What is the normal inspiratory to expiratory (I:E) ratio?

• A. 1:1
• B. 1:2
• C. 2:1
• D. 1:3

Answer: (B)

The normal inspiratory to expiratory (I:E) ratio in healthy individuals is typically around 1:2. This means that the duration of inhalation is about half that of exhalation. During normal breathing, inhalation is a somewhat shorter and more active phase, while exhalation is primarily passive and tends to take longer due to the recoil of the lungs and thoracic cavity.

In contrast, an I:E ratio of 1:1 might suggest a state of hyperventilation, while an I:E of 2:1 could indicate a situation where there is an extended inspiration, which might be seen in certain respiratory conditions. An I:E ratio of 1:3 would indicate prolonged exhalation, which can occur in obstructive lung diseases, but it is not representative of normal physiology.

Hence, the I:E ratio of 1:2 aligns with typical respiratory mechanics observed in healthy individuals, demonstrating the proper balance between inhalation and exhalation.