Dyspnea in acute asthma: relationship with other clinical and physiologic variables

This investigation comprised 58 patients (35 men, mean age 61 years) with acute asthma: mean FEV1 35% of the predicted. The dyspnea score (Borg's scale), breathing rate, pulse rate, blood pressure, FEV1, and PEF were measured on arrival and 30, 60, and 150 minutes after bronchodilator treatment. The level of clinical severity was evaluated using Hedstrand's asthma severity scale. The variables that correlated most closely with dyspnea score at arrival were asthma severity score (r = .51 P < .001) and breathing rate (r = .38, P < .01). The measurement of airflow obstruction with the closest correlation to improvement in dyspnea was FEV1 expressed as a percentage of the pretreatment value (r = -.30* after 30 min, r = -.42** after 60 and r = -.34* after 150 minutes, *P < .05, **P < .01). When examining the intraindividual correlation between the change in dyspnea score and FEV1, a correlation coefficient of more than 0.80 was found in 74% of the patients. Of 18 patients with an increase in FEV1 of less than 20% of baseline, 11 had a decrease in dyspnea score in 3 or more categories. We conclude that there is a discrepancy in the treatment of acute asthma between the effect on dyspnea and airflow obstruction, the clinical implication of which remains to be investigated.