An optimal or minimal work of breathing exists for any minute ventilation and any set of respiratory mechanics. Minute ventilation is the total amount of gas moved into and out of the lung in a minute. There is an optimum combination of rate and tidal volume to minimize work. The slowest units will be those which have high resistance and high compliance. The fastest units will be those which have low resistance and low compliance.
Obstructed lungs have long time constants due to increased resistance.
This means that they take a long time to exhale. Restricted lungs have short time constants due to low compliance. This means that they take a short time to exhale. Communications between lung units help to fill the lung evenly despite units with different time constants.