In the first part of this two part series on COPD, I stated that it's very important to make an accurate diagnosis of COPD. It's not only smokers who present to a doctor with shortness of breath. There is a certain attribute in a special select population that predisposes them to have an accelerated destruction and deterioration of lung function.
In order to achieve some accuracy in the diagnostic criteria, the European Thoracic Society and the American Thoracic Society developed what is known as the Global Initiative of Obstructive Lung Disease, also called the** GOLD** guidelines. GOLD was developed in 2009 and then revised in 2011. The guidelines take into account objective criteria such as pulmonary function tests (PFTs).
The most common metrics used to assess lung health is the vital capacity, which measures the most available air that comes out of the lungs, after they are inflated to maximum capacity, and the measurement includes how fast the air can be expelled from the lungs. An important component of the PFT assesses how much air comes out in the first second or two of expiration (forced expiratory volume or FEV1). The test compares the individual's results to other normal standards in the same sex, size, and age group.
One would think that a "below normal" is indicative of lung disease, but it's actually the slowness of the flow of expelled air that is specific to a diagnosis of COPD. Even if the volume of air expelled is normal, if the ratio of the volume in a time interval of one second is less than 70 percent, it is indicative of COPD. Age of onset of these findings is also important. The earlier in life that this change in vital capacity occurs, the more predictive it is of persistent and rapid deterioration of lung function.
**Why are the GOLD guidelines so important? **
They helped to centralize the criteria for recognition of COPD, and established stepwise recommendations for treatment of the condition. Medications that are dispensed target treatment goals that are different from the treatment goals of asthma. The goal in COPD is to decrease airway resistance to the flow of air. Typically, when we breathe, the diaphragm initiates negative pressure to push air out of the environment. To deliver air to the lungs, it must overcome the resistance of the airways. In normal individuals this resistance is in the upper and large airways, the larynx and the trachea. Once the air reaches the smaller airways, given that there are so many of them, flow occurs spontaneously without effort.
It's kind of like pushing a bowling ball. After the initial swing of the bowler's arm, the ball continues to roll spontaneously on its own. In COPD, however, the smaller airways are narrowed due to inflammation, and the effort of the diaphragm has to continue, trying to force the air through those many small airways. A person with COPD experiences the discomfort and uneasiness with this breathing challenge, which is even more pronounced during exertion or during exercise.
Preventing advancement of the disease
The other new finding in COPD is that it is the number of exacerbations that predicts the advancing state of disease. Once there is an exacerbation, even after it is treated and the individual has recovered, another inflammatory process has been triggered and continues, even after apparent recovery from the acute illness.
The new GOLD recommendations stress preventing exacerbations, and that goal is reflected by new core measures that the governmental agencies overseeing healthcare policies are now requiring from primary care physicians, in addition to proper recognition of the disease.
The current push in the world of pharmaceuticals is for medications that prevent exacerbations. The FDA requires that any such claims by a pharmaceutical company must be substantiated by a study proving that specific response. Currently, most studies done are using exacerbations as the primary end points, rather than improvement in the pulmonary functions, the primary goal in the past.
The bottom line
So to sum up the major highlights:
- Early signs of COPD disease progression may be subtle. A person might attribute shortness of breath while climbing stairs, to being out of shape or some other reasons. In truth, if COPD is present, the inflammatory process may have already begun.
- There is growing evidence that this inflammatory process does not only affect the lungs but also other systems, such as the development of osteoporosis or the beginning of vascular disease (a subject for another sharepost). The other point is that medications that work well for other airway diseases, like asthma, do not necessarily accomplish the desired therapeutic goals for COPD. The two disease processes are quite different.
Next up, I tackle a common question that patients routinely ask me. What are good exercises for the lungs - specifically, "What can I do to make my lungs stronger?"