A test of the interaction between central and peripheral respiratory chemoreflexes in humans
Bibliographic record
Abstract
Abstract How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured the peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic CO2 tensions () to determine the form of the relationship between PChS and central . Twenty participants (10F) completed three repetitions of modified rebreathing tests with end‐tidal () clamped at 150, 70, 60 and 45 mmHg. End‐tidal (), , ventilation (E) and calculated oxygen saturation (SCO2) were measured breath‐by‐breath by gas‐analyser and pneumotach. The E– relationship of repeat‐trials were linear‐interpolated, combined, averaged into 1 mmHg bins, and fitted with a double‐linear function (ES, L min−1mmHg−1). PChS was computed at intervals of 1 mmHg of as follows: the difference in E between the three hypoxic profiles and the hyperoxic profile (∆E) was calculated; three ∆E values were plotted against corresponding SCO2; and linear regression determined PChS (Lmin−1mmHg−1%SCO2−1). These processing steps were repeated at each to produce the PChS vs. isocapnic relationship. These were fitted with linear and polynomial functions, and Akaike information criterion identified the best‐fit model. One‐way repeated measures analysis of variance assessed between‐condition differences. ES increased (P < 0.0001) with isoxic from 3.7 ± 1.5 L min−1mmHg−1 at 150 mmHg to 4.4 ± 1.8, 5.0 ± 1.6 and 6.0 ± 2.2 Lmin−1mmHg−1 at 70, 60 and 45 mmHg, respectively. Mean SCO2 fell progressively (99.3 ± 0%, 93.7 ± 0.1%, 90.4 ± 0.1% and 80.5 ± 0.1%; P < 0.0001). In all individuals, PChS increased with , and this relationship was best described by a linear model in 75%. Despite increasing central chemoreflex activation, PChS increased linearly with indicative of an additive central–peripheral chemoreflex response. image Key points How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic carbon dioxide tensions () to determine the form of the relationship between PChS and central . Participants performed three repetitions of modified rebreathing with end‐tidal fixed at 150, 70, 60 and 45 mmHg. PChS was computed at intervals of 1 mmHg of end‐tidal () as follows: the difference in E between the three hypoxic profiles and the hyperoxic profile (∆E) was calculated; three ∆E values were plotted against corresponding calculated oxygen saturation (SCO2); and linear regression determined PChS (Lmin−1mmHg−1%SCO2−1). In all individuals, PChS increased with , and this relationship was best described by a linear (rather than polynomial) model in 15 of 20. Most participants did not exhibit a hypo‐ or hyper‐additive effect of central chemoreceptors on the peripheral chemoreflex indicating that the interaction was additive.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".