In a CPR situation, what oxygen delivery method should be used when an untrained person brings a medical oxygen delivery system?

In a CPR situation, using a CPR mask with an oxygen inlet at the highest flow rate is advantageous due to its effectiveness in providing supplemental oxygen to a patient in respiratory distress. This method allows for a targeted delivery of oxygen directly to the person receiving care, enhancing the chances of successful ventilation and oxygenation.

The CPR mask facilitates a seal around the patient's nose and mouth, which is crucial for minimizing air leakage and ensuring that the patient receives as much oxygen as possible, especially in a time-sensitive scenario like cardiac arrest. When using oxygen at the highest flow rate, it further increases the fraction of inspired oxygen, which is vital for a patient who may be hypoxic.

The other methods, while effective in certain situations, do not provide the same level of efficiency in oxygen delivery in a CPR scenario. Simple face masks and non-rebreather masks have their own limitations, such as less effective sealing for positive pressure ventilation. A bag-mask device is highly effective but requires training for proper use, which may not be feasible if the person administering CPR is untrained.