The effect of hypoxemia on muscle sympathetic nerve activity and cardiovascular function: a systematic review and meta-analysis
Bibliographic record
Abstract
We conducted a systematic review and meta-analysis to determine the effect of acute poikilocapnic, high-altitude, and acute isocapnia hypoxemia on muscle sympathetic nerve activity (MSNA) and cardiovascular function. A comprehensive search across electronic databases was performed until June 2021. All observational designs were included: population (healthy individuals); exposures (MSNA during hypoxemia); comparators (hypoxemia severity and duration); outcomes (MSNA; heart rate, HR; and mean arterial pressure, MAP). Sixty-one studies were included in the meta-analysis. MSNA burst frequency increased by a greater extent during high-altitude hypoxemia [ P < 0.001; mean difference (MD), +22.5 bursts/min; confidence interval (CI) = −19.20 to 25.84] compared with acute poikilocapnic hypoxemia ( P < 0.001; MD, +5.63 bursts/min; CI = −4.09 to 7.17) and isocapnic hypoxemia ( P < 0.001; MD, +4.72 bursts/min; CI = −3.37 to 6.07). MSNA burst amplitude was only elevated during acute isocapnic hypoxemia ( P = 0.03; standard MD, +0.46 au; CI = −0.03 to 0.90), and MSNA burst incidence was only elevated during high-altitude hypoxemia [ P < 0.001; MD, 33.05 bursts/100 heartbeats; CI = −28.59 to 37.51]. Meta-regression analysis indicated a strong relationship between MSNA burst frequency and hypoxemia severity for acute isocapnic studies ( P < 0.001) but not acute poikilocapnia ( P = 0.098). HR increased by the same extent across each type of hypoxemia [ P < 0.001; MD +13.81 heartbeats/min; 95% CI = 12.59–15.03]. MAP increased during high-altitude hypoxemia ( P < 0.001; MD, +5.06 mmHg; CI = 3.14–6.99), and acute isocapnic hypoxemia ( P < 0.001; MD, +1.91 mmHg; CI = 0.84–2.97), but not during acute poikilocapnic hypoxemia ( P = 0.95). Both hypoxemia type and severity influenced sympathetic nerve and cardiovascular function. These data are important for the better understanding of healthy human adaptation to hypoxemia.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.010 | 0.003 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".