1. Review a textbook section on respiratory volumes and capacities.
3. Obtain a handheld spirometer. Note that the needle can be set at zero by rotating the adjustable dial. Before using the instrument, clean it with cotton moistened with 70% alcohol and place a new disposable mouthpiece over its stem. The instrument should be held with the dial upward and air should be blown into the disposable mouthpiece. Movement of the needle indicates the air volume that leaves the lungs (fig. 54.2).
4. Tidal volume is the volume of air that enters (or leaves) the lungs during a respiratory cycle (one inspiration plus the following expiration). Resting tidal volume is the volume of air that enters (or leaves) the lungs during normal, quiet breathing (fig. 54.3). To measure this volume, follow these steps:
a. Sit quietly for a few moments.
b. Position the spirometer dial so that the needle points to zero.
c. Place the mouthpiece between your lips and exhale three ordinary expirations into it after inhaling through the nose each time. Do not force air out of your lungs; exhale normally.
d. Divide the total value indicated by the needle by 3 and record this amount as your resting tidal volume on the table in Part C of the laboratory report.
5. Expiratory reserve volume is the volume of air in addition to the tidal volume that leaves the lungs during forced expiration. To measure this volume, follow these steps:
a. Breathe normally for a few moments. Set the needle to zero.
b. At the end of an ordinary expiration, place the mouthpiece between your lips and exhale all of the air you can force from your lungs through the spirometer.
c. Record the results as your expiratory reserve volume in Part C.
Martin: Human Anatomy I 54. Breathing and I Text I © The McGraw-Hill and Physiology Respiratory Volumes and Companies, 2002
6. Vital capacity is the maximum volume of air that can be exhaled after taking the deepest breath possible. To measure this volume, follow these steps:
a. Breathe normally for a few moments. Set the needle at zero.
b. Breathe in and out deeply a couple of times, then take the deepest breath possible.
c. Place the mouthpiece between your lips and exhale all the air out of your lungs, slowly and forcefully.
d. Record the value as your vital capacity in Part C. Compare your result with that expected for a person of your sex, age, and height listed in tables 54.1 and 54.2. Use the meter stick to determine your height in centimeters if necessary or multiply your height in inches times 2.54 to calculate your height in centimeters. Considerable individual variations from the expected will be noted due to parameters other than sex, age, and height, which could include physical shape, health, medications, and others.
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