Teaching the distribution of pulmonary blood flow using a Starling resistor model and turbine flowmeters.

The distribution of pulmonary blood flow is uneven and can be described as a three-zone model, the West zones: zone 1 occurs whenever alveolar pressure exceeds arterial pressure; zone 2 when the arterial pressure is greater than alveolar but the alveolar pressure exceeds the venous pressure; and finally zone 3 when both arterial and venous pressures exceed alveolar pressure. Consequently, the blood flow is almost determined by the difference between the arterial and venous pressures in zone 3 and between arterial and alveolar pressures in zone 2 and ceases in zone 1. The understanding of this subject may be difficult to some medical students. Therefore, to improve the learning of this topic in our physiology course, we used a didactic model to demonstrate the core concept of flow down gradients and its application to pulmonary blood flow. We modeled a Starling resistor by placing a collapsible tube inside a hermetic chamber of variable pressure. Transparent turbine flowmeters were connected to the upstream and downstream extremities of the Starling resistor, and we generated a constant airflow with a brushless motor. By maintaining the input (arterial) pressure constant and varying the chamber (alveolar) pressure, we could simulate the three zones and demonstrate the resulting flow through the turbines. In conclusion, our demonstration using a Starling resistor model combined with visible turbine flowmeters can be used to facilitate comprehension of important concepts in physiology involving flow down gradients, such as pulmonary blood flow.NEW & NOTEWORTHY The understanding of respiratory physiology is a challenge to medical students. To improve the learning of pulmonary blood flow distribution through lung vessels in our physiology course, we modeled a Starling resistor model combined with visible turbine flowmeters. Our model can significantly improve the core concept of flow down gradients teaching and its application to West zones.

The relevance of vascular adjustments to hemodynamic control in the face of temperature change in Crotalus durissus.

The presence of cardiac shunts in ectothermic tetrapods is thought to be consistent with active vascular modulations for proper hemodynamic support. Local control of blood flow modulates tissue perfusion and thus systemic conductance (Gsys) is assumed to increase with body temperature (Tb) to accommodate higher aerobic demand. However, the general increase of Gsys presses for a higher right-to-left (R-L) shunt, which reduces arterial oxygen concentration. In contrast, Tb reduction leads to a Gsys decrease and a left-to-right shunt, which purportedly increases pulmonary perfusion and plasma filtration in the respiratory area. This investigation addressed the role of compensatory vascular adjustments in the face of the metabolic alterations caused by Tb change in the South American rattlesnake (Crotalus durissus). Cardiovascular recordings were performed in decerebrated rattlesnake preparations at 10, 20 and 30°C. The rise in Tb increased metabolic demand, and correlated with an augmentation in heart rate. Although cardiac output increased, systemic stroke volume reduced while pulmonary stroke volume remained stable. Although that resulted in a proportionally higher increase in pulmonary blood flow, the R-L shunt was maintained. While the systemic compliance of large arteries was the most relevant factor in regulating arterial systemic blood pressure, peripheral conductance of pulmonary circulation was the major factor influencing the final cardiac shunt. Such dynamic adjustment of systemic compliance and pulmonary resistance for shunt modulation has not been demonstrated before and contrasts with previous knowledge on shunt control.

Clinical characteristics, imaging findings, management, and outcomes of patients with scimitar syndrome at a tertiary referral healthcare center in Colombia.

Scimitar Syndrome is part of a complex spectrum of congenital cardiovascular anomalies related to anomalous pulmonary venous return. Depending on the extent of involvement, treatment can be either expectant or surgical. Prognosis and survival have been controversial, with some results supporting early surgical management. This research aims to disclose the outcomes and describe the management, clinical and imaging characteristics of patients diagnosed with Scimitar Syndrome treated in a tertiary referral healthcare center. Longitudinal descriptive observational study. The study included all patients diagnosed with scimitar syndrome in our institution between January/2011 and December/2022. A description of the sociodemographic and clinical characteristics, diagnostic tools used, treatment features, and patient outcomes is provided. Eleven patients were included, with a mean age at diagnosis of five years (CI 0-17), six of which were female (54.55%). Nine (81.82%) patients had evidence of a scimitar vein on the chest radiograph, six (54.55%) cardiac dextroposition, six (54.55%) pulmonary hypoplasia, five (45.45%) right pulmonary artery hypoplasia, and three (27.27%) had aortopulmonary collaterals. Four (36.36%) patients had horseshoe lungs, and four (36.36%) had bronchopulmonary sequestration. In the associations, two (18.18%) patients were found to have an atrial septal defect, three (27.27%) ventricular septal defect, and one (9%) had Tetralogy of Fallot. Pulmonary hypertension was demonstrated in two (18.18%) patients. Seven (63.64%) required surgical management to correct the scimitar vein, and two patients died due to unrelated complications. Scimitar syndrome presents diagnostic and treatment challenges, necessitating a multidisciplinary approach for timely care. Chest radiography and CT scans are primary diagnostic tools, with surgical intervention often warranted alongside other heart defects or significant hemodynamic repercussions. Medical management is effective for mild to moderate cases. Long-term patient outcomes remain uncertain due to study limitations, but improved life expectancy is anticipated with ongoing care.

Fisiología respiratoria: circulación pulmonar / Respiratory physiology: pulmonary circulation

El pulmón recibe sangre desde la circulación bronquial y pulmonar. La circulación pulmonar presenta importantes diferencias con la sistémica, sus vasos sanguíneos poseen características únicas que le permiten cumplir sus diferentes funciones, siendo la más importante el intercambio gaseoso. Existen múltiples factores, activos y pasivos, que están involucrados en la regulación de la resistencia vascular y flujo sanguíneo pulmonar.

The lung receives blood from the bronchial and the pulmonary circulation. The pulmonary circulation presents important differences with the systemic circulation, its blood vessels have unique characteristics that allow them to fulfill their different functions, the most important being gas exchange. There are multiple factors, active and passive, that are involved in the regulation of vascular resistance and pulmonary blood flow.

Caracterización de parámetros del intercambio gaseoso en la Ciudad de México / Characterization of gas exchange parameters in Mexico City

Introducción: en las grandes altitudes, el intercambio gaseoso suele estar deteriorado; en la altitud moderada de la Ciudad de México esto no está aún plenamente definido. Objetivo: caracterizar el intercambio gaseoso en la altitud moderada de la Ciudad de México. Material y métodos: mediante un estudio transversal analítico se estudiaron sujetos nacidos y habitantes de la Ciudad de México, de ambos géneros, con edades de 20 a 59 años sin enfermedad cardiopulmonar. Se registraron sus variables demográficas, espirometría simple y de gasometría arterial. Las diferencias en las variables se calcularon con ANOVA de una vía para grupos independientes y ajuste de Bonferroni. Una p < 0.05 se aceptó como significativa. Resultados: se estudiaron 335 sujetos, de los cuales 168 (50.15%) fueron hombres, la edad grupal fue de 45 ± 11 años, con índice de masa corporal 22.97 ± 1.54 Kg/m2. La relación volumen espiratorio forzado en el primer segundo/Capacidad vital forzada (VEF1/CVF) de 91.58 ± 12.86%. La presión arterial de oxígeno fue de 66 ± 5.02 mmHg, el bióxido de carbono: 32.07 ± 2.66 mmHg, la saturación arterial de oxígeno: 93.03 ± 1.80% y la hemoglobina: 14.07 ± 1.52 gr/dL. Conclusiones: la presión arterial de oxígeno y del bióxido de carbono están disminuidos a la altura de la Ciudad de México.

Background: At high altitude the gas exchange is impaired, in the moderate altitude of Mexico City they are not yet defined. Objective: To characterize the gas exchange in the moderate altitude of Mexico City. Material and methods: Through an analytical cross-sectional study, subjects born and inhabitants of Mexico City, both genders, aged 20 to 59 years without cardiopulmonary disease, were studied. Their demographic variables, simple spirometry and arterial blood gas were recorded. Differences in variables were calculated with one-way ANOVA for independent groups and Bonferroni adjustment. p < 0.05 was accepted as significant. Results: 335 subjects were studied, 168 (50.15%) men. Group age 45 ± 11 years old, body mass index 22.97 ± 1.54 Kg/m2. Forced expiratory volume ratio in the first second / Forced vital capacity (FEV1/FVC) 91.58 ± 12.86%. The arterial oxygen pressure was: 66 ± 5.02 mmHg, carbon dioxide: 32.07 ± 2.66 mmHg, arterial oxygen saturation: 93.0 3 ± 1.80%, and hemoglobin: 14.07 ± 1.52 gr/dL. Conclusions: The arterial oxygen pressure and carbon dioxide are lowered at the Mexico City altitude.

[Stent ductal implant by axillary via in a newborn with ductal dependent pulmonary blood flow]. / Implante de stent ductal por vía axilar en neonato con cardiopatía congénita con flujo pulmonar dependiente del conducto arterioso.

INTRODUCTION: Ductus arteriosus stenting is a palliative alternative for neonates with ductal-dependent pulmonary flow. OBJECTIVE: To present an alternative of arterial access for percutaneous coronary intervention in neonates. CLINICAL CASE: A term neonate with low weight diagnosed with pulmonary atresia with intact ventricular septum and severe hypoplasia of the tricuspid valve with dependent coronary circu lation. Due to the surgical risk and femoral artery damage and the anatomy of the ductus arteriosus, a left axillary arterial puncture was decided where a 3.5-millimeter coronary stent was successfully placed. The patient developed an axillary spasm that resolved spontaneously. CONCLUSION: Alternati ve arterial access other than the femoral artery route is an option for neonates with high surgical risk and low birth weight.

[Chronic exposure to altitude. Clinical characteristics and diagnosis]. / Exposición crónica a la altura. Características clínicas y diagnóstico

Chronic exposure to altitude has been associated with hypobaric hypoxia in its inhabitants. Two entities have been associated with it, high altitude pulmonary hypertension and chronic mountain sickness. Its physiological and pulmonary circulation characteristics are described, as well as its clinical profile and diagnosis.

La exposición crónica a la altitud se ha asociado a hipoxia hipobárica en quienes la experimentan. Dos entidades se han asociado a la hipoxia hipobárica: la hipertensión pulmonar de la alta altitud y el mal de montaña crónico. Se describen sus características fisiológicas y de la circulación pulmonar, así como su perfil clínico y el diagnóstico.

Investigation of patent foramen ovale as a mechanism for brain metastasis in patients without prior lung involvement.

PURPOSE: The mechanisms of brain metastasis are incompletely understood. Circulating tumor cells travel to the right heart and through the pulmonary circulation, where they may become lung metastases, and can circulate further to the left heart and brain. In patients who develop brain metastases without lung involvement, we hypothesized that cancer cells may travel directly from the right atrium to left atrium via a patent foramen ovale (PFO), akin to paradoxical embolism. If the prevalence of PFO is greater in these individuals compared to the general population (20-30%), PFO may play a role in brain metastasis, and prophylactic closure may provide benefit. Accordingly, we investigated the prevalence of PFO in patients with brain metastases without prior lung involvement. METHODS: We prospectively identified patients with brain metastases from a non-lung primary cancer with no preceding or concurrent lung involvement. Nine eligible participants underwent a transcranial Doppler study with intravenous agitated saline to assess for PFO. RESULTS: Among nine participants, primary cancers were breast (n = 6), upper gastrointestinal (n = 2), and thyroid (n = 1). A positive bubble study was identified in 2/9 (22.2%) participants: one female with breast cancer and one male with duodenal adenocarcinoma. No participants developed lung metastases on subsequent chest imaging. CONCLUSION: In this prospective pilot study, we found a similar prevalence of PFO in patients who developed brain metastases without preceding lung involvement compared to estimates for the general population. Through a larger study is needed, the development of brain metastases in these individuals may primarily reflect tumor-specific biological factors diecting metastasis organotropism.

Month-long Respiratory Support by a Wearable Pumping Artificial Lung in an Ovine Model.

BACKGROUND: A wearable artificial lung could improve lung transplantation outcomes by easing implementation of physical rehabilitation during long-term pretransplant respiratory support. The Modular Extracorporeal Lung Assist System (ModELAS) is a compact pumping artificial lung currently under development. This study evaluated the long-term in vivo performance of the ModELAS during venovenous support in awake sheep. Feedback from early trials and computational fluid dynamic analysis guided device design optimization along the way. METHODS: The ModELAS was connected to healthy sheep via a dual-lumen cannula in the jugular vein. Sheep were housed in a fixed-tether pen while wearing the device in a holster during support. Targeted blood flow rate and support duration were 2-2.5 L/min and 28-30 days, respectively. Anticoagulation was maintained via systemic heparin. Device pumping and gas exchange performance and hematologic indicators of sheep physiology were measured throughout support. RESULTS: Computational fluid dynamic-guided design modifications successfully decreased pump thrombogenicity from initial designs. For the optimized design, 4 of 5 trials advancing past early perioperative and cannula-related complications lasted the full month of support. Blood flow rate and CO2 removal in these trials were 2.1 ± 0.3 L/min and 139 ± 15 mL/min, respectively, and were stable during support. One trial ended after 22 days of support due to intradevice thrombosis. Support was well tolerated by the sheep with no signs of hemolysis or device-related organ impairment. CONCLUSIONS: These results demonstrate the ability of the ModELAS to provide safe month-long support without consistent deterioration of pumping or gas exchange capabilities.

Outcomes in Patients with Alagille Syndrome and Complex Pulmonary Artery Disease.

OBJECTIVE: To assess outcomes in a large cohort of patients with Alagille syndrome (ALGS) who underwent pulmonary artery reconstruction surgery for complex pulmonary artery disease. STUDY DESIGN: Patients with ALGS who underwent pulmonary artery reconstruction surgery at Lucile Packard Children's Hospital Stanford were reviewed. Patients were examined as an overall cohort and based on the primary cardiovascular diagnosis: severe isolated branch pulmonary artery stenosis, tetralogy of Fallot (TOF) without major aortopulmonary collateral arteries (MAPCAs), or TOF with MAPCAs. RESULTS: Fifty-one patients with ALGS underwent pulmonary artery surgery at our center, including 22 with severe branch pulmonary artery stenosis, 9 with TOF without MAPCAs, and 20 with TOF and MAPCAs. Forty-one patients (80%) achieved a complete repair. Five of the patients with TOF with MAPCAs (25%) underwent complete repair at the first surgery, compared with 8 (89%) with TOF without MAPCAs and 19 (86%) with isolated branch pulmonary artery stenosis. At a median follow-up of 1.7 years after the first surgery, 39 patients (76%) were alive, 36 with a complete repair and a median pulmonary artery:aortic systolic pressure of 0.38. Nine patients (18%), including 8 with isolated branch pulmonary artery stenosis, underwent liver transplantation. CONCLUSIONS: Most patients with ALGS and complex pulmonary artery disease can undergo complete repair with low postoperative right ventricular pressure. Patients with TOF/MAPCAs had the worst outcomes, with higher mortality and more frequent pulmonary artery interventions compared with patients with TOF without MAPCAs or isolated branch pulmonary artery stenosis. Complex pulmonary artery disease is not a contraindication to liver transplantation in patients with ALGS.

Multimodality imaging of the anomalous origin of the right pulmonary artery from the ascending aorta in an adult (hemitruncus arteriosus).

Anomalous origin of the pulmonary artery branches is a rare phenomenon. We describe a case of an adult with anomalous origin of the right pulmonary artery (hemitruncus arteriosus) associated with patent ductus arteriosus. Non-invasive imaging studies played an important role in the diagnosis and follow-up. Angiography allowed to determine the severity of pulmonary hypertension. He underwent surgical closure of patent ductus arteriosus, redirection of right pulmonary artery and atrioseptostomy with decrease of the pulmonary pressure in the follow-up. A high index of clinical suspicion of this entity is required in adults with heart failure, recurrent hemoptysis and pulmonary hypertension, because it could go unnoticed.

Pulmonary Hypertension in General Cardiology Practice.

The finding of pulmonary hypertension (PH) by echocardiography is common and of concern. However, echocardiography is just a suggestive and non-diagnostic assessment of PH. When direct involvement of pulmonary circulation is suspected, invasive hemodynamic monitoring is recommended to establish the diagnosis. This assessent provides, in addition to the diagnostic confirmation, the correct identification of the vascular territory predominantly involved (arterial pulmonary or postcapillary). Treatment with specific medication for PH (phosphodiesterase type 5 inhibitors, endothelin receptor antagonists and prostacyclin analogues) has been proven effective in patients with pulmonary arterial hypertension, but its use in patients with PH due to left heart disease can even be damaging. In this review, we discuss the diagnosis criteria, how etiological investigation should be carried out, the clinical classification and, finally, the therapeutic recommendations for PH.

Pulmonary Hypertension in General Cardiology Practice / Hipertensão Pulmonar na Prática do Cardiologista

Abstract The finding of pulmonary hypertension (PH) by echocardiography is common and of concern. However, echocardiography is just a suggestive and non-diagnostic assessment of PH. When direct involvement of pulmonary circulation is suspected, invasive hemodynamic monitoring is recommended to establish the diagnosis. This assessent provides, in addition to the diagnostic confirmation, the correct identification of the vascular territory predominantly involved (arterial pulmonary or postcapillary). Treatment with specific medication for PH (phosphodiesterase type 5 inhibitors, endothelin receptor antagonists and prostacyclin analogues) has been proven effective in patients with pulmonary arterial hypertension, but its use in patients with PH due to left heart disease can even be damaging. In this review, we discuss the diagnosis criteria, how etiological investigation should be carried out, the clinical classification and, finally, the therapeutic recommendations for PH.

Resumo O achado de hipertensão pulmonar (HP) em avaliação ecocardiográfica é frequente e preocupante. No entanto, o ecocardiograma é apenas um exame sugestivo e não diagnóstico de HP. Quando se suspeita de acometimento direto da circulação pulmonar, está indicada medida hemodinâmica invasiva para estabelecer o diagnóstico. Essa avaliação permite, além da confirmação diagnóstica, a correta identificação do território vascular predominantemente acometido (arterial pulmonar ou pós-capilar). O tratamento com as medicações específicas de HP (inibidores da fosfodiestarese 5, antagonistas do receptor de endotelina, análogos da prostaciclina e estimulador da guanilil ciclase solúvel) é comprovadamente eficaz para pacientes com hipertensão arterial pulmonar, mas seu uso em pacientes com HP decorrente de doença cardíaca de câmaras esquerdas pode até mesmo ser prejudicial. Discutiremos nesta revisão o critério diagnóstico, a maneira de proceder a investigação etiológica, a classificação clínica e, finalmente, as recomendações terapêuticas na HP.

Valoración de ecuaciones derivadas del flujo pulmonar y regurgitación tricuspídea: utilidad en el test de vasoreactividad pulmonar / Valuation of equations derived from Pulmonary Flow and Tricuspid Regurgitation: usefulness in Pulmonary Vasoreactivity Testing

RESUMEN: Antecedentes: La presión media arterial pulmonar (PMAP) es una variable hemodinámica indispensable para el diagnóstico, clasificación y pronóstico de la Hipertensión Pulmonar (HP). Su cuantificación se realiza en forma invasiva por cateterismo cardíaco derecho (CCD) y no invasivamente por ecocardiografía Doppler. Masuyama propuso su medición mediante el gradiente transvalvular pulmonar diastólico derivado de la velocidad máxima inicial de la regurgitación pulmonar (∆RPi2) correspondiendo cercanamente a la medición invasiva. Objetivos: Revalidar 3 métodos ecocardiográficos que estiman la PMAP y valorar la utilidad del método de Chemla en el Test de Reactividad Vascular Pulmonar (TRVP). Métodos: Estudio prospectivo, observacional, doble ciego divido en dos etapas. A) o I) 30 pacientes se realizó ecocardiografía Doppler diagnóstica en nuestro centro. Se midieron regurgitación tricuspídea (RT) y tiempo de aceleración pulmonar (TAP) para derivar las siguientes ecuaciones: 1) 0.61xPSAP+1.95 (Chemla) 2) Gradiente presión media RT (∆PmRT) +PAD (presión-aurícula derecha) (Aduen) y 3) 79-0.45xTAP o 90-0.60xTAP, según sea el valor del TAP. B) o II) 10 pacientes enrolados para realizar el TRVP comparando la medición ecocardiográfica (Chemla) con CCD. Resultados: En la primera parte del estudio se encontró alta correlación entre las 3 ecuaciones: ChemlaAduen, R2=0.91; Chemla-Kitabatake, R2=0.87; Aduen-Kitabatake, R2=0,91. En la segunda parte comparando la PMAP-Chemla y Cateterismo derecho (CD) obtuvimos alta correlación: en tiempo 0, 30 min y recuperación:(R2=0.87, 0.99, 0.98, respectivamente). Ambas partes del estudio mostraron límites de concordancia satisfactoria con valor medio de la diferencia entre los métodos cercano a 1 en el t30 y tR del TRVP. Conclusión: los métodos dependientes de la medición de la RT son efectivos y confiables para estimar la PMAP. El método de Chemla es útil en el TRVP.

ABSTRACTS: Background: Mean Pulmonary arterial pressure (PMAP)is an indispensable hemodynamic variable for the diagnosis, classification and prognosis of Pulmonary Hypertension (PH). Its quantification is performed invasively by cardiac catheterization and non-invasively by Doppler echocardiography. Masuyama proposed its measurement by the transvalvular diastolic pulmonary gradient derived from the initial maximum velocity of pulmonary regurgitation(ΔPRi2) corresponding closely to the invasive measurement. Objectives: to compare 3 known echocardiographic methods to estimate MPAP and demonstrate the usefulness of the Chemla method in the Pulmonary Vascular Reactivity Test (PVRT). Methods: prospective, observational, double-blind study divided into two stages. A) 30 patients underwent diagnostic Doppler echocardiography. Tricuspid regurgitation (TR) and pulmonary acceleration time (PAT) were measured to derive the equations: 1) 0.61xSPAP + 1.95 (Chemla) 2) Gradient mean pressure TR (ΔPmTR) + RAP (right atrium pressure) (Aduen).3) 79-0.45xPAT o 90-0.60xPAT depending on the value of PAT. B) 10 patients enrolled to PVRT comparing the echocardiographic measurement (Chemla) with right catheterization. Results: in the first part of the study a high correlation between the 3 equations was found : ChemlaAduen, R2 = 0.91; Chemla-Kitabatake, R2=0.87; Aduen-Kitabatake, R2=0.91. In the second part comparing the MPAP-Chemla and RHC we obtained a high correlation in time 0, 30 min and recovery: (R2=0.87,0,99,0.98, respectively). Both parts of the study showed satisfactory limits concordance with mean value of the difference between the methods close to 1 in the t30 and tR of the TRVP. Conclusion: the methods dependent on the measurement of the TR are effective and reliable for estimating MPAP. The Chemla method is useful in the PVRT.