Changing the I:E ratio from 1:3 to 1:2 increases inspiratory time by about what percent?

Changing the I:E ratio from 1:3 to 1:2 increases inspiratory time by about what percent?

• A. 5%
• B. 8%
• C. 20%
• D. 33%

Answer: (B)

The key idea is how the I:E ratio defines the share of the breathing cycle allocated to inspiration when the overall cycle time stays the same. An I:E of 1:3 means the cycle is 4 parts long, with inspiratory time equal to 1 part (1/4 of the cycle, 25%). Switching to 1:2 makes the cycle 3 parts long, with inspiratory time equal to 1 part (1/3 of the cycle, about 33.3%). The difference in the inspiratory portion of the cycle is 1/3 − 1/4 = 1/12 of the cycle, which is approximately 8.3% of the cycle—roughly 8%. So the inspiratory time increases by about 8% of the total respiratory cycle.

The key idea is how the I:E ratio defines the share of the breathing cycle allocated to inspiration when the overall cycle time stays the same. An I:E of 1:3 means the cycle is 4 parts long, with inspiratory time equal to 1 part (1/4 of the cycle, 25%). Switching to 1:2 makes the cycle 3 parts long, with inspiratory time equal to 1 part (1/3 of the cycle, about 33.3%).

The difference in the inspiratory portion of the cycle is 1/3 − 1/4 = 1/12 of the cycle, which is approximately 8.3% of the cycle—roughly 8%. So the inspiratory time increases by about 8% of the total respiratory cycle.