Effect of helium on cerebral blood flow: A n = 1 trial in a healthy young person

Abstract

Several experimental studies have shown that noble gases can have neuroprotective effects in cerebral ischemia. The exact mechanism is unknown; increased cerebral blood flow may play a role. In order to investigate this concept we performed a n = 1 trial measuring cerebral blood flow velocity by means of transcranial Doppler (TCD) in a healthy young woman inhaling air or heliox. Peak systolic velocity, mean flow velocity and pulsatility index were measured in the right middle cerebral artery, and oxygen saturation and heart rate were measured with pulse oximetry. After a baseline of 3 min breathing normal air, heliox (79% helium, 21% oxygen) was inhaled though an oral nasal mask for 5 min, followed by a washout period of 5 min breathing normal air. This protocol was repeated four times. No significant changes were observed in hemodynamic parameters, except for a small increase in pulsatility index during heliox inhalation (from 0.91 to 0.95; p = 0.01).

In conclusion, inhalation of heliox does not influence cerebral blood flow in a healthy young person. Any beneficial effects of helium in stroke patients are more likely due to other neuroprotective effects than to hemodynamic changes.