[Influence of the working posture on the flow-volume curve: an advanced identification of the "wave speed theory"]

The flow-volume (F-V) curves and routine ventilatory functions were performed with "point-measured method" on 473 healthy workers. 224 engaged in heavy work; 248 engaged in moderately heavy work and were compared with normal sedentary subjects. In workers who had heavy load, the flows at high lung volumes were reduced after 40 years of age, and the flows at low lung volumes were increased after 30 years both in males and females. There was a tendency of increase with age. In workers who had moderately heavy load, only the increase of flow at low lung volumes in individual age group was noticed. The same ventilatory functions were repeatedly measured on 7 healthy sedentary subjects who mimicked the working posture by bending forward. The same results were obtained with reduced flows at high lung volumes and increased flows at low lung volumes, and were also consistent with those of farmers measured previously. This fact suggested that the wave speed theory can also be applicable to the ventilatory behavior of the workers with forward bending of neck and trunk during heavily loaded working.