Dynamic changes of myocardial oxygen consumption at pacing increased heart rate – the first observation by the continuous measurement of systemic oxygen consumption
Bibliographic record
Abstract
OBJECTIVES: To assess dynamic changes in myocardial oxygen consumption (myoVO(2)) during atrial pacing increased heart rate by continuous measurement of systemic oxygen consumption (sysVO(2)). METHODS: Six mechanically ventilated pigs were atrially paced to increase heart rate from baseline 98 ± 9 to 120-140-160-180 bpm for 10 minutes at each stage, with 10 minute intervals without pacing between stages. sysVO(2) was continuously measured with a respiratory mass spectrometer. Left anterior descending coronary arterial flow, aorta and coronary sinus blood gases were measured to calculate index of whole heart myoVO(2). RESULTS: sysVO(2) peaked at the initiation of pacing in the first two to three minutes, followed by a decrease and subsequent stabilization. As heart rate increased, sysVO(2) increased by 0.08 ± 0.06 ml/kg/min, 0.14 ± 0.05 ml/kg/min and 0.17 ± 0.10 ml/kg/min, representing a 1.2 ± 0.9%, 2.1 ± 0.7% and 3.0 ± 1.8% increase of sysVO(2) respectively; myoVO(2) increased by 0.16 ± 0.12 to 0.31 ± 0.14 to 0.36 ± 0.24 ml/100 g/min, representing a 11 ± 9%, 21 ± 9% and 26 ± 12% increase of myoVO(2), respectively. The absolute and relative increases in sysVO(2) were significantly correlated with the increases in myoVO(2). CONCLUSIONS: On-line continuous sysVO(2) monitoring by respiratory mass spectrometry allows non-invasive assessments of dynamic changes in myoVO(2) in vivo. The mechanism for the peaked increase in sysVO(2) at the initiation of pacing remains to be explored.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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) | 0.001 | 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".