Sex differences in loop gain measured via superimposed end‐expiratory breath holds and inspired steady‐state hypoxia
Bibliographic record
Abstract
Abstract Acute low oxygen exposure (hypoxia) elicits a hypoxic ventilatory response (HVR), which increases ventilation and mitigates hypoxaemia. During sustained exposure to hypoxia, ventilatory acclimatization increases peripheral chemoreflex (HVR) sensitivity or chemoreflex loop gain (LG). Although increased ventilation protects oxygenation, increased LG contributes to ventilatory instability during sleep (central sleep apnoea; CSA). The HVR is highly variable between individuals, and the impact of sex on HVR variability and LG is unclear. At low altitude (1100 m), we aimed to characterize a novel breath hold method to quantify LG using a standardized series of short (∼10 s), voluntary, end‐expiratory breath holds (EEBH), using a background of steady‐state normobaric inspired hyperoxia (fraction of inspired oxygen; = 1.0), normoxia (i.e., ambient air; = 0.21) and hypoxia ( = 0.14; equivalent to ∼4300 m altitude). Further, we investigated sex differences in LG during differential oxygen exposure using this novel EEBH protocol to quantify LG. We hypothesized that (a) LG magnitude would follow an inverse oxygen‐dependent pattern with each inspired gas condition, and (b) that males would have higher LG than females. We recruited 36 healthy participants (18 females; 18 males). We found (a) a graded, inverse oxygen‐dependent effect on LG magnitude ( P < 0.0001), and (b) a sex‐specific effect, whereby males had significantly larger LG magnitudes than females, but only in steady‐state inspired hypoxia ( P < 0.032). Our EEBH protocol illustrates an intrinsic sex difference in chemoreflex LG in hypoxia, which may underlie known sex differences in CSA at high altitude and in heart failure populations.
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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) | 0.002 | 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".