Final answer:
If a patient was preoxygenated with a saturation of 100 percent before attempting RSI, the attempt should be stopped if the saturation drops below a certain level, typically around 90-95 percent.
Step-by-step explanation:
If a patient was preoxygenated with a saturation of 100 percent before attempting RSI (Rapid Sequence Intubation), the attempt should be stopped if the saturation drops below a certain level. The commonly accepted threshold is usually around 90-95 percent saturation. This is because a saturation level below 90 percent may indicate hypoxemia, which can be detrimental to the patient's oxygenation and overall health.