Which of the following is NOT a type of O2 delivery system?

The most accurate reason why ventilator systems are not classified as a type of oxygen delivery system in the same way as the other options is that they serve a different purpose. While low-flow systems, reservoir systems, and high-flow systems are specifically designed to deliver supplemental oxygen directly to patients who are capable of breathing independently, ventilator systems provide respiratory support for patients who are unable to breathe effectively on their own.

Oxygen delivery systems are fundamentally categorized based on how they supply oxygen to a patient and whether they rely on the patient's own respiratory effort. Low-flow systems and high-flow systems refer to the rate at which oxygen is delivered, while reservoir systems often use a bag or reservoir to store and supply extra oxygen. A ventilator, on the other hand, mechanically assists or takes over the breathing process altogether, which fundamentally distinguishes it from typical oxygen delivery systems. Thus, it's classified as a respiratory support device rather than a direct method of oxygen delivery.