title: Effects of temperature gradient reduction in three different carbon dioxide absorbents.
abstract: OBJECTIVE
  Temperature gradients in CO2 absorbents may locally increase the water content by condensation. We hypothesized that temperature gradient reduction (TGR) would prevent increased water content, thus preserving the reactivity of the CO2 absorbent and thereby increasing its time to exhaustion (longevity). The purpose of this study was to compare the effects of TGR on the longevity of CO2 absorbent with three different types of CO2 absorbents.
  
  
  METHODS
  We constructed a novel TGR canister. Experiments were conducted using three different types of CO2 absorbents: Drägersorb 800 Plus (D800), Drägersorb Free and Amsorb Plus. One kilogram of fresh CO2 absorbent of each type was placed into two types of canister: the conventional control canister (n = 6) and the TGR canister (n = 6).
  
  
  RESULTS
  In the case of Drägersorb Free, the TGR canister most effectively and specifically prevented local increase in water content of the CO2 absorbent and markedly increased the longevity (30% increase) compared with the control canister. In the case of Amsorb Plus, the TGR canister also prevented local excessive water content, but the increase in longevity was smaller (17% increase). In the case of D800, the TGR canister markedly increased the longevity (27% increase), but its prevention of local excessive water content was smaller.
  
  
  CONCLUSIONS
  TGR is a useful method to prevent local increase in water content and improve the longevity of CO2 absorbent. The effectiveness of TGR on longevity and water content changes varied in the different types of CO2 absorbent.
authors.affiliation: Department of Anaesthesiology, Hachioji Medical Center, Tokyo Medical University, Tokyo, Japan. goh@tokyo-med.ac.jp
authors.forename: Go
authors.initials: G
authors.lastname: Hirabayashi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Uchino
authors.forename: Takao
authors.initials: T
authors.lastname: Nakajima
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Ogihara
authors.forename: Nagao
authors.initials: N
authors.lastname: Ishii
mesh_terms: D000042:Absorption; D000764:Anesthesia, Closed-Circuit / Q000295:instrumentation*; D002122:Calcium Chloride; D002126:Calcium Hydroxide; D002245:Carbon Dioxide / Q000737:chemistry*; D015920:Gas Scavengers; D006813:Humidity; D013696:Temperature; D014867:Water
chemical_list: C400293:Amsorb; D014867:Water; D002245:Carbon Dioxide; D002122:Calcium Chloride; D002126:Calcium Hydroxide