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NonInvasive Monitoring of Vital Signs and Traumatic Brain Injuries
Published in Alexander D. Poularikas, Stergios Stergiopoulos, Advanced Signal Processing, 2017
Stergios Stergiopoulos, Andreas Freibert, Jason Zhang, Dimitrios Hatzinakos
Blood pressure and heart rate are critical vital signs to health care practitioners. Measurements are taken under various conditions, from routine check-ups to emergency evacuations. The blood pressure technique, which is the golden standard by health care practitioners, is the auscultatory method that incorporates a stethoscope and a mercury sphygmomanometer and consists of three basic steps that are schematically illustrated by the following three figures. During the first step, as shown in Figure 16.17, the cuff is inflated to a level one would consider higher than the systolic pressure. The artery is occluded and blood flow is stopped, therefore the artery is still silent. The pressure vs. time illustrated in Figure 16.17 shows the pressure in the cuff during the period that the cuff deflates. As the cuff pressure is slowly deflated (i.e., Step 2, Figure 16.18) a point is reached where the cuff pressure equals the systolic blood pressure. When blood begins to jet through the compressed brachial artery, the turbulent flow is audible due to friction of the blood at the artery wall, as the artery opens while the cuff pressure changes. The audible vibrations created from the artery walls are called the Korotkoff sounds [12,13]. Once the deflated cuff’s pressure reaches the person’s diastolic blood pressure, the artery is widely open. Then, the flow of blood in the brachial artery becomes laminar and smooth, and the Korotkoff sounds disappear. The moment that the last audible Korotkoff sound is heard by the health care practitioner, a person’s diastolic blood pressure is defined (i.e., Step 3, Figure 16.19).
Introduction to Noninvasive Medical Measurements
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
NI medical instruments can be broadly classified between those passive systems that put no energy into the body, and those that input some form of radiation energy, for example, microwaves, visible and UV light, x-rays, γ-rays, sound and ultrasound, and measure what energy is either absorbed, reflected, or transmitted at different wavelengths or frequencies. Among the purely passive systems, we have the well-known electrical measurements based on active nerve and/or muscle membranes. These include time-varying electrical potentials recorded from the skin surface from the heart (ECG), brain (EEG), muscles (EMG), ears (electrocochleogram [ECocG]), and eyes (EOG and ERG). Sounds from the body's interior can also be recorded from the skin surface, including sounds from the heart valves, pericardium (friction rub), blood vessels (bruit), lungs, bronchial system, pleural cavity, eardrums (spontaneous otoacoustic emissions), joints, etc. Body temperature can be sensed from the infrared radiation from the eardrum, or by physically measuring the temperature of the saliva and tissues under the tongue, or the temperature in the rectum by a liquid-in-glass thermometer, or a thermometer based on a thermistor or platinum resistance element (resistance temperature detector [RTD]). Tissue oxygen and carbon dioxide partial pressures (pO2 and pCO2) can be measured transcutaneously with special chemical electrodes. The only energy put in by endoscopes is white light required to visualize or photograph the tissue being inspected. Blood pressure can be measured noninvasively by Korotkoff sounds emitted by the brachial artery as the pneumatic pressure in a sphygmomanometer cuff is slowly reduced, allowing blood to surge into an artery.
Blood Pressure Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Shyam Rithalia, Mark Sun, Roger Jones
The auscultatory method most commonly employs a mercury column, an occlusive cuff, and a stethoscope. The stethoscope is placed over the blood vessel for auscultation of the Korotkoff sounds, which defines both SP and DP. The Korotkoff sounds are mainly generated by the pulse wave propagating through the brachial artery [4]. The Korotkoff sounds consist of five distinct phases. The onset of phase I Korotkoff sounds (first appearance of clear, repetitive, tapping sounds) signifies SP, and the onset of phase V Korotkoff sounds (sounds disappear completely) often defines DP [5].
Biomedical invasive pressure sensor coatings: calibration and waveform perspectives
Published in Journal of Medical Engineering & Technology, 2020
Q. Qananwah, W. Al-Zyoud, A. Al-Zaben
There are two methods of blood pressure measurements. The first one is non-invasive (indirect) blood pressure measurements, and the second one is invasive (direct) blood pressure measurements. The majority of non-invasive blood pressure devices are automated and rely on an experimentally resultant algorithm based on the oscillometric method. In most of the above devices, cuff occlusion is placed on the brachial artery in the upper arm closer to the heart, and not prone to the external noise. Auscultation of the Korotkoff sounds through electronics devices or sphygmomanometer is used to register systolic blood pressure and diastolic blood pressure. Reflective waves and impedance mismatch phenomena were observed when variations in a registered systolic pressure of 120 mmHg reached a variety of up to 125 mmHg and down to 110 mmHg among different devices, especially when measurements were on distal parts, such as the wrist [5]. The phenomena mentioned above were minimised by using plethysmography principle-based sensors, ultrasonic microphone sensors, and sensors to detect the velocity signal of pulse-wave [6].
Estimation of arterial pressure through cuffs constructed from different fabrics using simulation modelling
Published in The Journal of The Textile Institute, 2023
Shenela Naqvi, Prasad Potluri, Parthasarathi Mandal, Philip Lewis
During the cuff deflation, pressure inside the cuff was recorded at following three different conditions of fluid flow through rubber tube. All five phases of sounds for auscultatory method are discussed below.During blood pressure measurement, phase 1 of Korotkoff’s sounds is the indication of systolic blood pressure. This is the point when blood starts to reflow in brachial artery during cuff deflation manoeuvre. The five phases of Korotkoff’s sounds were detected through the observer’s auditory acuity. While in this study, the inside-cuff pressure at which glycerine solution just appeared in downstream of artificial artery can be considered as the highest value of arterial pressure (Systole) and termed as PsC.When the glycerine solution started to move drop by drop and partial reflow was resumed in artery during cuff deflation manoeuvre at this point, the cuff pressure was termed as PpC. This might speculatively be considered equivalent to Korotkoff’s phase 4 .This phase is also important if phase 5 goes to zero (Kim et al., 2004).The cuffs were kept deflating till full reflow of glycerine solution resumed in artery as when it was flowed before cuff inflation. At that point inside-cuff pressure was termed as PfC. This point might be considered equivalent to the diastole or phase 5 of Korotkoff sound when they disappear.
Auscl-D: a mercury-free digital auscultatory sphygmomanometer
Published in Journal of Medical Engineering & Technology, 2021
Vishal Kumar, Ravinder Kumar, Mohit Kumar, Gurpreet Singh Wander, Ashish Sahani
The device should ideally be mounted on to the cuff that will provide a clear view path to the clinicians. After the person sits comfortably on the chair, the cuff is fastened around to the brachial artery. Clinician places the stethoscope over the brachial artery near the elbow. The small handheld air pump (bulb) having air release valve attached to the cuff is used to apply the pressure above the expected SBP level. No pulsations are heard through the stethoscope at this point. After this, the clinician carefully looks for the Korotkoff sounds through the stethoscope while the pressure in the cuff is slowly released. The very first Korotkoff sound heard, i.e., K1 marks the systolic pressure and the last sound K5 marks the diastolic pressure [25].