The optimal pressure of sustained inflation for alveolar recruitment

Objective

To determine the optimal recruitment pressure of sustained inflation (SI) in treatment of rabbits with acute respiratory distress syndrome (ARDS).

Materials and methods

SI was applied at pressures of 1 ~ 6 times of mean airway pressure (P_m) for 20 s to saline-lavaged adult New Zealand rabbits. Hemodynamics, pulmonary mechanics and gas exchange were observed before SI, during, and 2 min, 5 min after applying SI. Lung histology was observed after experiment.

Results

When the pressure of SI was higher than 3 P_m, arterial oxygen tension (PaO₂) and arterial oxygen saturation were improved. The difference of PaO₂ before and during SI were (75 ± 39)mmHg and (52 ± 25)mmHg respectively in the 5 P_m and 6 P_m group, which were higher than 1 P_m group significantly ([-5 ± 4]mmHg, P < 0.05). The difference of dynamic pulmonary compliance before and during SI in 5 P_m group was increased markedly ([1.90 ± 0.20]ml/cmH₂O in 5 P_m group, [-0.02 ± 0.04]ml/cmH₂O in 1 P_m group, P < 0.05). 5 P_m resulted in immediate increased significantly in lung volume ([3.1 ± 2.1]ml/kg in the group, 5 P_m [8.3 ± 0.7]ml/kg in the 1 P_m group). Histologically, Smith lung injury score was 4.03 ± 1.79 in the 5 P_m group, which was less than the score in the group of ARDS model (6.10 ± 0.77). SI with 6 P_m led to alveolar overdistention. With the increasing of SI pressure, mean arterial pressure decreased markedly.

Conclusions

5 P_m (25 ~ 35 cmH₂O) may be the optimal recruitment pressure of SI in rabbits with ARDS.