Dynamics of capillary blood flow responses to acute local changes in oxygen and carbon dioxide concentrations
Notice bibliographique
Résumé
Objectives: We aimed to quantify the magnitude and time transients of capillary blood flow responses to acute changes in local oxygen concentration ([O 2 ]), and carbon dioxide concentration ([CO 2 ]) in skeletal muscle. Additionally, we sought to quantify the combined response to low [O 2 ] and high [CO 2 ] to mimic muscle microenvironment at the onset of exercise. Methods: 13 Sprague Dawley rats were anaesthetized, mechanically ventilated, and instrumented with indwelling catheters for systemic monitoring. The extensor digitorum longus muscle was blunt dissected and reflected over a microfluidic gas exchange chamber mounted in the stage of an inverted microscope. Four O 2 challenges (7-12%, 12-7%, 7-2%, 2-7%), four CO 2 challenges (5-0%, 0-5%, 5-10%, 10-5%), and a combined low O 2 (7–2%) and high CO 2 (5–10%) challenges were delivered to the muscle surface with simultaneous visualization of capillary blood flow responses. Recordings were made for each challenge over a 1-minute baseline period followed by a 2-minute step change. The combined challenge employed a 1-minute [O 2 ] challenge followed by a 2-minute change in [CO 2 ]. Analysis of intravital videos was completed offline using custom MATLAB software. Mean data for each sequence were fit using least-squared non-linear exponential models to determine the dynamics of each response. All animal protocols were approved by Memorial University’s Animal Care Committee. Results: Increased [O 2 ] from 7-12% and 2-7% provoked significant increases in red blood cell (RBC) saturation (SO 2 ) within 2 s with time constants of 1.01 and 1.27 s respectively. This increase was coupled with a significant decrease in RBC velocity and supply rate (SR) that occurred within 10 s. 7–2% [O 2 ] challenges decreased capillary RBC SO 2 within 2 s following the step change (46.53 ± 19.56% vs. 48.51 ± 19.02%, p < 0.0001, τ = 1.44 s), increased RBC velocity within 3 s (228.53 ± 190.39 μm/s vs. 235.74 ± 193.52 μm/s, p < 0.0003, τ = 35.54 s) with a 52% peak increase by the end of the challenge, hematocrit and RBC SR showed similar dynamics. 5–10% [CO 2 ] challenges increased RBC velocity within 2 s following the step change (273.40 ± 218.06 μm/s vs. 276.75 ± 215.94 μm/s, p = 0.007, τ = 79.34s), with a 58% peak increase, with RBC SR and hematocrit showing similar dynamics. Decreased local [CO 2 ] conditions from 5 to 0% caused a small yet significant decrease in RBC SO 2 within 1 s (τ = 0.84 s) while RBC velocity decreased significantly within 3 s (τ = 18.88 s) with a 77% peak decrease. Combined [O 2 ] and [CO 2 ] challenges resulted in additive responses to all microvascular hemodynamic measures with a 103% peak velocity increase by the end of the collection period. Conclusion: Microvascular level changes in muscle [O 2 ] and [CO 2 ] provoked capillary hemodynamic responses with differing time transients. Simulating exercise via combined [O 2 ] and [CO 2 ] challenges demonstrated the independent and additive nature of local blood flow responses to these agents. This project was supported by a Natural Sciences and Engineering Research Council of Canada Discovery grant awarded to GMF. Student support was provided by Memorial University's School of Graduate Studies and Faculty of Medicine. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».