Effect of altering breathing frequency on maximum voluntary ventilation in healthy adults

Background: Compared to other pulmonary function tests, there is a lack of standardization regarding how a maximum voluntary ventilation (MVV) maneuver is performed. Specifically, little is known about the variation in breathing frequency (f(R)) and its potential impact on the accuracy of test results. This study examines the effect of several preselected values for f(R) and one self-selected f(R) (f(Rself)) on MVV. Methods: Ten participants performed MVV maneuvers at various f(R) values, ranging from 50 to 130 breaths.min(-1) in 10 breaths.min(-1) intervals and at one f(Rself). Three identical trials with 2-min rest periods were conducted at each f(R), and the sequence in which f(R) was tested was randomized. Ventilation and related parameters were measured directly by gas exchange analysis via a metabolic measurement system. Results: A third-order polynomial regression analysis showed that MVV = -0.0001(f(R))(3) + 0.0258(f(R))(2)-1.38(f(R)) + 96.9 at preselected f(R) and increased up to approximately 100 breaths.min(-1) (r(2) = 0.982, P < 0.001). Paired t-tests indicated that average MVV values obtained at all preselected f(R) values, but not f(Rself), were significantly lower than the average maximum value across all participants. A linear regression analysis revealed that tidal volume (V-T) = -2.63(MVV) + 300.4 at preselected f(R) (r(2) = 0.846, P < 0.001); however, this inverse relationship between V-T and MVV did not remain true for the self-selected f(R). The V-T obtained at this f(R) (90.9 +/- 19.1% of maximum) was significantly greater than the V-T associated with the most similar MVV value (at a preselected f(R) of 100 breaths.min(-1), 62.0 +/- 10.4% of maximum; 95% confidence interval of difference: (17.5, 40.4%), P < 0.001). Conclusions: This study demonstrates the shortcomings of the current lack of standardization in MVV testing and establishes data-driven recommendations for optimal f(R). The true MVV was obtained with a self-selected f(R) (mean +/- SD: 69.9 +/- 22.3 breaths.min(-1)) or within a preselected f(R) range of 110-120 breaths.min(-1). Until a comprehensive reference equation is established, it is advised that MVV be measured directly using these guidelines. If an individual is unable to perform or performs the maneuver poorly at a self-selected f(R), ventilating within a mandated f(R) range of 110-120 breaths.min(-1) may also be acceptable.