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 puls
atile blood flow in the aorta. The system was tested for safety and efficac
y 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 a
nesthetized and intubated with an ECOM endotracheal tube. CO measurements f
rom the ECOM system were compared to transit time flow probe measurements u
sing linear regression and Bland-Altman analysis. Three different inotropic
states were studied: (1) baseline; (2) increased (dobutamine); and (3) dec
reased (esmolol). CO was changed at each inotropic state by impeding left v
entricular filling with the vena cava or pulmonary artery occluders. CO val
ues between 0 and 15 l/min were studied. Pigs were studied for 24 h consecu
tively.
Results: There was no deterioration of the impedance signal with time and n
o 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 (slo
pe = 0.94; intercept = 0.15 l/min; R-2 = 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,
Conclusion: Endotracheal CO monitor is a promising technology that needs fu
rther evaluation in clinical trials.