Chapter 5 Part Three Blood Pressure and flow by Ibrhim AlMohimeed BMTS /3/2013

BMTS 3532 Blood Flow 12/3/2013 Blood flow helps to understand basic physiological processes and e.g. the dissolution of a medicine into the body. Blood flow and changes in blood volume, are usually correlated with concentration of nutrients and other substance in the blood. Also, Blood Flow measurement reflects the concentration of O 2.

BMTS 3533 Cont. Blood Flow 12/3/2013 Normal blood flow velocity 0,5 m/s 1 m/s (Systolic, large vessel)

BMTS 3534 Blood Flow Measurement 12/3/2013 Blood Pressure

BMTS 3535 Ultrasonic Doppler Method 12/3/2013 Blood Pressure The blood cells in the fluid reflects the ultrasound signal with a shift in the ultrasonic frequency due to its movement. In the recent years ultrasound contrast agents have been used in order to increase the echoes. f = 2 – 10 MHz c c = m/s (1540 m/s) f = 1,3 – 13 kHz d

BMTS 3536 Cont. Ultrasonic Doppler Method 12/3/2013 Blood Pressure CW DOPPLERPULSED DOPPLER Range ambiguity Low flow cannot be detected No minimum range Simpler hardware Minimum range Accuracy No minimum flow (Maximum flow) x (range) = limited The ultrasound Doppler device can be either a continuous wave or a pulsed Doppler

BMTS 3537 Laser Doppler Flowmetry 12/3/2013 Blood Pressure The principle of measurement is the same as with ultrasound Doppler. The laser parameter may have e.g. the following properties: 5 mW He-Ne-laser 632,8 nm wavelength The method is used for capillary (microvascular) blood flow measurements.

BMTS 3538 Plethysmography Method (Strain Gage) 12/3/2013 Blood Pressure Plethysmography means the methods for recording volume changes of an organ or a body part. Strain gage is made of silicone rubber tubes, which are filled with conductive liquid (e.g. mercury) whose impedance changes with volume. Venous occlusion cuff is inflated to 40 – 50 mmHg. In this way there will be the arterial inflow into the limb but no venous outflow.

BMTS 3539 Plethysmography Method (Electric-Impedance) 12/3/2013 Blood Pressure Different tissues in a body have a different resistivity. Blood is one of the best conductors in a body. A constant current is applied via skin electrodes. The change in the impedance is measured. The accuracy is often poor.

BMTS Plethysmography Method (Photoelectric) 12/3/2013 Blood Pressure A beam of IR-light is directed to the part of the tissue which is to be measured for blood flow (e.g. a finger or ear lobe). The blood flow modulates the attenuated / reflected light which is recorded. The light that is transmitted / reflected is collected with a photo detector. Poor measure for changes in volume Very sensitive to motion artefacts Method is simple Heart rate is clearly seen

BMTS Blood Flow Measurement 12/3/2013 Blood Pressure

BMTS Indicator Dilution Methods (Dye Dilution) 12/3/2013 Blood Pressure A bolus of indicator, a colored dye (indocyanine green), is rapidly injected in to the vessel. The concentration is measured in the downstream The blood is drawn through a colorimetric cuvette and the concentration is measured using the principle of absorption photometry.

BMTS Indicator Dilution Methods (Thermal Dilution) 12/3/2013 Blood Pressure A bolus of chilled saline solution is injected into the blood circulation system (right atrium). This causes decrease in the artery temperature. Catheter-tip probes are used to measure the change in tempreture.

End of the Chapter 12/3/2013BMTS 35314