually 3-4 liters. It increased in obstructive conditions and decreased in restricted conditions, probably due to poor muscle tone.

Normal Respirations

When someone is breathing normally, the chest moves up and down in a rhythmic pattern. Inhaling and exhaling taking an equal amount of time with relaxation between movements.

     Breathing occurs approximately 12-20 times per minute for adults (including ages 12 and older).

For children, the respiratory rate is faster.

5-12 years breathes 20-25/min.

2-5 years breathes 25-30/min.

1-2 years breathes 25-35/min.

< 1 year breathes 30-40/min.

1-30 days breathe 30-60/min

Premature breathes 40-90/min.

Reference: Weber, Janet. (1993) Nurses’ Handbook of Health Assessment. (2nd. Ed.) Philadelphia: J.B. Lippincott Company. 142.

Listening for breath sounds
Listening for breath sounds
Anatomy of the normal respiratory system
Anatomy of the normal respiratory system

Lungs Sounds (Normal)

Normal Respiratory Function vs. Abnormal Breath Sounds – Hear the Difference

If you would like to hear the difference between normal versus abnormal breath sounds, the YouTube video above provides a good example of normal breath sounds.

After listening to “normal,” listen to the examples of abnormal breath sounds found on “Abnormal Breath Sounds.” In each case, the breathing is noisy and sounds stressed.

If your family member struggles to get a deep breath, has an oxygen saturation staying below 90 or bluish tented lips, call your doctor. Describe what you hear.  Don’t worry about putting a name to it; the doctor will do that later. All you need to do is say if the sound is soft or loud, wet or dry sounding, junky, full of rattles, crackles, or other sounds described in the videos.


American Lung Association

CDC Diseases & Conditions

American Cancer Society/Lung Cancer

When Do You Treat It Yourself or Call the Doctor?

asthma attack
What Should You Do? 

You can’t always know for sure, but most of the time, you’ll know by instinct because you know the person for whom you’re providing care so well. However, it doesn’t hurt to know the following essential pieces of information.

  1. What’s usually considered normal?
  2. What does “healthy” look like for the person under your care most of the time?
  3. What would a doctor consider a critical value for that lab test or vital sign if he/she were considering the information?
What is Normal? 

Each system of the body that produces an outcome has a “normal” level of function. When that system is working correctly, lab values measuring within a specific range are normal. If the lab work is outside that range, it is an indication that something may be wrong with the organs, such as stress or disease.

Do Genetics Play A Factor?

An interesting factor that you may not know is that gender and genetics can influence lab values. Normal values” take into consideration those differences. therefore, “normal” blood pressure in one area of the country might be slightly different due to racial or gender influences than in another. I mention this because, at times, you may see different values listed as “normal” in different areas of the county.

Why Are Vital Signs Important?

Record your family member’s vital signs periodically, so you know what is normal for them. You want to take several readings rather than just one or two because the average is best.