[Does exogenous airflow resistance reduce endogenous airway resistance in healthy persons?]

The aim of our investigation was to assess whether a preinserted model resistance of a certain magnitude will expand the airways during inspiration and thus reduce the resistance of the airways conceived as the sum of the value of the endogenous airway resistance without obstruction and the value of the exogenous pre-inserted model resistance. The model resistance and resistance of the airways were assessed by means of a whole-body plethysmograph. The airway resistance was evaluated in 10 healthy men during inspiration and expiration, using a dictated breathing pattern. When a model resistance of 0.75 kPa.l-1.s-1 was preinserted during dictated minute ventilation of 30 l.min-1 and an air current of 1 l.s-1 the value of the airway resistance increased markedly, as compared with the same breathing pattern without obstruction. The resistance increment was, however, by 30% lower than the expected value. At the same time the functional residual lung capacity increased.