Room air dilution of heliox given by facemask.

Objectives: To measure the extent of dilution of helium-oxygen (heliox) by room air when given via high concentration reservoir mask to spontaneously breathing subjects. Substantial dilution of heliox by room air under these circumstances might alter its physical properties sufficiently to negate any potential clinical benefit in obstructive respiratory failure.

Design: Healthy volunteers breathing different concentrations of helium in oxygen via two different masks in a randomised crossover design.

Lack of effects of guanfacine on executive and memory functions in healthy male volunteers.

Rationale: Guanfacine is an alpha2-adrenergic receptor agonist that has been shown to have beneficial effects on working memory and attentional functions in monkeys and in patients with attention deficit hyperactivity disorder.

Objectives: The aim of this study was to further investigate the cognitive-enhancing properties of guanfacine using an established battery of tasks measuring executive and memory functions.

Methods: Sixty healthy male volunteers were randomised into three groups.