Symptoms
Symptoms are patients' perceptions of "an abnormal physical, emotional, or cognitive state"6. Physical symptoms of particular interest in chronic lung disease are dyspnea, fatigue, chest congestion, sleep difficulties, and peripheral or sensory complaints.7 Cognitive symptoms include poor memory7, and other neuropsychological deficits.8 Emotional symptoms often associated with chronic lung disease are anxiety, depression, and irritability.7,9,10
In COPD, symptom intensity correlates weakly with measures of physiological impairment. For example, although dyspnea intensity has a low to moderate correlation with exercise tolerance, it has a consistently low correlation with pulmonary function.11 This weak correlation may result from the failure of instruments to tap the multiple dimensions of the symptom, from indirect measurement of the symptom by some questionnaires (particularly those rated by an observer other than the subject), or from adaptation occurring in patients experiencing dyspnea.
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