P2.11 ESTIMATION OF LV STROKE VOLUME BY IMPEDANCE CARDIOGRAPHY: ITS RELATION TO THE AORTIC RESERVOIR
Bibliographic record
Abstract
Abstract Impedance cardiography (ICG) is a noninvasive technique used to estimate left ventricular stroke volume (SVLV) using thoracic impedance (ΔZ). It remains controversial, partly because ICG parameters have not been successfully related to hemodynamic events.We hypothesized that the change in ΔZ may be proportional to the variation in thoracic blood volumes, primarily aortic blood volume. Nine anaesthetized dogs were divided into two groups: the “Aortic Volume Group” (n=5), where aortic and IVC (inferior vena cava) dimensions were measured ultrasonically, and the “Reservoir Volume Group”, where aortic and IVC reservoir volumes were calculated using the reservoir-wave approach. Measurements were made under control conditions, with nitroprusside, with methoxamine (Mtx), and after volume loading. In both groups, the maximum rate of increase in ΔZ, (dZ/dt)max, strongly correlated with the maximum rate of change in aortic/reservoir blood volume (r2 = 0.85 and 0.95, respectively), which in turn were proportional to SVLV. As shown in the figure, the aortic reservoir volume (VAo reservoir) explains SVLV in that measured aortic flow (QAo) equals the sum of dVAo reservoir/dt and calculated Qout. The LV and IVC contributions to ΔZ were small under control conditions (~5 and 1%, respectively), but the LV contribution increased slightly with administration of Mtx and after volume loading (to 7 and 10%, respectively). We conclude that the change in thoracic impedance (ΔZ) during the cardiac cycle is proportional to the change in aortic reservoir volume, which mechanistically explains why ICG and standard measures of cardiac output have sometimes been shown to correlate well.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.000 |
| 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".