The Effect Of Different Pre-Oxygenations During Induction Of General Anaesthesia On Daration Of Non-Hypoxic Apnoea

OBJECTIVE To study the differnce of duration of non-hypoxic apnoea following pre-oxygenation during induction of general anaesthesia in children and in adults.METHODS One hundred healthy patients undergoing elective surgery under general aneasthesia were included in this study.Of those,80 patients (ASAⅠ～Ⅱ,aged 18～65 yr) were randomly divided into four groups,group A (control group) and group B,C,D(n=20 each).Group E was composed of 20 children(ASAⅠ～Ⅱ,aged 2～12 yr). All patients breathed spontaneously before and during induction without control or assistant ventilation.Two minutes before intravenous induction, patients began to inhale 100% O2 via face mask continuously. Patients in group A and E inhaled oxygen in supine position;patients in group B in a 15°head-up tilt position;patients in group C in supine position with CPAP of 6cmH2O;patients in group D in a 15°head-up tilt position with CPAP of 6cmH2O. After induction with intravenous anesthtics and muscle relax and intubation,all patients were not ventilated until SpO2 decreased to 90%.The time from breath stopping to SpO2 of 99%,95%,92%,90%( the duration of non-hypoxic apnoea) were recorded separately.Stomach inflation was judged by surgeons.RESULTS The time from breath stopping to SpO2 of 99%,95%,92%,90% in group A were significantly longer than in group E. The duration of non-hypoxic apnoea period in group E was (341.68±86.27)s.Compared with group A, the time from breath stopping to SpO2 of 99%,95%,92%,90% in group B,C and D were significantly longer.Those was longer in group D than in group B and C.The duration of non-hypoxic apnoea period in group A,B,C and D respectively were462.00±136.05s ;562.31±96.64s;561.12±142.3s;687.98±142.19s. No Stomach inflation was observed in five groups.CONCLUTIONS Our result suggested that (1) The non-hypoxic period of apnoea were significantly longer in adults than in children following the same pre-oxygenation.(2) That application of 15°head-up tilt position and the application of CPAP(6 cmH2O) for 2 min during pre-oxygenation both prolong the non-hypoxic period of apnoea in adults. That application of 15°head-up tilt position combined with CPAP(6 cmH2O) for 2 min during pre-oxygenation prolongs the non-hypoxic period of apnoea in adults without side-effects.