Helium-oxygen mixtures in airway obstruction due to thyroid carcinoma.

The management of a patient with severe airway obstruction secondary to a thyroid mass is reported. When breathing room air the patient appeared in severe respiratory distress but when inspiring 22 per cent oxygen in helium she reported almost instantaneous relief and there was a marked decrease in respiratory rate, and increase in tidal volume and arterial oxygen tension. This improvement was to be expected because in situations where turbulent flow predominates a decrease in the density of inspired gases will result in an increase in flow rates. Contrary to established dogma a marked improvement was sustained when the patient was breathing 50 per cent oxygen in helium. The concentration of oxygen in helium was adjusted to obtain subjective relief for the patient in conjunction with adequate oxygenation.