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

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.

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.

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 (r² = 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 (r² = 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).

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.