Deep learning-based robust automatic non-invasive measurement of blood pressure using Korotkoff sounds

This paper proposes a method that automatically measures non-invasive blood pressure (BP) based on an auscultatory approach using Korotkoff sounds (K-sounds). There have been methods utilizing K-sounds that were more accurate in general than those using cuff pressure signals only under well-controlled environments, but most were vulnerable to the measurement conditions and to external noise because blood pressure is simply determined based on threshold values in the sound signal. The proposed method enables robust and precise BP measurements by evaluating the probability that each sound pulse is an audible K-sound based on a deep learning using a convolutional neural network (CNN). Instead of classifying sound pulses into two categories, audible K-sounds and others, the proposed CNN model outputs probability values. These values in a Korotkoff cycle are arranged in time order, and the blood pressure is determined. The proposed method was tested with a dataset acquired in practice that occasionally contains considerable noise, which can degrade the performance of the threshold-based methods. The results demonstrate that the proposed method outperforms a previously reported CNN-based classification method using K-sounds. With larger amounts of various types of data, the proposed method can potentially achieve more precise and robust results.

Retrospective Observational Single-Center Study of Complications of Arterial Indwelling Catheters for Invasive Blood Pressure in Intensive Care Unit Patients

This study aimed to analyze the incidence of complications resulting from the use of an indwelling arterial catheter (IAC). We compared the characteristics of the patients with an IAC who developed complications with those who did not present any complications. The study included 1,869 patients with an IAC hospitalized in intensive care units (ICUs) between 2017 and 2018. Most patients were male (58.7%), in the seventh decade of life, and had systemic arterial hypertension. The most common site of IAC implantation was the radial artery. Fifty-four (2.88%) cases of complications related to an IAC were identified including bleeding, hematomas, and thrombosis. Female patients had a higher risk of complications ( P = .030). Comorbidities such as arrhythmias ( P < .001) and peripheral arterial disease ( P = .041) also increased that risk. The use of vasoactive drugs ( P = .001), hemodialysis ( P = .001), and orotracheal intubation (OTI) ( P = .001) was significantly associated with the occurrence of complications as well as length of stay in ICUs ( P < .001) and IAC duration ( P = .001). IACs are safe devices commonly used in ICUs, with an incidence of complications of 2.88%.

PTT-based Contact-less Blood Pressure Measurement using an RGB-Camera

Commonly used blood pressure measurement devices have noticeable limitations in accuracy, measuring time, comfort or safety. To overcome these limitations, we developed and tested a surrogate-based, non-invasive blood pressure measurement method using an RGB-camera. Our proposed method employs the relation between the pulse transit time (PTT) and blood pressure. Two remote photoplethysmography (rPPG) signals at different distances from the heart are extracted to calculate the temporal delay of the pulse wave. In order to establish the correlation between the PTT values and the blood pressure, a regression model is trained and evaluated. Tests were performed with five subjects, where each subject was recorded fifteen times for 30 seconds. Since the physiological parameters of the cardiac system are different for each person, an individual calibration is required to obtain the systolic and diastolic blood pressure from the PTT values. The calibration results are limited by the small number of samples and the accuracy of the reference system. However, our results show a strong correlation between the PTT values and the blood pressure and we obtained a mean error of 0.18 +/- 5.50 mmHg for the diastolic blood pressure and 0.01 +/- 7.71 mmHg for the systolic pressure, respectively.

Artefacts in continuous overnight blood pressure assessment based on pulse transit time

Continuous non-invasive blood pressure measurements bear a high potential. Particular in Somnology they allow to derive comfortably the systolic and diastolic blood pressure from an electrocardiogram and a synchronous photoplethysmogram without sleep disruption. In this short article some possible problems of this method are discussed along overnight recordings with a SOMNOtouch NIBP device.