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Impact of Different Positive End-Expiratory Pressures on Lung Mechanics in the Setting of Moderately Elevated Intra-Abdominal Pressure and Acute Lung Injury in a Porcine Model.

ABSTRACT: The effects of a moderately elevated intra-abdominal pressure (IAP) on lung mechanics in acute respiratory distress syndrome (ARDS) have still not been fully analyzed. Moreover, the optimal positive end-expiratory pressure (PEEP) in elevated IAP and ARDS is unclear. In this paper, 18 pigs under general anesthesia received a double hit lung injury. After saline lung lavage and 2 h of injurious mechanical ventilation to induce an acute lung injury (ALI), an intra-abdominal balloon was filled until an IAP of 10 mmHg was generated. Animals were randomly assigned to one of three groups (group A = PEEP 5, B = PEEP 10 and C = PEEP 15 cmH₂O) and ventilated for 6 h. We measured end-expiratory lung volume (EELV) per kg bodyweight, driving pressure (?P), transpulmonary pressure (?P_L), static lung compliance (C_stat), oxygenation (P/F ratio) and cardiac index (CI). In group A, we found increases in ?P (22 ± 1 vs. 28 ± 2 cmH₂O; p = 0.006) and ?P_L (16 ± 1 vs. 22 ± 2 cmH₂O; p = 0.007), with no change in EELV/kg (15 ± 1 vs. 14 ± 1 mL/kg) when comparing hours 0 and 6. In group B, there was no change in ?P (26 ± 2 vs. 25 ± 2 cmH₂O), ?P_L (19 ± 2 vs. 18 ± 2 cmH₂O), C_stat (21 ± 3 vs. 21 ± 2 cmH₂O/mL) or EELV/kg (12 ± 2 vs. 13 ± 3 mL/kg). ?P and ?P_L were significantly lower after 6 h when comparing between group C and A (21 ± 1 vs. 28 ± 2 cmH₂O; p = 0.020) and (14 ± 1 vs. 22 ± 2 cmH₂O; p = 0.013)). The EELV/kg increased over time in group C (13 ± 1 vs. 19 ± 2 mL/kg; p = 0.034). The P/F ratio increased in all groups over time. CI decreased in groups B and C. The global lung injury score did not significantly differ between groups (A: 0.25 ± 0.05, B: 0.21 ± 0.02, C: 0.22 ± 0.03). In this model of ALI, elevated IAP, ?P and ?P_L increased further over time in the group with a PEEP of 5 cmH₂O applied over 6 h. This was not the case in the groups with a PEEP of 10 and 15 cmH₂O. Although ?P and ?P_L were significantly lower after 6 hours in group C compared to group A, we could not show significant differences in histological lung injury score.

SUBMITTER: Fiedler MO

PROVIDER: S-EPMC7830768 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Impact of Different Positive End-Expiratory Pressures on Lung Mechanics in the Setting of Moderately Elevated Intra-Abdominal Pressure and Acute Lung Injury in a Porcine Model.

Fiedler Mascha O MO Simeliunas Emilis E Deutsch B Luise BL Diktanaite Dovile D Harms Alexander A Brune Maik M Dietrich Maximilian M Uhle Florian F Weigand Markus A MA Kalenka Armin A

Journal of clinical medicine 20210115 2

The effects of a moderately elevated intra-abdominal pressure (IAP) on lung mechanics in acute respiratory distress syndrome (ARDS) have still not been fully analyzed. Moreover, the optimal positive end-expiratory pressure (PEEP) in elevated IAP and ARDS is unclear. In this paper, 18 pigs under general anesthesia received a double hit lung injury. After saline lung lavage and 2 h of injurious mechanical ventilation to induce an acute lung injury (ALI), an intra-abdominal balloon was filled until ...[more]

PMID: 33467666

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Project description:IntroductionIntra-abdominal hypertension (IAH) causes atelectasis, reduces lung volumes and increases respiratory system elastance. Positive end-expiratory pressure (PEEP) in the setting of IAH and healthy lungs improves lung volumes but not oxygenation. However, critically ill patients with IAH often suffer from acute lung injury (ALI). This study, therefore, examined the respiratory and cardiac effects of positive end-expiratory pressure in an animal model of IAH, with sick lungs.MethodsNine pigs were anesthetized and ventilated (48 +/- 6 kg). Lung injury was induced with oleic acid. Three levels of intra-abdominal pressure (baseline, 18, and 22 mmHg) were randomly generated. At each level of intra-abdominal pressure, three levels of PEEP were randomly applied: baseline (5 cmH2O), moderate (0.5 × intra-abdominal pressure), and high (1.0 × intra-abdominal pressure). We measured end-expiratory lung volumes, arterial oxygen levels, respiratory mechanics, and cardiac output 10 minutes after each new IAP and PEEP setting.ResultsAt baseline PEEP, IAH (22 mmHg) decreased oxygen levels (-55%, P <0.001) and end-expiratory lung volumes (-45%, P = 0.007). At IAP of 22 mmHg, moderate and high PEEP increased oxygen levels (+60%, P = 0.04 and +162%, P <0.001) and end-expiratory lung volume (+44%, P = 0.02 and +279%, P <0.001) and high PEEP reduced cardiac output (-30%, P = 0.04). Shunt and dead-space fraction inversely correlated with oxygen levels and end-expiratory lung volumes. In the presence of IAH, lung, chest wall and respiratory system elastance increased. Subsequently, PEEP decreased respiratory system elastance by decreasing chest wall elastance.ConclusionsIn a porcine sick lung model of IAH, PEEP matched to intra-abdominal pressure led to increased lung volumes and oxygenation and decreased chest wall elastance shunt and dead-space fraction. High PEEP decreased cardiac output. The study shows that lung injury influences the effects of IAH and PEEP on oxygenation and respiratory mechanics. Our findings support the application of PEEP in the setting of acute lung injury and IAH.

Project description:BackgroundThe intra-abdominal pressure (IAP) is an important clinical parameter that can significantly change during respiration. Currently, IAP is recorded at end-expiration (IAPee), while continuous IAP changes during respiration (?IAP) are ignored. Herein, a novel concept of considering continuous IAP changes during respiration is presented.MethodsBased on the geometric mean of the IAP waveform (MIAP), a mathematical model was developed for calculating respiratory-integrated MIAP (i.e. MIAPri=IAPee+i??IAP), where 'i' is the decimal fraction of the inspiratory time, and where ?IAP can be calculated as the difference between the IAP at end-inspiration (IAPei) minus IAPee. The effect of various parameters on IAPee and MIAPri was evaluated with a mathematical model and validated afterwards in six mechanically ventilated patients. The MIAP of the patients was also calculated using a CiMON monitor (Pulsion Medical Systems, Munich, Germany). Several other parameters were recorded and used for comparison.ResultsThe human study confirmed the mathematical modelling, showing that MIAPri correlates well with MIAP (R2 = 0.99); MIAPri was significantly higher than IAPee under all conditions that were used to examine the effects of changes in IAPee, the inspiratory/expiratory (I:E) ratio, and ?IAP (P <0.001). Univariate Pearson regression analysis showed significant correlations between MIAPri and IAPei (R = 0.99), IAPee (R = 0.99), and ?IAP (R = 0.78) (P <0.001); multivariate regression analysis confirmed that IAPee (mainly affected by the level of positive end-expiratory pressure, PEEP), ?IAP, and the I:E ratio are independent variables (P <0.001) determining MIAP. According to the results of a regression analysis, MIAP can also be calculated asMIAP=-0.3+IAPee+0.4??IAP+0.5?IE.ConclusionsWe believe that the novel concept of MIAP is a better representation of IAP (especially in mechanically ventilated patients) because MIAP takes into account the IAP changes during respiration. The MIAP can be estimated by the MIAPri equation. Since MIAPri is almost always greater than the classic IAP, this may have implications on end-organ function during intra-abdominal hypertension. Further clinical studies are necessary to evaluate the physiological effects of MIAP.

Project description:Biliary diseases known since ages constitute major portion of digestive tract disorders world over. Among these cholelithiasis being the fore runner causing general ill health, thereby requiring surgical intervention for total cure. The study was undertaken in an attempt to compare the hemodynamic changes in patient undergoing laparoscopic cholecystectomy using different intra-abdominal pressures created due to carbon dioxide insufflation. The patients were randomly allocated to one of the three groups in which different levels of intra-abdominal pressures (8-10 mmHg,11-13 mmHg and 14 mmHg and above) were maintained. The base line parameters monitored were heart rate, non invasive blood pressur(systolic and mean)and end tidal carbon dioxide. All the parameters were monitored at various intervals i.e. Immediately during insufflation, 5 min, 10 min, 20 min, 30 min after CO2 insufflation and after every 10 min if surgery exceeds 30 min, at exsufflation,10 min after CO2 exsufflation. Patients were ventilated with Pedius Drager Ventilator keeping tidal volume 8-10 ml/kg and respiratory rate 12-14 breaths/min. During surgery patients were placed in reverse Trendlenburg position (head up) at 15 °. The results obtained were evaluated statistically and analyzed. Baseline characteristics were found to be comparable. Hemodynamic variables were reported as mean and standard deviation. Statistical significance among groups was evaluated using Analysis of Variance and unpaired student t test (two tailed). Inter-group comparisons were made using Bonferroni test. A p-value of <0.05 was considered as statistically significant. In all the three groups the mean heart rate (baseline 84.08?±?12.50, 87.96?±?15.73 and 86.92?±?17.00 respectively) increased during CO2 insufflation and the rise in heart rate continued till exsufflation after which it decreased and at 10 min after exsufflation the heart rates were comparable with the baseline. The inter-group comparison of mean heart rate between I & III was statistically significant at 10, 20, 30 min after CO2 insufflation which continued at exsufflation and 10 min after CO2 exsufflation [p?<?0.05]. The inter-group comparison between I & III showed statistically significant difference in systolic blood pressure at 10, 20, 30 min after CO2 insufflation, at exsufflation and 10 min after exsufflation [p?=?0.0001] and mean arterial pressure at 5, 10, 20, 30 min after CO2 insufflation, at exsufflation and 10 min after exsufflation [p?=?0.0001]. Comparison between Group I and Group III & between Group II and Group III showed highly significant statistical difference in EtCO2 immediately after insufflation and the same trend was seen till the completion of surgery and even 10 min after exsufflation [p?=?0.001]. The conclusion drawn from the study was that laparoscopic cholecystectomy induces significant hemodynamic changes intraoperatively, the majority of pathophysiological changes are related to cardiovascular system and are caused by CO2 insufflation .A high intra-abdominal pressure due to CO2 insufflation is associated with more fluctuations in hemodynamic parameters and increased peritoneal absorption of CO2 as compared to low intraabdominal pressure so low pressure pneumoperitoneum is feasible for laparoscopic cholecystectomy and minimizes the adverse hemodynamic effects of CO2 insufflation.

Project description:IntroductionMechanical ventilation with high positive end-expiratory pressure (PEEP) has been used in patients with acute respiratory distress syndrome (ARDS) and intra-abdominal hypertension (IAH), but the role of PEEP in minimizing lung injury remains controversial. We hypothesized that in the presence of acute lung injury (ALI) with IAH: 1) higher PEEP levels improve pulmonary morphofunction and minimize lung injury; and 2) the biological effects of higher PEEP are more effective in extrapulmonary (exp) than pulmonary (p) ALI.MethodsIn 48 adult male Wistar rats, ALIp and ALIexp were induced by Escherichia coli lipopolysaccharide intratracheally and intraperitoneally, respectively. After 24 hours, animals were anesthetized and mechanically ventilated (tidal volume of 6 mL/kg). IAH (15 mmHg) was induced and rats randomly assigned to PEEP of 5 (PEEP5), 7 (PEEP7) or 10 (PEEP10) cmH2O for 1 hour.ResultsIn both ALIp and ALIexp, higher PEEP levels improved oxygenation. PEEP10 increased alveolar hyperinflation and epithelial cell damage compared to PEEP5, independent of ALI etiology. In ALIp, PEEP7 and PEEP10 increased lung elastance compared to PEEP5 (4.3 ± 0.7 and 4.3 ± 0.9 versus 3.1 ± 0.3 cmH2O/mL, respectively, P <0.01), without changes in alveolar collapse, interleukin-6, caspase-3, type III procollagen, receptor for advanced glycation end-products, and vascular cell adhesion molecule-1 expressions. Moreover, PEEP10 increased diaphragmatic injury compared to PEEP5. In ALIexp, PEEP7 decreased lung elastance and alveolar collapse compared to PEEP5 (2.3 ± 0.5 versus 3.6 ± 0.7 cmH2O/mL, P <0.02, and 27.2 (24.7 to 36.8) versus 44.2 (39.7 to 56.9)%, P <0.05, respectively), while PEEP7 and PEEP10 increased interleukin-6 and type III procollagen expressions, as well as type II epithelial cell damage compared to PEEP5.ConclusionsIn the current models of ALI with IAH, in contrast to our primary hypothesis, higher PEEP is more effective in ALIp than ALIexp as demonstrated by the activation of biological markers. Therefore, higher PEEP should be used cautiously in the presence of IAH and ALI, mainly in ALIexp.

Project description:BackgroundIn the 2014 PROtective Ventilation using HIgh versus LOw positive end-expiratory pressure (PROVHILO) trial, intraoperative low tidal volume ventilation with high positive end-expiratory pressure (PEEP = 12 cm H2O) and lung recruitment maneuvers did not decrease postoperative pulmonary complications when compared to low PEEP (0-2 cm H2O) approach without recruitment breaths. However, effects of intraoperative PEEP on lung compliance remain poorly understood. We hypothesized that higher PEEP leads to a dominance of intratidal overdistension, whereas lower PEEP results in intratidal recruitment/derecruitment (R/D). To test our hypothesis, we used the volume-dependent elastance index %E2, a respiratory parameter that allows for noninvasive and radiation-free assessment of dominant overdistension and intratidal R/D. We compared the incidence of intratidal R/D, linear expansion, and overdistension by means of %E2 in a subset of the PROVHILO cohort.MethodsIn 36 patients from 2 participating centers of the PROVHILO trial, we calculated respiratory system elastance (E), resistance (R), and %E2, a surrogate parameter for intratidal overdistension (%E2 > 30%) and R/D (%E2 < 0%). To test the main hypothesis, we compared the incidence of intratidal overdistension (primary end point) and R/D in higher and lower PEEP groups, as measured by %E2.ResultsE was increased in the lower compared to higher PEEP group (18.6 [16…22] vs 13.4 [11.0…17.0] cm H2O·L; P < .01). %E2 was reduced in the lower PEEP group compared to higher PEEP (-15.4 [-28.0…6.5] vs 6.2 [-0.8…14.0] %; P < .05). Intratidal R/D was increased in the lower PEEP group (61% vs 22%; P = .037). The incidence of intratidal overdistension did not differ significantly between groups (6%).ConclusionsDuring mechanical ventilation with protective tidal volumes in patients undergoing open abdominal surgery, lung recruitment followed by PEEP of 12 cm H2O decreased the incidence of intratidal R/D and did not worsen overdistension, when compared to PEEP ≤2 cm H2O.

Dataset Information

Impact of Different Positive End-Expiratory Pressures on Lung Mechanics in the Setting of Moderately Elevated Intra-Abdominal Pressure and Acute Lung Injury in a Porcine Model.

Publications

Impact of Different Positive End-Expiratory Pressures on Lung Mechanics in the Setting of Moderately Elevated Intra-Abdominal Pressure and Acute Lung Injury in a Porcine Model.

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