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BLOOD FLOW METER
(Blood perfusion rate meter)

Quantitative, non invasive blood flow rate monitoring by heat washin / heat washout.

 

The principle

The principle of the heat washin / heat washout method is to use heat as an indicator for blood flow. This is made possible by eliminating the heat loss to or the heat uptake from the surrounding air by a thermostatically controlled cap keeping the same temperature as the measuring disc in contact with the skin surface. A 2 to 5 °C change in temperature is introduced into the tissue in contact with the probe by heating or cooling.

After a steady state temperature is obtained the heating or cooling is interrupted and the temperature change in time is registered. These temperature values are corrected for the baseline temperature as measured in the steady state before cooling or heating and in the steady state when the temperature has returned to normal. A fine adjustment of the baseline temperature value can be made manually in 0.01 °C intervals.

The temperature washin / washout curves follow a monoexponential function equal to the blood flow rate. It is a quantitative measure of blood flow rate as verified by the 133Xenon washout method.

Calculation of an average value between the measured values by heat washin and heat washout, using an equal increase and decrease in temperature, gives an estimate of the blood flow rate during undisturbed conditions.

 

Display

The display shows the temperature of the measuring disc in contact with the tissue surface.

Analysis

Data analysis are performed in a computer connected to the apparatus.

 

Applications

A drop of contact fluid is placed on the skin surface and the measuring probe is fixed on the place by adhesive tape or with a double adhesive ring shaped tape.

The equipment is suitable for quantitative measurements of skin blood flow rates in clinical and

physiological research, in diagnostic work and in therapeutic control measurements.

It gives a possibility for measuring blood flow rate in skin areas without arterio-venous anastomoses and also in areas with arterio-venous anastomoses as present in fingers, toes, nose and ear lobes. This is due to the extremely high diffusion coefficient for heat in tissue being 100 times faster than for gasses. This gives the possibility for a fast equilibration of heat between tissue and blood not only in a capillary bed but also in areas with vessels having dimensions as great as arterio-venous anastomoses.

The measuring principle has been used since 1995. A correlation of heat washout data was found to those of the quantitative 133Xenon washout method in simultaneous experiments.

The correlation coefficient was 0.986 in these experiments.

Examples of areas for clinical use are: clinical research, routine clinical use in diagnostic work, and in control of therapeutic effect. This is of interest in the following groups of patients: skin diseases, white fingers, burn and cold injuries, diabetes mellitus, peripheral arterial and venous diseases. Furthermore, in supervision of patients: prematures, children, during anaesthesia, and intensive care, in heart diseases, thyrotoxicosis, and myxoedema, in skin grafts, during surgery, and after transplantation of organs.

The probe can be placed in a sterilized plastic tube foil when used during surgery.

An area of special interest is the temperature regulation research where it is possible to include the regulation of the blood flow rate in the arterio-venous anastomoses, an area of great importance in exercise physiology.

 

Analysis and output of data

The equipment can be programmed to perform repeated measurements automatically for supervision of patients.

The computer yields possibilities for further calculations and analysis, storage of data, and printout of graphs and tabulated results.

 

Blood Flow Meter Specifications

Quality control operates at all stages of manufacture.

Reliability is underlined by a two year warranty comprising mecanical and electric inefficiency occured by normal use.

Safety complies with international safety requirements demanded in new patient equipment.

 

Temperature measurement

Range: ± 5 °C.

 

Resolution

0.1 °C, accuracy: 0.1 °C.

 

Sampling rate

5 seconds time intervals

 

Output

The analog output from the measuring probe is converted by an interface, PICO®, ADC-16 to a digital output to the computer.

 

Software

WindowsTM based control, processing and analysis.

Data rate: per 5 seconds.

Trends: data review.

 

General

Power supply: 220 V, 50 Hz.

Dimension: W H D mm: 142×123×250.

Weight: 2.3 kg.

Operating temperature:15-30 °C.

The apparatus is tested according to UL EN 60601-1 and 60601-1-2

 

 

References to the heat washin/washout principle

Midttun M., Sejrsen P. & Colding-Jørgensen M. (1996) Heat-washout: a new method for measuring cutaneous blood flow rate in areas with and without arteriovenous anastomoses. Clin Physiol, 16, 259-274.

Midttun M. & Sejrsen P. (1996) Blood flow rate in arteriovenous anastomoses and capillaries in thumb, first toe, ear lobe, and nose. Clin Physiol, 16, 275-289.

Midttun M., Sejrsen P. & Paaske W.P. (1997) Blood flow rate during orthostatic pressure changes in the pulp skin of the first toe. Eur J Vasc Endovasc Surg, 13, 278-284.

Midttun M. & Sejrsen P. (1998) Cutaneous blood flow rate in areas with and without arteriovenous anastomoses during exercise. Scand J Med Sci Sports, 8, 84-90.

Midttun M., Sejrsen P. & Paaske W.P. (1999) Peripheral blood flow rates and microvascular responses to orthostatic pressure changes in claudicants before and after revascularisation. Eur J Vasc Endovasc Surg, 17, 225-229.

Midttun M., Sejrsen P. & Paaske W.P. (2000). Is non-specific aneurysmal disease of the infrarenal aorta also a peripheral microvascular disease? Eur J Vasc Endovasc Surg, 19, 625-629.

Midttun M. (2000) Blood flow rate in arteriovenous anastomoses: from the cradle to the grave. Clin Physiol, 5, 360-365.

Midttun, M. (2004) Thesis. Heat Washout: A New Method for Measuring Blood Flow Rate in Areas with and without Arterioveneous Anastomoses

Midttun, M. (2006) Poster presentation at the: "4.th Congress of the European Union Geriatirc Medicine Society, Geneva, Switzerland".

"Toe blood flow rate - a better way of controlling peripheral circulation in your diabetes patients". Conclusion: In these diabetic patients peripheral blood pressure is an insufficient measure of the pathological condition of the disease, as the measured peripheral blood pressure was not found correlate with the peripheral blood flow rate. 

 Hove, J., Rosenberg, I., Secher, N. H., Hove, K. (2006) Article accepted for publication in: "Clinical Physiology and Functional Imaging":

"Supraorbital cutaneous blood fow rate during carotid endarterevtomy". Conclusion: It is possible to optain an indirect measure of cerebral blood flow rate by measuring cutaneous blood flow rate in the supraorbital region medially by the heat washout method, as the cutaneous tissue in this region is supplyed with blood  via a side branch from the internal carotid artery. 

In this investigation simultaneous measurements were done with the near infrared spectroscopy (NIRS )in the forehead. The results obtained by this method showed a very small difference between two large walues. The NIRS-method, measures the reflection of near infrared light from the erythrocytes within the vessels in the tissue. Thus the NIRS-method yields a relative measure of the amount of erythrocytes in the tissue and is therefore not a measure of blood flow rate neither in the cutaneous tissue or in the brain.

 Midttun, Sejrsen, Paaske (2006) Article accepted for publication in: "Angiology": "Smokers have severely disturbed peripheral circulation", by Mette Midttun, Per Sejrsen, and WilliamPaaske.

Conclusion: Smokers, smoking less than 20 cigarettes per day, showed during smoking of one cigaret, a reduction of a factor of 2.6 in the blood flow rate in arteriovenous anastomoses in the finger pulps. 

In heavy smokers, smoking more than 20 cigarettes per day, blood flow rate was found unchanged in the arteriovenous anastomoses during smoking of one cigaret.

The capillary blood flow rate measured by the 133-Xenon washout method was more than twice as high as in non smokers in both groups.

A high capillary blood flow rate may be due to a degeneration of the elastic fibres in in the wall of the arteioles of smokers.       

 Midttun, M. (2006) Poster presentation at a meating for practising physicians in Korsør, Denmark:

"Toe blood flow rate - a better way of controlling peripheral circulationin your diabetes patients", by Mette Midttun

Conclusion: In these diabetic patients peripheral blood pressure is an insufficient measure of the pathological condition of the disease, as the measured peripheral blood pressure was not found correlated with the peripheral blood flow rate. 

Management:

Per Sejrsen, Chairman of the Board, M.D.

Frederiksborgvej 139 A

DK 4000 Roskilde

Tel. +45 4636 9251

E-mail: sejrsen@dadlnet.dk

Henrik Kruckow, CEO, M.Sc. economics

Kruckow.com

Møllebakken 3

DK 3200 Helsinge

Tel. +45 4871 2061

E-mail: mail@kruckow.com