Repairing a parietal defect of a large incisional hernia should not be limited to the closure of the breach by means of the modern biocompatible prosthetic sheets, but must also be able to restore a correct intra abdominal pressure, otherwise the derangement from the normal respiratory dynamics and the circulatory stasis in the abdominal veins and in those of the lower limbs remain unaltered. Overcorrecting the parietal abdominal tension on the contrary can cause a dangerous compartimental syndrome. The attempts of an intraoperative measurement of the correct intra abdominal pressure restoration has been generally hampered from the condition of curarization of the patient during the operation. Using the automatic mechanical ventilator fixed at volume and not at pressure priority, as usual, can offer the possibility to calibrate, following objective parameters, the propriety of the surgical repair still during the final phases of the reparative operation. The simplicity and ingenuity of the here proposed method and the normal availability in every operative theatre of the necessary means for this measurements descrive of attention among the surgeons and a large diffusions of its simple use.