Arterial Oxygen Saturation Variability Increases During Stepwise Steady State Inspired Hypoxia
Bibliographic record
Abstract
BACKGROUND: The magnitude of the hypoxic ventilatory response (HVR) elicited during exposure to hypoxia is highly variable between individuals. This may result in high variability in the pressure of arterial oxygen (PaO2) and O2 saturation (SaO2), particularly with more extreme hypoxia. The inter-individual variability in PaO2 and SaO2 during stepwise inspired hypoxia has not been well-characterized. PURPOSE: To assess the inter-individual variability in alveolar ventilation (V̇A), PaO2, and SaO2 during incremental stepwise steady-state inspired hypoxia at rest. METHODS: 28 healthy participants (10F, 18 M) were exposed to five stepwise plateaus of reduced inspired O2 with incremental reductions in the fraction of inspired O2 (FIO2) during supine rest, including 0.21 (ambient air), 0.18, 0.16, 0.14, and 0.12. Five serial blood samples were drawn through an indwelling radial arterial catheter over two minutes during each inspired O2 step, and V̇A (calculated from PaCO2), PaO2 and SaO2 values were averaged within each FIO2 stage for each participant. Levene’s tests were used to assess the differences in the variances across hypoxic stages (α = 0.05). RESULTS: Variances in V̇A and PaO2 were unchanged with hypoxia (p = 0.984 and p = 0.327, respectively), yet SaO2 variances were significantly different between FIO2 stages (F(4,135) = 11.91, p < 0.001), with increases in variance as FIO2 levels decreased from ambient air: 0.9, 2.7, 7.4, 19.1, and 37.1 SaO2% for FIO2 levels of 0.21, 0.18 (p = 0.148), 0.16 (p = 0.012), 0.14 (p = 0.01), and 0.12 (p = 0.009), respectively (Figure 1). CONCLUSIONS: The inter-individual variability in SaO2 responses increased with decreased levels of FIO2 at rest, despite unchanged variability in V̇A and PaO2. These data highlight the inherent inter-individual variability of integrated cardiorespiratory and blood gas responses during the physiological transport and uptake of O2 during exposure to acute stepwise hypoxia in healthy humans.NSERC Discovery Grant
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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 | 0.001 |
| 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 | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".