These authors from Santiago de Compostela, Spain, studied 38 infants (1 month to 2 years) with respiratory syncytial virus (RSV) positive bronchiolitis admitted to a Pediatric Intensive Care Unit (PICU). The first 19 were treated with supportive care that included careful monitoring, hydration, and nebulized epinephrine. The next 19 consecutive infants received heliox delivered via a mask (30% oxygen and 70% helium) in addition to the supportive care. Infants were enrolled if their modified Woods Clinical Asthma Score (MWCAS) was ≥5 (the maximum score is 10). The asthma score includes assessment of oxygen saturation, breath sounds, accessory muscle use, and mental status. Children with chronic cardiorespiratory conditions, a recent history of bronchiolitis, or use of corticosteroids were excluded. Vital signs, exhaled CO2, oxygen saturation, and a MWCAS were recorded hourly for both groups of patients and compared. Other collected clinical data included length of PICU stay and need for mechanical ventilation. Heliox was slowly discontinued when the MWCAS was <2 for at least 6 hours. If the oxygen saturation was <90%, supplemental oxygen was given via nasal prongs to achieve oxygen saturations of 90%.
The patients in the 2 groups had similar ages, MWCAS, vital signs, and prior duration of illness. No patient required mechanical ventilation. MWCAS, heart rate, respiratory rate, and oxygen saturation improved over the study time in both groups (P<.01 in each case). After 1 hour, the improvement in MWCAS was significantly greater in the heliox group when compared to the control group (P<.01). The average duration of heliox use was 54 hours and ranged from 24 to 112 hours. The average PICU length of stay was also significantly less (P<.01) in the children treated with heliox (3.5 +/−1.1 days versus 5.4 +/−1.6 days). No child was readmitted to the PICU after the study period.
The density of helium is much less than either nitrogen or oxygen. The lower gas density of helium allows for more laminar flow that, in turn, decreases resistance to gas flow and work of breathing. When oxygen is blended with helium, the density of the gas mixture increases. The density of 80% oxygen and 20% helium approaches the density of air. Therefore, if a patient requires high concentrations of oxygen the expected utility of helium therapy will be limited so patients must be able to tolerate low levels of oxygen in the range of 25–40% in order to be considered candidates for heliox therapy. Helium itself is nontoxic but a child on heliox should be monitored for hypoxia.
Heliox has been used to treat croup, post-extubation stridor, and asthma;1–,4 however, it is not routinely used in PICUs. Heliox must be administered with a tight-fitting mask or a hood and this can be difficult in agitated patients. Air leakage around a mask or administration of nasal prong oxygen will increase the...