The effect of positive end-expiratory pressure on cardiac output and oxygen delivery during cardiopulmonary resuscitation

Abstract

Background: Positive end-expiratory pressure (PEEP) is used to optimize oxygenation by preventing alveolar collapse. However, PEEP can potentially decrease cardiac output through cardiopulmonary interactions. The effect of PEEP on cardiac output during cardiopulmonary resuscitation (CPR) is not known. Methods: This was a preclinical randomized, controlled, animal study conducted in an animal research facility on 25 Landrace-Yorkshire pigs. After inducing cardiac arrest, CPR was performed with LUCAS 3. During CPR, pigs were ventilated at a PEEP of 0, 5, 10, 15, 20 cmH 2 O (randomly determined via lottery) for 9 min. Cardiac output, obtained via ultrasound dilution, and PaO 2 were measured, and oxygen delivery calculated for each PEEP. Results: A mixed-effects repeated-measures analysis of variance was used to compare the baseline value adjusted mean cardiac output, PaO 2 , and oxygen delivery between PEEP groups. Least significant difference test was used to conduct pairwise comparisons between PEEP groups. To determine optimum PEEP, Gaussian mixture model was applied to the adjusted means of cardiac output and oxygen delivery. Increasing PEEP to 10 and higher resulted in significant declines in cardiac output. A PEEP of 15 and higher resulted in significant declines in oxygen delivery. As PEEP was increased from 0 to 20, PaO 2 increased significantly. Gaussian mixture model identified the 0-5 PEEP group as providing optimal cardiac output and oxygen delivery, with PEEP of 5 providing the highest oxygen delivery. Conclusions: A PEEP of 0-5 resulted in the optimal oxygen delivery and cardiac output during CPR, with PEEP of 5 resulting in higher oxygen delivery, and a slightly lower, statistically insignificant cardiac output than PEEP of 0.

Effect of positive end-expiratory pressure on additional passive ventilation generated by CPR compressions in a porcine model

“…Alkalosis also shifts the oxyhemoglobin curve to the left, possibly reducing oxygen off-loading to tissues [7,[22][23][24]. These findings, suggesting that the optimal PEEP during CPR should be less than 10 cmH 2 O when lung compliance is high, are in line with results from another study by our laboratory, which demonstrate that in terms of oxygen delivery during CPR, the optimal PEEP level was a PEEP of 5 cmH 2 O, which optimized both oxygenation and cardiac output to achieve the best oxygen delivery [18].…”

“…Instead, we see that, other than for PEEP of 15 and 20 cmH 2 O, which show a slightly higher number for the volumetric capnography for PEEP of 15 compared with 20 cmH 2 O, the volumetric capnography does not follow the trend of the minute ventilation, increasing as PEEP is increased. (Perhaps the higher volumetric capnography value for PEEP of 15 compared with 20 cmH 2 O can be explained by the greater decrease in cardiac output seen at a PEEP of 20 compared with 15 cmH 2 O, as was demonstrated previously by this group [18].…”

“…This study was performed with Landrace-Yorkshire pigs weighing 35–38 kg ( n = 13 pigs). The cohort of animals used in this study was part of a larger study, which analyzed the effect of PEEP on cardiac output during CPR [ 18 ]. After seeing trends in carbon dioxide shift with the various PEEP levels with the first animals in the study, data were collected to formally analyze effect of PEEP on carbon dioxide clearance for the last 13 animals in the study.…”

High PEEP levels during CPR improve ventilation without deleterious hemodynamic effects in pigs

“…When using PEEP, lower shunt fractions could be detected, particularly in early resuscitation, suggesting improved recruitment and optimized ventilation. This aligns with studies that showed that using PEEP during resuscitation can prevent airway closure and ensure alveolar ventilation (19,20) and has positive effects on systemic oxygenation (4,5,21). In our trial, oxygenation was improved when using PEEP, especially in early resuscitation.…”

“…Interestingly, even when using high PEEP levels, we found no differences in the hemodynamic values although theoretically, a continuous application of PEEP and a consecutive high Ppeak and Pmean could lead to increased intrathoracic pressure which could cause impaired venous return and, consequently, cardiac output (CO) (10,11,21). A study evaluating the effects of PEEP on CO during CPR suggested a PEEP of 5 mbar as the optimal level in their model (21).…”