Method and apparatus for assessing cardiac output in veno-arterial extracorporeal blood oxygenation

Abstract

A system for calculating cardiac output (CO) of a patient undergoing veno-arterial extracorporeal oxygenation includes measuring first oxygenated blood flow rate by a pump in the extracorporeal blood oxygenation circuit as introduced into an arterial portion of the patient circulation system and a corresponding arterial oxygen saturation, then changing the pump flow rate, such as decreasing, to produce a corresponding change in arterial oxygen saturation (wherein such change is outside of normal operating variances, operating errors or drift), which change in the arterial oxygen saturation is measured. From the first flow rate and the second flow rate along with the corresponding measured arterial oxygen saturation, the CO of the patient can be calculated, without reliance upon a measure of venous oxygen saturation. Alternatively, the CO of the patient can be calculated, without reliance upon a change in flow rate by changing a gas exchange with the blood in the extracorporeal blood oxygenation circuit to impart corresponding changes in a blood parameter in the arterial portion of the patient circulation system and the blood delivered from the extracorporeal blood oxygenation circuit.

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         18 . A method for calculating cardiac output of a patient undergoing veno-arterial extracorporeal blood oxygenation, the method comprising:
 (a) calculating a cardiac output of the patient corresponding to (i) a first blood flow rate from a veno-arterial extracorporeal blood oxygenation circuit into an arterial portion of a patient circulation system, the veno-arterial extracorporeal blood oxygenation circuit including a blood oxygenator, (ii) an arterial blood oxygen saturation, and (iii) a mixed venous blood oxygen saturation.   
     
     
         19 . The method of  claim 18 , wherein the patient circulation system includes a right atrium and a vena cava, and the mixed venous blood oxygen saturation is from blood taken from one of the right atrium and the vena cava. 
     
     
         20 . The method of  claim 18 , wherein the mixed venous blood oxygen saturation is from blood not passing through the blood oxygenator in the veno-arterial extracorporeal blood oxygenation circuit. 
     
     
         21 . The method of  claim 18 , wherein calculating the cardiac output corresponds to  
       
         
           
             
               C 
               O 
               = 
               
                 Q 
                 b 
               
               × 
               
                 
                   
                     
                       100 
                       − 
                       S 
                       a 
                       
                         O 
                         2 
                       
                     
                   
                 
                 
                   
                     
                       S 
                       a 
                       
                         O 
                         2 
                       
                       − 
                       S 
                       v 
                       
                         O 
                         2 
                       
                     
                   
                 
               
               , 
             
           
         
       
       where CO is the cardiac output, Q b  is the first blood flow rate, SaO 2  is the arterial blood oxygen saturation in the patient circulation system, and SvO 2  is the mixed venous blood oxygen saturation in the patient circulation system. 
     
     
         22 . The method of  claim 18 , wherein the patient circulation system includes lungs and the mixed venous blood oxygen saturation is equal to the oxygen saturation of blood passing from the lungs. 
     
     
         23 . The method of  claim 18 , wherein the arterial blood oxygen saturation comprises a surrogate parameter for arterial blood oxygen saturation. 
     
     
         24 . The method of  claim 18 , wherein the mixed venous blood oxygen saturation comprises a surrogate parameter for the mixed venous blood oxygen saturation. 
     
     
         25 . The method of  claim 18 , wherein the arterial blood oxygen saturation, and the mixed venous blood oxygen saturation are measured during the first blood flow rate. 
     
     
         26 . The method of  claim 18 , wherein the first blood flow rate is provided by a pump in the extracorporeal blood oxygenation circuit. 
     
     
         27 . An apparatus for quantifying a cardiac output of a patient operably connected to an extracorporeal blood oxygenation circuit, the extracorporeal blood oxygenation circuit having an access line withdrawing blood from a patient circulation system, a blood oxygenator, a pump, and a return line returning oxygenated blood to an arterial portion of the patient circulation system, the apparatus comprising:
 (a) a controller configured to connect to one of the blood oxygenator and the pump, the controller configured to calculate the cardiac output of the patient corresponding to a first blood flow rate from the extracorporeal blood oxygenation circuit to the arterial portion of the circulation system, an arterial blood oxygen saturation, and a mixed venous blood oxygen saturation.   
     
     
         28 . The apparatus of  claim 27 , wherein the mixed venous blood oxygen saturation is from blood not passing through the blood oxygenator in the extracorporeal blood oxygenation circuit. 
     
     
         29 . The apparatus of  claim 27 , wherein the patient circulation system includes a right atrium and a vena cava, and the mixed venous blood oxygen saturation is from blood taken from one of the right atrium and the vena cava. 
     
     
         30 . The apparatus of  claim 27 , wherein the arterial blood oxygen saturation comprises a surrogate parameter for arterial blood oxygen saturation. 
     
     
         31 . The apparatus of  claim 27 , wherein the mixed venous blood oxygen saturation comprises a surrogate parameter for the mixed venous blood oxygen saturation. 
     
     
         32 . The apparatus of  claim 27 , wherein the controller is configured to calculate the cardiac output corresponding to  
       
         
           
             
               C 
               O 
               = 
               
                 Q 
                 b 
               
               × 
               
                 
                   
                     
                       100 
                       − 
                       S 
                       a 
                       
                         O 
                         2 
                       
                     
                   
                 
                 
                   
                     
                       S 
                       a 
                       
                         O 
                         2 
                       
                       − 
                       S 
                       v 
                       
                         O 
                         2 
                       
                     
                   
                 
               
               , 
             
           
         
       
       where CO is the cardiac output, Q b  is the first blood flow rate, SaO 2  is the arterial blood oxygen saturation in the patient circulation system, and SvO 2  is the mixed venous blood oxygen saturation in the patient circulation system. 
     
     
         33 . The apparatus of  claim 27 , wherein the patient circulation system includes lungs and the mixed venous blood oxygen saturation is equal to the oxygen saturation of blood passing from the lungs. 
     
     
         34 . The apparatus of  claim 27 , wherein the arterial blood oxygen saturation, and the mixed venous blood oxygen saturation are measured during the first blood flow rate. 
     
     
         35 . The apparatus of  claim 27 , wherein the first blood flow rate is provided by the pump in the extracorporeal blood oxygenation circuit.