1. Perception of
asthma by patients can be assessed from the relationship between symptom scores and peak expiratory flows. This study was designed to investigate the possibility that medication can affect perception of the sensation of
asthma independently of changes in lung function. 2. Twelve subjects whose
asthma was inadequately controlled by inhaled
bronchodilator alone were studied during four different
drug treatments over 3 months. Subjective self-assessment of
asthma was scored on
a 10 cm visual analogue scale and followed by three consecutive measurements of peak expiratory flow, using a coded electronic peak flow meter. This was recorded not less than three times daily on diary cards. Observations were recorded during the second week of each of four treatments: (i) a run-in period using only inhaled
salbutamol as required, (ii) inhaled
beclomethasone, (iii) inhaled
cromoglycate and (iv) oral
theophylline at a dose adjusted to achieve blood levels of 10-20 mg/l. Inhaled
salbutamol was permitted during the other treatments as required. Changes in the slope and position of the regression lines of
asthma scores on PEF were used to measure changes in perception of
asthma on each treatment. Dynamic lung volumes were measured in the clinic before the study and after each treatment period. 3. In the group as a whole,
theophylline improved lung function (mean peak flow and dynamic lung volumes) without affecting mean visual analogue scores,
beclomethasone improved mean visual analogue scores with much less effect on lung function, while
cromoglycate had a small though consistent effect on both. 4. Perception of
asthma, measured by the relationship between peak flow rate and visual analogue scores, was unaffected by
cromoglycate. On
theophylline, perception of
asthma was heightened in five subjects despite a definite improvement in their peak flow. On
beclomethasone, perception of
asthma was reduced in most subjects, often with no discernible improvement in mean peak flow or dynamic spirometry. 5. Perception of bronchoconstriction in
asthma can be affected by drugs independently of control of the condition.
Theophylline may produce a paradoxical increase in awareness of
asthma in some individuals. With
beclomethasone therapy a reduction in symptoms of
asthma may occur without any improvement in tests of air flow.