What is the effect of increasing the inspiratory time (I time) in a controlled ventilation mode?

• A. Increases inspiration duration
• B. Increases expiration duration
• C. Increases respiratory rate
• D. Decreases inspiratory flow

Answer: (A)

In a time-cycled, controlled ventilation mode, the inspiratory time is the portion of each breath during which gas is delivered. Increasing this time directly lengthens that inhalation phase, so the breath lasts longer and the duration of inspiration increases. It doesn’t inherently widen expiration duration (which is set by the overall cycle time) and it won’t by itself raise the breath rate; extending the inhalation typically lengthens the cycle, potentially reducing rate if the cycle time is kept constant. It also doesn’t inherently reduce inspiratory flow; the peak flow may actually decrease as delivery is spread over a longer interval, but the primary effect is a longer inspiration.