Corsano Vital Parameters

The software in the CardioWatch 287-2 System generates Vital Parameters with Corsano proprietary algorithms established within the Corsano Bracelet and Cloud as well managing unadjusted measurements with external devices.

Corsano Algorithm summary

The Firmware running on the Corsano Bracelet measures raw data of the PPG, Accelerometer and Temperature sensors and runs algorithms to compute the vital parameters:

• Pulse Rate
• Oxygen Saturation
• Respiration Rate
• NIBP (requires Corsano Cloud)
• Temperature
• Activity

Pulse Rate principal of operation

The Corsano Bracelet utilizes a Photoplethysmography (PPG) sensor that consists of Light Emitting Diodes (LEDs) and photodiodes to capture reflected light. PPG is a commonly used in determining Pulse Rate (BPM), Oxygen Saturation (SpO2) and Respiration Rate (RR).
The working principle of the PPG sensor is based on the emission of LED light which penetrates the skin and blood vessels. This light is then reflected and captured by the photodiodes in Corsano Bracelet to measure the blood stream.
The results of the PPG signal depend primarily on the flow of blood to the capillary vessels in each heartbeat. The waveform of the PPG signal indicates the changes in pulsatile blood flow from which the detection of signal peaks allows the calculation of peak-to-peak intervals. By determining the peak-to-peak distances between two subsequent PPG pulses, the algorithm derives the Pulse Rate of the patient.
The accelerometer (ACC) is utilized to compensate for movement artifacts. PPG and ACC are measured at 32Hz and data is processed by the algorithm to give a new reading of Pulse Rate every 28 seconds utilizing averaging to smooth pulse rate data and prevent inappropriate and transient artifacts from affecting stability of results.

Pulse Rate Specification

Spo2 principal of operation

Corsano Bracelet utilizes the Photoplethysmography (PPG) sensor photodiodes to capture reflected light calculates the patient’s oxygen saturation (SpO2) using pulse oximetry, a non-invasive technique to monitor oxygenation. It monitors the percentage of hemoglobin that is oxygen-saturated. The working principle is spectrophotometry: the relative absorption of red (absorbed by deoxygenated blood) and infrared (absorbed by oxygenated blood) light of the systolic component of the absorption waveform correlates to arterial blood oxygen saturations. Two light-emitting diodes, red with wavelength of 660 nm and infrared with a wavelength of 880 nm, are positioned so that they are opposite their respective photodiodes through 5-10 mm of tissue. Absorption of light at these wavelengths differs significantly between blood loaded with oxygen and blood lacking oxygen. Oxygenated hemoglobin absorbs more infrared light and allows more red light to pass through. Deoxygenated hemoglobin allows more infrared light to pass through and absorbs more red light. The accelerometer (ACC) is utilized to compensate for movement artifacts. Measurements of relative light absorption and ACC are measured at 32Hz and data is processed by the algorithm to give a new reading of SpO2 every 28 seconds utilizing averaging to smooth SpO2 data and prevent inappropriate and transient artifacts from affecting stability of results.

Spo2 Specification

The following shows correlation and Bland-Altman between CardioWatch 287-2 and the Nellcor PM10 from the non-invasive study (N=94572)

Correlation and Bland-Altman SpO2 vs Nellcor PM10

Respiration rate principal of operation

The Respiration Rate is the number of breaths a person takes per minute (RR). Corsano Bracelet utilizes a proprietary time-frequency algorithm to extract the respiratory-induced intensity, amplitude and frequency variation signals from the photoplethysmography (PPG) signal.

Respiration Rate Specification

Cuffless NIBP

Advanced photoplethysmography (PPG) signal analysis extracts the characteristics of the reflection waveforms. They are then fed to an artificial intelligence (AI) model. Thus, the model can predict systolic and diastolic blood pressure values.

The Corsano Bracelet makes use of the PPG sensor, which includes the emission of light by LEDs to the skin and the measurement of reflected light by photodiodes. The PPG signal is strongly dependent on the amount of light that is absorbed by the arterial blood in the tissue and reflectance on arterial/arteriole blood flow. As such, the PPG signal contains a pulsatile component that fluctuates with the blood volume changes in the peripheral tissue introduced during each cardiac cycle. This waveform contains information that is either directly or indirectly related to blood pressure. By extracting this information from the waveform and comparing it to previously acquired data from patients’ datasets, a prediction is made of blood pressure. The Corsano Bracelet extracts information from 6 simultaneously acquired waveforms, combining 3 wavelengths, 6 LEDs and 2 photodiodes.

From the PPG segments, features are extracted, which are used in the Machine learning model. To get a valid prediction, a combination of statistical features, time and frequency domain features, demographic features, first/second derivative features, width related PPG features and features from the PPG signal are used.

The Corsano CardioWatch 287-2 System was validated against the harmonized standard ISO 81060-2:2019 and AAMI/ESH/ISO collaboration statement "A Universal Standard for the Validation of Blood Pressure Measuring Devices" 2018. for Non-Invasive Blood Pressure measurement devices, in a clinical investigation on 97 subjects.

Correlation between Corsano Non-Invasive Blood Pressure measurement and the reference (Invasive measurement, Fysicon)

Bland-Altman plot comparing the Corsano Non-Invasive Blood Pressure measurement and the reference (Invasive measurement, Fysicon)

Non-Invasive Blood Pressure Specification

Corsano NIBP under HIIT Exercise

Correlation Predicted DIA & SYS during High Intensity Interval Training (HIIT)

ECG

The Corsano CardioWatch 287-2 Bracelet implements a 1-lead electrocardiographic (ECG) system featuring electromagnetic interference (EMI) filtering, internal lead biasing, right-leg drive and lead-off detection. 

The system is composed of 3 electrodes. Two electrodes are located on the case back of the Bracelet, contacting the wrist skin through dry contacts. They are the positive ECG electrode and the right-leg electrode. The right-leg electrode enables to increase the rejection of noise and common-mode signals. The third electrode is the metal frame on the top of the Bracelet. This is the negative ECG electrode.

The patient must wear the Bracelet on one wrist and touch the top frame with the other hand to enable the ECG system to measure the electrical heart signal flowing from one arm to the other.

ECG Electrodes and signal

The electrodes are internally connected to the low noise and high-performance ECG circuit comprising the latest generation of analog front-end (AFE) integrated circuits. The electronics layout implements noise reduction and immunity techniques to achieve the performances required by medical standards. The ECG circuit measures the heart electrical signal and rejects noise and common-mode signals, thanks to analogue and digital filters and right-leg drive. Lead-off detection enables to verify the proper contacts of electrodes and improves the usability of the Bracelet.

The Corsano CardioWatch 287-2 ECG system was validated according to the harmonized standard EN-IEC 60601-2-47:2015 for performance and safety of ambulatory ECG systems. The tests were performed by the accredited laboratory Kiwa Dare in Woerden, NL.

ECG Specification

Skin temperature principal of operation

Corsano Bracelet monitors skin temperature in direct mode from a sensor in the wearable device. Skin temperature is presented in °C, or in °F as configured in Settings/Profile.

Skin Temperature Specification

The accuracy of Corsano Bracelet temperature measurement was determined by the testing laboratory VDE Prüf- und Zertifizierungsinstitut GmbH, Offenbach, Germany in accordance with ISO 80601-2-56 - Medical electrical equipment Part 2-56: Particular requirements for basic safety and essential performance of clinical thermometers for body temperature measurement.

Core Body temperature principal of operation

CBT is one of the most relevant vital parameters to assess the state of the human body. Many processes in the human body are closely linked to CBT. However, CBT is also one of the most difficult parameters to monitor continuously and non-invasively.

A heat flux sensor in combination with PPG allows for reliable continuous monitoring of CBT as reported in prior scientific articles.

CardioWatch 287-2 integrates a heatflux sensor from GreenTeg and we combine its data with PPG derived BPM to improve accuracy.

CBT was validated versus electronic pills as a reference to assess the accuracy of the device and the algorithm. CardioWatch 287-2 raw measurement values were recorded during a clinical study with volunteers that were vaccinated for Covid, about half got a fever. Their body temperature was subsequently recorded and plotted against the temperature reference. The sensor signals were algorithmically combined to yield a single temperature output per day while at the same time compensating for physiological thermoregulation. The CBT algorithm is self-calibrating, meaning, after a certain calibration time, the algorithm will automatically determine several system parameters. From this moment on CBT can be calculated using these parameters. Following Bland-Altmann-plots represent the standard deviation from values to its reference.

Correlation CBT vs BodyCap ingestible CE Certified connected pill

Core Body Temperature Specification

Steps

Bland Altman Corsano Steps vs Actigraph

Note : the Activity (Steps) parameter is considered a software function intended to monitor and record daily energy expenditure and cardiovascular workout activities to allow awareness of one’s exercise activities to improve or maintain good cardiovascular health.

Conclusion / Claims

Given the bench and clinical testing, the following claims will be made: