Relationships between the Maximum Voluntary Ventilation and Various Expiratory Flow Rates

¹ Pulmonary Function Laboratory, Department of Medicine, State University of New York, Downstate Medical Center

(1) Data from a previous study¹ were reanalyzed to determine where in the VC best correlations could be found between MVV and EFR. The best correlations were generally found between 15 per cent and 25 per cent of the unexpired VC—low in the VC—for both sexes. This correlation occurs at a respiratory level where more than 75 per cent of the expiratory volume has been delivered and where the resistance of the lower air passageways strongly influences airflow. Fair correlations were also found at a level at which 35 per cent of the VC had been exhaled (for women only).

(2) The studies of correlation between half-maximum EFR and MVV are not conclusive. The MVV is best related to the swept fraction and respiratory rate with respect to prediction of expected MVV. Most prediction formulae are reducible to an approximate formula of MVV=34.4 x VC for respiratory rates between 40 and 60 per minute.

(3) The MVV is dependent upon many factors and is test of over-all ventilatory mechanics, whereas the MEFR is not dependent upon many variables. It is suggested that the lower airway resistance plays a relatively greater role in determining MVV than has been heretofore appreciated.