Impact of Positive End-Expiratory Pressure and FiO <sub>2</sub> on Lung Mechanics and Intrapulmonary Shunt in Mechanically Ventilated Patients with ARDS Due to COVID-19 Pneumonia
Bibliographic record
Abstract
Purpose: This study aimed to investigate the effects of inspired oxygen fraction (FiO 2 ) and positive end-expiratory pressure (PEEP) on gas exchange in mechanically ventilated patients with COVID-19. Methods: Two FiO 2 (100%, 40%) were tested at 3 decreasing levels of PEEP (15, 10, and 5 cmH 2 O). At each FiO 2 and PEEP, gas exchange, respiratory mechanics, hemodynamics, and the distribution of ventilation and perfusion were assessed with electrical impedance tomography. The impact of FiO 2 on the intrapulmonary shunt (delta shunt) was analyzed as the difference between the calculated shunt at FiO 2 100% (shunt) and venous admixture at FiO 2 40% (venous admixture). Results: Fourteen patients were studied. Decreasing PEEP from 15 to 10 cmH 2 O did not change shunt (24 [21-28] vs 27 [24-29]%) or venous admixture (18 [15-26] vs 23 [18-34]%) while partial pressure of arterial oxygen (FiO 2 100%) was higher at PEEP 15 (262 [198-338] vs 256 [147-315] mmHg; P < .05). Instead when PEEP was decreased from 10 to 5 cmH 2 O, shunt increased to 36 [30-39]% ( P < .05) and venous admixture increased to 33 [30-43]% ( P < .05) and partial pressure of arterial oxygen (100%) decreased to 109 [76-177] mmHg ( P < .05). At PEEP 15, administration of 100% FiO 2 resulted in a shunt greater than venous admixture at 40% FiO 2, ((24 [21-28] vs 18 [15-26]%, P = .005), delta shunt 5.5% (2.3-8.8)). Compared to PEEP 10, PEEP of 5 and 15 cmH 2 O resulted in decreased global and pixel-level compliance. Cardiac output at FiO 2 100% resulted higher at PEEP 5 (5.4 [4.4-6.5]) compared to PEEP 10 (4.8 [4.1-5.5], P < .05) and PEEP 15 cmH 2 O (4.7 [4.5-5.4], P < .05). Conclusion: In this study, PEEP of 15 cmH 2 O, despite resulting in the highest oxygenation, was associated with overdistension. PEEP of 5 cmH 2 O was associated with increased shunt and alveolar collapse. Administration of 100% FiO 2 was associated with an increase in intrapulmonary shunt in the setting of high PEEP. Trial registration: NCT05132933.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".