Effects of nocturnal periodic breathing on sympathetic nerve activity and ventilatory control at high altitude: a randomised, placebo-controlled, crossover study
Bibliographic record
Abstract
Nocturnal periodic breathing (nPB) is a common sleep-disordered breathing (SDB) in individuals exposed to high altitude (HA). At sea level, SDB activates the peripheral chemoreflex and promotes increases in sympathetic nerve activity (SNA) and ventilation that persist during wakefulness and affect cardiovascular health. Similar increases in chemoreflex activity, SNA and ventilation occur at HA and we investigated whether nPB contributes to these effects. In a randomised, crossover protocol, 12 healthy men completed two 3-day sojourns in hypobaric hypoxia equivalent 4,000m altitude. nPB was inhibited by increasing inspiratory CO<sub>2</sub> fraction during the nights of one (nPB-), but not the other sojourn (nPB+). Ventilation and plasma catecholamines were measured daily. Muscle SNA (MSNA) was assessed before and at the end of sojourns, without and with peripheral chemoreflex inhibition. The hypoxia-induced increases in MSNA burst frequency and incidence (both p≥0.79) were not different between sojourns. Catecholamine concentrations throughout sojourns were also similar (sojourn: p≥0.27, time×sojourn: p≥0.50). Ventilatory variables were not different between sojourns (sojourn: all p≥ 0.09, time×sojourn: all p≥ 0.06) except for a slightly greater tidal volume during nPB+ (sojourn: p=0.047, time×sojourn: p=0.48). Chemoreflex inhibition induced similar reductions in ventilation during both sojourns (all p≥0.15) and larger reductions in MSNA burst frequency and incidence after the nPB- than after the nPB+ sojourn (both p≤0.05). nPB does not contribute to the sympathoexcitation and increased ventilation associated with 3 days at HA, indicating that nPB at HA does not entail the adverse cardiovascular effects that SDB has at sea level.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".