This ratio expresses closing capacity as a percentage of total lung capacity, giving a size-independent way to track how much of the lung's volume range is affected by small-airway closure.
A rising share means airways close over a larger part of the breathing range.
Yes — conditions that reduce lung elastic recoil, like emphysema, can raise closing capacity independent of age, pushing the ratio up.
It gives a size-independent way to track how much of the lung's total volume range is affected by small-airway closure, so values are comparable across people of different sizes.
Loss of lung elastic recoil over time lets small airways close at higher volumes, so closing capacity — and therefore its ratio to TLC — increases progressively with age.
A higher ratio helps explain age-related increases in V/Q mismatch risk, especially under anesthesia or in the supine position.