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@#Pulmonary arterial hypertension (PAH) is a severe, progressive disease leading to right ventricular failure and finally death. Lung transplantation is recommended for PAH patients who do not respond to targeted drug combination therapy or World Health Organization functional class (WHO FC) Ⅲ or Ⅳ. However, only 3% of PAH patients can recieve the lung transplantation. A novel implantable interatrial shunt device (ISD) can create a relatively fixed right-to-left shunt established by balloon atrial septostomy (BAS). The device may decompress the right sided chambers, facilitate left heart filling, improve organ perfusion and reduce the likelihood of syncope, acute pulmonary hypertensive crisis and death. The systemic oxygen transport improves despite hypoxemia. Implantation is simple, feasible and safe, and the X-ray time and operation time are short. There is no severe complication or thrombosis during the mid-term follow-up of the clinical studies and the device remained patent. The syncope symptoms, six-minute walk distance, cardiac index and systemic oxygen transport improve significantly in the patients. ISD may be currently the last alternative treatment to improve symptoms and prolong survival in currently drug-resistant patients with severe PAH.
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La sangre normalmente transporta pequeñas cantidades de oxígeno (O2) disuelto en el plasma y altas cantidades combinadas en forma química con la hemoglobina. La presión parcial depende solo del oxígeno disuelto físicamente, lo que determina cuánto oxígeno se combinará con hemoglobina. La curva de disociación de la hemoglobina describe la reversibilidad de la reacción entre oxígeno y hemoglobina. Los factores habituales que aumentan o disminuyen la afinidad de la hemoglobina por el oxígeno son el pH, presión parcial de CO2, temperatura y 2,3 difosfoglicerato. La sangre también transporta grandes cantidades en forma de bicarbonato y bajas cantidades de CO2 disuelto en plasma y combinado con proteínas como compuestos carbamino. La desoxihemoglobina favorece la formación de compuestos carbamínicos y promueve el transporte del CO2 como bicarbonato uniéndose al hidrógeno proveniente de la disociación del ácido carbónico. A continuación se describe en forma detallada los mecanismos fisiológicos del transporte de gases en sangre.
Blood normally carries small amounts of oxygen dissolved in plasma and large amounts chemically combined with hemoglobin. Partial pressure of oxygen depends only on physically dissolved oxygen which determines how much oxygen will combine with hemoglobin. The oxygen-hemoglobin dissociation curve (or oxyhemoglobin dissociation curve) describes the reversibility of the reaction between oxygen and hemoglobin. The usual factors that increase or decrease the affinity of hemoglobin for oxygen are pH, CO2 partial pressure, temperature, and 2,3 diphosphoglycerate. Blood also carries large amounts of CO2 as bicarbonate and low amounts dissolved in plasma and combined with proteins as carbamino compounds. Deoxyhemoglobin favors the formation of carbamino compounds and promotes the transport of CO2 as bicarbonate by joining the hydrogen from the dissociation of carbonic acid. The physiological mechanisms of gas transport in blood are described in detail below.
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Humanos , Oxigênio/sangue , Fenômenos Fisiológicos Respiratórios , Dióxido de Carbono/sangue , Transferência de OxigênioRESUMO
After a short summary of the multifactorial models of maximal O2 consumption (VO2max) limitation, microgravity exposure is discussed as a convenient experimental condition to test these models. The following points are highlighted: 1) The decrease of (VO2max) in microgravity concerns specifically exercise performed in upright posture upon resumption of gravity exposure; 2) The decrease of (VO2max) after microgravity exposure has two components: one is fast and is related to cardiovascular adaptation, the other is slow and is related to the development of muscle atrophy; 3) (VO2max) does not decrease during microgravity or in supine posture upon resumption of gravity exposure, if the time in microgravity is sufficiently short; 4) cardiovascular oxygen transport accounts for 70% of (VO2max) limitation also after microgravity exposure.
Luego de un breve resumen de los modelos multifactoriales de la limitación del consumo máximo de oxígeno (VO2max), se analiza la exposición a la microgravedad como condición experimental conveniente para evaluar tales modelos. Se destacan los siguientes aspectos: 1) El decrecimiento en la microgravedad tiene que ver específicamente con los ejercicios realizados en posición vertical después de reanudar la exposición a la gravedad; 2) El decrecimiento posterior a la exposición a la microgravedad tiene dos componentes: uno es rápido y está relacionado con la adaptación cardiovascular, el otro es lento y está relacionado con la aparición de la atrofia muscular; 3) No decrece durante la microgravedad o en posición supina después de reanudarse la exposición a la gravedad, siempre que el tiempo transcurrido en microgravedad sea suficientemente corto; 4) el transporte de oxígeno cardiovascular representa el 70 % de la limitación también después de la exposición a la microgravedad.
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Objective Delivery of oxygen in tissues is limited in the space where oxygen must diffuse between the vascular and the surrounding tissues. Normal capillaries are relatively straight and well spaced, in contrast, the tumor vascular networks usually display more irregularity and the vessel wall shows higher permeability and less elasticity. The purpose of this study was to investigate the effect of capillary elasticity and tortuosity on the oxygen distribution and make further investigation on the mechanism of the formation of hypoxic regions in tumor. Method One-dimensional capillary model was coupled with the oxygen diffusion model. Oxygen transport was investigated in a Krogh and tortuous tissue model. The capillarygeometrywas obtained bythe one-dimensional model and transferred to the tissue model. Finite element method was employed in the analysis. Result The capillary radii along the flow direction under pressures were obtained for different initial radii and the oxygen distribution in the Krogh cylinder tissue model and the model with a tortuous capillary were computed. Conclusions when the capillary radius is small, the effect of vessel elasticity may have not significant effect on the oxygen distribution. However, with the capillary radius increasing, the effect on the oxygen transport becomes obvious. Moreover, with the tortuosity of the capillary increasing, the oxygen distribution becomes more heterogeneous, which is in agreement with the result in available reference. This work will be helpful to the investigation of oxygen transport within tumor.
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Objective Delivery of oxygen in tissues is limited in the space where oxygen must diffuse between the vascular and the surrounding tissues. Normal capillaries are relatively straight and well spaced, in contrast, the tumor vascular networks usually display more irregularity and the vessel wall shows higher permeability and less elasticity. The purpose of this study was to investigate the effect of capillary elasticity and tortuosity on the oxygen distribution and make further investigation on the mechanism of the formation of hypoxic regions in tumor. Method One-dimensional capillary model was coupled with the oxygen diffusion model. Oxygen transport was investigated in a Krogh and tortuous tissue model. The capillarygeometrywas obtained bythe one-dimensional model and transferred to the tissue model. Finite element method was employed in the analysis. Result The capillary radii along the flow direction under pressures were obtained for different initial radii and the oxygen distribution in the Krogh cylinder tissue model and the model with a tortuous capillary were computed. Conclusions when the capillary radius is small, the effect of vessel elasticity may have not significant effect on the oxygen distribution. However, with the capillary radius increasing, the effect on the oxygen transport becomes obvious. Moreover, with the tortuosity of the capillary increasing, the oxygen distribution becomes more heterogeneous, which is in agreement with the result in available reference. This work will be helpful to the investigation of oxygen transport within tumor.
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Objective Delivery of oxygen in tissues is limited in the space where oxygen must diffuse between the vascular and the surrounding tissues. Normal capillaries are relatively straight and well spaced, in contrast, the tumor vascular networks usually display more irregularity and the vessel wall shows higher permeability and less elasticity. The purpose of this study was to investigate the effect of capillary elasticity and tortuosity on the oxygen distribution and make further investigation on the mechanism of the formation of hypoxic regions in tumor. Method One-dimensional capillary model was coupled with the oxygen diffusion model. Oxygen transport was investigated in a Krogh and tortuous tissue model. The capillarygeometrywas obtained bythe one-dimensional model and transferred to the tissue model. Finite element method was employed in the analysis. Result The capillary radii along the flow direction under pressures were obtained for different initial radii and the oxygen distribution in the Krogh cylinder tissue model and the model with a tortuous capillary were computed. Conclusions when the capillary radius is small, the effect of vessel elasticity may have not significant effect on the oxygen distribution. However, with the capillary radius increasing, the effect on the oxygen transport becomes obvious. Moreover, with the tortuosity of the capillary increasing, the oxygen distribution becomes more heterogeneous, which is in agreement with the result in available reference. This work will be helpful to the investigation of oxygen transport within tumor.
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Objective:To investigate the effects of resuscitation with different fluids on hemodynamics,oxygen transport and extravascular lung water after acute hemorrhage in dogs. Method:Fifteen dogs were anesthetized and bled to a mean arterial pressure of 4.67 kPa to develop the hemorrhagic shock model.Then the animals were infused with one of three randomly selected fluid:lactated Ringer's solution, blood and polygeline.The terminal point of fluid resuscitation was at the level of PAWP of 2.0 kPa. Hemodynamics, oxygen transport and extravascular lung water values were measured. Result:colloids fluids infusion has more better efficacy and less extravascular lung water than crystalloids fluids infusion in hemorrhagic shock resuscitation,and polygeline infusion could restore hemodynamics better, meanwhile blood infusion could restore oxygen transport better.
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To investigate the perioperative oxygenation of the patient undergoing coronary artery bypass grafting procedure (CABG). Method: The relationship between oxygen transport (TO_2) and oxygen consumption (VO_2), and serum lactate level were examined in 55 patients undergoing CABF, anesthetized with midazolam, vecuronium and a moderate dose of fentanyl. Result: Good correlations between TO_2 and VO_2 at the weaning from CPB (r=0.7817, P
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Acute normovolemic hemodilution is widely used to conserve blood and to minimize the need for homologous blood transfusion during operation. To evaluate the effects of aeute isovolemic hemodilution on hemodynamics and oxygen transport, pulmonary artery catheter and radial artery catheter were introduced in 8 patients in whom maxillofacial or Wertheim's operation were performed. Blood(estimated from allowable blood loss) was withdrawn from radial artery, and simultaneously replaced by intravenous administration of 5% plasmanate and Hartmann solution. Acute isovolemic hemodilution decreased the hematocrit level from 33.2+/-3.7% to 29.6+/-2.9%. Cardiac output increased significantly, which was associated with decreased systemic vaacular resistance. Oxygen transport and oxygen consumption increased despite a decrease in oxygen carrying capacity. Heart rate, mean arterial perssure, mean pulmonary arterial pressure, central venous pressure, and pulmonary capillary wedge pressure did not change significantly during hemodilution. The results indicate that blood perfusion and oxygenation to tissue were well maintained in the hemodilution of the magnitude used in this study. Therfore it could be concluded that acute isovolemic hemodilution is a safe and relatively simple method of conserving blood and minimizing homologous blood transfusion.
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Humanos , Administração Intravenosa , Pressão Arterial , Transfusão de Sangue , Débito Cardíaco , Catéteres , Pressão Venosa Central , Recursos Naturais , Frequência Cardíaca , Hematócrito , Hemodiluição , Hemodinâmica , Oxigênio , Consumo de Oxigênio , Perfusão , Artéria Pulmonar , Pressão Propulsora Pulmonar , Artéria RadialRESUMO
Acute normovolemic hemodilution is widely used to conserve blood and to minimize the need for homologous blood transfusion during operation. To evaluate the effects of aeute isovolemic hemodilution on hemodynamics and oxygen transport, pulmonary artery catheter and radial artery catheter were introduced in 8 patients in whom maxillofacial or Wertheim's operation were performed. Blood(estimated from allowable blood loss) was withdrawn from radial artery, and simultaneously replaced by intravenous administration of 5% plasmanate and Hartmann solution. Acute isovolemic hemodilution decreased the hematocrit level from 33.2+/-3.7% to 29.6+/-2.9%. Cardiac output increased significantly, which was associated with decreased systemic vaacular resistance. Oxygen transport and oxygen consumption increased despite a decrease in oxygen carrying capacity. Heart rate, mean arterial perssure, mean pulmonary arterial pressure, central venous pressure, and pulmonary capillary wedge pressure did not change significantly during hemodilution. The results indicate that blood perfusion and oxygenation to tissue were well maintained in the hemodilution of the magnitude used in this study. Therfore it could be concluded that acute isovolemic hemodilution is a safe and relatively simple method of conserving blood and minimizing homologous blood transfusion.
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Humanos , Administração Intravenosa , Pressão Arterial , Transfusão de Sangue , Débito Cardíaco , Catéteres , Pressão Venosa Central , Recursos Naturais , Frequência Cardíaca , Hematócrito , Hemodiluição , Hemodinâmica , Oxigênio , Consumo de Oxigênio , Perfusão , Artéria Pulmonar , Pressão Propulsora Pulmonar , Artéria RadialRESUMO
Hemodilution, which is usually induced by autotransfusion, cardiopulmonary bypass and replace-ment therapy for blood loss, has some advantages in saving blood, improving blood flow and reducing the work-load of myocardium. But the safety and compensatory mechanism can be jeopardized by multiple factors, such as changes in inspired oxygen fraction (FIO,), cardiovascular diseases and drugs with potent cardiovascular actions, because of the disadvantageous hemodynamic changes and reduction of oxygen carrying capacity during hemodilution. Calcium channel blockers (CCB), which have recently gained a great popularity in treating several cardiovascular diseases, can affect cardiovascular system and compensatory mechanism during hemodilution. Therefore, to evaluate the effect of CCB on acute isovolemic hemodilution under the condition of hypoxia, we observed the parameters of hemodynamics and oxygen transport during acute isovolemic hemodilution after bleeding (20 ml/kg) in 16 experimentally induced hypoxic (FIO 0.15) dogs divided into verapamil and diltiazem treated groups. The results were as follows; 1) Hemodynamics; (a) In verapamil treated group, mean arterial pressure (MAP) was lower during experiment, but after hemodilution, central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) increased greater than in diltiazem treated group. Verapamil showed a greater negative inotropic effect. (b) Verapamil brought more vasodilatory effect than diltiazem. A significant increase of pul-monary vascular resistance (PVR) appeared after hypoxia, which meant hypoxic pulmonary vasocon-striction in diltiazem treated group. (c) In both groups, cardiac output (CO) was maintained well but heart rate (HR), MAP and rate pressure product (RPP) were decreased afrter hypoxia, bleeding and hemodilution. CCB reduce the work load of heart and myocardial oxygen consumption, thereby protect the myocardium. This effect was greatest after bleeding. 2) Oxygen transport; (a) Arterial oxygen tension (PaO2) was increased after hypoxia, bleeding and hemodilution in both groups and arterial carbon dioxide tension (PaCO2) was decreased after hemodilution in verapamil treated group. Ventilation-perfusion mismatch was improed in both groups, more prominently in verapamil treated group. (b) Oxygen flux (O2Flux) and oxygen consumption (VO2) were maintained well in both groups but oxygen extraction ratio (O2ER) after hypoxia and bleeding, and arterial and mixed venous oxygen content difference (Ca-vO2) after hypoxia were increased in diltiazem treated group. After hemodilu-tion, O2ER was decreased in both groups and Ca-VO2, was decreased in verapamil treated group. In diltiazem treated group, pH of arterial blood (pHa) and mixed venous oxygen tension (PvO2) were decreased after hypoxia, and PvO2 were decreased after hypoxia, and , was also decreased after hemodilution. Oxygen deficit was not seen in either group and oxygen utilization was more satisfactory in verapamil treated group. 3) After hemodilution with dextran-40, colloid osmotic pressure (COP) increased and ionized calcium (Ca++) decreased in both groups. The above findings indicated that use of CCB during acute isovolemic hemodilution in hypoxic dogs is safe because CCB showed adequate maintenance of cardiac output without any sign of heart failure or reduction of myocardial work despite a negative inotropic effect and vasodilatory effect hemodynamically, and also revealed improvement of ventiltion-perfusion mismatch and smooth maintenance of oxygen transport. Both of the effects were more prominent with verapamil than diltiazem in an equimolar dose.
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Animais , Cães , Hipóxia , Pressão Arterial , Transfusão de Sangue Autóloga , Bloqueadores dos Canais de Cálcio , Canais de Cálcio , Cálcio , Dióxido de Carbono , Débito Cardíaco , Ponte Cardiopulmonar , Doenças Cardiovasculares , Sistema Cardiovascular , Pressão Venosa Central , Coloides , Recursos Naturais , Diltiazem , Coração , Insuficiência Cardíaca , Frequência Cardíaca , Hemodiluição , Hemodinâmica , Hemorragia , Concentração de Íons de Hidrogênio , Miocárdio , Pressão Osmótica , Oxigênio , Consumo de Oxigênio , Pressão Propulsora Pulmonar , Resistência Vascular , VerapamilRESUMO
Dogs were bled and maintained at the mean arterial pressure(MAP)of 6.67 kPa(moderate shock)or of 5.33 kPa(severe shock)for 2 hours.Then the blood shed was transfused back to the animals and observation on the dogs was carried on for 2 more hours.26 mongrel dogs,weighing 10~16 kg,were randomized into Group I of normoxia and moderate shock(NMS,n=7),Group I of normoxia and severe shock(NSS,n=7).Group I of hypoxia at a simulated alti- tude of 4 000 m and moderate shock(HMS,n=6),and Group IV of hypoxia and severe shock(HSS,n=6).The changes of the cardiovascular function and the oxygen transport were observed in these animals after anesthetization.It was found that the cardiovascular function was similar in HMS and NMS groups.The decrease of VO2 of HMS animals was similar to that of NSS dogs.Decompensation occurred earlier in HSS animals and resulted in high mortality.