blood pressure Archives

‘Tis the Season for Stress: Research Tools for Anxious Times

Holiday-related stress is as much of a seasonal tradition as family gatherings, frantic shopping forays, and over-indulgence in food and drink. Add to this potent mixture nearly two years of pandemic-induced tension and we have a volatile cocktail of emotions and anxiety awaiting us in November and December. What better time to study the causes and effects of stress?

Research has established strong links between stress and our moods and sense of well-being, not to mention overall mental and physical health. While certain types of stress during development can teach individuals to adapt to life’s many challenges, excessive and prolonged stress is shown to contribute to chronic disease and a range of psychological disorders. According to the American Psychological Association, which conducts an annual survey monitoring stress, the COVID pandemic has had an unprecedented impact on stress levels across all demographics, particularly among young people.

The pandemic is just one of many factors driving demand for new approaches to stress research. Thankfully, researchers now have access to a myriad of technologies to support any experiment design. In a recent webinar on techniques for measuring physiological changes related to stress, BIOPAC head of European Sales, Alex Dimov, outlined a range of stress-connected physiological responses that can be measured in the lab with available technologies. These include heart rate, heart rate variability (HRV), trans-radial-ulnar electrical bioimpedance velocimetry (TREV), cardiac output, blood pressure, EDA, pulse, respiration, EMG, EEG, and functional near infrared spectroscopy (fNIRS).

One of the challenges of measuring stress in a natural environment is finding the right data gathering tools to support the mobility of test participants. A 2019 study tackled this by examining a variety of techniques for measuring stress in day-to-day life using mobile phones and wearable sensors. Settings included the lab, automobile, office, school, and other daily life locations. Along with consumer products like smartphones, smartwatches, and fitness bands, researchers also employed wearable sensors, including the BioNomadix wireless PPG transmitter to measure blood volume pulse (BVP) using a photo plethysmogram (PPG) signal. Researchers found that the BIOPAC device provided a high level of accuracy (80%) when employed outside of the traditional lab environment.

Stress research technologies are not limited to data gathering. Stimulus presentation tools offer researchers options for both inducing and alleviating stress in the lab. A 2019 University of Wisconsin study investigating the role scents can play in reducing stress utilized EDA, heart rate, and respiratory rate to measure how rose scent reduced anxiety among students taking a difficult test. Respiratory rate was measured using a BIOPAC respiratory transducer while EDA data was collected with an EDA finger transducer. Data was collected and analyzed via the Biopac Student Lab System. While rose scent was delivered using scented lotion, it should be noted that BIOPAC offers a new modular scent delivery system that is capable of delivering up to eight scents per experiment, with more than 120 scent options.

With so many data gathering tools available, planning your next experiment should not leave you feeling on edge. Let your BIOPAC sales rep help you take the stress out of stress research.

BIOPAC offers a wide array of wired and wireless equipment that can be used in your research. To find more information on solutions for recording and analyzing signals such as ECG, heart rate, respiration, and more using any platforms mentioned in this blog post, you can visit the individual application pages on the BIOPAC website.

Ensuring Error-free NIBP Measurements & Accurate Data

Correct subject set-up of upper arm cuff, CNAP® NIBP finger sensor and CNAP® controller is essential to ensure accurate data reading and collection of continuous blood pressure and hemodynamics with the NiBP 100D throughout the measurement.

By Dr. Jürgen Fortin, CEO, CNSystems

The NIBP100D provides proven accuracy for blood pressure and, using the NIBP100-HD, full hemodynamics with validation in a number of settings and against research and clinical gold standards. Subject setup with the NIBP100D upper arm cuff and reusable finger sensor is extremely easy, however, please keep the following practical tips in mind to ensure accurate data collection:

1. Upper arm Cuff: Sizing and placement

Over the years, upper arm cuffs have become a standard measurement in basic research setup providing brachial pressure intermittently (timed intervals) rather than continuously (for every heart beat).

The NIBP100D has an upper arm cuff (Suntech Medical) integrated to provide calibration for the continuous finger sensor. For accurate calibration please mind the following steps:

Size: using a too small or too big upper arm cuff can lead to significant over- /or under- reading of blood pressure. Always ensure you choose the right size ( four sizes are provided with the NIBP100D) by using the range marker on the inside of the cuff–see image #3 in the photo above or review setup procedures here:

When wrapping the cuff around the upper arm before fixing the Velcro, ensure the white “index” arrow points into the indicated range area. If it does not, use the bigger or the smaller cuff!

Placement: always align the artery marker (white arrow) on the cuff with the brachial artery (in the crook of the arm). The cuff can be placed ipsilaterally or contralaterally to the arm with the CNAP finger sensor on.

Wrapping: pull the upper arm cuff so tight that you could still get about 2 fingers under the wrapped cuff (air volume).

SunTech has developed a short video on the basics of measuring blood pressure. Although designed for a clinical audience, the video provides good information for researchers. Watch the SunTech NBP training video here.

2. CNAP finger sensor: Sizing and placement

Using a too small or too big finger sensor cuff can distort the continuous blood pressure readings. Avoid placing the sensor on finger joints, which may lead to a poor or even no signal.

Size: Choose the right size from three different sizes by using the size indicator on the top of the CNAP Controller:

Put the proximal phalanx of the index finger on the indicator align with the grey line on the left. Choose the sensor size indicated on the shortest bar which is still visible.
Always use the larger sensor if you are in doubt about the size.
In some subjects it may be difficult to place the finger sensors on the proximal limb (i.e. finger-arthrosis, too short finger joints). In these cases, try placing the finger sensors on the middle limbs. However, make sure that the sensors are not placed over the finger joints. Hold the sensor in place or use medical tape until the sensor is inflated (start of measurement).

With the CNAP Software V5.2, sensor sizing becomes even easier—the size of the finger sensor is checked automatically upon start and the software gives notice if it does not fit.

Placement: The finger sensor is placed on two neighboring fingers and slid back fully to the proximal limb!
Make sure not to place them on the finger joints!

3. CNAP Controller: correct placement

The slide for the CNAP Controller allows for slight hand movement without dislocating the CNAP finger sensor. It is very important that the CNAP Controller is correctly placed:

Placement: Make sure that the CNAP Controller is placed in central position of the slide.
If the CNAP Controller is not placed correctly, the CNAPfinger sensor might be pushed forward on the finger joints.
View detailed pictures of CNAP Monitor Set Up Overview here.

4. Further recommendations

4.1. Start of measurement

Make sure that the subject keeps still and does not move his/her hand.
Do not change body posture during until a continuous signal is displayed!

4.2. Improving signal quality if signal is poor

Warm up fingers to improve blood flow (cover hand, hold hand in warm water prior to measurement, use disposable exam glove)
Check position of CNAP finger sensor: the sensor must not be placed on the finger joints.
Check if CNAP finger sensor size is correct.
Try to measure on the other hand.

4.3 Manual calibration with NBP

Trigger a manual NBP after moving or repositioning the subject/the subject’s hand or whenever hydrostatic change/offset happens.
Trigger a manual NBP whenever you feel that an update to the NBP reading may be beneficial
Triggering a manual NBP is possible at any time and in any mode.
Additional information—view the CNAP NIBP100D operator’s manual here.

4.4 Removal of CNAP finger sensor

Do not remove the CNAPfinger sensor when a measurement is still in progress. Stop measurement first, then remove the sensor!

4.5. Battery

Never completely discharge the battery.
Immediately connect to power supply if battery charge status is below 25%.

To read a recent study which evaluated the agreement of the continuous noninvasive cardiac output measurements by CNAP in comparison with cardiac output measurements obtained invasively using transpulmonary thermodilution (TDCO), go here.

The NIBP100D provides validated, proven accuracy for blood pressure and, with the NIBP100-HD model, full hemodynamics. To ensure the acquisition of good data and accurate readings, researchers should follow the setup procedures outlined above.
For more information on BIOPAC’s Noninvasive Blood Pressure monitoring and measurement systems and advanced functionality in the area of cardiovascular hemodynamics, to include CNAP noninvasive blood pressure systems, visit BIOPAC’s NIBP page or view BIOPAC’s NIBP amplifiers (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 www.biopac.com.

CNAP Noninvasive Blood Pressure Technology – An Overview

The interaction of an easy-to-use finger sensor with unique control loops and algorithms as well as with NBP provides high accuracy of the BP signal – equivalent to invasive arterial line.

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 Cuff – Automated 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]

Notes:

[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 .