Objectives: To test symptom perception in asthma under natural circumstances and to establish relationships between changes in airway obstruction as indicated by wheeze, dyspnea, general sensations, and emotional state.
Design: Continuous in vivo monitoring.
Method: Symptom perception was tested in 30 adolescents with severe, unstable asthma. They were continuously monitored in their homes for 72 h. Symptom perception was defined as the relation between self-reported dyspnea and airway obstruction as evident from audible wheeze. Tracheal sounds were continuously recorded with wireless telemetry for wheeze assessment. Dyspnea was assessed four times per day on a Likert-type 10-point scale, as well as four times randomly after pager remote command. The subjects kept records of use of medication, daily activities, general symptoms, and mood state in a diary.
Results: There were nine subjects with one or two wheeze episodes, another three subjects with three or four episodes, and one subject with almost continuous wheeze. The presence of wheeze in general related significantly to a rise (from individual baseline) in dyspnea of > 2.5 scale points. Acute wheeze was the best predictor of a rise in dyspnea, but prolonged wheeze correlated significantly with negative mood and general symptoms.
Conclusion: Patients with prolonged airway obstruction perceived symptoms less well and were more vulnerable to negative effects of asthma than patients with acute onset airway obstruction.