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How to Calculate Inspiratory Reserve

Your lung volume is made up of several factors like vital capacity, tidal volume and inspiratory and expiratory reserve. Even when you think there is absolutely no air left in your lungs, there is a reserve. Your inspiratory reserve is how much air from inspiration you have available to use above tidal inspiration level. It is measured with a tool called a spirometer then a calculation.

Things You'll Need

  • spirometer
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Instructions

  1. Measuring Inspiratory Reserve Accurately

    • 1

      Set up the spirometer. You will need either a new disposable mouthpiece to attach to the machine or you must clean the attached mouthpiece. Be sure that the spirometer is properly calibrated and has no leaks before using it to test lung volume. Read through and follow the specific directions for your machine.

    • 2

      Explain the spirometer and the tests. Tell the person being tested how the spirometer works and what you will be testing. You can show him how it works by demonstrating with it or you can give a breathing lesson. Since the test can be affected by factors like nervousness, misuse or improper breathing, an explanation is necessary.

    • 3

      Ask the person being tested to breathe normally for several minutes before testing. A spirometer can look intimidating or frightening, especially to someone who has never used one. Get the client calm and comfortable breathing before doing any specific tests.

    • 4

      Test for tidal volume before inspiratory capacity. Explain the procedure first. The client will take a normal inhalation then exhale into the spirometer. The measurement will be this person's tidal volume.

    • 5

      Explain how inspiratory capacity is tested. Tell your subject that she will need to breathe in deeply and fully, filling her lungs as much as possible. Then she will blow out the air inhaled into the spirometer for measurement. Explain that the exhalation into the machine is not forceful but complete. Then have the subject perform the actual inspiratory capacity test.

    • 6

      Calculate inspiratory reserve (IRV = IC -- TV). To do so, take the measurement for inspiratory capacity (IC) and subtract the individual's tidal volume (TV) from this amount. The result is the individual's inspiratory reserve (IRV).

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