semi-open anesthesia

[sĕm′ē-ōpən, sĕm′ī-]
n.
  1. Inhalation anesthesia in which a portion of inhaled gases is derived from an anesthesia circuit while the remainder consists of room air.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.