The effects of different ventilatory modes and spontaneous breathing after recruitment maneuver in acute respiratory distress syndrome. Experiment with dogs

Abstract

To investigate the role of different ventilatory modes and spontaneous breathing (SB) in prevention of derecruitment in acute respiratory distress syndrome (ARDS). Eighteen dog ARDS models were established by injection of oleic acid into the central vein and ventilated with volume controlled ventilation (VCV,) with the positive end expiratory pressure (PEEP) of 16 cm H(2)O, tidal volume (V(T)) of 10 ml/kg, and respiratory rate (RR) of 30 bpm, and the steady state in this mode was defined as baseline (0 min). After the baseline state was reached, all dogs accepted recruitment maneuver (RM) in pressure controlled ventilation (PCV) mode at the level of 15 cm H(2)O and PEEP of 35 cm H(2)O for 1 min, and then assigned into three groups and ventilated for 4 hs: VCV group (VCV with V(T) of 15 ml/kg), PCV group in which the peak inspiratory airway pressure was adjusted for keeping 15 ml/kg of V(T), and SB grouping which PCV with SB activity and inspiratory airway pressure were adjusted for keeping 15 ml/kg of V(T). PEEP of 10 cm H(2)O, RR of 20 bpm, and inspiratory/expiratory ratio of 1/2 were kept for all animals. Four hours later the dogs were killed and their lungs were taken out. (1) The lower inflection points were identified as 16.1 +/- 1.9, 17.4 +/- 1.5, and 17.1 +/- 1.6 cm H(2)O for the VCV, PCV, and SB group respectively. (2) After RM, the PaO(2) levels of the PCV and SB groups were kept higher than baseline, but the PaO(2) level was as same as that in the baseline state in the VCV group. Compared with the VCV group, higher PaO(2) the PaO(2) level 30 min after RM in the SB group was found (P < 0.05). The intrapulmonary shunt 5 min, 30 min and 1 hr after RM in the SB group were all lower than those in the VCP group, however, not significantly (P = 0.077, 0.058, 0.076). (3) Compared with baseline levels, the plateau pressure and mean airway pressure in all animals were decreased significantly after RM. The plateau pressure in the SB group was significantly lower than that in the VCV group (P < 0.05). PCV with spontaneous breathing activity can offset the effect of antiderecruitment for lower PEEP; it would be more safe and effective than VCV.