The effect of heliox in acute severe asthma: a randomized controlled trial.

STUDY OBJECTIVES To evaluate the effect of heliox on airflow obstruction and dyspnea in patients with acute severe asthma. DESIGN A prospective, randomized, controlled study. SETTING A university hospital. PATIENTS Twenty-three patients presenting to the emergency department with acute severe asthma were randomized to receive 70%/30% heliox or 30% oxygen. MEASUREMENTS Peak expiratory flow (PEF), dyspnea score, heart rate, respiratory rate (RR), and BP were measured at baseline and 20, 120, 240, 360, and 480 min after starting the test gas. After baseline, the PEF was measured by using the gas that was randomized to the treatment program. RESULTS In the first 20 min, there was a 58.4% increase in percent predicted PEF (%PEF) in the heliox group (p<0.001), whereas there was only a 10.1% increase in %PEF for the oxygen group (p>0.1). Eighty-two percent of the heliox group had >25% improvement in %PEF at 20 min, whereas only 17% of the oxygen group did (p<0.01). The next significant improvement in %PEF in the heliox group occurred at 480 min. At the end of the study in the heliox group, the PEF did not significantly (p>0.1) change immediately after the heliox was discontinued (270.6 to 264.2 L/min). In the heliox group in the first 20 min, there was a significant decrease in dyspnea score and RR (p<0.05), but there were no further significant improvements for the rest of the study. In the oxygen group, no variables significantly improved until 360 min. CONCLUSION Heliox rapidly improves airflow obstruction and dyspnea in patients with acute severe asthma and may be useful as a therapeutic bridge until the corticosteroid effect occurs.