- Email: [email protected]
Laser doppler flowmetry. A new non-invasive measurement of microcirculation in intensive care?
Resuscitation,
12 (1984)
31-39
31
Elsevier Scientific Publishers Ireland Ltd.
LASER DOPPLER FLOWMETRY. A NEW NON-INVASIVE MEASUREMENT OF MICROCIRCULATION IN INTENSIVE
JEAN MICHEELS,
BJARNE ALSBJORN
Dept. of Anesthesiology, of Plastic Surgery and (Denmark)
CARE?
and BENT SORENSEN
H6pitaJ de Bavidre, University of LiSge (Belgium) and Dept. Bums Unit, Hvidovre Hospital, University of Copenhagen
(Received July 25th, 1983)
---SUMMARY
Laser doppler flowmetry (LDF) is a new non-invasive technique by which microcirculation changes in tissue can be studied. In recent papers, this technique has been used to measure microflow in standardized fluid models, in animals and in human clinical situations. LDF utilizes the doppler shift, i.e. the frequency (wave length) change that light as well as all waves undergo being reflected by moving objects such as, e.g. red blood cells. A beam of low power laser light (2 mW He-Ne at 632.8 nm) is led by an optical fibre to a measuring head. From here it enters the tissue to which it is applied by a hemisphere with a 1 mm radius. Blood cells traversing this volume are struck by the light and reflect it, whereby the light undergoes a doppler shift. The surrounding tissue also reflects the light, but in an unshifted manner. Thus the volume of illumination is a mixture of an unshifted and a doppler shifted component, the magnitude and frequency of the latter being related to the number of moving cells and their velocity. The measured microflow is proportional to an arbitrary scale (0 to 10). Our own experience with some applications in human clinical situations is described: -
Normal Normal Patient Patient
skin in a control group. skin and burned area in burned patients. in hypothermia with general anesthesia. in shock.
LDF seems to be an interesting new non-invasive technique, supplying a good definition of the skin microflow. In the future, this technique could be one of the non-invasive techniques used for intensive care, defining the microcirculation state of a patient. Address all correspondence and reprint requests to: Doct. Liege, Hbpital de Baviere, Service d’Anesth&iologie, 66, Liege, Belgium.
Jean Micheels, Universiti! de bd. de la Constitution. 4020
0300-9572/84/$03.00 o 1984 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
32 INTRODUCTION
Sepsis remains one of the major causes of death in intensive care units. For this reason, non-invasive techniques are fields of research leading to better control, and to manage the patients better without risk of contamination. Another reason to try to avoid invasive methods is to avoid disturbing or changing the parameter to be measured. That is especially true about the microcirculation. In the human clinical situation, there am now many routine techniques in competition to define microcirculation non-invasively: thermography with a thermographic camera; electro-optic techniques. The principle is to compute the spectral analysis of reflected light from the tissues (Afromowitz and Heimbach, 1979); for many years, authors have used PO, sensors. Cutaneous PO, monitoring is still one way to measure microflow in tissues; ‘33Xe clearance is used to define washout and thus, the microflow from a limited area of tissues. Only epicutaneous techniques are really non-invasive, since injections of labelled Xe could change the measured microflow (Sejrsen, 1968, 1971); “Heating power” is also used: the quantity of heat required to maintain a constant temperature in a sensor in close contact with the explored tissue reflects its microflow; Laser Doppler Flowmetry (LDF) is one of the recent techniques used to define microcirculation (Stern, 1975; Holloway and Watkins, 1977). LDF permits repetitive measurements without any discomfort to the patient. In addition, this measurement is not related to the PaO, or cutaneous PO, changes. This technique is not influenced by heat exchange or by evaporative water loss. The temperature of the target does not influence the measurements. Those advantages could be of great interest in the human clinical situation. PATIENTSANDMETHODS
The principle is to measure the doppler shift, i.e. the frequency change (wave length) that light waves undergo when they are reflected by moving objects such as red blood cells (Fig. 1). A beam of low power laser light (2 mW He-Ne at 6323 nm) is led by an optical fibre to a measuring head. From here it enters the tissue to which it is applied by a hemisphere with a 1 mm radius. Blood cells traversing this volume am struck by the light and reflect it, whereby the light undergoes a doppler shift. The surrounding tissue also reflects the light, but in an unshifted manner. Thus, the volume of illumination is a mixture of an unshifted and a doppler shifted component, the magnitude and frequency of the latter being related to the number of moving cells and their velocity. The measured microflow is proportional to an arbitrary scale. The basic principle is the same as in all doppler instrumentation, but the originality in this particular method is that monochromatic light from a low
33
Photo detector
Extracted Doppler Signal
/ Laser /
/
Optical Fibres-
LASER DOPPLER FLOWMETRY
( LDF)
Fig. 1. Schematic description of laser doppler flowmeter.
power laser is used. The Periflux PFId (Perimed, Sweden) was used (Nilsson, Teland and Oberg, 1980). A thermostat probe holder supplying a defied temperature (26--44”(Z) has been used in close contact with the target (Fig. 1). A functional test has been carried out in each measured point by applying a topical temperature load with the thermostat probe holder (42°C for 2 min), in this way creating maximum possible vasodilatation. We thus recorded firstly the microflow in a comfortable environmental temperature, and secondly, the microflow after topical load of temperature, and we measured the physiological ability to vasodilate. We used an arbitrary scale of flow from 0 to 10. We decided in human clinical situation to define preferential reference points. We explored these points in a group of 5 volunteers (38 points) and in different patients. During this first evaluation, we avoided using areas in the face, hands and feet, because those areas have very particular changes in their microcirculation. We compared those microflow values to microfl w measurements in reference points of!a patient in shock and of another e patient in hypothermia with general anesthesia. In burned patients, we measured the microflow of different kinds of bums and reference points of normal skin in each patient.
34 RESULTS
Reference group Figure 2 shows typical records of different reference points in the same volunteer. The temperature load test (2 min, 42°C) shows typical physiological vasodilatation ability. We have demonstrated that there were no significant differences between the values found at points on one person (intrapatient), or between the total number of volunteers (inter-patient) (Threeside variances analysis). For these preferential reference points in the control group of volunteers resting in the comfortable environmental conditions of 29°C with a relative humidity of 50%, we demonstrated that those measurements could be reproduced with good significance. Patient in shock Table I shows the comparison between the values of a patient in the control group and those of a patient in shock. This patient in clinical shock L DF - RECORD TOPICAL T* LOAD (42’C,
Zmin.)
FIOW 10 -
s
0
1
2:
1
20
1
20
1
2 Min.
Fig. 2. LDF records in the same volunteer:
functional
tests with topical temperature
load.
35 TABLE I COMPARISON BETWEEN CONTROL (UNHEATED SKIN AND TEMPERATURE
GROUP AND LOAD TEST)
PATIENTS
IN
SHOCK
LDF Patient in shock (n = 10)
Control group (n = 38)
Unheated skin
0.6 + 0.1 (S.E.M.)
1.4 + 0.12 (SEM)
Heated skin (42”C, 2 min)
0.6 + 0.1 (S.E.M.)
5.1 ?I 0.12 (S.E.M.)
Arbitrary Scale 0 to 10. 4 kHZ.
shows a very low flow without the ability to increase this flow to the topical temperature test. The problem is not, of course, to demonstrate that patients in shock are in vasoconstriction, but to demonstrate the ability of LDF to define microcirculation in well-known pathophysiological conditions. Patient in hypothermia with anesthesia This example (Table II) shows measurements of a specific physiopathological situation. This patient was in hypothermia with general anesthesia. We know that in this particular situation, despite hypothermia, those patients are in vasodilatation. LDF shows these microflows very well. This is a high flow in comparison with the control group and we demonstrate a very good ability to increase this microflow using the topical temperature test, more than with the control group. Burned areas The optimal goal of measuring microflow in burned areas is to use it for prediction (Micheels, Alsbjom and Sorensen, 1984). It is of great interest to TABLE II COMPARISON BETWEEN CONTROL GROUP AND PATIENTS IN HYPOTHERMIA WITH ANESTHESIA (UNHEATED SKIN AND TEMPERATURE LOAD TEST) LDF
Unheated skin Heated skin (42°C
2 min)
Arbitrary Scale 0 to 10. 4 kHZ.
Patient in hypothermia with anesthesia (Core T : 34°C)
Control group
5.8 + 0.87 (S.E.M.)
1.4 + 0.12 (S.E.M.)
7.4 + 1.33 (S.E.M.)
5.1 +0.12
(Core ‘I“ : 36.9”C)
(S.E.M)
36
be able to measure microflow in doubtful areas and thus be able to decide, at an early stage, if grafting must take place or not. We present here only preliminary results, since evaluation in a clinical situation of a bums unit is still going on. Figure 3 shows LDF records from an epidermal bum. On the first day, the patient had a high microflow with poor ability to vasodilate. After a few days, the same area had a normal evolution of microflow, and the normal ability to vasodilate to the temperature test had been restored. On the other hand, in clinically and histologically defined third degree subdermal burns, we demonstrated low flow. The majority of these burns were characterized by microflow lower than than the unheated skin values with a total inability to vasodilate on applying topical temperature load. Figure 4 shows this low flow in comparison with the normal skin of the same patient. Figure 5 shows records from a burned area defined as “deep dermal” by the clinical team and as “superficial dermal” by the pathologist. What about LDF? Day 1 shows a quite important microflow, without any ability to vasodilatation after the topical temperature load test. Day 12 shows a similar picture, but with a slight decreased flow. Figure 6 shows records from another burned area, also defined as “deep dermal” by the clinical team and as “superficial dermal” by the pathologist. Day 1 shows an increased flow in LDF_RECORD
@
Flow
MY1
0 1-
DAY 2-
1
20
1
LDF-RECORD
NORMALSKIN FIOW
EPIDERMAL BURN (I’)
SUBDERMALBURN
2
Mtn.
Fig. 3. Epidermal bum: same area on day 1 and day 2. Day 2 shows normalization with temperature load test. Fig. 4. Normal skin and subdermal bum in the same patient.
@
LDF-RECORD CLINICAL TEAM z DEEP MRMAL BURN HlsTolDGV =suPERFlclAL DERMM BLHW
flow lo
WA
9
6 7
6 5 4 3 2 1 0
Fig. 5. Example of doubtful
bum; same area on day 1 and day 12.
LDF-RECORD @ CLINICAL TEAM t DEEP DERMAL BURN HISTOLDGV= SUPERFICIAL DERMAL BURN Flow DAVl . ..Mu 1 q-T--? : I ! I I
0
1
2
Min.
Fig, 6. Example
of doubtful
bum; same area on day 1 and day 12.
37
38
this area without the possibility of any temperature load effect. Day 12 shows a more increased flow and a small possibility of increasing this flow using the temperature load test. These two pathological evolutions reflected by LDF records are different. We have seen an example of difference between clinical and histological diagnosis. The third aspect in the case is the LDF result. We are now investigating this, in order to add the LDF results more precisely to the doubtful situations of burned areas. DISCUSSION
Laser doppler flowmetry is a new non-invasive technique by which microcirculation changes in tissue can be studied. In recent papers, this technique has been used to measure microflow in standardized fluid models, in animals and in human clinical situations: recording of blood microflow in the fomarm skin at different contact pressures between skin and probe; studying the effect of skin temperature on finger circulation; the contralateral vascular response to cold stimuli, and the effect of deep inspiration on the peripheral circulation (Nilsson, Teland and Oberg 1980); recording the skin blood flow in allergy patch tests (Nilsson, in press); measuring the testis blood flow when norepinephrine was administrered intravenously in rat; the bone blood flow in the jaw of the pig when vasopressin was administered (Nilsson, in press); examining the rhythmic vasoconstriction in human skin (Salarud, Nilsson, Teland and Oberg, 1981); studying the effect of alternating magnetic fields on the blood flow in peripheral circulation in the human body (Veno, Kall, Lovsund and Oberg, 1981); the use of Nipride in dog (Eberhard, Mindt and Schafer, 1983); comparison between the 133Xe washout technique and LDF in human volunteers (Kristensen and Engelhardt, 1983); the clinical use in a burns unit (Micheels, Alsbjorn and Sorensen, 1984). Our own experience using LDF with control group, with burned patients, with shock and with hypothermia and anesthesia leads us to believe that this non-invasive technique is easy to use, and measures microflow in the intenssive care unit, without bacteriological problems. The following technical problems remain to be solved: calibration, since we are currently using an arbitrary scale; artefacts, created by the movements of the patient, leads to the selection of comprehensive patients. Nevertheless, we conclude that, in the future, this technique could be one of the interesting non-invasive techniques used in intensive care, for defining the state of the microcirculation in patients. REFERENCES Afromowitz, M.A. and Heimbach, D.M. (1979) Electra-optic bum depth indicator. Proceedings on XII International Conference on Medical and Biological Engineering, Jerusalem, August, 19-24, 10.1.
39
Eberhard, P., Mindt, N. and Schafer, R. (1983) Reliability of methods for skin blood flow measurement during cutaneous PO, monitoring. In: Continuous Transcutaneous Blood Gas Monitoring, Editors: R. Huch and A. Huch. Marcel Dekker. Kristensen, J.K. and Engelhardt, M. (1983) Evaluation of cutaneous blood flow responses by ’“Xenon washout and a laser-doppler flowmeter. J. Invest. Dermatol., 80, 12-l 5. Holloway, G.A. and Watkins, D.N. (1977) Laser doppler measurement of cutaneous blood flow. J. Invest. Dermatol., 69, 3, 306. Micheels, J., Alsbjom, B. and Sorensen, B. (1984) Clinical use of laser doppler flowmetry. Stand. J. Plast. Reconstr. Surg., in press. Nilsson, G.E., Teland, T. and Oberg, A. (1980) Evaluation of a laser doppler flowmeter for measurement of tissue blood flow. IEEE Trans. Biomed. Eng., BME 27, 1. Salarud, G., Nilsson, G.E., Teland, T. and Oberg, P.A. (1981) Rhythmic vasomotion in human skin studied by laser doppler flowmetry. Proceedings of the 5th Nordic Meeting on Med. and Biol. Eng., Linkiiping, and 25th Anniversary Swedish Sot. for Med. Eng., Umea, Sweden, 216. Sejrsen, P. (1968) A traumatic local labelling of skin by inert gas, epicutaneous application of Xenon-133. J. Appl. Physiol., 24, 570. Sejrsen, P. (1971) Measurement of cutaneous blood flow by freely diffusible radioactive isotopes. Thesis, Copenhagen, 1971. Dan. Med. Bull,, Suppl. 18. Stern, M.D. (1975) In vivo evaluation of microcirculation by coherent light scattering. Nature, 254, 56. Veno, Sh., Kall, T., Lovsund, A. and Oberg, P.A. (1981) The effect of alternating magnetic fields on the blood flow in peripheral circulation in the human body. Proceedings of the 5th Nordic Meeting on Med. and Biol. Eng., Linkoping, and 25th Anniversary Swedish Sot. for Med. Eng., Umea, Sweden, 265.
12 (1984)
31-39
31
Elsevier Scientific Publishers Ireland Ltd.
LASER DOPPLER FLOWMETRY. A NEW NON-INVASIVE MEASUREMENT OF MICROCIRCULATION IN INTENSIVE
JEAN MICHEELS,
BJARNE ALSBJORN
Dept. of Anesthesiology, of Plastic Surgery and (Denmark)
CARE?
and BENT SORENSEN
H6pitaJ de Bavidre, University of LiSge (Belgium) and Dept. Bums Unit, Hvidovre Hospital, University of Copenhagen
(Received July 25th, 1983)
---SUMMARY
Laser doppler flowmetry (LDF) is a new non-invasive technique by which microcirculation changes in tissue can be studied. In recent papers, this technique has been used to measure microflow in standardized fluid models, in animals and in human clinical situations. LDF utilizes the doppler shift, i.e. the frequency (wave length) change that light as well as all waves undergo being reflected by moving objects such as, e.g. red blood cells. A beam of low power laser light (2 mW He-Ne at 632.8 nm) is led by an optical fibre to a measuring head. From here it enters the tissue to which it is applied by a hemisphere with a 1 mm radius. Blood cells traversing this volume are struck by the light and reflect it, whereby the light undergoes a doppler shift. The surrounding tissue also reflects the light, but in an unshifted manner. Thus the volume of illumination is a mixture of an unshifted and a doppler shifted component, the magnitude and frequency of the latter being related to the number of moving cells and their velocity. The measured microflow is proportional to an arbitrary scale (0 to 10). Our own experience with some applications in human clinical situations is described: -
Normal Normal Patient Patient
skin in a control group. skin and burned area in burned patients. in hypothermia with general anesthesia. in shock.
LDF seems to be an interesting new non-invasive technique, supplying a good definition of the skin microflow. In the future, this technique could be one of the non-invasive techniques used for intensive care, defining the microcirculation state of a patient. Address all correspondence and reprint requests to: Doct. Liege, Hbpital de Baviere, Service d’Anesth&iologie, 66, Liege, Belgium.
Jean Micheels, Universiti! de bd. de la Constitution. 4020
0300-9572/84/$03.00 o 1984 Elsevier Scientific Publishers Ireland Ltd. Printed and Published in Ireland
32 INTRODUCTION
Sepsis remains one of the major causes of death in intensive care units. For this reason, non-invasive techniques are fields of research leading to better control, and to manage the patients better without risk of contamination. Another reason to try to avoid invasive methods is to avoid disturbing or changing the parameter to be measured. That is especially true about the microcirculation. In the human clinical situation, there am now many routine techniques in competition to define microcirculation non-invasively: thermography with a thermographic camera; electro-optic techniques. The principle is to compute the spectral analysis of reflected light from the tissues (Afromowitz and Heimbach, 1979); for many years, authors have used PO, sensors. Cutaneous PO, monitoring is still one way to measure microflow in tissues; ‘33Xe clearance is used to define washout and thus, the microflow from a limited area of tissues. Only epicutaneous techniques are really non-invasive, since injections of labelled Xe could change the measured microflow (Sejrsen, 1968, 1971); “Heating power” is also used: the quantity of heat required to maintain a constant temperature in a sensor in close contact with the explored tissue reflects its microflow; Laser Doppler Flowmetry (LDF) is one of the recent techniques used to define microcirculation (Stern, 1975; Holloway and Watkins, 1977). LDF permits repetitive measurements without any discomfort to the patient. In addition, this measurement is not related to the PaO, or cutaneous PO, changes. This technique is not influenced by heat exchange or by evaporative water loss. The temperature of the target does not influence the measurements. Those advantages could be of great interest in the human clinical situation. PATIENTSANDMETHODS
The principle is to measure the doppler shift, i.e. the frequency change (wave length) that light waves undergo when they are reflected by moving objects such as red blood cells (Fig. 1). A beam of low power laser light (2 mW He-Ne at 6323 nm) is led by an optical fibre to a measuring head. From here it enters the tissue to which it is applied by a hemisphere with a 1 mm radius. Blood cells traversing this volume am struck by the light and reflect it, whereby the light undergoes a doppler shift. The surrounding tissue also reflects the light, but in an unshifted manner. Thus, the volume of illumination is a mixture of an unshifted and a doppler shifted component, the magnitude and frequency of the latter being related to the number of moving cells and their velocity. The measured microflow is proportional to an arbitrary scale. The basic principle is the same as in all doppler instrumentation, but the originality in this particular method is that monochromatic light from a low
33
Photo detector
Extracted Doppler Signal
/ Laser /
/
Optical Fibres-
LASER DOPPLER FLOWMETRY
( LDF)
Fig. 1. Schematic description of laser doppler flowmeter.
power laser is used. The Periflux PFId (Perimed, Sweden) was used (Nilsson, Teland and Oberg, 1980). A thermostat probe holder supplying a defied temperature (26--44”(Z) has been used in close contact with the target (Fig. 1). A functional test has been carried out in each measured point by applying a topical temperature load with the thermostat probe holder (42°C for 2 min), in this way creating maximum possible vasodilatation. We thus recorded firstly the microflow in a comfortable environmental temperature, and secondly, the microflow after topical load of temperature, and we measured the physiological ability to vasodilate. We used an arbitrary scale of flow from 0 to 10. We decided in human clinical situation to define preferential reference points. We explored these points in a group of 5 volunteers (38 points) and in different patients. During this first evaluation, we avoided using areas in the face, hands and feet, because those areas have very particular changes in their microcirculation. We compared those microflow values to microfl w measurements in reference points of!a patient in shock and of another e patient in hypothermia with general anesthesia. In burned patients, we measured the microflow of different kinds of bums and reference points of normal skin in each patient.
34 RESULTS
Reference group Figure 2 shows typical records of different reference points in the same volunteer. The temperature load test (2 min, 42°C) shows typical physiological vasodilatation ability. We have demonstrated that there were no significant differences between the values found at points on one person (intrapatient), or between the total number of volunteers (inter-patient) (Threeside variances analysis). For these preferential reference points in the control group of volunteers resting in the comfortable environmental conditions of 29°C with a relative humidity of 50%, we demonstrated that those measurements could be reproduced with good significance. Patient in shock Table I shows the comparison between the values of a patient in the control group and those of a patient in shock. This patient in clinical shock L DF - RECORD TOPICAL T* LOAD (42’C,
Zmin.)
FIOW 10 -
s
0
1
2:
1
20
1
20
1
2 Min.
Fig. 2. LDF records in the same volunteer:
functional
tests with topical temperature
load.
35 TABLE I COMPARISON BETWEEN CONTROL (UNHEATED SKIN AND TEMPERATURE
GROUP AND LOAD TEST)
PATIENTS
IN
SHOCK
LDF Patient in shock (n = 10)
Control group (n = 38)
Unheated skin
0.6 + 0.1 (S.E.M.)
1.4 + 0.12 (SEM)
Heated skin (42”C, 2 min)
0.6 + 0.1 (S.E.M.)
5.1 ?I 0.12 (S.E.M.)
Arbitrary Scale 0 to 10. 4 kHZ.
shows a very low flow without the ability to increase this flow to the topical temperature test. The problem is not, of course, to demonstrate that patients in shock are in vasoconstriction, but to demonstrate the ability of LDF to define microcirculation in well-known pathophysiological conditions. Patient in hypothermia with anesthesia This example (Table II) shows measurements of a specific physiopathological situation. This patient was in hypothermia with general anesthesia. We know that in this particular situation, despite hypothermia, those patients are in vasodilatation. LDF shows these microflows very well. This is a high flow in comparison with the control group and we demonstrate a very good ability to increase this microflow using the topical temperature test, more than with the control group. Burned areas The optimal goal of measuring microflow in burned areas is to use it for prediction (Micheels, Alsbjom and Sorensen, 1984). It is of great interest to TABLE II COMPARISON BETWEEN CONTROL GROUP AND PATIENTS IN HYPOTHERMIA WITH ANESTHESIA (UNHEATED SKIN AND TEMPERATURE LOAD TEST) LDF
Unheated skin Heated skin (42°C
2 min)
Arbitrary Scale 0 to 10. 4 kHZ.
Patient in hypothermia with anesthesia (Core T : 34°C)
Control group
5.8 + 0.87 (S.E.M.)
1.4 + 0.12 (S.E.M.)
7.4 + 1.33 (S.E.M.)
5.1 +0.12
(Core ‘I“ : 36.9”C)
(S.E.M)
36
be able to measure microflow in doubtful areas and thus be able to decide, at an early stage, if grafting must take place or not. We present here only preliminary results, since evaluation in a clinical situation of a bums unit is still going on. Figure 3 shows LDF records from an epidermal bum. On the first day, the patient had a high microflow with poor ability to vasodilate. After a few days, the same area had a normal evolution of microflow, and the normal ability to vasodilate to the temperature test had been restored. On the other hand, in clinically and histologically defined third degree subdermal burns, we demonstrated low flow. The majority of these burns were characterized by microflow lower than than the unheated skin values with a total inability to vasodilate on applying topical temperature load. Figure 4 shows this low flow in comparison with the normal skin of the same patient. Figure 5 shows records from a burned area defined as “deep dermal” by the clinical team and as “superficial dermal” by the pathologist. What about LDF? Day 1 shows a quite important microflow, without any ability to vasodilatation after the topical temperature load test. Day 12 shows a similar picture, but with a slight decreased flow. Figure 6 shows records from another burned area, also defined as “deep dermal” by the clinical team and as “superficial dermal” by the pathologist. Day 1 shows an increased flow in LDF_RECORD
@
Flow
MY1
0 1-
DAY 2-
1
20
1
LDF-RECORD
NORMALSKIN FIOW
EPIDERMAL BURN (I’)
SUBDERMALBURN
2
Mtn.
Fig. 3. Epidermal bum: same area on day 1 and day 2. Day 2 shows normalization with temperature load test. Fig. 4. Normal skin and subdermal bum in the same patient.
@
LDF-RECORD CLINICAL TEAM z DEEP MRMAL BURN HlsTolDGV =suPERFlclAL DERMM BLHW
flow lo
WA
9
6 7
6 5 4 3 2 1 0
Fig. 5. Example of doubtful
bum; same area on day 1 and day 12.
LDF-RECORD @ CLINICAL TEAM t DEEP DERMAL BURN HISTOLDGV= SUPERFICIAL DERMAL BURN Flow DAVl . ..Mu 1 q-T--? : I ! I I
0
1
2
Min.
Fig, 6. Example
of doubtful
bum; same area on day 1 and day 12.
37
38
this area without the possibility of any temperature load effect. Day 12 shows a more increased flow and a small possibility of increasing this flow using the temperature load test. These two pathological evolutions reflected by LDF records are different. We have seen an example of difference between clinical and histological diagnosis. The third aspect in the case is the LDF result. We are now investigating this, in order to add the LDF results more precisely to the doubtful situations of burned areas. DISCUSSION
Laser doppler flowmetry is a new non-invasive technique by which microcirculation changes in tissue can be studied. In recent papers, this technique has been used to measure microflow in standardized fluid models, in animals and in human clinical situations: recording of blood microflow in the fomarm skin at different contact pressures between skin and probe; studying the effect of skin temperature on finger circulation; the contralateral vascular response to cold stimuli, and the effect of deep inspiration on the peripheral circulation (Nilsson, Teland and Oberg 1980); recording the skin blood flow in allergy patch tests (Nilsson, in press); measuring the testis blood flow when norepinephrine was administrered intravenously in rat; the bone blood flow in the jaw of the pig when vasopressin was administered (Nilsson, in press); examining the rhythmic vasoconstriction in human skin (Salarud, Nilsson, Teland and Oberg, 1981); studying the effect of alternating magnetic fields on the blood flow in peripheral circulation in the human body (Veno, Kall, Lovsund and Oberg, 1981); the use of Nipride in dog (Eberhard, Mindt and Schafer, 1983); comparison between the 133Xe washout technique and LDF in human volunteers (Kristensen and Engelhardt, 1983); the clinical use in a burns unit (Micheels, Alsbjorn and Sorensen, 1984). Our own experience using LDF with control group, with burned patients, with shock and with hypothermia and anesthesia leads us to believe that this non-invasive technique is easy to use, and measures microflow in the intenssive care unit, without bacteriological problems. The following technical problems remain to be solved: calibration, since we are currently using an arbitrary scale; artefacts, created by the movements of the patient, leads to the selection of comprehensive patients. Nevertheless, we conclude that, in the future, this technique could be one of the interesting non-invasive techniques used in intensive care, for defining the state of the microcirculation in patients. REFERENCES Afromowitz, M.A. and Heimbach, D.M. (1979) Electra-optic bum depth indicator. Proceedings on XII International Conference on Medical and Biological Engineering, Jerusalem, August, 19-24, 10.1.
39
Eberhard, P., Mindt, N. and Schafer, R. (1983) Reliability of methods for skin blood flow measurement during cutaneous PO, monitoring. In: Continuous Transcutaneous Blood Gas Monitoring, Editors: R. Huch and A. Huch. Marcel Dekker. Kristensen, J.K. and Engelhardt, M. (1983) Evaluation of cutaneous blood flow responses by ’“Xenon washout and a laser-doppler flowmeter. J. Invest. Dermatol., 80, 12-l 5. Holloway, G.A. and Watkins, D.N. (1977) Laser doppler measurement of cutaneous blood flow. J. Invest. Dermatol., 69, 3, 306. Micheels, J., Alsbjom, B. and Sorensen, B. (1984) Clinical use of laser doppler flowmetry. Stand. J. Plast. Reconstr. Surg., in press. Nilsson, G.E., Teland, T. and Oberg, A. (1980) Evaluation of a laser doppler flowmeter for measurement of tissue blood flow. IEEE Trans. Biomed. Eng., BME 27, 1. Salarud, G., Nilsson, G.E., Teland, T. and Oberg, P.A. (1981) Rhythmic vasomotion in human skin studied by laser doppler flowmetry. Proceedings of the 5th Nordic Meeting on Med. and Biol. Eng., Linkiiping, and 25th Anniversary Swedish Sot. for Med. Eng., Umea, Sweden, 216. Sejrsen, P. (1968) A traumatic local labelling of skin by inert gas, epicutaneous application of Xenon-133. J. Appl. Physiol., 24, 570. Sejrsen, P. (1971) Measurement of cutaneous blood flow by freely diffusible radioactive isotopes. Thesis, Copenhagen, 1971. Dan. Med. Bull,, Suppl. 18. Stern, M.D. (1975) In vivo evaluation of microcirculation by coherent light scattering. Nature, 254, 56. Veno, Sh., Kall, T., Lovsund, A. and Oberg, P.A. (1981) The effect of alternating magnetic fields on the blood flow in peripheral circulation in the human body. Proceedings of the 5th Nordic Meeting on Med. and Biol. Eng., Linkoping, and 25th Anniversary Swedish Sot. for Med. Eng., Umea, Sweden, 265.