Relationship of Static Respiratory Muscle Pressure and Maximum Voluntary Ventilation in Normal Subjects

Abstract

40 normal subjects performed spirometry, maximum voluntary ventilation (MW), and tests of static inspiratory (P_i max) and expiratory (P_e max) respiratory muscle pressure. Forced expiratory volumes in 0.5 (FEV_0.5), in 0.75 (FEV_0.75), and 1 sec (FEV₁) correlated significantly with MW (r = 0.805, 0.804, 0.779, respectively). When P_i max was considered as a second independent variable, the probability of predicting MVV from timed forced expiratory volumes was enhanced (r = 0.914, 0.900 and 0.872 for FEV_0.5, FEV_0.75, and FEV₁, respectively). Statistical analysis indicated that multiple regression with Pi max was superior to regression with timed forced expiratory volume alone in the prediction of MW. For any given FEV₁ however, Pi max was widely dispersed (range: -60 to -200 cm H₂O). MW values, expressed as percentage difference between largest and smallest value, varied less than did P_i max. P_e max, vital capacity, height and age did not enhance the ability of timed forced expiratory volumes to predict MVV. These data indicate that while respiratory muscle strength is important for sustaining maximal ventilation, the MW is not a sensitive indicator of respiratory muscle strength.