Effects of cyclic opening and closing at low- and high-volume ventilation on bronchoalveolar lavage cytokines*
Bibliographic record
Abstract
OBJECTIVE: To examine the mechanisms of ventilator-induced lung injury at low and high lung volumes. DESIGN: Prospective, randomized, laboratory study. SETTING: University research laboratory. SUBJECTS: Eighty-eight adult male Sprague-Dawley rats. INTERVENTIONS: Mechanical ventilation using low and high lung volumes. MEASUREMENTS AND MAIN RESULTS: An ex vivo rat lung model was used. In study I (ventilation at low lung volumes), rat lungs (n = 40) were randomly assigned to various modes of ventilation: a) opening and closing with positive end-expiratory pressure (PEEP; control): tidal volume 7 mL/kg and PEEP 5 cm H2O; b) opening and closing from zero end-expiratory pressure (ZEEP): tidal volume 7 mL/kg and PEEP 0; or c) atelectasis. Peak inspiratory pressure was monitored at the beginning and end of 3 hrs of ventilation. At the end of 3 hrs of ventilation, the lungs were lavaged, and the concentrations of tumor necrosis factor-alpha, macrophage inflammatory protein-2, and interleukin-6 cytokines were measured in the lavage. In study II (ventilation at high volumes), rat lungs (n = 45) were randomly assigned to a) cyclic lung stretch: pressure-controlled ventilation, peak inspiratory pressure 50 cm H2O, and PEEP 8 cm H2O; b) continuous positive airway pressure at 50 cm H2O (CPAP50); or c) CPAP at the mean airway pressure of the cyclic stretch group (CPAP 31 cm H2O). Bronchoalveolar lavage cytokine concentrations (tumor necrosis factor-alpha, macrophage inflammatory protein-2, and interleukin-6) were measured at the end of 3 hrs of ventilation. In the low volume study, there was no difference in bronchoalveolar lavage cytokine concentrations between the PEEP group and the atelectatic group. All cytokines were significantly higher in the ZEEP group compared with the atelectasis group. Macrophage inflammatory protein-2 was significantly higher in the ZEEP group compared with the PEEP group. Lung compliance, as reflected by change in peak inspiratory pressure, was also significantly worse in the ZEEP compared with the PEEP group. In the high-volume study, tumor necrosis factor-alpha and interleukin-6 were significantly higher in the cyclic stretch group compared with the CPAP 31 group. There was no significant difference between the cytokine concentrations in the cyclic stretch group compared with the CPAP 50 group. CONCLUSION: We conclude that at low lung volumes, cyclic opening and closing from ZEEP leads to greater increases in bronchoalveolar lavage cytokines than atelectasis. With high-volume ventilation, over time, the degree of overdistension is more associated with increases in bronchoalveolar lavage cytokines than cyclic opening and closing alone.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".