University of Arkansas System
Type of paper: Thesis/Dissertation Chapter
The use of heliox for patients experiencing an asthma attack
Heliox is a mixture of oxygen and helium and is used in the management of different respiratory conditions. Although beneficial evidence in the use of heliox to manage acute exacerbation of asthma is conflicting and highly contested, recent reports as well as clinical trials have shown positive reports among certain patients. One important property of heliox is that it’s insoluble and biologically inert in the body thus lacking anti-inflammatory or bronchodilator effect ( Lieberman, 1999, p. 31).
During an asthma attack, heliox lowers the difficulties of gas flow in the airways and allows increased ventilation. The main reasons are twofold. First, breathing this gas reduces the number of Reynolds, converting the strenuous flow into a smooth laminar flow. Second, since it has a low density, the pressure gradient required to attain a certain amount of turbulent flow is decreased, and this in theory minimizes the problem of breathing.
It’s important to understand that heliox is not used in treating upper airways obstruction and asthma, but in reducing airways resistance and the work of respiratory muscles until necessary treatment acts can be performed (Moonie, et al, 2006, p. 67). Anecdotal evidence shows that for heliox to effectively reduce airways resistance, the amount of helium concentration must be relatively high, at least 70% of the mixture of the inhaled gases. This limits the oxygen amounts delivered simultaneously.
Since helium is inert, lacking effect on a person’s metabolism, available literature shows that breathing heliox does not pose adverse reactions among patients. The higher the severity of obstruction, the more beneficial and recommended the administration of heliox (Smith & Buros). Although the use of heliox has generally been known to be safe, its continued use may have certain side effects. Helium is associated with high thermal conductivity and this may contribute to low body temperature when administered for long periods, implying that patients temperature should be monitored regularly.
A randomized controlled trial was carried out by Dorfman et al comparing the use of helium and oxygen mixture in ratio of 80:20, with air and continued nebulised ipratropium and albuterol in 40 patients (Wheeler, et al, 2006, p. 13). They did not find any major difference in changes relating to baseline characteristics, but only the heart rate increased. The respiratory rate, diastolic pressures, systolic and oxygen saturation did not have a significant difference. A similar trial was carried out by Henderson et al on patients in the emergency department having exacerbations of asthma, using heliox therapies.
Application of additional heliox to a standard asthma regimen did not have a beneficial value on patients in the emergency department having moderate to mild asthma exacerbations. Verbeek and Chopra analyzed the usefulness of breathing a mixture of 70:30 helium-oxygen on FEV1 in people with acute exacerbations of asthma (Gershwin, 2002, p. 23). Heliox was studied as a treatment option and not just conventional therapies of asthma. No positive improvement was found in absolute FEV1 or a certain percentage of it but even some patients showed a slight decline.
However, the researchers confirmed that the patients they concentrated on had a little chance of benefitting from heliox therapy since the obstruction of their airway was not severe. Certain schools of thought say that patients with exacerbation of asthma and having a rapid onset portray severe characteristics clinically but recover quickly than those having slow onset episodes. Although concrete evidence in the use of heliox to manage asthma is scarce, many centers are starting to use this form of treatment to mange exacerbations of asthma.