The first section described the limitations of making a diagnosis from cough and sputum alone. In more severe disease, there is a much wider range of symptoms and signs, which are well described. The classic textbook descriptions of the 'pink puffer' and the 'blue bloater' refer to two of the more severe manifestations of end-stage COPD. But even these extreme states are not exclusive to COPD, and the overlap with other causes of respiratory and sometimes cardiac insufficiency is significant. It is worth considering how the COPD patient progresses from rude health to these severe manifestations over a period of up to 40 years or more.
The young 25-year-old smoker has no symptoms or measurable signs, despite a decade of smoking. Large epidemiological studies can demonstrate small statistically significant decrements in lung function, but the magnitude (25mL) is too small to be detectable in the individual . Although the disease process is already active, the exercise ability of young people is usually limited by the cardiovascular system, and the in-built respiratory reserve (about 30% of respiratory function) is never called upon. Only a minority of these smokers will even report a smoker's cough.
It is only when the continuing damage from smoking erodes the respiratory reserve and lung function becomes abnormal that patients begin to notice the first signs of breathlessness—in their 40s or 50s. Even at this stage, only a minority will report cough and sputum, and breathlessness on heavy exertion may be the only symptom. Those who do not have a heavy task or who do perform active physical exercise will be unaware that their maximum performance is becoming limited. There are likely to be few detectable signs at rest, and even a wheeze on auscultation can only be elicited on forced expirations. Many smokers succeed in hiding (or denying) breathlessness either by blaming 'normal ageing', or by avoiding breathlessness by giving up heavy exertion (e.g. retiring from competitive sport), or by avoidance of activity (e.g. using the car).
When the changes in lung function become moderately severe (an FEV1 of 50% predicted for age and gender), breathlessness on moderate exertion is difficult to conceal, since it interferes with everyday activity. More than half of continuing smokers will report troublesome cough and phlegm, and the mechanical changes consequent on hyperinflation change the configuration of the chest. As the disease progresses, the degree of exercise restriction increases and the clinical signs become more obvious. The limited airflow is audible as expiratory wheezing, and there is prolongation of the expiratory (compared to inspiratory) phase of the breathing cycle — often observable from across the room. The hyperinflation leads to an elevation of the ribcage and the apparent barrel-shaped chest — although in fact a barrel-shaped chest (defined as an anteroposterior diameter that exceeds the lateral diameter) is actually more common in kyphosis. It is not known whether the extreme pink puffer and blue bloater characteristics are actually distinct variants or part of a continuum of disease. In the former, the features of a pink, thin individual with rapid shallow breathing and a prominent ribcage demonstrate the dyspnoea and weight loss common in severe disease, while the cyanosis and fluid retention with swollen ankles and a raised jugular venous pressure show the problems of hypoxia and pulmonary hypertension that are also common late features.
Thus, the signs change over the years, and it is not possible to apply a common rule at all ages. Moreover, none of the features are specific to COPD. Any cause of pulmonary hypertension can lead to hypoxia and fluid retention. Wheeze can occur in asthma and in left heart failure. Cough may be part of asthma or bronchiectasis, or may be due to gastric reflux. Breathlessness is a feature of heart as well as chest disease. Thus, symptoms either singly or in combination can make the clinician suspect COPD, but are rarely sufficient for a firm diagnosis.
The only way of confirming that airflow limitation is present is to measure it. Just as no doctor would diagnose hypertension without measuring blood pressure, or diabetes without measuring blood sugar, so no patient should be diagnosed as having COPD without a positive confirmation that airflow limitation is present—i.e. spirometry must be done .
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