[The Bain circuit. Theoretical aspects and clinical use]

After a concise theoretical presentation of the present stage of semiclosed circuits, the authors assess their personal experience in the use of the Bain system. Under controlled respiration, adminstration of a fresh flow of gases of 70 ml per Kg of body weight-1 per minute-1 (between 4,5 and 6 1 per minute-1) prevents reinchalation. By its characteristics, which include: on optimal control of PaCO2 by a simple variation of the flow of fresh gases, universality, economy, the Bain system has demonstrated its utility in the anesthetics practice.