Calculating cardiac output of a patient undergoing veno-venous extracorporeal blood oxygenation

Abstract

A system for calculating cardiac output of a patient on an extracorporeal blood oxygenation circuit, such as veno-venous extracorporeal membrane oxygenation, includes determining (i) a first arterial carbon dioxide content or surrogate and (ii) a first carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the first removal rate of carbon dioxide from the blood; establishing a second removal rate of carbon dioxide from the blood in the oxygenator in the extracorporeal blood oxygenation circuit; determining (i) a second arterial carbon dioxide content or surrogate and (ii) a second carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the second removal rate of carbon dioxide from the blood; and calculating a cardiac output of the patient corresponding to a blood flow rate through the extracorporeal blood oxygenation circuit, the first arterial carbon dioxide content or surrogate, the first carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the first removal rate of carbon dioxide from the blood; the second arterial carbon dioxide content or surrogate and the second carbon dioxide content or surrogate in the blood delivered to the patient after passing the oxygenator corresponding to the second removal rate of carbon dioxide from the blood.

1 . A method for calculating cardiac output of a patient undergoing veno-venous extracorporeal blood oxygenation, the method comprising:
 (a) measuring a blood flow rate of an extracorporeal blood oxygenation circuit passing blood into a venous portion of a circulatory system of a patient;   (b) establishing a first removal rate of carbon dioxide from the blood in an oxygenator in the extracorporeal blood oxygenation circuit;   (c) determining through at least one of a representative parameter or a surrogate of each of (i) a first arterial carbon dioxide content and (ii) a first carbon dioxide content of the blood delivered to the patient after passing the oxygenator corresponding to the first removal rate of carbon dioxide from the blood;   (d) establishing a second removal rate of carbon dioxide from the blood in the oxygenator in the extracorporeal blood oxygenation circuit;   (e) determining through at least one of a representative parameter or a surrogate each of (i) a second arterial carbon dioxide content and (ii) a second carbon dioxide content of the blood delivered to the patient after passing the oxygenator corresponding to the second removal rate of carbon dioxide from the blood; and   (f) calculating a cardiac output of the patient corresponding to the blood flow rate, the first arterial carbon dioxide content and the first carbon dioxide content in the blood delivered to the patient after passing the oxygenator corresponding to the first removal rate of carbon dioxide from the blood, and the second arterial carbon dioxide content and the second carbon dioxide content in the blood delivered to the patient after passing the oxygenator corresponding to the second removal rate of carbon dioxide from the blood.   
     
     
         2 . The method of  claim 1 , wherein establishing the first removal rate of carbon dioxide from the blood in the oxygenator in the extracorporeal blood oxygenation circuit includes establishing a first sweep gas flow rate through the oxygenator. 
     
     
         3 . The method of  claim 1 , further comprising measuring a recirculation in the extracorporeal blood oxygenation circuit and adjusting the calculated cardiac output corresponding to the measured recirculation. 
     
     
         4 . The method of  claim 1 , wherein measuring the blood flow rate is provided by a pump in the extracorporeal blood oxygenation circuit. 
     
     
         5 . The method of  claim 1 , further comprising operably connecting a first dilution sensor to a venous line of the extracorporeal blood oxygenation circuit and a second dilution sensor to an arterial line of the extracorporeal blood oxygenation circuit. 
     
     
         6 . The method of  claim 5 , further comprising measuring a recirculation including introducing an indicator into the extracorporeal blood oxygenation circuit upstream of the second dilution sensor and downstream of the first dilution sensor. 
     
     
         7 . The method of  claim 6 , wherein measuring the recirculation includes sensing a dilution indicator with the first dilution sensor. 
     
     
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         16 . An apparatus for quantifying a cardiac output of a patient operably connected to an extracorporeal blood oxygenation circuit, the extracorporeal blood oxygenation circuit having a venous line withdrawing blood from a circulatory system of the patient, a blood oxygenator, a pump, and an arterial line returning oxygenated blood to a venous portion of the circulatory system, the apparatus comprising:
 (a) a controller configured to connect to one of the blood oxygenator and the pump, the controller configured to calculate a cardiac output of the patient based on a flow rate of oxygenated blood from the extracorporeal blood oxygenation circuit, a first arterial carbon dioxide content and a first carbon dioxide content of the blood delivered to the patient circulatory system corresponding to a first gas removal rate in the blood oxygenator in the extracorporeal blood oxygenation circuit; and a second arterial carbon dioxide content and a second carbon dioxide content of the blood delivered to the patient circulatory system corresponding to a second gas removal rate in the oxygenator in the extracorporeal blood oxygenation circuit.   
     
     
         17 . The apparatus of  claim 16 , further comprising an indicator injection port in the venous line. 
     
     
         18 . The apparatus of  claim 16 , wherein the controller is further configured to calculate a recirculation. 
     
     
         19 . The apparatus of  claim 16 , wherein the first gas removal rate in the blood oxygenator corresponds to a second flow rate of sweep gas though the blood oxygenator, wherein the second flow rate of sweep gas though the blood oxygenator is different than the first flow rate of sweep gas though the blood oxygenator. 
     
     
         20 . The apparatus of  claim 16 , further comprising an oximeter operably connected to the controller. 
     
     
         21 . The apparatus of  claim 16 , wherein at least one of (i) the first arterial carbon dioxide content comprises a first surrogate of arterial carbon dioxide content, (ii) the first carbon dioxide content of the blood delivered to the patient circulatory system comprises a first surrogate of carbon dioxide content in the blood delivered to the patient, (iii) the second arterial carbon dioxide content comprises a second surrogate of arterial carbon dioxide content, and (iv) the second carbon dioxide content of the blood delivered to the patient circulatory system comprises a second surrogate of the second carbon dioxide content of the blood delivered to the patient circulatory system. 
     
     
         22 . The apparatus of  claim 16 , wherein the controller is further configured to calculate a recirculation in the extracorporeal blood oxygenation circuit and adjust the calculated cardiac output corresponding to the calculated recirculation. 
     
     
         23 . The apparatus of  claim 16 , wherein the blood flow rate from the extracorporeal blood oxygenation circuit is provided by the pump in the extracorporeal blood oxygenation circuit. 
     
     
         24 . The apparatus of  claim 16 , further comprising a first dilution sensor and a second dilution sensor in the extracorporeal blood oxygenation circuit, wherein the controller is further configured to calculate a recirculation, wherein the calculated recirculation corresponds to an introduced indicator in the extracorporeal blood oxygenation circuit upstream of the second dilution sensor and downstream of the first dilution sensor. 
     
     
         25 . The method of  claim 1 , wherein establishing the second removal rate of carbon dioxide from the blood in the oxygenator in the extracorporeal blood oxygenation circuit includes establishing a second sweep gas flow rate through the oxygenator. 
     
     
         26 . The method of  claim 1 , wherein measuring the blood flow rate includes measuring at least one of a representative parameter or a surrogate of the blood flow rate.