Effect of Transit Time and Gas Density on the Conservation of Agitated Saline Contrast in an <i>in vitro</i> Model of the Pulmonary Circulation
Notice bibliographique
Résumé
Agitated saline contrast echocardiography is often used as a tool to subjectively measure blood flow through intrapulmonary arteriovenous anastomoses (Q̇ IPAVA ). This method assumes that an intravenous injection of agitated saline contrast will not survive the pulmonary circulation or reach the left heart unless it travels through a shunt. However, agitated saline contrast is unstable, and contrast lost to microbubble dissolution likely impacts its utility for measuring Q̇ IPAVA . We applied indicator dilution theory to acoustic intensity‐time curves obtained from a bolus injection of hand‐agitated saline contrast to acquire a quantitative index of contrast mass. Using this methodology and an in vitro model of the pulmonary circulation, the purpose of this study was to determine the effect of transit time on the conservation of contrast mass between two detection sites separated by a convoluted network of vessels with a variable volume (300–600 ml). In addition, we wished to determine if agitating saline with a high density, low solubility gas (sulfur hexafluoride, SF 6 ) could improve contrast mass conservation by minimizing microbubble dissolution. We hypothesized that the contrast lost between the in‐ and out‐flow detection sites would increase with increasing transit times and would be reduced by using microbubbles composed of SF 6 instead of air. The experimental apparatus consisted of a reservoir of 0.9% saline connected to a centrifugal pump and a network of latex surgical tubing mimicking the pulmonary circulation. An in‐ and out‐flow detection site passed under a 3.5 MHz ultrasound transducer to record acoustic intensity‐time curves. A 6 ml bolus of agitated saline contrast (10:1 ratio of saline and gas) was injected into the circuit proximal to the in‐flow detection site and distal to a calibrated flow probe. Transit time was manipulated in two ways: (1) setting flow rate to 1.5 or 2.0 l min −1 ; and, (2) reducing the volume of the circulatory network (no reduction, 25%, 50%, 75%). Five trials were conducted for each combination. Contrast conservation was measured as the ratio of outflow contrast mass to inflow contrast mass, where contrast mass is the respective area under the acoustic intensity‐time curve. Inflow contrast mass did not differ amongst all conditions (P>0.05). Transit time ranged from 9.12 ± 0.03 to 24.47 ± 0.03s as the cross sectional area and flow of the system changed. For air, 53.2 ± 3.4% of contrast was conserved at a transit time of 9.25 ± 0.02s but dropped to 16.0 ± 1.0% at a transit time of 10.17 ± 0.06s. Compared to air, SF 6 contrast conservation was significantly greater (P<0.01) with 98.3 ± 11.5 % and 94.8 ± 5.8% of contrast conserved at a transit time of 10.40 ± 0.21s and 13.46 ± 0.04s respectively. In summary, acoustic‐intensity‐time curves can be used to quantify agitated saline contrast mass but loss of contrast due to microbubble dissolution makes measuring Q̇ IPAVA across varying transit time difficult. Agitated saline mixed with SF 6 is stabilized and may be a suitable alternative for Q̇ IPAVA measurement. Support or Funding Information Funding: NSERC, CFI
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 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 source (Gemma direct ou Codex distillé), 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 ».