What does I-time refer to on a ventilator?

• A. Expiration time on ventilator
• B. Inspiration time on ventilator
• C. Ratio of inspiration to expiration
• D. Minute volume

Answer: (B)

I-time is the duration of the inspiratory phase in each ventilator breath—the time the machine actively delivers gas during inspiration. It’s how long the inhalation lasts in every cycle. This is distinct from expiration time, which is how long exhalation occurs. The I:E ratio describes how long inspiration lasts relative to expiration (for example, an I:E of 1:2 means inspiration is one part of a three-part cycle, so the I-time is about one third of the total breath cycle). Minute volume, on the other hand, is the total amount of air delivered per minute (tidal volume times respiratory rate), not the length of inspiration itself.