cardiovascular hemodynamics Archives

Tick, Tock: Pulse Transit Time Offers Noninvasive Physiological Insights

A split second can reveal much about the cardiovascular system and the other physiological systems it influences. Pulse Transit Time (PTT) captures one of those critical moments, the brief interval it takes for the pressure wave generated by contraction of the left ventricle to travel from the heart to a peripheral site in the body. That tiny stretch of time tells us something important about the arteries—namely, how stiff or flexible they are in that moment. When blood pressure rises and the vessel walls tighten, the pulse wave travels more quickly, so PTT gets shorter. When the vessels are relaxed and more elastic, the wave slows down, and PTT becomes longer. Because of this back-and-forth relationship, PTT gives researchers a simple, noninvasive way to track changes in vascular tone, blood flow dynamics, and autonomic nervous system activity.

PTT is determined by measuring the volume or pressure pulse at a proximal artery (such as the carotid or brachial) and at a distal artery (such as the finger or toe). To prevent confusion in PTT nomenclature across different methods, some researchers use labels formed from the first one or two letters of the starting and arrival signals. PTT-PP refers to PTT recorded using PPG between a proximal and a distal artery, PTT-EP refers to PTT measured between electrocardiogram (ECG) proximally and photoplethysmogram (PPG) distally and PTT-IP refers to PTT recorded between Impedance Cardiogram proximally and PPG distally.

PTT-EP is recorded by simultaneously recording ECG and PPG. PPG is usually recorded at the finger using a small infrared light to detect changes in blood flow with each heartbeat. As blood pulses into the area, the amount of light absorbed changes, creating a waveform with a clear rise and peak. To calculate PTT-EP, researchers measure the time between the ECG spike and a specific point on the PPG wave, typically the point at which the wave first rises or reaches its peak. Strictly speaking PTT-EP is not a true PTT as it includes pre-ejection period, a short delay between electrical activation of the ventricles and actual ejection of blood. For that reason, it is sometimes referred to as Pulse Arrival Time (PAT). Even so, the ECG-to-PPG approach remains widely used because it is noninvasive, reliable, relatively inexpensive, and straightforward to implement across a range of study designs.

Typical lab configurations focus on integrated, multimodal data acquisition systems that allow researchers to record ECG and PPG signals simultaneously using dedicated amplifier modules, with analysis performed via software. These systems enable precise channel synchronization, automated waveform feature detection, beat-by-beat PTT computation, and data export for statistical analysis. In some studies, researchers also integrate noninvasive blood pressure (NIBP) modules to directly examine the relationship between PTT and systolic or mean arterial pressure, strengthening the interpretation of vascular changes.

Obtaining high-quality PTT data requires attention to detail and careful planning. Participants should rest in a quiet, temperature-controlled room, since vascular tone can be affected by stress, ambient temperature, and sympathetic activation. Avoid testing immediately after meals or the consumption of caffeine or nicotine, which can alter cardiovascular dynamics. Proper sensor placement and stable contact pressure are critical for minimizing motion artifacts and waveform distortion. Consistent measurement timing, accounting for diurnal variation, helps ensure consistent data quality across sessions. Signal processing choices also matter. Careful filtering (see example study below), accurate event marking, and careful peak or foot detection are essential to ensure that the measured interval truly reflects physiological timing rather than processing artifacts.

When these best practices are followed, PTT becomes a versatile research tool. It has been used to study stress reactivity, autonomic regulation, arterial stiffness, posture-related hemodynamics, exercise physiology, sleep physiology, and the development of cuffless blood pressure estimation technologies. Recent studies illustrate both the promise and the practical considerations of PTT measurement.

At the Georgia Institute of Technology, researchers explored whether noninvasive nerve stimulation applied at the ear, neck, or wrist could reduce acute stress responses in healthy young adults. During laboratory sessions that included mental arithmetic and cold exposure tasks, cardiovascular signals were recorded using a BIOPAC MP data acquisition unit and a PPG100C to capture ECG and fingertip PPG. PTT served as a key marker of sympathetic (“fight-or-flight”) activation. The research team found that stimulation at the ear and wrist significantly reduced stress-related cardiovascular changes compared to a sham condition, supporting the potential for wearable systems that integrate neuromodulation and real-time cardiovascular monitoring.

In another study published in Nature, researchers at Columbia University tackled a common problem in cuffless blood pressure monitoring: when wearable sensors sit above or below heart level, changes in arm position create hydrostatic pressure errors that skew estimates based on PTT. Cuffless systems frequently use PTT to estimate blood pressure, but arm movements can distort that timing and reduce accuracy. To investigate this, the team collected synchronized physiological data using a BIOPAC data acquisition system to record high-resolution ECG signals via a BIOPAC ECG amplifier and fingertip PPG signals via BIOPAC PPG100C, while a BIOPAC NIBP module measured reference blood pressure using upper-arm and finger cuffs. Participants also wore wrist and upper-arm inertial sensors (IMUs) to track how the arm was positioned relative to the heart. The research team then developed a method called IMU-Track, which uses motion data and deep learning to correct PTT for arm height effects, improving the accuracy of blood pressure predictions across different postures. Their findings showed that accounting for sensor position dramatically reduced errors in cuffless blood pressure estimation, suggesting that combining motion tracking with PTT measurements could make wearable BP monitoring more reliable in everyday use.

When applied correctly, PTT provides a potent, noninvasive tool for assessing cardiovascular function—one measured in milliseconds but capable of revealing meaningful physiological change. For more information on integrating PTT into research, see our PTT webinar.

If you are planning to use PTT in your next study, don’t hesitate to reach out for our highly capable team of experts for assistance in identifying the equipment and procedures to ensure your success.

A System of Systems: Network Physiology Connects the Dots

In the field of physiology, it is tempting to see the human body as a collection of independent systems performing a range of functions—converting food to energy, protecting us from harm and disease, and helping us react to and interact with our environments, to name a few. It is easy to overlook that these systems often work together and are interconnected. The field of network physiology does just that—look at how these systems (nervous, cardiovascular, muscular, etc.) work together, seeing them as part of a dynamic network rather than a collection of independent parts.

The author of the article linked above, Boston University research professor of physics Plamen Ivanov, first coined the term “network physiology” in 2006. Through his work as director of the Keck Laboratory of Network Physiology, Ivanov and his team pioneered research in this new and rapidly growing field. The latest research methods, breakthroughs, and ideas in network physiology will take center stage this summer at the Fourth International Summer Institute on Network Physiology (ININP) hosted at the Lake Como School of Advanced Studies in Italy.

Researchers are exploring various ways to apply the concepts of network physiology, including how stress affects both the brain and the body. Medical researchers are looking into how to identify early warning signs of future health problems in how various physiological systems interact when developing treatments that address multiple bodily systems. While this may sound like the multimodal approach to physiology—collecting data simultaneously and synchronously from multiple systems—the two terms are not synonymous. Network physiology uses multimodal methods to collect data, but goes further by connecting the dots between the various systems.

A study by a team of researchers from the University of New York and the University of Houston demonstrated how combining data from different body systems can give a more complete picture of how the brain and body work together, specifically in response to music and mental effort. The study explored how different types of music—either calming or exciting—affect a person’s working memory (the ability to retain and use information for short periods) and overall brain and body arousal. During the experiment, participants completed memory tasks while listening to either calming or exciting music. Researchers collected detailed data from the body using a set of BIOPAC sensors and electrodes, including general-purpose electrodes for gathering electrocardiogram (ECG) signals, a respiratory effort transducer, a wireless skin temperature sensor, a wireless pulse transducer for photoplethysmogram (PPG) data, and electrodes to measure electrodermal activity (EDA), blood flow in the finger, and muscle activity in the shoulders. These multimodal signals were gathered using a BIOPAC data acquisition and analysis system. The data was collected at 2 kHz to capture even small changes in the body’s responses. The research team found that while the difficulty of the memory tasks didn’t significantly impact arousal levels, the type of music did. Exciting music helped participants feel more alert and even improved their performance on some tasks.

A 2024 South Korean study investigated how the autonomic nervous system (ANS) responds differently to social pain (such as emotional distress from losing a loved one) versus physical pain (like discomfort from a pressure cuff). Researchers used a BIOPAC 16-channel data acquisition and analysis system running AcqKnowledge software to collect a range of signals from 73 healthy young adult participants. The following signals were gathered synchronously using a variety of sensors and transducers: ECG electrodes placed on both wrists and the left ankle to monitor heart activity, EDA sensors attached to the index and middle fingers to assess skin conductance (indicating stress levels), PPG sensor on the thumb to measure blood volume changes, chest-wrapped sensor to track breathing patterns, and a temperature sensor on the ring finger to monitor peripheral temperature changes. Participants experienced social pain via a 60-second grief-themed film clip and physical pain through a blood pressure cuff inflated to 250 mmHg. Social pain increased heart rate and skin conductance, while lowering blood volume pulse, pulse transit time, breathing rate, and finger temperature, reflecting a mix of sympathetic and parasympathetic nervous system activity. Physical pain, on the other hand, raised heart rate variability and skin conductance, reduced blood volume pulse and pulse transit time, but left finger temperature unchanged, suggesting activation of the body’s stress response system. These distinct patterns show how different types of pain trigger unique responses across interconnected body systems.

A multimodal approach was employed in a study by researchers from several institutions including the University of Southern California, University of California, Irvine, Rutgers University, Vanderbilt University, and Wayne State University School of Medicine to examine how daily heart rate variability (HRV) biofeedback training influences brain function, emotional regulation, and physiological responses in both younger and older adults. In the study, 193 participants were randomly assigned to either increase or decrease their heart rate oscillations through daily biofeedback sessions over five weeks. Before and after the intervention, participants underwent various assessments, including MRI scans, psychological evaluations, and sleep monitoring using wristband sensors. During the MRI sessions, physiological data such as blood pressure, pulse, respiration (using a BIOPAC MRI-safe respiration transducer and module), and end-tidal CO₂ were continuously recorded. During stress tasks, blood pressure and hemodynamic measurements were taken using a noninvasive blood pressure monitor and transferred to a BIOPAC data acquisition and analysis system. The study’s findings suggest that HRV biofeedback can positively impact both brain function and physiological health, highlighting the interconnected nature of bodily systems, a central concept in network physiology.

These are just a few examples of how network physiology is being applied in research today. For more information on the topic, including links to related webinars, citations, and events, see our Network Physiology applications page.

Are you planning to integrate a range of signals for your next network physiology study? Our customer service specialists can help identify the best equipment and strategies for the synchronous collection of high-quality multimodal data.

A Heartbeat Away: HRV Unlocks Autonomic Insights

The beating of the heart holds the key to a myriad of physiological questions that are of interest to researchers. The measured variation in time intervals between consecutive heartbeats, otherwise known as Heart Rate Variability (HRV), provides valuable insights into the activity of the autonomic nervous system, reflecting the balance between sympathetic and parasympathetic influences on the heart.

HRV allows researchers to assess cardiac health, stress levels, and overall autonomic function, making it an invaluable component of physiological studies to investigate numerous areas such as cardiovascular health, mental health, stress, and exercise physiology to name just a few.

A recent study applied HRV to examine the effectiveness of yoga and Ayurveda, a form of alternative medicine traditionally practiced in India and Nepal, to regulate and treat lymphedema. Lymphedema is tissue swelling caused by an accumulation of protein-rich fluid that’s usually drained through the body’s lymphatic system. Because lymph drainage has been connected to autonomic function, researchers postulated that HRV would provide meaningful insight into the effectiveness of yoga and Ayurveda programs in treating lymphedema. A BIOPAC two-channel BSL data acquisition system was employed to gather HRV and respiration data of participants who underwent an intensive regimen of yoga exercise, limb soaking, herbal baths, and manual lymph drainage. Initial comparisons of HRV data between both the test and control groups showed significant improvement in the lymphedema patients following treatment.

In many cases, researchers choose to combine HRV with other signals to provide a more detailed picture of a participant’s autonomic response to stimuli. A 2020 study sought to identify an effective noninvasive measure of how the sympathetic nervous system (SNS) responds to stimuli. Typically, such measurements involve the invasive recording of muscle sympathetic neural activity at the peroneal nerve. This study examined HRV and electrodermal activity (EDA), both separately and in combination, to see which provided the most effective measurement of SNS activity. Researchers measured participants’ SNS response to both a cold-pressor test (submerging hand in ice water) and while viewing emotionally challenging video images. Throughout both tests, continuous ECG and EDA signals were acquired and analyzed using a BIOPAC four-channel data acquisition system. An ECG100C and EDA100C were used to acquire the ECG and EDA signals, respectively. From their results, researchers concluded that the combination of HRV and EDA provided a better metric for SNS activity than HRV alone.

Whether alone or in combination with other signals, HRV offers researchers a powerful tool for measuring how the autonomic nervous system responds to a wide range of stimuli and conditions with applications across a broad spectrum of fields. Visit our Webinars page for multiple examples of how HRV is being used in research and check our HRV citations as well.

Are you designing a study that features HRV? BIOPAC’s regional sales reps can help you access the right tools for the job to ensure the best possible results. Contact us today!

Body Electric: Bioimpedance in Physiology Research

With nearly 70 percent of our bodies made up of water as well as a variety of dissolved salts, humans are natural conductors of electrical current. However, various elements of the human body restrict or impede the flow of electrical current, a phenomenon termed “bioimpedance.” Variations in restrictiveness to the flow of electrical current through an organism can provide researchers with a wealth of information on a range of physiological conditions.

Bioimpedance can be defined as the response of an organism to an externally applied electrical current. For more than a century, researchers have used bioimpedance as a safe and noninvasive metric for a range of physiological data, from measuring body composition through bioimpedance analysis (BIA) to investigating various biological systems such as cardiovascular function via impedance cardiography.

While not new, breakthroughs in technology and techniques for recording and analyzing bioimpedance have made it increasingly accessible to researchers. Through impedance cardiography and cardiac output, researchers gain access to a wide range of cardiovascular and hemodynamic data, including heart rate (HR), cardiac output (CO), acceleration index (AI), mean blood pressure (MBP), stroke index (IA), stroke volume (SV), and systemic vascular resistance, to name just a few.

The recent development of trans-radial electrical bioimpedance velocimetry (TREV) has provided researchers with a heightened level of accessibility when attempting to record high-quality data. Unlike traditional transthoracic methods of recording impedance cardiography signals, TREV measures blood movement through the radial and ulnar arteries of the forearm. The approach streamlines electrode placement, making it less prone to complications associated with other impedance cardiography methods.

One example of the practical application of impedance cardiography is in research on stress as it relates to coronary health. A 2019 study published by researchers at the University of Illinois at Urbana-Champaign compared the stress response of a group of young participants to that of participants over the age of 55 who had been diagnosed with coronary artery disease (CAD). Researchers recorded physiological signals, including electrocardiogram (ECG), impedance cardiogram (ICG), and continuous BP during rest, stress, and recovery. ECG and ICG signals were collected using BIOPAC BN-NICO wireless amplifiers and BN-EL50-LEAD4 leads. Researchers found ICG provided a reliable metric for stress response.

Recently, a team from the University of California, Santa Barbara (UCSB) employed TREV to demonstrate how this newer bioimpedance metric can be used to track event-related contractility in a maximal grip force experiment. The experiment employed TREV electrodes attached to the participant’s forearm and amplified by a NICO100D smart amplifier. Additionally, ECG electrodes were amplified by an ECG100D while the respiration cycle was recorded via a TSD221-MRI respiration belt. All data signals were acquired and analyzed using an MP160 system running AcqKnowledge software. The experiment confirmed the effectiveness of TREV as a reliable metric for connecting the cardio-sympathetic drive to other physiological conditions, such as force production.

While not new to physiological research, the application of bioimpedance continues to flourish and evolve. To learn more about how bioimpedance is being applied in the research setting as well as new techniques, check out BIOPAC’s webinar on bioimpedance and cardiac output focusing on TREV.

To learn more about incorporating impedance cardiography and TREV in your study, contact your regional BIOPAC sales representative today.

T4 Conference Wrap-up

August is a month of barbecues, baseball, and last-minute vacations against the backdrop of a fading summer, and the eighth month of 2019 proved to be an equally exciting time at BIOPAC, with something of a pleasant vacation thrown in. On August 12-14, BIOPAC hosted its 2nd Biennial “Tools, Trends, Techniques, and Technology” Human Physiology Conference, known as “T4” to our friends and partners around the world. This three-day event, first held in 2017, featured lively, informative sessions hosted by BIOPAC staff, partners, noted academics, and industry experts, and covered a wide range of physiological techniques and disciplines. Over 150 attendees joined BIOPAC at the 2019 T4 Conference staged once again at the beautiful University of California at Santa Barbara campus. Participants and instructors winged in from China, Australia, Germany, Sweden, Italy, Spain, U.K., Ireland, and Egypt, as well as from wide regions of the U.S and Canada to soak up the idyllic surroundings of this ocean-side campus.

The focus of BIOPAC’s T4 Conference was to provide a fun, relaxed environment while hosting nearly 40 hands-on, human physiology training workshops chaired by over 20 distinguished instructors from around the globe. One of the many conference highlights was the “Mindfulness, Meditation, and Measurement: Mindfulness Exercises in Physiological Monitoring” session, hosted by Dr. Allan Weiss of the University of Southern California and BIOPAC Co-founder and Director of R & D Alan Macy. These sessions, conducted in two parts over a two day period were booked beyond capacity, even though the early morning fog hadn’t yet lifted from the campus skyline.

The varied additional sessions covered a range from the basics, “Setting Up Your Lab, Getting Great Data and Troubleshooting,” (hosted by Dr. Terry Blumenthal of Wake Forest University, and BIOPAC’s Alan Macy and Tim Cook), and “Creating Your Own Lessons Using BSL PRO,” (hosted by Dr. Taffeta Elliot of the New Mexico Institute of Mining and Technology), to exciting new technologies such as “Integrating Screen-based Eye Trackers with AcqKnowledge,” with Keith Jackson of BIOPAC partner company EyeTech, BIOPAC CEO Frazer Findlay, and BIOPAC Engineering Manager Ed Peterlin. Additional wide-ranging physiological disciplines were also covered, including MRI techniques, stimulation, and exercise physiology. All sessions were conducted using BIOPAC hardware and software systems, as well as platforms provided by BIOPAC partners such as Cedrus, fNIR, WorldViz, Psychology Software Tools, and CNSystems. At the end of each day, it was time to relax and unwind with a beverage of choice, a a walk along the beach, and some good conversation. Each evening featured excellent meals and camaraderie in the relaxed yet elegant environment of some of Santa Barbara and Goleta’s most stunning surroundings. After three great days of immersive sessions, it came time for everyone to part ways, having forged new collaborative partnerships and an enhanced knowledge about the full potential of BIOPAC and BIOPAC partner products.

You don’t have to wait for T4 2021 to learn more about life science data—watch Fundamentals of Physiological Data Recording now!

For a closer look at T4, and a preview of what is sure to be an exciting 2021 event, we invite you to visit our T4 Human Physiology Conference page.

Looking for additional resources, tips, tricks, and expert advice on BIOPAC and BIOPAC Partner products? Please also visit our Webinars and Video Tutorial pages.

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.

Stressing over the effects of stress

Several studies show chronic stress is typically detrimental to health, while acute stress may be linked to positive effects in addition to the negative counterparts

With April comes National Stress Awareness Month, and it bears noting that different types of stress have varying effects. Where chronic stress is typically detrimental to health, acute stress may be linked to positive effects in addition to the negative counterparts. But is this trade-off worth it?

In a biological psychology experiment testing the effect of oxytocin on acute social stress, researchers found different results between men and women. Subjects underwent several stress tasks while their electrocardiography and impedance cardiography were recorded with a BIOPAC MP Research System and amplifiers. The researchers found that after being given oxytocin during the stressful event, men had less negative affect and women had greater math performance (compared to the control group).

A neurobiology study examined the effect stress had on an extinction memory process when a competing association was paired with a previously aversive cue. To test this, participants were presented with two images, one that was paired with a shock from a BIOPAC bar electrode, and one that was not. Extinction memory training immediately followed this stimulus, with extinction retrieval testing following a day later. Data gathered by a BIOPAC data acquisition system suggested significantly lower retrieval in the group that experienced the acute stress stimulus.

Another biopsychology experiment measured the effect of acute stress on pro-inflammatory cytokine levels in the blood. BIOPAC equipment was used to measure ECG while participants were given the Trier Social Stress Test. After reviewing the data and blood samples, the researchers determined that levels of the cytokine cell, interleukin-1β, increased significantly immediately after the stress test.

The physiological and psychological impacts of stress are clearly multifaceted with many potential results. In some situations, a heightened positive affect or greater analytical thinking may be beneficial. But is this boost in mental performance worth the increase of inflammatory cells and lower memory retention? As with many aspects of life, moderation is the safest answer, ensuring the negative effects do not become chronic problems.

For more information on BIOPAC’s wide range of tools for recording, displaying, and analyzing ECG measurements from human and animal subjects including respiration, heart rate variability, and RSA, visit BIOPAC’s electrocardiography pages and view BIOPAC’s full line of electrodes, amplifiers, and wearable, wireless transmitters and loggers.

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.

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 .

CNAP HD: Noninvasive Hemodynamic Monitoring in Research

Cardiac Output (CNCO® ) and further essential hemodynamic parameters calculated from the continuous non-invasive arterial pressure curve (CNAP®) by means of the Pulse Contour Analysis shows high accuracy and high trending ability (precision) compared to invasive clinical standards (e.g. thermodilution and PiCCO) with valuable benefit for scientific and clinical research.

By Dr. Jürgen Fortin, CEO, CNSystems

Pulse Contour Analysis (PCA) for deriving complete Hemodynamics from continuous blood pressure wave (CNAP)

Pulse Contour Analysis (PCA)[1] derives important physiological information on preload, contractility, afterload and compliance of the heart from the well validated CNAP^® Continuous Noninvasive Arterial Pressure Curve[2]^,[3]. By adding biometric patient data Stroke Volume (SV) and therefrom Continuous Noninvasive Cardiac Output (CNCO^®), both essential hemodynamic markers, are calculated. Further hemodynamic parameters such as Systemic Vascular Resistance (SVR) as well as all indexed values SI, CI or SVRI are derived completing the hemodynamic picture.

Validation: CNCO^® is clinically validated against invasive methods

Non-invasive continuous CNCO^® is the non-invasive continuous cardiac output calculated from CNAP^® Arterial Pressure as described above.

Accuracy of CNCO^® compared to clinical standards such as invasive thermodilution (TD) or PiCCO is expressed as percentage error. In 1999, Critchley and Critchley suggested a percentage error of 30% or less[4]. In clinical practice, however, percentage errors of 40-45% are more realistic for the interchangeability between two CO-measurement methods (meta-analysis by Peyton and Chong[5]).

Trending ability is the precise tracking of changes in CO. According to Critchley, Lee and Ho, reliable trending ability[6] is indicated by concordance rates of > 90%. Vincent and colleagues state that following hemodynamic trends may be more important than absolute values[7].

CNCO^® shows both high accuracy as well as high trending ability (precision) compared to the invasive clinical standards thermodilution and PiCCO fulfilling all Critchley criteria:

Bland-Altman plots show

Small bias and narrow limits of agreement
Percentage errors ≤ 30% (according to strict Critchley standard [8]^,[9])
Concordance rates ≥ 90% (according to standard [10])

Read more on CNAP accuracy here and here.

Benefit of continuous BP, CO & SVR in research (examples)

Blood pressure, cardiac output and vascular resistance are used to differentiate between challenge and threat states (positive and negative stress)[11]^,[12] and to quantify emotional response[13] in psychophysiological studies. A challenging situation causes a far bigger rise in cardiac output than a threating state. Total peripheral resistance rises in threat state but shows strong decrease in the challenging situation.

CNCO^® is available with the CNAP^® HD feature, currently only available in Europe.

For more information on CNAP, to include references to studies and research and plots, click here.

[1] https://en.wikipedia.org/wiki/Cardiac_output#Pulse_Pressure_methods
[2] 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
[3] Biais, M. et. al. Continuous non-invasive arterial pressure measurement: Evaluation of CNAPTM device during vascular surgery Ann Fr Anesthesia
[4] Critchley, L. A., & Critchley, J. A. (1999). A meta-analysis of studies using bias and precision statistics to compare cardiac output measurement techniques. Journal of clinical monitoring and computing, 15(2), 85–91
[5] Peyton PJ, Chong SW: Minimally invasive measurement of cardiac output during surgery and critical care. Anesthesiology 2010; 113:1220-35

[6] Critchley LA, Lee A, Ho AMH: A critical review of the ability of continuous cardiac output monitors to measure trends in cardiac output. Anesth Analg 2010; 111:1180-92.

[7] Vincent JL et al.: Clinical review: Update on hemodynamic monitoring – a consensus of 16. Critical Care 2011, 15:229.

[8] Critchley, L. A., & Critchley, J. A. (1999). A meta-analysis of studies using bias and precision statistics to compare cardiac output measurement techniques. Journal of clinical monitoring and computing, 15(2), 85–91

[9] Peyton PJ, Chong SW: Minimally invasive measurement of cardiac output during surgery and critical care. Anesthesiology 2010; 113:1220-35.

[10] Critchley LA, Lee A, Ho AMH: A critical review of the ability of continuous cardiac output monitors to measure trends in cardiac output. Anesth Analg 2010; 111:1180-92.

[11] Kirby, L. D., & Wright, R. A. (2003). Cardiovascular correlates of challenge and threat appraisals: A critical examination of the Biopsychosocial Analysis. Personality and Social Psychology Bulletin, 7, 216-233.

[12] Tomaka, J., Blascovich, J., Kelsey, R. M., & Leitten, C. L. (1993). Subjective, physiological, and behavioral effects of threat and challenge appraisal. Journal of Personality and Social Psychology, 65, 248-260.

[13] Lackner, H. K., Weiss, E. M., Schulter, G., Hinghofer-Szalkay, H., Samson, A. C., & Papousek, I. (2013). I got it! Transient Cardiovascular Response to the Perception of Humor. Biological Psychology, 93, 33–40.

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 (MRI and small animal applications are also supported) and related equipment for a wide variety of research applications .