Final answer:
The mode of ventilatory support where a ventilator holds a preset pressure for a specified time before ending inspiration is known as a time-cycled mode.
Step-by-step explanation:
The mode of ventilatory support described where a ventilator reaches a preset pressure early in inspiration and holds it for a specific time, after which inspiration ends, is known as a time-cycled mode. In this mode of ventilation, pressure is defined and limited, but the cycle from inspiration to expiration is based on a set amount of time, not on reaching a specific volume or pressure. This is different from other modes such as pressure-limited, which would end inspiration when a certain pressure is reached, or volume-limited which would deliver a preset volume regardless of the pressure reached.