Non-invasive monitoring of pulmonary blood flow, functional residual capacity, and shunt index in a porcine model
Bibliographic record
Abstract
Abstract Background Management of mechanically ventilated patients can be improved with monitoring of key pulmonary function parameters that facilitate individualization and optimization. The VQm Pulmonary Health Monitor™ (PHM) (Rostrum Medical Innovations Inc., Vancouver, Canada) is a new monitor that continuously measures pulmonary blood flow (PBF), functional residual capacity (FRC) and a novel parameter: shunt index (Qsi). The goal of this study was to provide an initial assessment of the performance of the VQm PHM™ when compared with reference measures of PBF, FRC and intra-pulmonary shunt. Methods This was a prospective, experimental, large animal (porcine) study. After baseline measurements, three interventions were performed: increased cardiac output (CO) using dobutamine infusion, increased PEEP (from 4 to 12 cmH2O), and experimental shunt induced by an extracorporeal circuit. PBF, FRC and shunt were measured by the VQm Pulmonary Health Monitor™ (PHM) before and after each intervention. The PHM™ uses sequential gas delivery to deliver targeted alveolar concentrations of CO2 or N2O. PBF and FRC were calculated using CO2 bolus delivery and the modified differential Fick equation. Shunt was estimated from the number of breaths required to eliminate N2O after a 25-breath N2O bolus and expressed as Qsi. PHM™-derived PBF and Qsi were compared to thermodilution CO and calculated Berggren shunt, respectively. Results Studies were completed in 19 animals. Measurements of PBF, FRC and Qsi obtained from the PHM™ trended as expected following each intervention. The mean difference between paired values of PBF was − 0.2 ± 0.9 L/min and the 95% limits of agreement were 1.5 and − 1.9 L/min. Concordance was 94.1%. The mean baseline FRC was 1.7 $$\pm$$ 0.4 L and increased to 2.0 $$\pm$$ 0.6 L, following the increase in PEEP (p = 0.0078). For shunt (Qsi), the mean values during low (1 L/min) and high (50% of baseline CO) shunt value were 40 $$\pm$$ 4 and 27 $$\pm$$ 5, respectively, p = 0.002. Conclusions PBF obtained through the modified differential Fick equation and Qsi obtained through N2O uptake and decay dynamics by the VQm PHM™ provide comparable results to reference standards. FRC measurements trended as expected following interventions.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 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".