An unconscious Neelix with a blood-gas infuser on the side of his head
A blood-gas infuser was a medical device used to supply a body with oxygen. It could not, however, replace the function of the lungs on a long-term basis.
In 2371, The Doctor used a blood-gas infuser when Neelix's lungs were removed by a Vidiian. (VOY: "Phage")
Concept artwork of the blood-gas infuser, illustrated by Sternbach