[Problems in respiratory mechanics within the assessment of physical working capacity].

Ventilatory capacity was studied in a group of 16 subjects suffering from bronchial obstruction during scaled 30-watt interval exertion tests. A flow volume curve with normal and forced expiratory volume at rest and immediately after muscular exertion was made for all subjects in order to have a clear picture of the flow restrictions of the airways and their extent. The subjects were divided into four groups on the basis of the extent of impairment of vital capacity and the size of the obstruction indices: it was found that while reduction in the volume of moveable air (vital capacity) does not impair ventilatory capacity, a reduction in flow causes a relative hypoventilation during muscular exercise. This finding was also confirmed experimentally by applying an extrathoracic resistance during muscular exertion in two subjects. The authors conclude that the scaled type exertion test as proposed to the E.E.C., which is based on a linear ventilation pattern during tolerated exertion, is totally unsuitable for assessing the working capacity of subjects with restricted ventilatory capacity connected with an increase in airway resistance. In such cases, ventilation in the course of exertion decreased with increased flow impairment, so that at low work loads the situation resembles that of normal or even very well physically trained subjects.