[Monitoring of mechanical ventilation during IPPV: implications due to the intrapulmonary entrapment of gas. Study on a physical model of the lung].

This work was undertaken to determine the possible influence of gas trapping on the values of total respiratory system compliance and on the air flow resistance at the air ways obtained by conventional effects of positive telespiratory alveolar pressure (auto-PEEP) typical of gas trapping on ventilatory dynamics. This study has been carried out in a physical model of the lung. The results support the contention that in the above situation: 1) the total compliance of the respiratory system measured as the quotient between the current volume and the plateau pressure (C.DIN) shows lower values than those of the static compliance (C.EST), and 2) flow resistance at the air ways must be measured as the quotient between the time constant and the plateau pressure. It should not be measured as the quotient between the time constant and the static compliance since in that case the values would be lower than the real ones.