Effect of different oxygen inhalation concentrations on safe duration of apnea during tracheal intubation under general anesthesia

Objective To investigate the effect of different oxygen inhalation concentrations on safe duration of apnea during tracheal intubation under general anesthesia. Methods Eighty patients with ASA grades I to II underwent elective surgery during tracheal intubation under general anesthesia. According to the fraction of inspired oxygen (FIO2) during mask ventilation under general anesthesia, all patients were randomly divided into 4 groups: group A (FIO2=1, n=20) , group B (FIO2=0.8, n=20) , group C (FIO2=0.6, n=20) , and group D (FIO2=0.4, n=20) . The mask ventilation and tracheal intubation were performed by three experienced anesthesiologists. The oxygen concentration, pulse oxygen saturation (SPO2) and related indicators were adjusted by the assistants. The ventilation was not completed after the performance of tracheal intubation in each group until the SPO2 was reduced to 90%. Cases were deemed as failure where the SPO2 decreased below 90% before the tracheal intubation was completed. The number of failure cases, safe duration of apnea (duration of SPO2≥90% without ventilation) and duration of tracheal intubation were recorded. Results There was no failure case in each group. The safe duration of apnea in groups A, B, C and D was (493.4±172.7) s, (380.9±93.7) s, (276.2±103.1) s and (160.30±54.7) s, respectively. The duration of tracheal intubation was (38.3±9.7) s, (32.7±7.5) s, (36.7±9.0) s, and (35.9±10.3) s, respectively. The 99% confidence intervals for safe duration of apnea and duration of tracheal intubation was (382.9, 604.0) s and (32.1, 44.6) s in group A, (320.9, 440.9) s and (27.9, 37.6) s in group B, (210.2, 342.2) s and (31.0, 42.5) s in group C, and (125.3, 195.3) s and (29.3, 42.5) s in group D. The safe duration of apnea was significantly longer than the duration of tracheal intubation in each group (P 0.05) . Conclusion For experienced anesthesiologists, mask ventilation during induction of general anesthesia with 40% FIO2 may provide adequate safe duration of apnea to complete tracheal intubation. Key words: Different oxygen concentration; General anesthesia; Safe duration of apnea; Tracheal intubation