Simultaneous pO<sub>2</sub> and HbO<sub>2</sub> measurement to determine absolute HbO<sub>2</sub> concentration for <i>in vivo</i> near infrared spectroscopy
Why this work is in the frame
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Bibliographic record
Abstract
Purpose : Near infrared spectroscopy (NIRS) monitors absolute changes in concentration of chromophores from an unquantified baseline. A change in oxygenation is required to obtain information. Clinically, knowing initial chromophore concentration is desirable. We sought absolute initial concentrations by combining NIRS measurements with simultaneous Eppendorf histograph measurement (absolute values of tissue partial pressure of oxygen (pO 2 )). Methods : There were 22 trials on 9 occasions in 2 adult volunteers. Following local anaesthetic, the histograph probe was inserted into the forearm muscle and NIRS optodes applied. A sphygmomanometer cuff was inflated over the upper arm to produce ischaemia and hypoxia. Change in pO 2 was determined as a percentage of the initial pO 2 . Change in HbO 2 was measured, and the initial HbO 2 calculated by assuming the percentage change in HbO 2 equaled the percentage change in pO 2 . Results : Mean percentage change in pO 2 was 20.7 ± 9.6. Mean change in HbO 2 was 22.4 ± 3.4 µ mol/l(tissue). Calculated initial HbO 2 was 146.4 ± 108.7 µ mol/l(tissue), range 51 to 508 µ mol/l(tissue). Correlation ( r 2 ) between pO 2 and HbO 2 was 0.97 ± 0.03. Conclusion : Although changes in pO 2 and HbO 2 were highly correlated, calculation of initial absolute concentration of HbO 2 was not achieved by this method. A reliable method of obtaining absolute concentrations of HbO 2 in vivo remains to be found.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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 it