Table 5.1 Evaluation of the symptomatic COPD patient.
• Spirometry Impairment
• Exercise performance: Disability
Ventilatory reserve Gas exchange
• Peripheral muscle strength
• Health status Handicap ing discomfort that consists of qualitatively distinct sensations that vary in intensity'. Exertional dyspnoea in COPD consists of multiple qualitative dimensions: the majority of patients describe predominant inspiratory difficulty with only a minority describing significant expiratory difficulty at the peak of symptom-limited exercise . The perception of inspiratory difficulty further encompasses an awareness of unsatisfied inspiration ('can't get enough air in', or 'my breath does not go in all the way'), which appears to be peculiar to the diseased state and not encountered in healthy subjects even at the breakpoint of exhaustive exercise . Dyspnoea in COPD is provoked or aggravated by activity, so it is only fitting that mechanistic studies on symptom generation are carried out during exercise. Pathophysiological factors known to contribute to the quality and intensity of exertional dyspnoea and to exercise limitation in COPD include:
1 Intrinsic mechanical loading (elastic and resistive) of the inspiratory muscles.
2 Increased mechanical (volume) restriction during exercise.
3 Functional inspiratory muscle weakness.
4 Excessive ventilation.
5 Gas exchange abnormalities.
6 Dynamic airway compression in expiration.
7 Cardiovascular factors.
8 Any combination of the above .
These factors are highly interdependent and their relative contribution to dyspnoea intensity may vary considerably among different COPD patients. In general, as the disease advances, more of these factors become instrumental in dyspnoea causation .
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