In the context of mechanical ventilation, the term "controlled" means:

In the context of mechanical ventilation, the term "controlled" signifies that the ventilator is set to provide breaths to the patient at a specified rate and volume, regardless of the patient's own spontaneous efforts. This mode ensures that the patient receives consistent and adequate ventilatory support, especially in situations where they may not be able to breathe effectively on their own due to respiratory failure or sedation.

In this scenario, the ventilator takes over the primary responsibility for ventilation, ensuring that the required tidal volume and respiratory rate are maintained. This is particularly critical in emergencies or during transport when patient stability is of utmost importance. Using controlled ventilation allows healthcare providers to manage the patient’s oxygenation and carbon dioxide removal precisely, which is essential in critical care settings.

Other answer choices do not accurately reflect the meaning of "controlled" in this context. For example, the option suggesting that the patient has total control of their own breathing would indicate a different mode of ventilation, such as assisted or spontaneous mode. Additionally, the description of settings being adjustable by the patient implies a level of autonomy inconsistent with the controlled mode, and standby mode does not provide active ventilation support at all.