The ventilatory response to modified rebreathing is unchanged by hyperoxic severity: implications for the hyperoxic hyperventilation paradox
Bibliographic record
Abstract
Normobaric hyperoxia stimulates ventilation (V̇E) in a time- and dose-dependent manner. Whether this occurs via an oxygen (O2)-specific mechanism or secondary to carbon dioxide (CO2) retention at the central chemoreceptors remains unclear. We measured the ventilatory response to hyperoxic CO2 rebreathing with O2 clamped at increasingly higher pressures. We hypothesized that the V̇E versus PCO2 relationship is fixed and independent of PO2. On four occasions, twenty participants (10F; mean±SD age: 24±4 years) performed three repetitions of modified rebreathing in 4, randomized, isoxic-hyperoxic conditions: mild: PO2=150 mmHg; moderate: PO2=200 mmHg; high: PO2=300 mmHg; and extreme: PO2≈700 mmHg. Breath-by-breath V̇E, end-tidal CO2 (PETCO2) and O2 (PETO2) were measured by pneumotach and gas analyzer. For each rebreathing trial, the PETCO2 at which V̇E rose was identified as the ventilatory recruitment threshold (VRT, mmHg), data before VRT provided baseline V̇E (V̇EBSL, L∙min-1) and the slope of the response above VRT gave central chemoreflex sensitivity (V̇ES, L∙min-1∙mmHg-1). For each condition, VRT, V̇EBSL, and V̇ES from like-trials were averaged and repeated measures ANOVA assessed between-condition differences. There were no effects of PETO2 on V̇EBSL (mild: 7.4±4.2 L∙min-1; moderate: 6.9±4.2 L∙min-1; high: 6.5±3.7 L∙min-1; extreme: 7.5±2.7 L∙min-1; p=0.24), VRT (mild: 42.8±3.2 mmHg; moderate: 42.5±2.7 mmHg; high: 42.3±2.7 mmHg; extreme: 41.8±2.7 mmHg; p=0.07), or V̇ES (mild: 4.88±2.6 L∙min-1∙mmHg-1; moderate: 4.76±2.2 L∙min-1∙mmHg-1; high: 4.81±2.3 L∙min-1∙mmHg-1; extreme: 4.39±1.9 L∙min-1∙mmHg-1; p=0.41). The V̇E-PCO2 relationship is unaltered across a range of mild to extreme PO2. Brief exposure to normobaric hyperoxia may not independently stimulate breathing nor does it alter central chemoreflex sensitivity.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 | 0.003 |
| 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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".