maximum voluntary ventilation(MVV) is a measure of the maximum amount of air that can be inhaled and exhaled with in one minute.
For the comfort of the patient this is done over a 15 second time period before being extrapolated to a value for one minute expressed as liters/minute.
Average values for males and females are 140-180 and 80-120 liters per minute respectively.

ryo..,there is an evidence based proof which says that mvv is used in COPD pts.to inprove respiratory muscle endurance & exercise performance refer the followg research....
Respiratory Muscle Endurance Training in Chronic Obstructive Pulmonary Disease
(Impact on Exercise Capacity, Dyspnea, and Quality of Life)
THOMAS A. SCHERER et.al.
(but the maneuver is highly dependent on patient cooperation and effort, and is normally repeated at least three times to ensure reproducibility ).
even though a first yr student; hope this will help u.