Effect of Central Chemoreceptors on the Peripheral Chemoreflex Response to Hypoxia
Bibliographic record
Abstract
In the absence of central chemoreceptor input, the slope of the hypoxic ventilatory response (HVR) to progressive oxyhemoglobin desaturation (L · min -1· mmHg -1· %SaO 2 -1 ) – a measure of peripheral chemoreflex sensitivity – increases linearly with carbon dioxide tension (PCO 2 ). We assessed whether this relationship remains linear with increasing central PCO 2 in humans. Over four days, 20 participants (10 females; mean±SD age: 24±4 years) completed three repetitions of modified rebreathing with end-tidal PO 2 (P ET O 2 ) clamped at 150, 70, 60, and 45 mmHg. End-tidal PCO 2 (P ET CO 2 ), P ET O 2 , ventilation (V̇ E ), and SaO 2 were measured breath-by-breath by dual gas analyser, pneumotach, and pulse oximetry. The V̇ E vs P ET CO 2 relationship in the hyperoxic test gave the central chemoreflex response to PCO 2 and the hypoxic tests provided a combined central-peripheral chemoreflex response. The V̇ E vs P ET CO 2 relationship of repeated trials were linear-interpolated, combined, averaged into 1 mmHg bins, and fit with a linear function (V̇ E S, L · min -1· mmHg -1 ) to provide hyperoxic and hypoxic profiles. HVR was computed at 1 mmHg intervals of P ET CO 2 as follows: the difference in V̇ E between the three hypoxic profiles and the hyperoxic profile (ΔV̇ E ) was calculated; these three ΔV̇ E values were plotted against their corresponding SaO 2 ; and linear regression determined HVR (L · min -1· mmHg -1 ·%SaO 2 -1 ). Steps were repeated at each P ET CO 2 to produce the HVR vs PCO 2 relationship. Each participant’s HVR vs P ET CO 2 relationship was fit with a linear and polynomial function and Akaike Information Criterion identified the best-fit model. One-way repeated measures analysis of variance assessed between-condition differences. V̇ E S rose (p<0.001) with isoxic PO 2 from 3.7±1.5 L · min -1· mmHg -1 at 150 mmHg to 4.4±1.8, 5.0±1.6, and 6.0±2.2 L · min -1· mmHg -1 at 70, 60, and 45 mmHg, respectively. Mean SaO 2 fell progressively (99.3%, 93.7%, 90.4%, and 80.5% for 150, 70, 60, and 45 mmHg, respectively; p<0.001). In all individuals, HVR increased with P ET CO 2 and this relationship was best described by a linear model in 75% of participants. In most participants, the peripheral chemoreflex-mediated HVR maintained a linear relationship with P ET CO 2 despite increasing central chemoreflex activation. Data suggest that central chemoreceptors did not alter the peripheral chemoreflex response to low O 2 . Natural Sciences and Engineering Research Council of Canada This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
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How this classification was reachedexpand
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 | 0.000 | 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".