Clinical Study of the Duration of CO2 Absorption of ROK and USA-produced Soda Lime and Their Re-use Time after Being Exhausted

Seung, Ik Sang; Kim, Dong Wun; Sim, Jae Chul

Abstract

BACKGROUND: In a circle system, gas that is to be reused is cleared of carbon dioxide by passing through a canister containing a chemical CO2 absorbent. In anesthesia textbooks the utilization time of carbon dioxide is nearly always specified to last about 5 hours. The soda lime used was noted to regenerate its efficiency for CO2 absorption after being exhausted. Two different types of soda lime (a ROK product and USA product) were analyzed in patients for their duration of carbon dioxide absorption from the anesthetic closed circle system and re-use time after being exhausted.
METHODS
General inhalation anesthesia was performed using a PhysioFlex anesthesia machine. To determine the duration of carbon dioxide absorption by soda lime and the re-use time after being exhausted, twenty seven (ROK; 20 and USA; 7) and fifty (ROK; 22 and USA; 28) adult patients were studied. Duration of CO2 absorption was determined as the time for the inspired CO2 concentration to reach 0.5%. The color change of ethyl violet in soda lime was observed throughout the study. Duration of CO2 absorption was compared by unpaired t-test. Re-use time of each group was analysed by simple regression; p less than 0.05 was considered significant.
RESULTS
Duration of CO2 absorption was 2.67 +/- 2.12 hrs for the ROK product and 9.52 +/- 0.68 hrs of USA product, and they were different significantly (P < 0.05). Regression equations of ROK- and USA-products werey (min) = 5.761x + 45.701 (r2 = 0.0438, P = 0.3496, x means day after being exhausted) and y = 0.6x + 33.179 (r2 = 0.0158, P = 0.5233) respectively. A color change of ethyl violet in ROK soda lime was not observed throughout the chemical reaction.
CONCLUSIONS
From the above results we suggest that ROK soda lime is not effective yet to use for CO2 absorption in clinical anesthesia. It is marked shorter than that of the USA soda lime. A color change of ethyl violet was not observed throughout the chemical absorption reaction in ROK soda lime. Re-use time of both soda limes were not related with the duration after being exhausted.