Spirometry- what is it and why do I need it? #8

   Spirometry is a type of lung test that measures how much and how fast air can be moved into and out of your lungs. It is one of the tests used to determine (a) the diagnosis of asthma and (b) its severity. Unlike peak flow meters, this test is not performed to determine an asthmatic's "personal best" or impending attack. 
   The effectiveness of a spirometric test is dependent on the patient's cooperation and effort. Usually children under the age of 6 may not be capable of understanding and following instructions. In addition, this test is not suitable in patients who are unconscious, heavily sedated or those who's lung capacity is so limited they cannot give the forceful breathing action necessary to complete the test.
   I mentioned that this one test that is used in diagnosing asthma not the only test. Asthmatics often have normal lung function between attacks. This limits spirometry's ability to diagnosis a decrease in lung function.
   When you take this test, that should be performed periodically to make sure lung function has not decreased too much, there are many phrases and abbreviations you may hear. I will try to explain some of the more common ones.
   FVC (Forced Vital Capacity)- this is the volume of air that can be forcibly blown out  after a full inspiration. It is a very common spirometry action.
   FEV1 (Forced Expiratory Volume in 1 second)- It is usually shown as a number between 80% and 120% of an average that is detemined by sex, age, height/weight, and ethnicity. If you want to see what your predicted normal FEV1 is , check this site (http://www.dynamicmt.com/dataforms3.html).
   FEV1/FVC (also called FEV1%)- in healthy adults this number is between 75-80%. In people with obstructive conditions like asthma, COPD, chronic bronchitis and emphysema, the FEV1 is usually lower because of increased airway resistance while the FVC may be reduced but not to the same amount. Regardless, the FEV1/FVC number will be reduced compared to normal healthy adults.
  There are other terms and abbreviations used in spirometry but I will limit or blog to these three.
   You may be asked to take a spirometry test before and after using your rescue inhaler. This is done to determine (a) whether there is airway obstruction, (b) how severe it is, (c)whether is is reversible over a short term. This is important since individual asthmatics have different ideas about how bad their airflow obstruction really is.