STUDY OBJECTIVE: To determine the effect of different air-O(2) mixtures and fresh gas flows (FGF) on the relationship between the delivered (F(Del)O(2)) and inspired O(2) fraction (FIO(2)) in a circle system. STUDY DESIGN: Randomized clinical study. SETTING: Large teaching hospital. PATIENTS: 160 ASA physical status I, II, and III patients undergoing a variety of cardiovascular procedures with general endotracheal anesthesia. INTERVENTIONS:160 patients were randomly assigned to one of 20 groups (n = 8 each), depending on the combination of total FGF (0.5, 1, 2, 4, or 8 L/min) and air-O(2) mixture used (ratios of 4/1, 3/2, 2/3, or 1/4), corresponding to a F(Del)O(2) of 0.37, 0.53, 0.68, and 0.84. For each combination of FGF and air-O(2) mixture, FIO(2) after equilibration was compared with F(Del)O(2). MEASUREMENTS AND MAIN RESULTS: With any air-O(2) mixture with a FGF < or = 2 L/min, FIO(2) became lower than F(Del)O(2). Because FIO(2) decreased below 0.25 after 13 and 26 minutes in the first two patients of the 4/1 0.5 L/min air-O(2) group, this study limb was terminated. CONCLUSIONS: When using air-O(2) mixtures in a circle system, FIO(2) becomes lower than the F(Del)O(2) with FGF < or = 2 L/min. The relative proportion of O(2) in the FGF has to be increased accordingly.
RCT Entities:
STUDY OBJECTIVE: To determine the effect of different air-O(2) mixtures and fresh gas flows (FGF) on the relationship between the delivered (F(Del)O(2)) and inspired O(2) fraction (FIO(2)) in a circle system. STUDY DESIGN: Randomized clinical study. SETTING: Large teaching hospital. PATIENTS: 160 ASA physical status I, II, and III patients undergoing a variety of cardiovascular procedures with general endotracheal anesthesia. INTERVENTIONS: 160 patients were randomly assigned to one of 20 groups (n = 8 each), depending on the combination of total FGF (0.5, 1, 2, 4, or 8 L/min) and air-O(2) mixture used (ratios of 4/1, 3/2, 2/3, or 1/4), corresponding to a F(Del)O(2) of 0.37, 0.53, 0.68, and 0.84. For each combination of FGF and air-O(2) mixture, FIO(2) after equilibration was compared with F(Del)O(2). MEASUREMENTS AND MAIN RESULTS: With any air-O(2) mixture with a FGF < or = 2 L/min, FIO(2) became lower than F(Del)O(2). Because FIO(2) decreased below 0.25 after 13 and 26 minutes in the first two patients of the 4/1 0.5 L/min air-O(2) group, this study limb was terminated. CONCLUSIONS: When using air-O(2) mixtures in a circle system, FIO(2) becomes lower than the F(Del)O(2) with FGF < or = 2 L/min. The relative proportion of O(2) in the FGF has to be increased accordingly.
Authors: Sofie De Cooman; Caroline Schollaert; Jan F A Hendrickx; Philip J Peyton; Tom Van Zundert; Andre M De Wolf Journal: J Clin Monit Comput Date: 2014-10-01 Impact factor: 2.502