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The relevance of FEV1 measurement in COPD

Posted Jul 10 2008 4:09pm


 

FEV1is a key value to be known by smokers and COPD patients in order to assess the severity of the disease. FEV1means Forced Expiratory Volume in the First Second of a full forced exhalation after a full inhalation. It is obtained during the spirometry and represents the amount of air that leaves the lung when all the effort is put into exhalation. After the first second of a full exhalation there’s no much more opportunity to exhale additional amounts of air from the lungs.

 

How to get the FEV1value

 

It’s like blowing the candles in a birthday cake: the last ones require other inhalation to get turned off.

 

Although during the spirometry there’re no candles, the patient needs to exhale until he/she can not anymore and not breathing in. If there’s an interruption during FEV1measurement, this value will not be real and the interpretation will be wrong.

 

To obtain a FEV1value the continuous exhalation effort should last 6 seconds at least, when there’s no more flow from the lungs to the spirometer.

 

How different is FEV1value between COPD and asthma

 

FEV1gives a good estimate of obstruction in COPD and Asthma. In COPD, doesn’t revert so much. In most cases of asthma, it reverts when there aren’t any symptoms.

 

Everybody has a FEV1that modifies itself with aging. It increases until middle adulthood and starts to decrease 30 mL every year. In susceptible smokers, the rate of decrease of the FEV1is 60 mL every year which means that it is accelerated.

 

What’s the importance of FEV1value in research?

 

Dr. Robert Wise from John Hopkins University School of Medicine, Baltimore, Maryland, USA has been an advocate of the FEV1relevance as a key value in the assessment of COPD (Am J of Med 2006:119;S4-S11). This value represents the focus of investigations when evaluating the efficacy of approaches for the management of COPD.

 

Several years ago, in a famous, standard, reference publication Charles Fletcher and Richard Peto (Brit Med J, 1977:1:1645-1648) provided with data focused on FEV1change. Fletcher and Peto found thatFEV1falls over time in London working men and this decline is accentuated in susceptible smokers. They also found that smoking cessation is the most effective measure to slow the acceleration toward the normal trend (particularly in those who stop smoking before 45 years old).

 

How the FEV1value defines COPD severity

 

COPD stages are based on FEV1values and on how much it represents of the predicted value for gender, race, age, weigh, and height. For instance:

 

  • Mild COPD exists when FEV1is 80% or more of predicted
  • Moderate COPD exists when FEV1is 50% or more but less than 80% of predicted
  • Severe COPD exists when FEV1is 30% or more but less than 50% of predicted
  • Very severe COPD exists when FEV1is less than 30% of predicted or less than 50% of predicted with chronic respiratory failure (very low oxygen in blood and high levels of carbon dioxide)

 

Then… should we know the FEV1value in case of COPD?

 

Then, it’s good to know the FEV1to have a clear idea of the severity and change of the disease. This value is only obtained through spirometry and supports appropriate decisions for right measures to avoid rapid decline.

 

Remember: the most effective action to have a normal FEV1change during lifetime is quitting smoking as soon as possible.

 

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