The speed of decreasing of arterial oxygen saturation following induction of anesthesia, using 3 methods of pre-oxygenation techniques

Determination of preoxygenation before anesthesia is an important factor in prevention of hypoxia and its complications. Regarding the height of Shahrekord from the sea surface (2061 m) and low level of oxygen pressure in this area (600 mg), this study was aimed to determine the onset of desaturation of oxygen following, using of three pre-oxygenation methods in apnostic adult healthy patients. In this clinical single blind study, sixty-six healthy, non-smoker adults undergoing elective surgery were randomly divided into three groups. Following the record of systolic and diastolic blood pressure and heart pulse from the patients, group one were not pre-oxygenated, groups two and three were pre-oxygenated with 50% oxygen and nitrous oxide and 100% oxygen, respectively for three minutes. After induction of the same anesthesia in the 3 groups, the patients were kept in apnostic until their saturated pressure O2 (SpO2) decreased to 91%. Subsequently, their systolic and diastolic blood pressure and heart pulse required to achieve SpO2 of 91% were measured. The data were analyzed using Chi-square and ANOVA tests. Mean age of the patients was 30.5±14.1 in whom 58% of them were male. All of the three groups were sex and age matched (p>0.05). The delay time to achieve SpO2 in group one, group two and group three were 44±16, 114.3±36.8 and 241.6±84, respectively (p<0.001). In all of the 3 groups, the increasing of heart pulse after the intervention was significantly different compared to before that (p<0.001). However, the difference was not significant between the groups. Pre-oxygenation of the patients for 3 min. before induction of anesthesia with normal breathing and with 100% oxygen would significantly increase the time required for oxygen saturation of the patients to 91%.