Table II.

Comparison for impedance measurement techniques for cardiac applications

Device	Advantages	Limitations	Assumptions
Band electrode method	Noninvasive, low-cost, simple to use, continuous time-dependent monitoring Can give assessment of relative cardiac output changes in response to therapy	Some questionable accuracy and consistency of cardiac output measurements for late-stage, chronic heart failure, and patients in unstable conditions Unresolved discrepancies in measurement (pulmonary edema, body size, irregular blood flow, blood volume)	No valve defects No respiratory diseases No renal failure, no implanted pacing device
Implanted device-based method	Noninvasive (external), early detection of symptoms before hospitalization Continuous monitoring Sensitive to fluid accumulation, localized to thorax	Invasive (implant), some unresolved impedance sources (blood volume, lung resistivity) No cardiac output, SVR, or filling pressure monitor No detection of peripheral edema or hypertension	No valve defects No acute pulmonary processes (eg, pneumonia)