Continuous noninvasive arterial pressure
Continuous noninvasive arterial blood pressure measurement (CNAP) combines the advantages of the following two clinical “gold standards”: it measures blood pressure (BP) continuously in real-time like the invasive arterial catheter system (IBP) and it is non-invasive like the standard upper arm sphygmomanometer (NBP).
][1] a nationally representative survey among 200 German and Austrian physicians[2] and additional expert interviews provide strong evidence that in only 15% to 18% of inpatient surgeries blood pressure is measured continuously with invasive catheters (IBP).
[4] CNAP facilitates hemodynamic optimization using continuous blood pressure and its parameters derived from physiological rhythms and pulse wave analysis.
The concept has found acceptance in anesthesia and critical care: The evaluation of Pulse Pressure Variation (PPV) allows for goal-directed fluid management in sedated and ventilated patients.
[7] A meta-analysis of 29 clinical trials evidences that goal-directed therapy using these hemodynamic parameters leads to lower rates of morbidity and mortality in moderate and high-risk surgical procedures.
The Czech physiologist Jan Peňáz introduced this type of measurement of continuous noninvasive arterial blood pressure in 1973 by means of an electro-pneumatic control loop.
When the heart ejects stroke volume to the arteries, it takes a certain transit time until the blood pressure wave arrives in the periphery.
Even the comparison between the two clinical “gold standards” invasive continuous blood pressure at the arteria radialis and noninvasive, but intermittent, upper arm cuff shows large differences.
Small arteries beginning from arteria radialis downwards to the periphery have smooth muscles in order to open (vasodilation) and close (vasoconstriction).
It establishes correct mean arterial blood pressure in the finger cuff by checking typical characteristics of the pulse wave.
This algorithm needs to interrupt the blood pressure tracings for recalibration purposes, which results in short data loss during that time.
The overall accuracy of CNAP devices has been demonstrated in comparison with the current gold standard invasive blood pressure (IBP) monitoring in numerous studies during the last few years.[when?]
