title: Duration of carbon dioxide absorption by soda lime at low rates of fresh gas flow.
abstract: OBJECTIVE
  To determine the impact of a low fresh gas flow rate on the duration of carbon dioxide (CO2) absorption by soda lime.
  
  
  METHODS
  Nonclinical, experimental.
  
  
  METHODS
  Experimental laboratory.
  
  
  METHODS
  In vitro test with Sodasorb and a semiclosed breathing circle ventilating a test lung with a CO2 inflow of 250 ml per minute. Fresh gas flow rates of 0.25, 0.5, 1, 2, and 4 L/min were studied.
  
  
  RESULTS
  CO2 was measured at the breathing circuit test lung interface with a mainstream capnometer. Duration of CO2 absorption was determined as the time for the inspired CO2 tension (PICO2) to increase from 0 mm to 7 mm of mercury. The times of this interval were recorded four times for each fresh gas flow rate and compared by analysis of variance; p less than 0.05 was considered significant. Time to soda lime failure was significantly longer at 2 L/min than at 1 L/min fresh gas flow and at 1 L/min than at 0.25 L/min fresh gas flow.
  
  
  CONCLUSIONS
  Because soda lime color indicators are unreliable, when a semiclosed breathing circle is used at a low rate of fresh gas flow without CO2 monitoring, the CO2 absorbent must be replaced more frequently.
authors.affiliation: Department of Anesthesiology, University of Florida College of Medicine, Gainesville.
authors.forename: M
authors.initials: M
authors.lastname: Ohrn
authors.forename: N
authors.initials: N
authors.lastname: Gravenstein
authors.forename: M L
authors.initials: ML
authors.lastname: Good
mesh_terms: D000042:Absorption; D000764:Anesthesia, Closed-Circuit; D017610:Calcium Compounds; D002245:Carbon Dioxide / Q000493:pharmacokinetics*; D006801:Humans; D066298:In Vitro Techniques; D010087:Oxides; D012972:Sodium Hydroxide
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D002245:Carbon Dioxide; C004569:soda lime; D012972:Sodium Hydroxide