Study objectives: To evaluate the effect of heliox on
airflow obstruction and dyspnea in patients with acute severe
Design: A prospective, randomized, controlled
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.
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