Endotracheal cardiac output monitor.
BACKGROUND
The endotracheal cardiac output monitor (ECOM) is a new device that uses an endotracheal tube with multiple electrodes to measure cardiac output (CO). It measures the changes in electrical impedance caused by pulsatile blood flow in the aorta. The system was tested for safety and efficacy in 10 swine.


METHODS
Swine (60-80 kg) were chronically instrumented with a transit time flow probe on the ascending aorta and vascular occluders on the vena cava and pulmonary artery. After a minimum recovery of 4 days, the animals were anesthetized and intubated with an ECOM endotracheal tube. CO measurements from the ECOM system were compared to transit time flow probe measurements using linear regression and Bland-Altman analysis. Three different inotropic states were studied: (1) baseline; (2) increased (dobutamine); and (3) decreased (esmolol). CO was changed at each inotropic state by impeding left ventricular filling with the vena cava or pulmonary artery occluders. CO values between 0 and 15 l/min were studied. Pigs were studied for 24 h consecutively.


RESULTS
There was no deterioration of the impedance signal with time and no tracheal injury from the ECOM electrodes. There is a linear relationship between the ECOM and transit time flow probe CO between 0 and 15 l/min (slope = 0.94; intercept = 0.15 l/min; R2= 0.77). The mean difference between the two measures (bias) is 0.15 l/min and the SD is 1.34 l/min. The limits of agreement are -2.53 to 2.82 l/min.


CONCLUSIONS
Endotracheal CO monitor is a promising technology that needs further evaluation in clinical trials.
Wallace
A W
AW
Department of Anesthesiology, University of California-San Francisco and the San Francisco Veterans Affairs Medical Center, 94121, USA. awallace@cardiacengineering.com
Salahieh
A
A
Lawrence
A
A
Spector
K
K
Owens
C
C
Alonso
D
D
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000465:Algorithms; D000818:Animals; D002302:Cardiac Output / Q000187:drug effects*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology*; D017097:Electric Impedance; D004566:Electrodes; D004867:Equipment Design; D005260:Female; D007442:Intubation, Intratracheal / Q000009:adverse effects / Q000295:instrumentation*; D008991:Monitoring, Physiologic / Q000295:instrumentation*; D011412:Propanolamines / Q000494:pharmacology*; D013552:Swine; D014132:Trachea / Q000293:injuries / Q000473:pathology
D000319:Adrenergic beta-Antagonists; D002316:Cardiotonic Agents; D011412:Propanolamines; D004280:Dobutamine; C036604:esmolol