BACKGROUND: In emergency rooms or intensive care units, we have shown delivery of higher fractions of oxygen promptly for respiratory or cardiac arrest patients by using resuscitating instruments, especially the resuscitator bag. Previously we studied the variables affecting the fraction of delivered oxygen (FDO2) under varying ventilating techniques and conditions. In this paper, using corrugated tubes as substitute for reservoir bag, we measured FDO2 and compared two. METHODS: We designed a special wooden box, which held the Laerdal resuscitator bag. We measured the FDO2 with or without reservoir bags and corrugated tubes at various tidal volumes, respiration rates and oxygen flows. RESULTS: With a 500 ml corrugated tube, FDO2 were higher than with a 250 ml corrugted tube but lower than with a reservoir bag. CONCLUSIONS: Corrugated tube is less effective to deliver high fractions of oxygen than the reservior bag, but it is acceptable to use corrugated tube as a substitute for a reservior bag than not to use it at all.