Noninvasive Blood Pressure Measurement by the Nexfin Monitor During Reduced Arterial Pulsatility: A Feasibility Study

Noninvasive blood pressure measurements are difficult when arterial pulsations are reduced, as in patients supported by continuous flow left ventricular assist devices (cf-LVAD). We evaluated the feasibility of measuring noninvasive arterial blood pressure with the Nexfin monitor during conditions of reduced arterial pulsatility. During cardiopulmonary bypass (CPB) in which a roller pump based or a centrifugal pump based heart-lung machine generated arterial blood pressure with low pulsatility, noninvasive arterial pressures (NAP) measured by the Nexfin Monitor were recorded and compared with invasively measured radial artery pressures (IAP). We also evaluated NAP in 10 patients with a cf-LVAD during a pump speed change procedure (PSCP). During CPB in 18 patients, the NAP-IAP average difference was -1.3 +/- 6.5 mm Hg. The amplitude of pressure oscillations were 4.3 +/- 3.8 mm Hg measured by IAP. Furthermore, in the cf-LVAD patients, increase in pump speed settings led to an increase in diastolic and mean arterial pressures (MAP) while the NAP acquired a sinusoidal shape as the aortic valve become permanently closed. In conclusion, NAP was similar to IAP under conditions of reduced arterial pulsatility. The device also measured the blood pressure waveform noninvasively in patients supported by a cf-LVAD. ASAIO Journal 2010; 56:221-227