Airway 3: Heliox Treatment Portal
Heliox
is a mixture of helium and oxygen that can be made with varying
concentrations of these two gases. Helium is an inert gas of low
density but of greater viscosity than air (that consists of 79%
nitrogen). Helium also has a lower density and a higher viscosity than
oxygen. Thus the helium/oxygen mixture in heliox has a lower density
and a higher viscosity than 100% oxygen.1 Experiments indicate the
breathing of heliox results in lower resistance to flow, higher tidal
volumes, and higher maximum airflow than the breathing of air or 100%
oxygen.2,3 Large airway obstruction is theorized to convert laminar
airflow to turbulent airflow.1-4 The turbulence of air is proportional
to its density and inversely proportional to its viscosity. Thus, the
flow of helium, which has a lower density and higher viscosity than
oxygen or nitrogen, helps to convert the turbulent flow seen with
airway obstruction to a smoother or more laminar flow.1 Not only does
ventilating gases with laminar flow require less work than ventilating
gases with turbulent flow, but more laminar flow also results in an
increased flow velocity of the ventilating gases. Thus, at least in
large airways, it is believed that helium increases gas flow velocity
and decreases the work of breathing by this conversion of turbulent
airflow back to a more laminar flow.
The efficacy of heliox is
believed to be best at the highest concentrations of helium (ie, 80%).1
In a study by Houck,5 it was shown that for any given constriction of
the endotracheal tubes, helium decreased resistance and increased flow
in a linear fashion proportional to its concentration. It was
also demonstrated that the effect of helium was minimal for minor
obstruction and more profound for tight constrictions of the
endotracheal tube.5 Therefore, the mixture of 80% helium to 20% oxygen
appears to be the most useful concentration. Heliox in this
concentration may be obtained in premixed tanks. Heliox is relatively
inexpensive and has an almost indefinite tank life.
Uses of Heliox
Heliox
has been reportedly used successfully as initial treatment for a wide
range of airway obstruction problems. These include:
- Severe viral croup manifested by severe respiratory distress with extreme sternal and intercostal retraction and profound stridor1,6;
- Acute severe asthma with peak expiratory flows of less then 200 L/min unresponsive to initial treatment with nebulized albuterol7;
- Laryngeal edema with significant respiratory distress, stridor, and suprasternal retractions1;
- Laryngotracheal obstruction due to angioedema8;
- Respiratory failure from obstruction of the main stem bronchi due to mass effect of cancerous lymph nodes9 or lymphoma of the larynx and trachea10; and
- Respiratory distress in a burn patient with post intubation stridor11
Technique for Administering Heliox
- Use the highest concentration of helium possible, preferably starting with 80% helium and 20% oxygen.
- Use high-flow rates (10 to 15 L/min) of heliox with a mask. The high rate of flow prevents the entrain of air around the mask during inspiration. Alternatively, a true, tight-fitting mask system with a reservoir and one-way valves may be used for gas delivery.1
- If the O2 saturation does not remain above 89%, additional oxygen may be added by nasal cannula. This necessarily reduces the percentage of helium that may reduce the effectiveness of the heliox.
- The heliox needs to be continued until other forms of treatment have become effective. In the case of viral croup or asthma, this is usually 6 to 8 hours; but when the airway obstruction is due to a fixed defect like a tumor, the heliox may safely be continued for a number of days to allow the use of radiation or chemotherapy to shrink the tumor.
Conclusion
Heliox rapidly improves
airflow obstruction caused by asthma or upper airway obstruction of
many different etiologies. By lowering the resistance to air flow, the
use of heliox results in an improved tidal volume and peak expiratory
flow. Heliox is safe to use with its only potential side
effect
being hypoxia, which can be readily detected with the use of close
observation with pulse oximetry. The onset of action of heliox is
rapid. Frequently, a distressed patient will notice a decrease in
symptoms within a few minutes and sometimes as quickly as 10 to 15
seconds after starting heliox. If no effect is observed within 15 to 20
minutes, the provider team should consider other emergency options for
dealing with the patient’s respiratory distress. While the effects of
heliox in patients with marked respiratory distress may be rapid and
dramatic, the provider team must remember that heliox is only a
temporizing measure and that the underlying cause must be aggressively
addressed. If the etiology of the respiratory distress is not
reasonably stable and reversible, the heliox must be used only as a
bridge measure until definitive airway control can be achieved.
References
- Smith SW. Relief of imminent respiratory failure from upper airway obstruction by use of helium-oxygen: a case series and brief review. Academic Emerg Med. 1999;6:953-956.
- Barnett TB. Effects of helium and oxygen mixtures on pulmonary mechanics during airway constriction. J App. Physiol. 1967;22:707-713.
- Otis AB, et al. Effect of gas density on resistance to respiratory gas flow in man. J App. Physiol. 1949;2:300-300.
- Barach AL. The use of helium in the treatment of asthma and obstructive lesions of the larynx and trachea. Ann Intern Med. 1935;9:730-765.
- Houck JR, et al. Effect of helium concentration on experimental upper airway obstruction. Ann Otol Rhinol Laryngol. 1990;99:556-561.
- Nelson DS, et al. Helium-oxygen mixtures as adjunctive support for refractory viral croup. Ohio State Med J. 1982;78:729-730.
- Kass JE, et al. The effects of heliox in acute severe asthma. Chest. 1999; 116:296-300.
- Boorstein JM, et al. Using helium-oxygen mixtures in the emergency management of acute upper airway obstruction. Ann Emerg Med. 1989;18:688-690.
- Mizrahi S, et al. Major airway obstruction relieved by helium/oxygen breathing. Crit Care Med. 1986;14:986-987.
- Hessan H, et al. Airway obstruction due to lymphoma of the larynx and trachea. Laryngoscope. 1988;98:176-180.
- Kemper KJ, et al. Treatment of postextubation stridor in a pediatric patient with burns: the role of heliox. J Burn Care Rehab. 1990;11:337-339.