Reliability of a Rebreathing Procedure to Evaluate Respiratory Chemoreflex Control
Bibliographic record
Abstract
0858 PURPOSE: To examine the reliability and reproducibility of a modified rebreathing procedure and assess its utility as a research/diagnostic tool. METHODS: The rebreathing technique used was modified to include 5 minutes of prior hyperventilation and maintenance of iso-oxia at hyperoxic (150 mmHg) or hypoxic (50 mmHg) oxygen tensions during rebreathing (Duffin et al., Respir. Physiol., 2000). Twentyeight healthy subjects (14 men, 14 women) performed both hyperoxic and hypoxic rebreathing experiments in the morning (AM) and evening (PM) of the same day, with 12–13 hours separating AM and PM tests. Reliability was examined using the Pearson product-moment correlation coefficient. A three-way ANOVA was used to evaluate the reproducibility. Within and between-subject coefficients of variation (CVs) were calculated. RESULTS: Mean hyperoxic and hypoxic ventilatory responses to carbon dioxide (CO2) did not differ between the AM and PM. Significant reliability coefficients were observed for hyperoxic (r = 0.45 – 0.75) and hypoxic (r = 0.67 – 0.78) rebreathing responses. Bland-Altman plots confirmed no systematic bias between AM and PM tests. Between-subject CVs for basal (41.0 and 39.1%) and sensitivity (34.3 and 33.7%) responses, for hypoxic and hyperoxic tests were similar, but the CVs for the chemoreflex threshold for CO2 were much less (4.8 and 4.9%) for both hyperoxic and hypoxic tests. Within-subject CVs for basal (23.9 ± 4.1 and 20.7 ± 3.7%), threshold (2.6 ± 0.4 and 2.6 ± 0.4%) and sensitivity (17.5 ± 3.1 and 19.9 ± 2.6%) responses to CO2, for hyperoxic and hypoxic tests, were reasonably low. CONCLUSIONS: The results support the within-day reliability and reproducibility of the modified rebreathing procedure. These data support the use of the modified rebreathing procedure to investigate the effects of interventions/physiological perturbations on the chemoreflex control of breathing. However, its use to diagnose disorders in respiratory chemoreflex control in individual patients is not supported. Supported by the William M. Spear Foundation and Ontario Thoracic Society.
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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 | 0.008 | 0.019 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".