title: Effects of temperature gradient correction of carbon dioxide absorbent on carbon dioxide absorption.
abstract: BACKGROUND
  The effects of temperature gradients in CO(2) absorbents on water content and CO(2) absorption are not clear. We constructed a novel temperature gradient correction (TGC) canister, and investigated the effects of temperature gradient correction on the water content and longevity (time to exhaustion) of CO(2) absorbent using a simulated anaesthesia circuit.
  
  
  METHODS
  Experiments were divided into two groups according to the type of canister used: the TGC canister (n=6) or the conventional canister (n=6). One kilogram of fresh CO(2) absorbent was placed into the canister. The anaesthetic ventilator was connected to a 3 litre bag and 300 ml min(-1) of CO(2) was introduced. Oxygen (500 ml min(-1)) was used as fresh gas. The anaesthetic ventilator was set at a ventilatory frequency of 12 bpm, and tidal volume was adjusted to 700 ml.
  
  
  RESULTS
  Before the experiment, the water content of the fresh CO(2) absorbent in the conventional canister and TGC canister was 16.1 (0.9)% and 15.7 (1.1)%, respectively. After the experiment, the water content of CO(2) absorbent near the upper outer rim of the canister increased to 32.4 (0.7)% in the conventional canister, but increased to only 20.6 (1.3)% in the TGC canister (P<0.01). The longevity of CO(2) absorbent in the conventional canister and TGC canister was 434 (9) min and 563 (13) min (P<0.01).
  
  
  CONCLUSIONS
  Temperature gradient correction prevented a local excessive increase in water content and improved the longevity of CO(2) absorbent.
authors.affiliation: Department of Anaesthesiology, Hachioji Medical Center Tokyo Medical University, 1163 Tatemachi, Hachioji, Tokyo 193-0998, Japan. goh@tokyo-med.ac.jp
authors.forename: G
authors.initials: G
authors.lastname: Hirabayashi
authors.forename: H
authors.initials: H
authors.lastname: Uchino
authors.forename: T
authors.initials: T
authors.lastname: Sagara
authors.forename: T
authors.initials: T
authors.lastname: Kakinuma
authors.forename: Y
authors.initials: Y
authors.lastname: Ogihara
authors.forename: N
authors.initials: N
authors.lastname: Ishii
mesh_terms: D000042:Absorption; D000764:Anesthesia, Closed-Circuit / Q000295:instrumentation*; D002245:Carbon Dioxide / Q000737:chemistry*; D004355:Drug Stability; D015920:Gas Scavengers; D006801:Humans; D013696:Temperature; D014867:Water / Q000032:analysis
chemical_list: D014867:Water; D002245:Carbon Dioxide