Studies on the optimal inspiratory pattern to correct the heterogeneous distribution of alveolar pressure during mechanical ventilation in septic pulmonary edema

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It has been reported that a heterogeneous distribution of alveplar pressure occurs during mechanical continuous positive pressure ventilation even in the normal lung. Regulating an inspiratory flow rate, pattern, and a duration of an added end inspiratory pause (EIP) can produse variable inspiratory patterns. We studied which inspiratory pattern is optimal to homogenize the heterogeneous distribution of alveolar pressure during mechanical ventilation. We performed simultaneous alveolar pressure measurements in each of lobes dynamically with an alveolar capsule method. After the control study in normal lung models, we tried to determine an optimal inspiratory pattern in the models with septic pulmonary edema made by administration of interleukin-1 and tumor necrosis factor.In normal lung models, addition of EIP pattern significantly decreased an end inspiratory alveolar pressure gradient between a nondependent zone (NDZ) and a dependent zone (DZ) compared to the slow inspiratory flow pa … More ttern. The EIP pressure patterns showed a gradual decreasing wave in NDZ and a gradual increasing wave in DZ.Alveolar pressures significantly decreased in MDZ and increased in DZ at the end of EIP compared to those at the beginning of EIP.Alveolar pressures were higher in NDZ and lower in DZ at the initial inspiratory phase during mechanical ventilation. Pressure distribution became more homogeneous when EIP was applied due to redistribution of alveolar pressure from NDZ to DZ.In septic lung models, measurements of alveolar pressures with the alveolar capsule method were very difficult by increased secretion from alveoli.We made it clear that the distribution of alveolar pressure becomes more homogeneous when EIP was added during mechanical ventilation in normal lung models. Addition of EIP may correct the heterogeneous distribution of alveolar pressure in septic lung models. It will be necessary to improve the methods to measure alveolar pressures for the additional investigations about septic lung models. Less