It is considered that a portable oxygen source easy to tranport and manipulste is very useful in any emergency situation. The effect of a portable inhaler "O2-Pack" were studied by comparing the arterial blood gas analysis before and after transportation of patients in dividing two groups of each 20 patients from respiratory intensive care unit to surgical intensive care unit or ward. One group of 20 patients were not given the "O2-Pack" and another group of 20 patients was administered oxygen with the "O2-Pack" . The results were as follows: 1) There were no significant changes in arterial pH, PCO2 and HCO2(-) regardless of the use of the inhaler "O2-Pack" during transportation. 2) There were no significant differences in PaO2 before transportation between both groups. PaO2 of the after-transportation without "O2-Pack" compared with the before-transportation of the two groups and the aftertransportation using the "O2-Pack" during transportation. Considering the above results the authors conclude that the application of portable inhaler "O2-Pack" during transportation of critically ill patients is very useful in maintaining the adequate oxygen level in the arterial blood.