Inspiratory time
I-time the time of the inhalation phase of a breath. A normal I-time is 0.8-1.2 seconds. This combined with the time of exhalation makes up the I:E ratio. The exhalation time depends on our set rate. When setting our I-time, we are less concerned with the actual time and more concerned with the I:E ratio. A normal I:E ratio is 1:2, so we try to target that ratio based on our set rate. Patients with COPD or asthma may benefit for a longer expiratory phase. They will have a normal I:E ratio of 1:3 or 1:4.
Example: We have a rate of 12 and an I-time of 1.0. With the rate of 12, we have a total breath cycle time of 5 seconds. 5 seconds – 1.0 second = 4 seconds left over.
Now we know that our I-time is 1.0 second, and our exhalation time is 4 seconds.
If we express this as ratio, we have an I:E ratio of 1:4.