why is there a pause between inhalation and exhalation?

Answer 1

let me answer this by asking another question. why does a ball pause at it's max height when thrown straight up?

Answer 2

There is time required for the air in the lungs to diffuse into the blood stream and the waste in the blood stream to go back to the lungs.

The longer the pause the more effeceint the lungs at using the MOST oxygen possible. Also the more effecient the body, the less oxygen needed. People with good cardio fitness breath much slower. - Just as a side note.

Answer 3

There may be a finite time required for the intercostal muscles and diaphragm to change from contracting to relaxing. This is reflected in the time delay.