ESTIMATION OF VENTILATORY CAPACITY DURING SUBMAXIMAL EXERCISE

There is presently no precise way to determine ventilatory capacity fo r a given individual during exercise; however, this information would be helpful in evaluating ventilatory reserve during exercise. Using sc hematic representations of maximal expiratory flow-volume curves and i ndividual maximal expiratory flow-volume curves from four subjects, we describe a technique for estimating ventilatory capacity. In these su bjects, we measured maximal expiratory flow-volume loops at rest and t idal flow-volume loops and inspiratory capacity (IC) during submaximal cycle ergometry. We also compared minute ventilation (VE) during subm aximal exercise with calculated ventilatory maxima (VE(max Cal)) and w ith maximal voluntary ventilation (MVV) to estimate ventilatory reserv e. Using the schematic flow-volume curves, we demonstrated the theoret ical effect of maximal expiratory flow and lung volume on ventilatory capacity and breathing pattern. In the subjects, we observed that the estimation of ventilatory reserve with use of VE/VE(max Cal) was most helpful in indicating when subjects were approaching maximal expirator y flow over a large portion of tidal volume, especially at submaximal exercise levels where VE/VE(max Cal) and VE/MVV differed the most. The se data suggest that this technique may be useful in estimating ventil atory capacity, which could then be used to evaluate ventilatory reser ve during exercise.