Selective Reductions in Pulmonary Artery Pressure Lowers Sympathetic Neural Activity in Healthy Humans at High Altitude
Bibliographic record
Abstract
Chronically elevated sympathetic neural activity is a characteristic of many disease states. Tonic chemoreflex activation has been implicated in the development of sympathetic overactivity; however, other reflexes may also contribute. For example, in an animal model, stimulation of pulmonary baroreceptors induces a reflex increase in sympathetic neural activity. In humans, pulmonary pressure has been shown to be related to basal sympathetic activity in pulmonary hypertension; however a critical step in determining a causal link is to establish whether changing pulmonary pressure alters sympathetic outflow. In this pilot study, we exposed thirteen healthy humans (5 females, 28 [ ± 7] years) to high altitude hypoxia (HA; 4383m), a setting known to increase both pulmonary pressure and sympathetic activation, before selectively lowering pulmonary pressure via inhalation of the pulmonary vasodilator nitric oxide. Muscle sympathetic nerve activity (MSNA; Microneurography), blood pressure (BP; Photoplethysmography), heart rate (HR; Electrocardiogram), and peripheral oxygen saturation (SPO 2 ; Pulse oximetry) were continually measured during ambient air breathing (Amb) and during a 6‐minute inhalation of nitric oxide (iNO; 40ppm in 21% O 2 ). Pulmonary artery systolic pressure (PASP), pulmonary vascular resistance (PVR) and stroke volume (SV) were determined via cardiac ultrasound. iNO reduced PASP (−23 ± 12%) and PVR (−21 ± 16%) compared to Amb (Table 1). iNO also reduced MSNA burst frequency (−18 ± 18%), burst incidence (−16 ± 17%) and total activity (−21 ± 20%) compared to Amb. MSNA changes during iNO were not related to changes in SPO 2 (r = −0.16, P = 0.61) or MAP (r = −0.28, P = 0.35). Our data demonstrate that selectively reducing pulmonary pressure reduces sympathetic nerve activity in healthy humans; therefore, this provides evidence for a causal link in the relationship between pulmonary pressure and basal sympathetic activity. Further investigation is warranted to establish whether elevated pulmonary pressure is a mechanism contributing to chronically elevated sympathetic outflow in disease. Support or Funding Information This study was supported by the Natural Sciences and Engineering Research Council of Canada and a Canada Research Chair in Cerebrovascular Physiology grant. This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .
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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 | 0.000 |
| 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".