is it true that in fact you can never give 100 % of oxygen to the patient?
when you ventilate the patient with bag en mask with oxygen reservoir and a flow of 15l/min then you have approximately an administration of 85 % ( that is wat is mentioned in the new guidelines ) so thus this mean that in fact you never can give 100 % oxygen to the patient , I suppose you can ?
Assuming what comes out of the cylinder is 100%, then you can give 100% by using a closed sytem such as tracheal intubation with balloon and ventilator. However with intubation and bagging, there is invariably a air contamination so it is probably somewhat lower.
Without tracheal intubation then you are correct it is accepted that you are giving about 80-85%, 90% max. using an oxygen flow of 15%
This is different if the air contains more oxygen, as in an oxygen tent or hyperbaric chamber.