Rev Neurol 1999 Mar 16-31;28(6):535-43
[Neurophysiological study of thin myelinated and unmyelinated fibers]. [Article in Spanish] Espinosa ML, Santiago S, Guzman JJ, Prieto J, Ferrer T; Laboratorio de SNA, Hospital General La Paz, Madrid, Espana.
INTRODUCTION: Standard neurophysiological techniques evaluate thick myelinated fibers. Yet, peripheral nerves are equally composed of thin myelinated and unmyelinated fibers. The latter are responsible for autonomic function as well as temperature and pain perception. DEVELOPMENT: Microneurographic studies are restricted to investigation laboratories. Since the techniques are complex and invasive, their performance is still poor for clinical purposes and some of the components to be analyzed, such as cardiovagal, cannot be directly recorded. The clinical need to evaluate the functions regulated by the autonomic nervous system (ANS) had led to devising a series of tests which, in most cases, rely on reflex responses evoked by already known standardize stimuli. The battery chosen has to be non invasive, reproducible, specific, providing relevant data to the investigated function, with a readily available technology, which has to be managed being aware of the physiological and pathological factors that might bear an influence on the results. The recent development of heart rate blood pressure power spectral analysis, provides a new interesting insight for quantification of ANS abnormalities. The study of thermography and thermometry of body surface brings forward evidence on the activity of other thin and unmyelinated fibers components of the peripheral nerve spectrum. CONCLUSION: The adequate management of the above mentioned tests gives rise to a more extensive and appropriate knowledge of the whole peripheral nerve fiber spectrum.

Diabetes Res Clin Pract 1998 Oct;42(1):29-34
Peripheral vascular reactions to smoking--profound vasoconstriction by atherosclerosis. Fushimi H, Kubo M, Inoue T, Yamada Y, Matsuyama Y, Kameyama M; Department of Medicine, Sumitomo Hospital, Osaka, Japan.
Analyses of direct effects of smoking on peripheral arteries were done using thermography, blood fluorometry and echography on 97 habitual smoker-diabetics without triopathy. There were found to be four types of thermographic changes following smoking, which varied according to the degree of atherosclerosis of the artery. The smoking-stimulated thermographic pattern in the control group of healthy volunteers was a small wavy pattern, fluctuating along the base line every few minutes within a temperature range of 1.0-1.5 degrees C (N type). In diabetics, four types of thermographic patterns were produced: normal (N) type as control, increasing (I) type (increasing in skin temperature), decreasing (D) type (decreasing in temperature), and F type (no changes in temperature). The most significant finding was the decreasing pattern which closely connected to clinical and echographic aspects of macroangiopathic changes. The increasing type was characterized by a paradoxical increase in temperature after smoking in order diabetics with good blood glucose control and who were less atherosclerotic. Blood flow was correlated to the skin temperature at the base state and changes after smoking. Moreover, blood flow changes measured by fluorometry suggest that vasoconstriction or vasodilatation following smoking took place. These results suggest that this smoking test might be a good tool for diagnosing for the degree of atherosclerosis and for its following up.

Clin Physiol 1991 Mar;11(2):135-41
Thermography and laser-Doppler flowmetry for monitoring changes in finger skin blood flow upon cigarette smoking. Bornmyr S, Svensson H.; Department of Clinical Physiology, Allmanna Sjukhuset, Malmo, Sweden.
Haemodynamic changes after smoking two 1.1 mg nicotine cigarettes were monitored in 24 smokers on two different occasions. Smoking caused an increase in heart rate and arterial blood pressure, whereas finger temperature as measured by thermography and finger skin blood flow as measured by laser-Doppler flowmetry (LDF) decreased. Lowest values were seen within 15 min by LDF, and after 30 min by thermography. Changes in the two methods correlated closely, however, when maximum responses during a 45-min period after smoking were compared. The wider distribution of LDF values would seem to be due to the small measuring volume which is susceptible to differences in vascular anatomy and reactivity. In both methods, responses showed a high degree of reproducibility.

Hand-Arm Vibration Syndrome
 
Br J Surg 1999 May;86(5):694-5
Vascular surgical society of Great Britain and Ireland : analysis of cold provocation thermography in the objective diagnosis of the hand-arm vibration syndrome. Coughlin P, Chetter IC, Kent PJ, Kester RC; St James's University Hospital, Leeds, UK.
BACKGROUND: The hand-arm vibration syndrome (HAVS) is the commonest prescribed disease in the UK . Presently the diagnosis is subjective and the need for an objective investigation to support the diagnosis has been highlighted. This study analyses the potential of cold provocation thermography (CPT) to fulfil this role. METHODS: CPT was performed in ten controls (five men, five women; median age 35 (range 24-78) years) and 21 patients with HAVS (20 men, one woman; median age 45 (range 29-81) years). With an infrared camera, a precooling (PC) image was taken and then, following hand cooling in water at a temperature of 5 degrees C for 1 min, further rewarming images were taken every minute for 10 min. RESULTS: Patient finger tip temperatures were significantly cooler than control temperatures at all time points (P < 0.01, Student's t test). The following Table shows the sensitivity, specificity and PPV of CPT. CONCLUSION: CPT provides strong objective evidence to support the clinical diagnosis of HAVS.

Carpal Tunnel:
Pain 1995 Mar;60(3):295-302
Parameters of thick and thin nerve-fiber functions as predictors of pain in carpal tunnel syndrome.
Neundorfer B, Handwerker HO; Neurologische Klinik, Lang E, Claus D, Friedrich-Alexander-Universitat Erlangen-Nurnberg, Germany.
Pain intensity in carpal tunnel syndrome (CTS) was correlated with neuro- and psychophysiological parameters related to the function of different nerve fiber classes within the median nerve in 23 patients. Control data were obtained from 16 normal subjects. Mean intensity of all pain attacks which occurred 14 days before surgical treatment was assessed on visual analogue scales (average CTS pain). Functions of thick myelinated nerve fibers were determined by motor and sensory nerve conduction studies. Functions of thin myelinated and unmyelinated nerve fibers were evaluated by measuring thresholds of warmth, cold and heat pain on the index and little finger. Pain intensity and neurogenic vasodilatation following noxious mechano-stimulation on the interdigital web between index and middle finger provided additional information on the functioning of nociceptive nerve fibers. Sympathetic reflexes induced by these painful stimuli were assessed by means of infrared thermography and photoplethysmography. Mean intensity of pain attacks (40 +/- 19% VAS) correlated significantly with latency (r = 0.58, P < 0.01) and amplitude (r = -0.50, P < 0.01) of the compound action potential from abductor pollicis brevis muscle following distal median nerve stimulation. Thresholds of warmth, cold and heat pain on index finger were significantly increased during CTS when compared to the control subjects. The magnitude of neurogenic vasodilatation and sympathetic vasoconstrictor reflexes were not significantly different. Average CTS pain correlated inversely to the threshold of heat pain on index (r = -0.46, P < 0.05), but also on the little finger (r = -0.41, P < 0.05), which is not innervated by the median nerve.

Open Heart Surgery:
 
Med Eng Phys 1998 Sep;20(6):443-51
Thermographic imaging in the beating heart: a method for coronary flow estimation based on a heat transfer model.
Gordon N, Rispler S, Sideman S, Shofty R, Beyar R; Heart System Research Center, Department of Biomedical Engineering, Technion-IIT, Haifa, Israel.
Intraoperative thermographic imaging in open-chest conditions can provide the surgeon with important qualitative information regarding coronary flow by utilizing heat transfer analysis following injection of cold saline into the aortic root. The heat transfer model is based on the assumption that the epicardial temperature changes are mainly due to convection of heat by the blood flow, which may, therefore, be estimated by measuring the temperature variations. Hearts of eight dogs were exposed and imaged by a thermographic camera. Flow in the left arterial descending (LAD) coronary branch was measured by a transit-time flowmeter. 20 ml of cold saline were injected into the aortic root (just after the aortic valve) and the epicardial temperature images were recorded at end-diastole, for 20-30 s. Different flow rates were achieved by 1 min occlusion of the LAD, which affected a reactive hyperemic response. The dynamics of the temperature in the arterial coronary tree was obtained by averaging the temperature over an edge-detected arterial segment for each frame. The heat transfer equation was curve-fitted, and the flow-dependent heat transfer index was correlated with the experimentally determined coronary flow (r = 0.69, p < 0.001). In summary: a method for quantitative estimation of coronary blood flow by thermography and heat transfer analysis was developed and tested in animal experiments. This method can provide important information regarding coronary blood flow during open-chest surgical procedures.

Cardiovasc Intervent Radiol 1998 Nov-Dec;21(6):481-6
 
Can rotational atherectomy cause thermal tissue damage? A study of the potential heating and thermal tissue effects of a rotational atherectomy device.
Gehani AA, Rees MR; Cardiac Research Unit, Killingbeck Hospital , Leeds , United Kingdom .
PURPOSE: Thermal tissue damage (TTD) is customarily associated with some lasers. The thermal potential of rotational atherectomy (RA) devices is unknown. We investigated the temperature profile and potential TTD as well as the value of fluid flushing of an RA device. METHODS: We used a high-resolution infrared imaging system that can detect changes as small as 0.1 degree C to measure the temperature changes at the tip of a fast RA device with and without fluid flushing. To assess TTD, segments of porcine aorta were subjected to the rotating tip under controlled conditions, stained by a special histochemical stain (picrisirius red) and examined under normal and polarized light microscopy. RESULTS: There was significant heating of the rotating cam. The mean "peak" temperature rise was 52.8 +/- 16.9 degrees C. This was related to rotational speed; thus the "peak" temperature rise was 88.3 +/- 12.6 degrees C at 80,000 rpm and 17.3 +/- 3.8 degrees C at 20,000 rpm (p < 0.001, t-test). Fluid flushing at 18 ml/min reduced, but did not abolish, heating of the device (11.8 +/- 2.9 degrees C). A crater was observed in all segments exposed to the rotating tip. The following features were most notable: (i) A zone of "thermal" tissue damage extended radially from the crater reaching adventitia in some sections, especially at high speeds. This zone showed markedly reduced or absent birefringence. (ii) Fluid flushing of the catheter reduced the above changes but increased the incidence and extent of dissections in the media, especially when combined with high atherectomy speeds. (iii) These changes were observed in five of six specimens exposed to RA without flushing, but in only one of six with flushing (p < 0.05). (iv) None of the above changes was seen in control segments. CONCLUSION: RA is capable of generating significant heat and potential TTD. Fluid flushing reduced heating and TTD. These findings warrant further studies in vivo, and may influence the design of atherectomy devices.