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By Dr. Jürgen Fortin, CEO, CNSystems

Continuous noninvasive arterial blood pressure measurement (CNAP®) is the technique for measuring blood pressure (BP) that is, as the title describes, both continuous and noninvasive. 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 noninvasive, like the standard upper arm sphygmomanometer (NBP).

The CNAP principle is the intelligent interaction and synergy of IP-protected features and functions based on the well-known Vascular Unloading Principle by Penaz (with significant improvement over the past 15 years) [1], on unique control algorithms (e.g. VERIFI) [2] and on calibration mechanisms, making it a reliable and accurate method with results comparable to the intra-arterial measurement.

Pulsating blood flow detected by infrared light sensors is kept constant by the counter pressure exerted on the artery through inflating or deflating the integrated cuff. The resulting pressure in the finger sensor corresponds to the real arterial pressure [1]. The pressure system is controlled by multiple digital feedback loops. The “VERIFI-algorithm” is used for high fidelity signal processing and artifact rejection. This is a superior method for filtering vasomotoric influences, in contrast to Standard methods based on Vascular Unloading Principle, which can show false BP shifts due to influence of vasomotoric tone.

In terms of calibration, CNAP is the only available technology calibrating to directly measured upper arm values, providing blood pressure variations in absolute values at heart-level. The interaction of finger sensor with NBP provides high accuracy of the BP signal – equivalent to invasive arterial line.

Use of CNAP provides researchers with several benefits, including: 

  •  NBP CuffAutomated scaling to brachial pressure (gold standard) at start of measurement and user programmable
  • Double finger sensor – Quick and error-free application
  • Continuous waveform – Continuous tracing of hemodynamic changes without interruptions to recalibrate; beat-to-beat systolic, diastolic, mean BP values
  • Connectivity – Plug-and-play integration into all common data acquisition systems and patient monitors
  • Data storage and analysis – Unlimited data storage via USB interface. Data format (*.csv) for import into all common data analysis software packages (e.g. BIOPAC’s AcqKnowledge®, Matlab, MS Excel, SPSS, etc.)
  • Accuracy – Reliably equivalent to invasive blood pressure (IBP) [3], [4]


[1]  Jan Penaz, Brno, Czech Republic 1973.

[2]  Fortin J et al.: Continuous non-invasive blood pressure monitoring using concentrically interlocking control loops. Comput in BiolMed 36 (2006) 941 – 957.

[3]  Jeleazcov C et. al. Precision and accuracy of a new device (CNAP) for continuous noninvasive arterial blood pressure monitoring: assessment during general anaesthesia. BJA. 2010; 105(3):264-272.

[4]Biais, M. et. al. Continuous non-invasive arterial pressure measurement: Evaluation of CNAP device during vascular surgery Ann Fr Anesthesia.

Studies documenting the CNAP device’s performance can be found below:

Arterial stiffness is higher in older adults with increased perceived fatigue and fatigability during walking

Does conscious intention to perform a motor act depend on slow cardiovascular rhythms?

The Effect of Mainstream Media on Body Image and Stress Reactivity in Latina Females

For more information on BIOPAC’s Noninvasive Blood Pressure monitoring and measurement and cardiology research solutions, to include CNAP noninvasive blood pressure systems, visit BIOPAC’s NIBP page or view BIOPAC’s NIBP amplifiers (MRI and small animal applications are also supported) and related equipment for a wide variety of research applications.

BIOPAC Systems, Inc. provides life science researchers and educators with data acquisition and analysis systems that inspire people and enable greater discovery about life.  Visit us at

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