Anaesth. Intens. Care (1977), 5, 231
THERMOGRAPHIC ASSESSMENT OF PERIPHERAL ARTERIAL OCCLUSION P. ]. D.
EVANS,*
D.
J.
MACEyt AND
J. H.
KERRt
NujJield Department of Anaesthetics, Radcliffe Infirmary, Oxford, U.K. SUMMARY
Infra-red thermography was used to confirm the observation that the temperature differences between corresponding areas of skin on opposing hands are normally minimal and to demonstrate that the skin temperature of the hand distal to an occluded radial or brachial artery was lower than that of the contra-lateral hand. Temperature differences between the two hands decreased with time and had disappeared by the time that recannulation of the occluded artery, gauged by the modified" Allen" test, had occurred. Thermography is a simple and non-invasive technique and provides a useful indicator of the incidence and progress of peripheral arterial occlusion such as that which may follow arterial cannulation. Infra-red radiation is emitted constantly by all objects with an intensity that is largely determined by the temperature of the object. Thermography is a method of mapping the temperature of a surface and when applied to man provides a thermal map of the skin (Reece 1974). Several clinical applications have been found for thermography including the identification of malignant tumours of the breast (LloydWilliams et al. 196]), and in the investigation of occlusive vascular disease (Lance and Somerville 1972, Capistrant and Gumnit 1973). The skin temperature is not constant over the whole body surface and in the upper limbs it can vary by as much as 3°C. under constant environmental conditions (Sheard 1943). These differences are due to the variation in blood flow in superficial vessels whose calibre is controlled principally by the autonomic nervous system and to a lesser extent by circulating catecholamines and local tissue metabolites. Good thermal balance normally exists between contra-lateral areas of the body, and in healthy subjects examined in a constant ambient temperature the differences have been reported to be less than 1°C (Lloyd-Williams et al. 1961). • M.B., B.S., F.F.A.R.C.S., Registrar. B.Sc., Ph.D., Physicist, Churchill Hospital, Oxford. t D.M., F.F.A.R.C.S., Consultant Anaesthetist.
t
Address for reprints: Dr. Peter ]. D. Evans, P.O. Box 224, Wentworthville, N.S.W. 2145, Australia.
In this study, thermography has been used to investigate the skin temperature pattern in the hands of normal subjects and of selected patients whose radial or brachial arteries appeared to be occluded following arterial cannulation. METHOD
Measurements were made with an AGA Thermovision 665 camera which had an indium antimonide (InSb) detector sensitive to infrared radiation in the range between 2·0 and 5·6 fLm. The camera had a temperature resolution of ± 0·2°C and provided an instantaneous temperature display over a field size of about 25 X 30 cm with a spatial resolution of about 2·5 mm (Macey and Oliver 1972). A permanent record of the thermogram could be made by taking a polaroid photograph of the visual display. All thermograms were taken in a draught-free room maintained at 20°C. Thirty minutes were allowed for subjects to reach thermal equilibrium with the environment, the arms being exposed and restrictive objects such as rings and watches being removed on arrival. Before recording, subjects were seated one metre from the camera with the arms held dependant and the palmar or dorsal surface of the hands towards the camera. After the initial record a further thermogram was taken at 30 minutes to determine the stability of the observed pattern. Simultaneous temperature measurements were made at corresponding points on the two limbs.
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
232
P. ]. D.
EVAKS ET AL.
TABLE
1
Details of Patients, Sites of Apparently Occluded Arteries, and Temperatures at Corresponding Points on the Two Hands When Examined at Intervals after Arterial Cannulation. Temperature (cC) Sex
Age
Operation
-------1·------ - - - - - . - - - - -
Cannulation Site
Visit 2
Visit 3
- L - I - R - L - -I-{- --L-I-I-{- - + - - - - - - - - . 1 - - - - - - - 1 -3-0-.5 31 ·4
~
28·6
28·7
32·4
30·0
30·0
31·0 131.0
== Visit 4
L-I-I-{-
----1----------1------ --- --- --- --- --- --- --- --30· ii 29·0 30· :; 2\J· 4 32· 1 32·2 -------1--- --- --- --- --- --- --- --28·6 32·6 29·0 32· fl 31 ·1 33·6 27·0 27·0
31·1
~
3:!
- - - 1 - - - - - - - - - 1 - - - - - - - 1 - --.-- 28.4133~ 32· 29 8
On the dorsal surfaces of the hands, the proximal interphalangeal joints of the middle fingers were ('ompared, while on the palmar surface the
FIGURE 1.- Thermogram showing the dorsal surfaces of both hands of one of the normal subje( ts. The numbered scale 011 the left side is the temperature range, in this case flOC. The scale along the base is graded in shades of grey with 1· 0 being 5°C warmer than the point labelled O.
41--1------
·-;-:33.01--- ------ ---
thenar eminences were chosen for comparison because both areas were easily defined on the thermogram.
2.-Thermogram of the palmar surfaces of both hands of a patient with an occluded right radial artery. The thenar eminence of the right hand is 2·0°C cooler than that of the left and none of the fingers of the right hand is entirely visible FIGURE
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
233
PERIPHERAL ARTERIAL OCCLUSION
Two groups of subjects were studied. One consisted of 8 healthy adults who were each examined once. The other comprised 6 patients (Table 1) whose radial or brachial arteries appeared, as judged by a modified "AlIen" test (Evans and Kerr 1975) to be occluded
The six patients with occluded arteries were studied as soon as it was possible to move them to the temperature controlled examination room. All had abnormal thermograms in which the most significant feature was lack of definition of the affected hand due to an overall reduction in its temperature (Figures 2 and 3). The temperature difference between corresponding points on the two hands ranged between 1°C and 4 QC (Table 1, Figure 5) although none of the patients had themselves noticed any difference between their hands. When re-examined during
3.-Thermogram of the dorsal surfaces of both hands of a patient with an occluded left brachial artery. The left hand is only just visible on the thermogram. The temperature differences between the proximal interphalangeal joints of the middle fingers was 4°C. FIGURE
FIGURE 4.-Thermogram of the dorsal surfaces of both forearms and hands of the patient with an occluded left brachial artery taken 6 weeks after the initial thermogram. The temperature difference between the two hands was decreased to 2· 5°C. Eight weeks after this photograph was taken, there was no significant temperature difference between the two hands. Blood flow in the previously occluded artery appeared to be fully restored.
following cannulation of the vessel in the operating theatre or intensive therapy unit. These patients were each studied on up to four occasions. RESULTS
All the healthy adults demonstrated similar thermograms. Both hands were clearly defined with the warmest areas appearing white on the polaroid photographs (Figure 1). The finger tips, thenar eminences and superficial veins on the dorsum of the hands were the warmest areas, while intervening areas of skin surface were at least 0 ·5°C cooler. The temperature differences between corresponding points on opposing limbs recorded from the 8 healthy subjects did not exceed 0 ·3°C.
follow-up, the differences became less marked (Figure 4) and disappeared when blood flow in the occluded vessel appeared to have become re-established. DISCUSSION
Thermography is a simple technique with several accepted medical applications. This study demonstrates its value in the investigations
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
P.
234
J. D.
EVANS ET AL.
of peripheral arterial occlusion although the full sensitivity of the method is obscured to some extent in the monochrome polaroid prints because the human eye is capable of distinguishing only about seven shades of difference between white and black, whereas the AGA camera can detect at least 25 divisions over the same scale.
a
7 SI WEEKS AF'1ER
TI
15
CANNULATlON
FIGURE 5.-Graph showing the results from Table 1. Where the temperature gradient (T°C) between the normal and abnormal hands is compared with the period after cannulation. .Patient 1, 0 Patient 2, .Patient 3, Z Patient 4, n Patient 5, x Patient 6.
The prints therefore provide a crude photographic record of the findings, whereas the absolute temperature levels and differences were obtained and recorded at the time of examination. All the healthy subjects displayed minimal temperature differences between corresponding points on the two hands and these results compared well with those reported previously by Lloyd-Williams et al. (1961) who considered differences greater than 1 QC abnormal. Factors which could give rise to differences in skin temperature between the hands include disturbances in autonomic enervation or control, changes in thermal conductivity, increased local metabolism and structural abnormalities of the
vessels (Phillips and Lloyd-Williams 1974). In the group of patients studied, local trauma to the arteries seems the most likely explanation for the observed differences and this conclusion is supported by the observation that they had disappeared when blood flow in the damaged vessel appeared to have become re-established. The affected hands were generally cooler than the normal ones, suggesting an overall reduction in blood flow through at least the superficial blood vessels following occlusion of a peripheral artery. The distribution of the coolest areas did not however show an obvious correlation with the areas of skin normally considered to be supplied by the affected artery and these changes presumably reflected on general reduction and imbalance in the blood flow to the forearm and hand. Thermography would seem therefore to provide a useful, non invasive method of assessing and following the degree of impairment of blood flow into the hand following arterial cannulation and possible occlusion. REFERENCES
Capistrant, T. D., and Gumnit, R. J. (1973) : "Detecting Carotid Occlusive Disease by Thermography", Stroke, 4, 57. Evans, P. J. D., and Kerr, J. H. (1975): "Arterial Occlusion after Cannulation", Brit. Med. j., 2, 197. Lance, J. W., and Somerville, B. (1972): "The Detection of Stenosis or Occlusion of the Internal Carotid Artery by Facial Thermography", Med. j. Aust., 1, 97. Lloyd-Williams, K., Lloyd Williams, F. J., and Handley, R. S. (1961): "Infra-red Thermometry in the diagnosis of Breast Disease", Lancet, 2, 1378. Macey, D. J., and Oliver, R. (1972): "Image Resolution in Infra-red Thermography", Physics in Medicine and Biology, 17, (4) 563. Phillips, B. H., and Lloyd-Williams, K. (1974): "The Clinical use of Thermography", Brit. j. Hospital Med., Equipment Supplement, 12, 17. Recce, B. L. (1974): "Technical and Scientific Aspects of Thermography", Brit. j. Hosp. Med., Equipment Supplement, 12, 5. Sheard, C. (1943) : Medical Physics, Editor, O. Glasser, Chicago Year Book Publishers, p. 1523.
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
THERMOGRAPHIC ASSESSMENT OF PERIPHERAL ARTERIAL OCCLUSION P. ]. D.
EVANS,*
D.
J.
MACEyt AND
J. H.
KERRt
NujJield Department of Anaesthetics, Radcliffe Infirmary, Oxford, U.K. SUMMARY
Infra-red thermography was used to confirm the observation that the temperature differences between corresponding areas of skin on opposing hands are normally minimal and to demonstrate that the skin temperature of the hand distal to an occluded radial or brachial artery was lower than that of the contra-lateral hand. Temperature differences between the two hands decreased with time and had disappeared by the time that recannulation of the occluded artery, gauged by the modified" Allen" test, had occurred. Thermography is a simple and non-invasive technique and provides a useful indicator of the incidence and progress of peripheral arterial occlusion such as that which may follow arterial cannulation. Infra-red radiation is emitted constantly by all objects with an intensity that is largely determined by the temperature of the object. Thermography is a method of mapping the temperature of a surface and when applied to man provides a thermal map of the skin (Reece 1974). Several clinical applications have been found for thermography including the identification of malignant tumours of the breast (LloydWilliams et al. 196]), and in the investigation of occlusive vascular disease (Lance and Somerville 1972, Capistrant and Gumnit 1973). The skin temperature is not constant over the whole body surface and in the upper limbs it can vary by as much as 3°C. under constant environmental conditions (Sheard 1943). These differences are due to the variation in blood flow in superficial vessels whose calibre is controlled principally by the autonomic nervous system and to a lesser extent by circulating catecholamines and local tissue metabolites. Good thermal balance normally exists between contra-lateral areas of the body, and in healthy subjects examined in a constant ambient temperature the differences have been reported to be less than 1°C (Lloyd-Williams et al. 1961). • M.B., B.S., F.F.A.R.C.S., Registrar. B.Sc., Ph.D., Physicist, Churchill Hospital, Oxford. t D.M., F.F.A.R.C.S., Consultant Anaesthetist.
t
Address for reprints: Dr. Peter ]. D. Evans, P.O. Box 224, Wentworthville, N.S.W. 2145, Australia.
In this study, thermography has been used to investigate the skin temperature pattern in the hands of normal subjects and of selected patients whose radial or brachial arteries appeared to be occluded following arterial cannulation. METHOD
Measurements were made with an AGA Thermovision 665 camera which had an indium antimonide (InSb) detector sensitive to infrared radiation in the range between 2·0 and 5·6 fLm. The camera had a temperature resolution of ± 0·2°C and provided an instantaneous temperature display over a field size of about 25 X 30 cm with a spatial resolution of about 2·5 mm (Macey and Oliver 1972). A permanent record of the thermogram could be made by taking a polaroid photograph of the visual display. All thermograms were taken in a draught-free room maintained at 20°C. Thirty minutes were allowed for subjects to reach thermal equilibrium with the environment, the arms being exposed and restrictive objects such as rings and watches being removed on arrival. Before recording, subjects were seated one metre from the camera with the arms held dependant and the palmar or dorsal surface of the hands towards the camera. After the initial record a further thermogram was taken at 30 minutes to determine the stability of the observed pattern. Simultaneous temperature measurements were made at corresponding points on the two limbs.
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
232
P. ]. D.
EVAKS ET AL.
TABLE
1
Details of Patients, Sites of Apparently Occluded Arteries, and Temperatures at Corresponding Points on the Two Hands When Examined at Intervals after Arterial Cannulation. Temperature (cC) Sex
Age
Operation
-------1·------ - - - - - . - - - - -
Cannulation Site
Visit 2
Visit 3
- L - I - R - L - -I-{- --L-I-I-{- - + - - - - - - - - . 1 - - - - - - - 1 -3-0-.5 31 ·4
~
28·6
28·7
32·4
30·0
30·0
31·0 131.0
== Visit 4
L-I-I-{-
----1----------1------ --- --- --- --- --- --- --- --30· ii 29·0 30· :; 2\J· 4 32· 1 32·2 -------1--- --- --- --- --- --- --- --28·6 32·6 29·0 32· fl 31 ·1 33·6 27·0 27·0
31·1
~
3:!
- - - 1 - - - - - - - - - 1 - - - - - - - 1 - --.-- 28.4133~ 32· 29 8
On the dorsal surfaces of the hands, the proximal interphalangeal joints of the middle fingers were ('ompared, while on the palmar surface the
FIGURE 1.- Thermogram showing the dorsal surfaces of both hands of one of the normal subje( ts. The numbered scale 011 the left side is the temperature range, in this case flOC. The scale along the base is graded in shades of grey with 1· 0 being 5°C warmer than the point labelled O.
41--1------
·-;-:33.01--- ------ ---
thenar eminences were chosen for comparison because both areas were easily defined on the thermogram.
2.-Thermogram of the palmar surfaces of both hands of a patient with an occluded right radial artery. The thenar eminence of the right hand is 2·0°C cooler than that of the left and none of the fingers of the right hand is entirely visible FIGURE
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
233
PERIPHERAL ARTERIAL OCCLUSION
Two groups of subjects were studied. One consisted of 8 healthy adults who were each examined once. The other comprised 6 patients (Table 1) whose radial or brachial arteries appeared, as judged by a modified "AlIen" test (Evans and Kerr 1975) to be occluded
The six patients with occluded arteries were studied as soon as it was possible to move them to the temperature controlled examination room. All had abnormal thermograms in which the most significant feature was lack of definition of the affected hand due to an overall reduction in its temperature (Figures 2 and 3). The temperature difference between corresponding points on the two hands ranged between 1°C and 4 QC (Table 1, Figure 5) although none of the patients had themselves noticed any difference between their hands. When re-examined during
3.-Thermogram of the dorsal surfaces of both hands of a patient with an occluded left brachial artery. The left hand is only just visible on the thermogram. The temperature differences between the proximal interphalangeal joints of the middle fingers was 4°C. FIGURE
FIGURE 4.-Thermogram of the dorsal surfaces of both forearms and hands of the patient with an occluded left brachial artery taken 6 weeks after the initial thermogram. The temperature difference between the two hands was decreased to 2· 5°C. Eight weeks after this photograph was taken, there was no significant temperature difference between the two hands. Blood flow in the previously occluded artery appeared to be fully restored.
following cannulation of the vessel in the operating theatre or intensive therapy unit. These patients were each studied on up to four occasions. RESULTS
All the healthy adults demonstrated similar thermograms. Both hands were clearly defined with the warmest areas appearing white on the polaroid photographs (Figure 1). The finger tips, thenar eminences and superficial veins on the dorsum of the hands were the warmest areas, while intervening areas of skin surface were at least 0 ·5°C cooler. The temperature differences between corresponding points on opposing limbs recorded from the 8 healthy subjects did not exceed 0 ·3°C.
follow-up, the differences became less marked (Figure 4) and disappeared when blood flow in the occluded vessel appeared to have become re-established. DISCUSSION
Thermography is a simple technique with several accepted medical applications. This study demonstrates its value in the investigations
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
P.
234
J. D.
EVANS ET AL.
of peripheral arterial occlusion although the full sensitivity of the method is obscured to some extent in the monochrome polaroid prints because the human eye is capable of distinguishing only about seven shades of difference between white and black, whereas the AGA camera can detect at least 25 divisions over the same scale.
a
7 SI WEEKS AF'1ER
TI
15
CANNULATlON
FIGURE 5.-Graph showing the results from Table 1. Where the temperature gradient (T°C) between the normal and abnormal hands is compared with the period after cannulation. .Patient 1, 0 Patient 2, .Patient 3, Z Patient 4, n Patient 5, x Patient 6.
The prints therefore provide a crude photographic record of the findings, whereas the absolute temperature levels and differences were obtained and recorded at the time of examination. All the healthy subjects displayed minimal temperature differences between corresponding points on the two hands and these results compared well with those reported previously by Lloyd-Williams et al. (1961) who considered differences greater than 1 QC abnormal. Factors which could give rise to differences in skin temperature between the hands include disturbances in autonomic enervation or control, changes in thermal conductivity, increased local metabolism and structural abnormalities of the
vessels (Phillips and Lloyd-Williams 1974). In the group of patients studied, local trauma to the arteries seems the most likely explanation for the observed differences and this conclusion is supported by the observation that they had disappeared when blood flow in the damaged vessel appeared to have become re-established. The affected hands were generally cooler than the normal ones, suggesting an overall reduction in blood flow through at least the superficial blood vessels following occlusion of a peripheral artery. The distribution of the coolest areas did not however show an obvious correlation with the areas of skin normally considered to be supplied by the affected artery and these changes presumably reflected on general reduction and imbalance in the blood flow to the forearm and hand. Thermography would seem therefore to provide a useful, non invasive method of assessing and following the degree of impairment of blood flow into the hand following arterial cannulation and possible occlusion. REFERENCES
Capistrant, T. D., and Gumnit, R. J. (1973) : "Detecting Carotid Occlusive Disease by Thermography", Stroke, 4, 57. Evans, P. J. D., and Kerr, J. H. (1975): "Arterial Occlusion after Cannulation", Brit. Med. j., 2, 197. Lance, J. W., and Somerville, B. (1972): "The Detection of Stenosis or Occlusion of the Internal Carotid Artery by Facial Thermography", Med. j. Aust., 1, 97. Lloyd-Williams, K., Lloyd Williams, F. J., and Handley, R. S. (1961): "Infra-red Thermometry in the diagnosis of Breast Disease", Lancet, 2, 1378. Macey, D. J., and Oliver, R. (1972): "Image Resolution in Infra-red Thermography", Physics in Medicine and Biology, 17, (4) 563. Phillips, B. H., and Lloyd-Williams, K. (1974): "The Clinical use of Thermography", Brit. j. Hospital Med., Equipment Supplement, 12, 17. Recce, B. L. (1974): "Technical and Scientific Aspects of Thermography", Brit. j. Hosp. Med., Equipment Supplement, 12, 5. Sheard, C. (1943) : Medical Physics, Editor, O. Glasser, Chicago Year Book Publishers, p. 1523.
Anaesthesia and Intensive Care, Vol. V, No. 3, August, 1977
