Mercy Family Practice SC
Table of Contents
Asthma is a chronic inflammatory disease that is characterized by inflammation of bronchioles which them become hypersensitive which results in smooth muscle contraction and reduction in the diameter of the airways. This results in increased resistance to flow which results in air trapping and wheezing. In some cases, Asthma is due to allergens in the environment. This is referred to as extrinsic asthma. In most cases, the cause is unknown. This is referred to as intrinsic asthma.
Chronic Obstructive Pulmonary Disease (COPD) is another lung disease that is often caused by smoking. Air pollutions, occupational exposure and passive smoke inhalation may contribute. There are a minority of cases that are idiopathic (no known reason). As the name implies, the pathophysiology of COPD is similar to Asthma in that there is inflammation, bronchospasm, resistance to airflow, air trapping, and wheezing. For decades physicians made a distinction between the two. Asthma in the purest sense was considered a reversible airway disease of both large and small airways where prudent use of broncodilators known as short acting beta agonists (SABA) or inhaled corticosteroids (ICS) could return the airway back to normal. COPD in its purest case is considered a fixed loss in small air cells in which SABA or ICS will not return normal lung function, although they do help to maximize what reduced lung function is left. Asthma often starts in childhood or young adulthood where COPD often starts after 30 years of cigarette smoking.
However, there is now mounting evidence that Asthma is not a stable and fully reversible disease as once thought. It turns out that there is a lot of overlap between Asthma and COPD. It is now thought that it may be the same disease manifest as a spectrum with Asthma on the one hand and COPD on the other. It is now referred to as Asthma-COPD Overlap Syndrome (ACOS). Treatment is similar in both groups and the guidelines for treatment in one is often applied for the other. For example, for decades steroids were reserved for Asthmatics and rarely used in COPD. However, over the years, clinicians looked at the patient clinically, and often added ICS regardless of these distinctions. Now we have literature that supports what we have been doing clinically for years.
Figure 1, Natural Progression of COPD & Asthma
The far left shows the pathophysiology of COPD and on the far right that of Asthma. In the center left is the natural progression of the disease over time with Forced Expiratory Volume in one second (FEV1) on the y-axis, and age on the x-axis. In the center right is a similar graph showing the natural progression of Asthma. You should notice the similarity of each disease which are virtually indistinguishable. COPD is characterized by marked drop in lung function with each exacerbation where Asthma tends to return to its former baseline. In spite of these distinctions, both show an unrelenting deterioration over time.
Emphysema may be considered a severe case of COPD in which so many air cells (alveoli) have been lost that air exchange has been compromised between the inhaled air and the blood stream. Clinically this is manifest by reduced oxygenation of the blood stream. This can be measured either as oxygen in the blood directly through a blood gas sample, or it can be measured indirectly through the wavelength of oxygen through an oximeter, which is a hand held device. The normal range of the partial pressure of oxygen (PaO2) is 75 - 100 mmHg, and for oxygen saturation, is 97 to 100%. You can also get a measure of diffusing capacity across the alveoli membrane using carbon monoxide through a pulmonary function test called the diffusing capacity (DLCO). A normal range is 80-100%.
Chronic bronchitis is a form of COPD with emphysema in which there is an excessive amount of mucous secretions. These patients were often described as “blue bloaters” in which they became cyanotic from reduced air exchange along with mucous plugging from excessive secretions.
In general a patient with Asthma experiences tightness in the chest associated with shortness of breath, coughing or wheezing. If certain symptoms are present then they suggest a diagnosis of Asthma. These include: a patient who has recurrent attacks of wheezing; a person who has symptoms at night while recumbent; a person who has symptoms after exercise, a person who has symptoms following exposure to airborne allergens or pollutants; a person who has symptoms following an Upper Respiratory Infection (URI) which do not resolve after 10 days and persist for more than 6 weeks; and a person whose symptoms improve or resolve following treatment with bronchodilators.
Pulmonary function tests are the gold standard for making the diagnosis. Often the patient is sent to the hospital to have formal testing done. The patient breaths into a machine. They are often asked to take a deep breath, and then blow out has hard and as long as they can. Then they are asked to inhale, and repeat the process, perhaps three or four times. The process of often repeated after administering a short acting beta agonist (SABA). Several measurements are taken;
Table 1. Spirometry Values
Flow is defined as the change of volume divided by time (V/t). A flow volume loop is constructed by graphing Flow on the y-axis and time on the x-axis. The diagnosis of Asthma is made when the FEV1/FVC is blow 75% and there is a 15% improvement in the FEF25-75 after bronchodilator therapy. If the downward portion of the curve is concave (non linear) then this suggests airway obstruction. In other words, flow that drops rapidly at first, then diminishes slowly over time is diagnostic for trapping of airflow. A typical Flow Volume loop and tale appears as follows:
Figure 2, Flow Volume Loop
Table 2, Pulmonary Function Test Example
In the above example, the FEV1/FVC under 75% and the FEF25-75 improvement of 59% indicates both air trapping and a marked improvement after a brochodilator treatment. The concavity of the curve and the near linearity after treatment supports the diagnosis.
Asthma is classified into one of four groups: Intermittent, Mile Persistent, Moderat Persistent or Severe Persistent. Current consensus is based on the baseline symptoms at time of diagnosis and the intensity of treatment required to achieve good control.
Treatment of Asthma
The Global Initiative for Asthma (GINA) is a guideline used for the treatment of Asthma.
The GINA guideline is comprehensive and does not include an easy to follow algorithm. In lieu of this, I will give my personal approach to Asthma. I use a stepwise approach to control symptoms. First, I initiate a short acting beta agonist (SABA). The most cost effective drug is albuterol (ProAir) as a hand held device. It is given as a puff separated by two minutes administered every four hours as needed. Often this is referred to as a rescue inhaler. Examples of SABA are listed in the table below.
If SABA do not control symptoms, the next step in Asthma is to add an ICS. Most physicians will use a combination inhaler such as Advair or Symbicort. There is recent literature that challenges this approach in theat a SABA taken with a LABA may be sufficient as a next step.
If hand held inhalers are not sufficient, then nebulized solutions are often used. Duoneb via nebulizer every 4-6 hours as needed is a common medication combination.
If ICS are not sufficient for controlling symptoms, the next step is to add oral corticosteroids such as prednisone. Exacerbations are often treated with a pulse of oral steroids such as a step down approach, such as initiating with 40 mg orally per day for 3 days, dropping to 30 mg per day for 3 days, dropping to 20 mg per day for 3 days, dropping to 10 mg per day for 3 days, then off. Another approach is to give 40 mg orally per day for 5 days, then off. Oral steroids are met with a long list of complications which is why ICS are preferred.
The GINA uses the following table as a step-wise approach:
Table 3, GINA Step-wise Therapy for Asthma
Treatment of COPD
The Global Initiative for Obstructive Lung Disease (GOLD), is a guideline used for the treatment of Chronic Obstructive Pulmonary Disease (COPD).
The GOLD guideline takes a Dyspnea Scale and an FEV1 Score, and combines them into a Classification scheme: A, B, C, D. Class A is mild disease and Class D is severe disease.
Table 4, Gold Classification
Table 5, Modified Medical Research Council (mMRC) Dyspnea Scale
Table 6, FEV1 Score
Based on the above GOLD Classification, this will help guide therapy by the following table:
Table 7, Treatment for COPD According to GOLD Groups
Traditionally, in COPD, in the GOLD Class C patients, usually physicians will advance to an inhaled corticosteroid (ICS) plus Long Acting Beta Agonist (LABA) or a Long Acting Muscarinic Antagonist (LAMA). Now there is a study that supports the use of a LABA-LAMA combination. The use of Stiolto may now be used and avoid some of the Adverse Drug Events (ADEs) which may occur with inhaled corticosteroids (ICS).
Table 8. Bronchodilators
Short Acting Beta Agonist (SABA)
Short Acting Muscarinic Antagonist (SAMA)
Long Acting Beta Agonist (LABA)
Long Acting Muscarinic Antagonist (LAMA)
Inhaled Corticosteroid (ICS)
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