It has been reported that artificial ventilation causes significant elevation of elastic recoil and similar changes have also been reported in vivo. However, several investigators reported no remarkable changes in pressure-volume (P-V) curves after artificial ventilation.
In our present study, 5 rabbits were ventilated as controls and 20 rabbits were ventilated with a tidal volume of 60-70% TLC for 3 hours with an end-expiratory pressure (EEP) of 0cmH2O (EEP: 0, 10 cases) and with EEP: 2cmH2O (10 cases). After ventilation, arterial blood was obtained and the lungs were excised following exsanguination and P-V curves were recorded by means of a body plethysmograph with air. Then saline P-V curves were recorded with 2 control lungs and 3 lungs of each ventilated group. Others were used for the measurement of the wet and dry weight ratio.
Ventilated lungs with EEP: 0cmH2O showed significantly higher elastic recoil with air than controls and ventilated lungs with EEP: 2cmH2O. Ventilated lungs with EEP: 2cmH2O also showed higher elastic recoil with air than controls but the difference was not significant statistically. Saline P-V curves showed no remarkable differences in each group. The Wet/Dry ratio was significantly elevated in ventilated lungs with EEP: 0cmH2O in comparison with those of controls and ventilated lungs with EEP: 2cmH2O.
These results indicated that the artificial ventilation performed at low lung volume with large tidal volume may cause the alteration in surface forces, which may partially be due to edema formation in the lung.
