Table 3.

Features of minimally invasive CO techniques and devices

Technique/Device	Invasiveness	Estimate of Cardiac Preload	Limitations/Considerations
Echocardiogram	Noninvasive	Yes	Not continuous
			Trained interpreter required
Esophageal Doppler flow	Esophageal probe required	Yes	Patient needs to be immobile
			Probe must be in proper position
			Specialized training required
Partial CO2 rebreathing technique	Noninvasive	No	Affected by V/Q mismatch
			Affected by changes in metabolism
TEB	Noninvasive	No	Decreased accuracy with edema and cardiac arrhythmias
			Only modest correlation with thermodilution
Transpulmonary thermodilution	Venous and arterial access	Yes (ITBV)	Good correlation with pulmonary artery thermodilution
Lithium dilution	Venous and arterial access	No	Calculation of CO depends on accurate sodium and hemoglobin concentration
			Multiple blood draws
			Potential for lithium adverse effects
Pulse contour analyses	Arterial catheter One technique	Yes	See Table 4
	(PICCO) requires central access

^aTEB, thoracic electrical bioimpedance; ITBV, intrathoracic blood volume.