Increased perception of dyspnea by inhalation of short acting beta2 agonist in patients with asthma of varying severity.

BACKGROUND

Poor perception of dyspnea in asthma may lead to a delay in starting appropriate treatment which is probably one of the factors contributing to death from asthma.

OBJECTIVE

This study was carried out to determine whether impaired perception of dyspnea in patients with asthma of varying severity can be corrected by inhalation of short acting beta2 agonist treatment.

METHODS

We enrolled 20 patients with asthma of varying severity. Forced expiratory volume in one second (FEV1) was measured before and 10 minutes after two puffs of salbutamol administered by metered dose inhaler. Perception of dyspnea was scored on the Borg scale during breathing through an inspiratory muscle trainer.

RESULTS

After inhalation of short acting beta2 agonist treatment, the baseline Borg score was decreased significantly from 2.20 +/- 0.32 to 1.80 +/- 0.31 (P < .01). The Borg score during breathing with the highest resistance, on the contrary, was increased significantly from 6.25 +/- 0.35 to 6.90 +/- 0.35 after inhalation of short acting beta2 agonist treatment (P < .01). Highest resistance-induced score difference from the baseline value (highest resistance-load score) was increased significantly from 4.10 +/- 0.46 to 5.25 +/- 0.42 (P < .01). There was no relationship between the change of Borg score from baseline value at each resistive load and the % change of FEV1 after inhalation of short acting beta2 agonist treatment.

CONCLUSION

These studies demonstrate that inhalation of short acting beta2 agonist treatment decrease dyspnea, but increase perception of dyspnea induced by a resistive load in patients with asthma, and the mechanism of the increased perception may not be related to the increased airflow rate. It may be due to some local or central effects of bronchodilator drug on perception of asthma.