[The oscillation method for the diagnosis of respiratory function of adults--arrangement and possibilities for optimization. 4. The oscillatory residual volume determination (RVOS)].

The residual volume can oscillatorily be estimated in an easy way with the help of diving-gas. The oscillatory unit, furnished with a sensor of density, serves as a quick helium-analyser. An overestimation of the residual volume can appear as a result of the high volatility of the used gas, an underestimation can result because of the non-registration of lung parts with entrapped air. Therefore a differentiated interpretation of the curve of wash-in is suggested. Thus a good conformity can be found with the body plethysmographic results also in patients with obstructive airways diseases including persons with disturbances of ventilatory distribution.