The hyperaemic and metaboreflex response of the diaphragm during fatiguing diaphragmatic work in humans
Bibliographic record
Abstract
Abstract During inspiratory pressure‐threshold loading (ITL), the inspiratory muscle metaboreflex (IMM) increases respiratory muscle blood flow, but its effect on diaphragm blood flow (Q̇di) and fatigue in humans, is unclear. Females exhibit an attenuated IMM compared to males during diaphragmatic loading, suggesting less diaphragm blood flow impedance and metaboreflex activation. We hypothesized that diaphragm hyperaemia would relate positively to metaboreflex sensitivity (i.e. mean arterial pressure change; ΔMAP) and fatigue development (i.e. transdiaphragmatic twitch pressure change; ΔPdi,tw), and be less for females than males. Healthy males and females (11 males and 11 females) completed 6 min of ITL targeting a transdiaphragmatic pressure (Pdi) of 80 cmH2O. Contrast‐enhanced ultrasound was used to quantify Q̇di at baseline, 50% and 100% of task completion. The ΔMAP during loading and the pre‐ to post‐task ΔPdi,tw, via bilateral phrenic nerve electrical stimulation, assessed metaboreflex activation and fatigue, respectively. The accumulated pressure‐time‐product for Pdi (14,177±1,497 cmH2O·s; mean ± SD) and percentage of maximal Pdi (%Pdi,max, 51 ± 8%) was not different between sexes (P > 0.600). At 100% of task completion, IMM activation (ΔMAP, +21 mmHg; 95% confidence interval (CI) = 18–24 mmHg; P < 0.0001), diaphragm fatigue (ΔPdi,tw, −18.1 mmHg; 95% CI = −22.2 to −13.9%; P < 0.0001) and hyperaemia (ΔQ̇di, +15.8 AU s−1; 95% CI = 12.5–19.1 AU s−1; P < 0.0001) did not differ between sexes (P ≥ 0.352). There was a significant positive relationship between ΔQ̇di and %Pdi,max (r2 = 0.211; P = 0.0317), but no relationship between ΔQ̇di and either ΔMAP (r2 = 0.011; P = 0.638) or ΔPdi,tw (r2 = 0.001, P = 0.914). Our data demonstrate that diaphragm hyperaemia relates to relative exercise intensity (%Pdi,max) but is not associated with metaboreflex sensitivity, diaphragm fatigue or sex. image Key points The inspiratory muscle metaboreflex is activated during fatiguing diaphragmatic loading to redistribute blood flow to working muscles. How diaphragm hyperaemia relates to metaboreflex sensitivity or diaphragm fatigue development is unknown. Compared to males, females are reported to have an attenuated inspiratory muscle metaboreflex during both equal absolute and relative intensities, as well as greater diaphragm fatigue resistance during absolute workloads. We investigated whether these sex‐based differences result from a lesser hyperaemic response for females compared to males. We found that hyperaemia of the diaphragm was positively correlated with fractional transdiaphragmatic pressure but did not relate to the degree of diaphragm fatigue or metaboreflex sensitivity. Females and males without differences in diaphragmatic strength did not differ in the magnitude of diaphragm hyperaemia, metaboreflex response, or fatigue development.
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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) | 0.001 | 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".