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Respiratory Volumes

Your lung capacity allows you to provide your body with the oxygen it needs. Different volumes of air are moved in and out of the lungs with changes in your respiratory rate and depth. There are 4 different respiratory volumes that can be measured:

  1. Tidal Volume (TV) - amount of air that can be inhaled and exhaled during normal, quiet breathing. (Average adult amount is 500ml)
  2. Inspiratory Reserve Volume (IRV) - amount of air that can be forcibly inhaled beyond a TV. (average for women is 2,000ml and men is 3,000ml)
  3. Expiratory Reserve Volume (ERV) - amount of air that can be forcibly exhaled beyond a TV. (average for women is 700ml and men is 1,200ml)
  4. Residual Volume (RV) - amount of air remaining in lungs after ERV. (about 1,200ml for women and men)

First, open Introduction to Spirometers & Lung Diseases, scroll down, and read the section on spirometers. As shown in the Introduction and in this article, spirometry is one of the Pulmonary (relating to the lungs) Function Tests (PFT) used to check the health of lungs and respiratory passages.

Next, open Lung Volumes and Capacities to see illustrations and animations of the four respiratory volumes. Be sure to click the play button beneath each type of volume to see the animation.

Check your Understanding

- Which of the respiratory volumes measures the volume of air forcibly exhaled?

- What is the adult average of air volume breathed in and out at rest?

- What did you notice different about the TV waveforms and the IRV waveform at the Get Body Smart website?

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Respiratory Capacities

Combining two or more respiratory volumes together will give you a respiratory capacity measurement. There are 4 different respiratory capacities in the list. The volumes that make up each capacity are also listed.

  1. Vital capacity (VC) - total amount of air that can be expired after fully inhaling (4.8L)
    1. VC = TV + IRV + ERV
  2. Inspiratory capacity (IC) - maximum amount of air that can be inspired (3.6L)
    1. IC = TV + IRV
  3. Functional residual capacity (FRC) - amount of air remaining in the lungs after a normal expiration (2.4L)
    1. FRC = RV + ERV
  4. Total lung capacity (TLC) - maximum amount of air that can fill the lungs (6 liters)
    1. TLC = TV + IRV + ERV + RV

These lung capacity measurements are used in medicine to help determine the health of the respiratory airway and lung tissue in patients. The next tab will direct you to the Lung Capacity Lab where you will learn more about this.

Check your Understanding

-Which lung capacity measurement is calculated from all 4 respiratory volumes?

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Lung Capacity Lab

You will complete a lab that mixes a virtual component with a hands-on component. In the lab, you will be calculating your own vital capacity through the use of a formula and through the measurement of the amount of air you exhale into a balloon. You will make comparison of your resting and jogging vital capacities.

Supplies Needed: An 11-inch balloon or larger and a metric ruler

Point Value: 100 points

You will also be completing a discussion post about your lab data results in Task #2 for 10 points.

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