Chest
Laboratory and Animal InvestigationsThe Effect of Varying Inspiratory to Expiratory Ratio on Gas Exchange in Partial Liquid Ventilation
Section snippets
Animal Preparation and Instrumentation
Eighteen New Zealand White rabbits (2.6 ± 0.5 kg) were used for this study. In group 1 (n = 9), the I:E ratio was changed by adjusting the inspiratory pause at a fixed inspiratory flow rate. In group 2 (n = 9), the I:E ratio was changed by adjusting the inspiratory flow rate. The experimental protocol was approved by the Animal Care Committee of our institute, and the rabbits were cared for and handled according to the guidelines of the National Health Institute. The rabbits were placed supine
Results
With increasing I:E ratio in all animals, Pao2/Fio2increased (80 ± 24 mm Hg at 1:2/1:3; 143 ± 74 mm Hg at 1:1; and 147 ± 88 mm Hg at 2:1; p = 0.001) and Paco2 decreased (74 ± 15 mm Hg, 66 ± 16 mm Hg, and 66 ± 15 mm Hg, respectively; p = 0.006). With an increasing I:E ratio in group 1, Pao2/Fio2increased (p = 0.001) and Paco2 and Vd/Vt decreased (both p < 0.05; Table 1). In group 2, on the other hand, Pao2/Fio2at 2:1 was lower than at 1:1 (p < 0.05), and Paco2 and Vd/Vt did not change (Table 2).
Discussion
In at least two animal studies, the superior lung and the inferior lung were observed to be inflated in sequence during PLV.16 The current study was intended to evaluate the effect of an increased I:E ratio on gas exchange in this situation of sequential lung inflation. In our results, extending the I:E ratio in PLV increased oxygenation and decreased Paco2 of acutely injured rabbit lung. In the application of a high I:E ratio in PLV, adding inspiratory pause was superior to lowering
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This study was supported in part by the Asan Institute for Life Sciences, Seoul, Korea.