Is There an Optimal PEEP for Pulmonary Hemodynamics in Acute Injured Lungs?
Bibliographic record
Abstract
Abstract RATIONALE: Several methods exist for setting positive end-expiratory pressure (PEEP), often leading to different PEEP levels. These variations may not only influence respiratory mechanics but also affect other critical factors, such as pulmonary vascular responses. OBJECTIVES: The main goal of this study was to estimate the impact of PEEP on pulmonary hemodynamics in acutely injured lungs. We compared three strategies of PEEP titration – highest respiratory system compliance (CRS), electrical impedance tomography (EIT) crossing point, and positive end-expiratory transpulmonary pressure (PL) – in terms of PEEP level and pulmonary hemodynamics. METHODS: Experimental study in two porcine models of acute lung injury induced by surfactant lavage and high stretch ventilation: I) Bilateral(n=37), injury induced in both lungs, generating a highly recruitable model; and II) Asymmetrical(n=13), injury induced in one lung while the other was collapsed, generating a poorly recruitable model. In all experiments, a decremental PEEP titration was performed monitoring PL, EIT (collapse, overdistension, and regional ventilation), respiratory mechanics, and pulmonary and systemic hemodynamics. PRELIMINARY RESULTS: PEEP titration based on CRS, EIT, and end-expiratory PL, resulted in three different levels of optimal PEEP in bilateral lung injury: mean PEEP were 13±2cmH2O, 11±2cmH2O, and 9±3cmH2O cmH2O, respectively (p<0.001). Our model of bilateral lung injury is highly recruitable, with a median R/I ratio of 1.24 (0.90-1.40). In this model, PEEP had a quadratic relationship (U shape) with mean PAP, represented by the formula “MeanPAP=4-(1.5xPEEP)+(0.1xPEEP2)”, R2=0.94, p<0.001, and with RV transmural pressure. In the asymmetrical lung injury, only PEEP at expiratory PL slightly positive (6±4cmH2O) was lower than both PEEP at the EIT crossing point (9±2cmH2O, p=0.047) and PEEP at the highest CRS (9±3cmH2O, p=0.023). Our model of asymmetrical lung injury had low-to-moderate lung recruitability, with a median R/I ratio of 0.67(0.29-0.98). In this model, it was also evident the quadratic relationship between PEEP with mean PAP and with RV transmural pressure. We measured PVR to verify if the response in mean PAP to PEEP would represent the response in PVR, and PVR behaved exactly like mean PAP. Systemic hemodynamics behaved similarly to pigs with bilateral lung injury. CONCLUSIONS: In porcine models of acute lung injury, both very low and very high levels of PEEP may impair pulmonary hemodynamics. The relationship between mean PAP and PEEP has a U shape, with the best level of mean PAP at individualized levels of PEEP.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".