Cálculo de la presión positiva teleespiratoria óptima en un modelo experimental de síndrome de distrés respiratorio

Abstract

One of the therapeutic weapons to address the respiratory distress syndrome is treated with mechanical ventilation with lung protective parameters. However, within those parameters, there is no consensus on what the optimal level of PEEP should be applied when ventilating these patients. The aim of this study is to assess the gas exchange and hemodynamic effect of applying different levels of PEEP, calculated on the inspiratory or expiratory branches of the pressure-volume loop, and the impact on lung parenchyma. To perform this study was used 35 female Wistar rats, aged 90 ± 15 days and a weight of 215 ± 35 grams. The rats were anesthetized with intraperitoneal administration of ketamine (75 mg/kg) and dexmetomidina (30 mg/kg); once reached an adequate level of hypnosis, endotracheal intubation was performed with a 16G Teflon catheter. Then were connected to pressurecontrolled respirator and were catheterized left carotid artery to monitor the HR and ABP and left jugular vein with two 24G Teflon catheters. ARDS was made with saline washes as described by Rosenthal in 1998. The data of HR, ABP, PaO2, PaCO2, pH, HCO3, PEEP, Paw, RR, I / E ratio, VT, and VM were collected at times: before ARDS, 30 minutes after producing the ARDS, and 15, 30, 60 and 120 minutes to establish ventilation treatment. Six groups were established according to the treatment ventilatory: with or without an alveolar recruitment maneuver after ARDS, and one level or another depending on the PEEP level was estimated at inspiratory or expiratory branches of the P/V loop. ARDS values (baseline) were compared intragroups and intergroups with respect to other times through an analysis of variance with repeated measures (ANOVA). By a Tukey test was studied the similarity in the behavior of 15 to 120 minutes of ARDS among different groups. There is a significant improvement in oxygenation in all groups between ARDS and 120 minutes, except for those groups that did not apply PEEP. Furthermore the groups ventilated with PEEP calculated branch expiratory (lower level of PEEP), which had less damage anatomopathological groups ventilated with PEEP calculated branch inspiratory (higher level of PEEP), with no significant differences in oxygenation.