[Inversed ratio ventilation (IRV). Role of the respiratory time ratio in artificial respiration in ARDS].

Considering the advantages shown by the experiences of Reynolds on prolonged inspiration time it was suggested to study this type of ventilation also in ARDS. We tried the inverse ratio ventilation (IRV) in patients with ARDS and in postoperative cardiac surgical patients. An obvious improvement of gas transfer in the lung is seen and becomes better with increased duration of this type of ventilation. A better filling of various parts of the lung with longer time constants is achieved with prolonged inspiration. An effect similar to PEEP caused by an air trapping mechanism, can be seen with the shortening of expiration time. This air trapping mechanism is followed by autonomous adaption of PEEP for the local situation in various parts of the lung. A higher PEEP in poorly ventilated areas is automatically adjusted with IRV, than in areas with a short time constant (individual PEEP).