Noninvasive Cardiac Output Determination Using Applanation Tonometry-Derived Radial Artery Pulse Contour Analysis in Critically Ill Patients

Abstract

Conventional thermodilution cardiac output (CO) monitoring is limited mainly to intensive care units and operating rooms because it requires the use of invasive techniques. To reduce the potential for complications and to broaden the applicability of hemodynamic monitoring, noninvasive methods for CO determination are being sought. Applanation tonometry allows noninvasive CO estimation through pulse contour analysis, but the method has not been evaluated in critically ill patients. We therefore performed noninvasive radial artery applanation tonometry in 49 critically ill medical intensive care unit patients and compared CO estimates to invasive CO measurements obtained using a pulmonary artery catheter or the PiCCO® transpulmonary thermodilution system. One-hundred-sixteen measurements were performed, and patients were receiving vasopressor support during 78 measurements. When the data were analyzed with bias and precision statistics, a large bias of 2.03 L · min−1 · m−2 and a high percentage error of 85% were found between the invasive measurements and applanation tonometry-derived CO estimates, with the noninvasive CO results being significantly lower than the invasive ones (P