Blood pressure measurement

Blood pressure measurement Observation of blood pressure allows dynamic tracking of pathology and physiology affecting to the cardiovascular system, which has profound effects to all other organs of the body High value increases the risk of heart attack and strokes Low value increases the risk of lower oxygen perfusion e.g. in brains However, the ’normal values’ differ from person to another Values should be lower than 120 / 80 mmHg (systolic pressure (SP) / diastolic pressure (DP)) Mean pressure (MP) average pressure during one cardiac cycle driving force of the peripheral perfusion. an estimate can be done by using an empirical formula: SP and DP may vary significantly throughout the arterial system but MP is quite uniform (in normal situations) Pulse pressure (PP) = SP-DP MP = DP+PP/3

Blood Pressure Classification BP classification SBP (mmHg) DBP (mmHg) Normal <= 120 And <= 80 Prehypertension 121 – 139 Or 81-89 Stage 1 Hypertension 140 – 159 Or 90 – 99 Stage 2 >= 160 Or >= 100

Blood Flow in our body Devices: Aneroid. Mercury. Electronic.

Measurements in Blood 1 3 2 4 Blood Pressure Blood Flow Ultrasound Doppler Palpatory Method (Riva-Rocci Method) 3 Laser Doppler Flowmetry Auscultatory Method Strain Gage Plethysmography Non-Invasive Ultrasonic Method Electric-Impedance Plethysmogr. Oscillometric Method Photoelectric Plethysmography Tonometry Thermal Convection Probes 2 4 Extravascular Sensor Dye Dilution Method Invasive Intravascular Sensor Thermal Dilution Method General on System Parameters Radioisotopes

Measurement of BP in the clinic patient must be seated in a chair with arm support on both sides. The setting should be quiet and relaxed. It must be easy to adjust the height of the arm so that the middle of the cuff is at heart level (at the 4th intercostal space).

Indirect Methods in Blood Pressure Measurements Indirect measurement = non-invasive measurement Brachial artery is the most common measurement site Close to heart Convenient measurement Other sites are e.g.: forearm / radial artery wrist (tends to give much higher SP) The most common indirect methods are auscultation and oscillometry

Korotkoff’s method: Putting a cuff around the upper part of the arm(veins are not occluded) While air is leaked from the cuff, the korotkoff’s sounds are picked by a special piezoelectric sensor. Amplified, bandpass filtered More errors

Rheographic method: 3 electrodes B electrode is common electrode – mid line A and C placed at a distance from B A high frequency current passes through A and C. Impedance between these two elctrodes are measured.

Rheographic method:

Palpatory Method (Rheographic Method) An occlusive cuff is placed on arm and inflated to Pcuff > SP. Then the cuff is deflated gradually and the measurement of blood flow is done The occlusive cuff should be of a correct size in order to transmit the pressure to the artery evenly and thus to obtain accurate results A short cuff requires special attention in placement. Longer cuff reduces this problem. The cuff should be placed at the heart level in order to minimize the hydrostatic effects When the cuff is deflated, there is a palpable pulse in the wrist. Pcuff = BP Several measurements should be done as the respiration and vasomotor waves modulate the blood pressure levels ADVANTAGES The blood pressure can be measured in noisy environment too Technique does not require much equipment DISADVANTAGES Only the systolic pressure can be measured (not DP) The technique does not give accurate results for infants and hypotensive patients

Differential Asculatory method: A pair of pressure sensitive element acts as an electrode. Systolic: first opening of the artery occurs Diastolic: relaxed state of blood flow.

Differential Asculatory method:

Differential Asculatory method:

Oscillometric measurement: Advanced than ausculatory method. No need of microphone Oscillometric pulses are generated in the cuff during inflation or deflation

Oscillometric measurement:

Oscillometric measurement:

Ultrasonic Doppler shift method: Arterial movement produces the Doppler frequency shift. λc= Vc / fc λc = wavelength (in m) of carrier frequency in the medium Vc = velocity of the carrier frequency in the medium (1480 m/sec in water) fc = carrier frequency in the medium

Ultrasonic Doppler shift method:

Ultrasonic Doppler shift method:

Direct method

Features: Highest degree of accuracy Dynamic response Invasive Catheter tube. A steady flow of sterile saline is passed through the catheter to prevent blood clotting. Blood samples can be taken

Set up of direct method of BP measurement:

During measurement:

The actual pressure sensor can be e.g. Extravascular Sensor The ’normal’ measuring system The sensor is located behind the catheter and the vascular pressure is transmitted via this liquid-filled catheter. The actual pressure sensor can be e.g. strain gage, variable inductance, variable capacitance, optoelectronic, piezoelectric, etc… The hydraylic link is the major source of errors. The system’s natural frequency may be damped and degraded due (e.g.):

Blood Flow O 2 Blood Flow Blood Pressure ECG O and other nutrition concentration in the cells are one of the primary measurements. 2 2 Blood flow helps to understand basic physiological processes and e.g. the dissolution of a medicine into the body. Blood Flow It also helps to understand many pathological conditions, since many diseases alter the blood flow. Also the blood clots in the arterial system can be detected. Blood Pressure Usually the blood flow measurements are more invasive than blood pressure measurements / ECG ECG

Blood Flow (2) Normal blood flow velocity 0,5 m/s – 1 m/s (Systolic, large vessel)

Heart Sounds LUB----------DUB We have all heard the heart make the usual sounds. LUB----------DUB Lub is the first sound or S1 Dub is the second heart sound or S2

Systole The time between the S1 and S2 sounds is: Lub------------Dub The ventricles contracting Blood flowing from the heart to the lungs and body Blood flowing across the Pulmonic and Aortic valves

Diastole Dub----------Lub The time between S2 and S1 is : The blood is flowing from the atria to the ventricles. The blood flowing across the bicuspid and tricuspid valves. The atrial contraction also occurs now.

S1 – First Heart Sound (LUB) This sound is primarily because of the closing of the bicuspid and tricuspid valves. Anatomically they are located between the atria and the ventricles They close because the ventricles contract The Pulmonic and Aortic valves are opening and blood is being forced into the arteries

S2 – Second Heart Sound (DUB) The sounds are because of the closing of the Pulmonic and Aortic valves as the pressure from the arteries is greater then the pressure in the ventricles. This is the end of systole

S3 – Third Heart Sound also called a protodiastolic gallop, ventricular gallop caused by Rapid ventricular filling. It occurs at the beginning of diastole after S2. The third heart sound is benign in youth, some trained athletes, and sometimes in pregnancy The commonest causes are left ventricular failure and mitral regurgitation It is best heard with the bell-side of the stethoscope at the apex of the heart .

S4 – Fourth Heart Sound called a presystolic gallop or atrial gallop. This gallop is produced by the sound of blood being forced into a stiff/hypertrophic ventricle. It is a sign of a pathologic state, (left ventriclular hypertrophy, hypertension, aortic stenosis) It is best heard with the bell-side of the stethoscope at the apex of the heart .