It is well known that small amounts of sterilant "ethylene oxide" (EOG) generally remain in the disposable medical devices after sterilization.Several studies regarding tissue damage caused by residual EOG in the device have been reported.The simple simulations were done for the determination of amount of EOG transported from endotracheal tube to the intratracheal tissues during endotracheal intubation.The two methods used are as follow : That is, first as a simulation of the contact of the tube with living tissues, small pieces of the tubes were allowed to immerse in physiological saline solution at 37℃ and the content of EOG eluted from the outer surface of tube into saline was determined.Secondly, as a simulation for the release of EOG from the tube by simulated respiratory motion, the content of EOG released from the inner surface of the tube was determined by varying air-flow rate.From these studies, it is inferred that 0.90×10^<-3>〜1.94×10^<-3> of EOG transported to the tissue from the endotracheal tube, assuming that a patient is treated by intubation of the tube containing EOG at the safety level of 250 ppm (4.31×10^<-3> of EOG), giving by U.S.FDA regulation.

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An oxygen concentrator (MO-40) developed by Matsusita Seiko, Co. Ltd. was applied clinically to 32 patients undergoing open heart surgery.The purpose of this study was to examine if it could serve as an oxygen source for low oxygen therapy in the postoperative respiratory care.Sixteen patients had acquired valve disorder, 9 had ischemic heart diseaes, 5 had congenital cardiac anomalies and the remaining two had miscellaneous illnesses. Age of the patients ranged from 13 to 68 years (mean 45).After the intratracheal tube was removed, 100% oxygen was supplied through either facemask or nasal canula in 3-5 L/min. for 30-60 min.Thereafter, 40%-concentrated oxygen was provided from MO-40 in the same manner in 5-7 L/min. for about 30 min. Finally, the patient was allowed to breathe room air (21% oxygen) for 30 min.There were little changes of heart rate, blood pressure and respiratory frequency : all of these parameters were within normal physiologic range throughout study. PaO_2 values were normal in both 100% and 40% oxygen therapy : 142±33 torr and 103±24 torr, respectively. By contrast, room air breathing yielded 75±33 torr in average, which was significantly lower (p<0.001) than that obtained from 40% oxygen.None of the patients complained unfavorable feeling in use of MO-40. In all but 1 patients (97%), the oxygen concentrator (MO-40) was proved useful, with the latter having decreased cardiac function. These results indicate that the oxygen concentrator can be safely and easily utilized for patients who may require low rather than high oxygen therapy.

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