To compare the distribution of an inhaled labeled radioaerosol (diethilenotriaminopenthacetate labeled with technetium-99m) when either oxygen or heliox was used as a gas vehicle of nebulization.
Randomized, double-blind, controlled study.
Nuclear medicine imagining department of tertiary university-affiliated hospital.
Twenty children (5–15 yrs old) with confirmed diagnosis of chronic lower airway obstruction and referred for a ventilatory scintigraphy study.
Patients were randomized to use either the heliox mixture (helium/oxygen, 80:20) or oxygen during the scintigraphy study. The maximal cumulative irradiation absorbed by the lungs and the slope of the curve of the cumulative irradiation incorporated into the lungs over the time were used to compare the groups. Student’s t-test, one-way analysis of variance, chi-square test, and Fisher’s exact test were used to compare the groups.
Measurements and Main Results
Ten patients were allocated to each group with no differences in demographic data, main diagnosis, and pulmonary function tests. Ninety-five percent of the particles produced by both gases had a diameter <2.4 μ. The heliox group showed a higher slope of the irradiation incorporated curve (p < .05) than the oxygen group. When broken down into groups, these changes were more significant in those patients classified by the pulmonary function tests as having severe lower airway obstruction. They showed higher cumulative lung irradiation (p = .045) and better slope of the irradiation incorporated curve (p = .017) when heliox rather than oxygen was used as a vehicle for the diethilenotriaminopenthacetate labeled with technetium-99m. Nevertheless, in those patients with mild lower airway obstruction, heliox did not show any advantage over oxygen in the distribution the radioaerosol into the lungs.
Related to its physical properties, heliox gas seems to have a strong and pronounced effect when used in patients with severe lower airway obstruction. However, in the absence of severe lower airway obstruction, there is no advantage to using heliox instead of oxygen as a vehicle of nebulization.