It is not always easy to determine where asthma ends and COPD starts.
Young asthmatics who smoke or who are exposed to noxious agents in the workplace tend to have an early onset of COPD. A common mistake, however, is to label wheezy COPD patients as asthmatics. Asthma is a disease that tends to have its onset in the teens or early adulthood, is usually associated with allergic symptoms like hay fever and is caused by readily definable antigens that induce attacks of airway obstruction. (For the sake of specific treatment, the attending physician has to make a decision of where asthma ends and COPD starts). Treatment and prognosis for asthma is completely different to that for COPD, with a favourable response to treatment in asthmatics and less so in COPD patients.
Symptoms and diagnosis
In spite the well-known risk factors, the majority of COPD patients (up to 70%) remain undiagnosed. In the early phases, patients may have respiratory symptoms, like cough with sputum production, but may have no exercise impairment or may not be physically active enough for their shortness of breath to become evident. It is only by a regular measurement of lung functions in patients at risk, that the disease will be unmasked in its early stages.
COPD should be considered in any patient who has a chronic cough, sputum production, shortness of breath and/or history of exposure to risk factors. The cornerstone of the diagnosis of COPD is the measurement of lung function by spirometry. Spirometry is a test in which patients are asked to exhale a full in-breath (in other words, to breathe fully in and then fully out) as fast as they can. Measurements include the amount of air blown out in one second, called the forced expiratory volume in one second (FEV1), the total amount of air blown out in the entire forced exhalation, called the forced vital capacity (FVC), and ratio between the two, called the FEV1/FVC ratio. Normal lungs can almost completely empty in one second, but when airflow obstruction is present, the time taken to empty the lungs is lengthened and so the volume of air exhaled in one second decreases. When this ratio is less than 70%, airflow obstruction is said to be present. To determine the severity of the obstruction, the FEV1 as a percentage of the normal predicted value for a person of the same age, gender, height and ethnicity is examined.
The importance of early diagnosis is that preventative measures, including avoidance of risk factors, can be instituted. This will have major long-term benefits for affected individuals.
Symptoms are frequently precipitated by a respiratory infection, usually during the wintertime when influenza and colds are endemic. These patients commonly complain of a change in their baseline level of shortness of breath, together with a productive cough and a change in their sputum colour.
Smokers usually have a much longer recovery time than non-smokers and experience more severe symptoms during acute exacerbations of COPD.
In patients with severe respiratory impairment, these attacks may lead to respiratory failure. Oxygenation becomes so limited that a blue tongue and lips indicate severe impairment of oxygen uptake. Acute exacerbations may also be accompanied by evidence of failure of the right ventricle to pump adequately due to increased pressure in the vascular bed of the lungs, which is characterised by swollen ankles and legs, an enlarged liver and elevated neck veins. Symptoms of respiratory and right heart failure usually justify admission to hospital. Active treatment of these conditions can reverse the heart or lung failure, while identification of factors that cause exacerbation e.g. respiratory infections; fluid overload or lung clots should be remedied, thereby preventing further acute incidents.
Staging of COPD
A staging system for COPD severity has been established by the Global Initiative for Chronic Obstructive Lung Disease (GOLD). This staging system defines disease severity according to airflow limitation. It can be used as a guide for the management of patients with stable COPD.
(Written by Prof J.R. Joubert, MSc, MBChB (Stell), FCP (SA), MMed (Int. Med), MD (Stell.))
(Reviewed by Dr Greg Calligaro, physician at the Lung Unit, Groote Schuur Hospital and University of Cape Town, August 2010)