Reproducibility of CO-Derived Intravascular Volumes and Hemoglobin Mass in a Diverse Cohort of Healthy Individuals using the Detalo OpCO Device
Bibliographic record
Abstract
The objective of this study was to determine the test-retest reproducibility of carbon monoxide (CO) rebreathing-derived measures of intravascular volumes (e.g., total blood volume, plasma volume, and red cell volume) and hemoglobin (Hb) mass (Hbmass) using the automated OpCO device (Detalo, Zürich, Switzerland). We hypothesized that all hematological variables would remain consistent between days. Fifteen healthy participants (7 females; mean age ± SD [range]: 53 ± 15 [22-75] years; height: 172 ± 10 [159-190] cm; body mass: 77.6 ± 11.0 [57-91] kg) performed a CO rebreathing test on two days separated by an average of 11 days (range: 2-34 days). Following a 1-minute preconditioning phase of 100% oxygen inhalation, in the semi-supine position, with legs elevated to level of the heart, participants received a single bolus of 99.997% chemically pure CO (dosing: 0.8 ml·kg-1 for males; 0.7 ml·kg-1 for females) and respired this CO-enriched gas mixture for a duration of 4 minutes. Before and immediately after the CO rebreathing procedure, 2 mL of blood was sampled from an antecubital vein from which [Hb] and fractional concentration of carboxyhemoglobin were measured by blood gas analyser (ABL90, Radiometer, Copenhagen, Denmark). Hematocrit (Hct) was also measured using capillary tubes and centrifugation. These variables were used to calculate Hbmass and, blood, plasma, and red cell volumes using standard equations. Paired t -tests and Pearson’s correlation coefficient (R) evaluated between-day reproducibility for [Hb], Hct, Hbmass, blood volume, plasma volume, and red cell volume. For all variables there were no significant Day 1 vs. Day 2 differences: i) [Hb]: 14.8 ± 1.1 vs. 14.8 ± 1.0 g·dl-1 (p = 0.788, R = 0.940); ii) Hct: 43.5 ± 3 vs. 43.4 ± 3.3% (p = 0.441, R = 0.980); iii) Hbmass: 872 ± 238 vs. 876 ± 260 g (p = 0.827, R = 0.970); iv) total blood volume: 5.85 ± 1.3 vs. 5.86 ± 1.5 L (p = 0.873, R = 0.967); v) plasma volume: 3.28 ± 0.62 vs. 3.29 ± 0.73 L (p = 0.955, R = 0.958); and vi) red cell volume: 2.57 ± 0.71 vs. 2.57 ± 0.81 L (p = 0.975, R = 0.975). CO rebreathing-derived measures of intravascular volumes and Hbmass mass using the automated OpCO device exhibited excellent test-retest reproducibility between-days even if separated by 1-3 weeks. Daniel A. Keir was supported by a NSERC Discovery Grant and the Canadian Foundation for Innovation. Robin Faricier was supported by an Ontario Graduate Scholarship. This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.
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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 | 0.002 | 0.006 |
| 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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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 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".