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Forearm compartment syndrome: anatomical analysis of surgical approaches to the deep space.

Forearm compartment syndrome is a surgical emergency that usually requires release of the superficial muscle compartments. In some clinical situations it is imperative to also explore the deep muscle compartments. There are no anatomical guides for surgical exploration of the deep compartments that would minimize collateral damage to surrounding vessels, nerves, and muscles. Surgical injury in the setting of ischemia, especially vascular injury, compounds the tissue damage that has already occurred. The authors evaluated four surgical approaches (three volar and one dorsal) to the deep forearm by performing detailed anatomical dissections on 10 embalmed and plastinated cadavers. They used a scoring system to rate the approaches for their ability to visualize the deep space without causing iatrogenic injury to superficial muscles, arteries, and nerves. In the volar forearm, an ulnar approach to the deep space is simple, causes the least iatrogenic surgical injury, and provides access to the deep volar forearm structures. The plane of dissection is between the flexor carpi ulnaris and the flexor digitorum superficialis. Dividing one or two distal segmental branches of the ulnar artery to the distal flexor digitorum superficialis exposes the pronator quadratus. Lifting the ulnar neurovascular bundle with the flexor digitorum superficialis in the middle third of the forearm exposes the flexor digitorum profundus and the flexor pollicis longus. This approach to the deep space requires no sharp dissection. In the dorsal forearm, a midline approach between the extensor digitorum communis and the extensor carpi radialis brevis is simple and safe.

Adult↗

Superficial dorsal artery of the forearm: case report and review of the literature.

Although abnormalities of vascular anatomy in the forearm are common, variations of the radial and ulnar arteries are rare. Nevertheless, arterial variants in the forearm may present clinically with neurovascular signs or symptoms. Even when anomalous arteries are not apparent, they may complicate surgery of the forearm and hand, as well as reconstructive surgery that involves the harvest of radial or ulnar artery-based forearm free flaps. For example, the superficial ulnar artery has an incidence of 2.7% and has been well described as a "hidden trap" in the harvest of radial forearm flaps. We present a case report of a variant of the radial artery-the superficial dorsal artery of the forearm. This artery has an estimated incidence of 0.75% and is associated with either an absent or small-caliber radial artery. We believe this is the first report of such an artery presenting to clinical attention, as well as the first imaging of this structure with magnetic resonance angiography. The embryology of this structure and its clinical implications to the hand surgeon, peripheral vascular surgeon, and reconstructive microsurgeon, are also discussed.

Adult↗

Reproducibility of forearm vasodilator response to intra-arterial infusion of calcitonin gene-related peptide assessed by venous occlusion plethysmography.

AIMS: To assess the reproducibility of the forearm blood flow (FBF) response to intra-arterial infusion of calcitonin-gene related peptide (CGRP), measured by venous occlusion plethysmography. In addition, to compare different ways of expressing the FBF response and perform sample size calculations. METHODS: On two separate visits, CGRP (10 ng min(-1) dl(-1) forearm) was infused for 45 min into the brachial artery of six healthy subjects. Reproducibility was assessed by calculating mean difference, repeatability coefficient, within-subject coefficient of variation (WCV) and intraclass correlation coefficient. RESULTS: CGRP increased FBF from 2.8 +/- 0.4 and 3.2 +/- 0.7 (at baseline) to 15.4 +/- 1.4 and 15.2 +/- 1.5 ml min(-1) dl(-1) forearm (at 45 min) on visits 1 and 2, respectively (P < 0.0001 for both visits). Mean difference in FBF at 45 min between both visits was 0.3 ml min(-1) dl(-1) forearm (repeatability coefficient: 4.1 ml min(-1) dl(-1) forearm). This FBF response appeared to be more reproducible when expressed as absolute FBF in the infused arm (WCV 11%) compared with absolute FBF-ratio between both arms (WCV 37%), percentage change from baseline in FBF in the infused arm (WCV 29%) and percentage change from baseline in FBF-ratio (WCV 40%). When expressed as absolute FBF, a sample size of five (95% confidence interval: 2-12) subjects gives 90% power at a type I error probability of 0.05 to detect a 25% shift in FBF response. CONCLUSIONS: Intra-arterial infusion of CGRP results in a forearm vasodilator response which is reproducible between days. This response is most reproducible when expressed as absolute FBF. The presented methodology provides a suitable pharmacodynamic model to assess the in vivo activity of CGRP-receptor antagonists in a small number of subjects.

Adult↗

Mechanical properties of human forearm and vulvar skin.

Using a newly developed suction device, the mechanical properties of forearm and vulvar skin were studied in 22 healthy women, 12 before and 10 after the menopause. The ratio between viscous deformation (Uv) and elastic deformation (Ue) and the biological elasticity, i.e. the ratio between immediate recovery (Ur) and total deformation (Uf), were both significantly lower in vulvar than in forearm skin. Ur/Uf decreased significantly with load in vulvar, but not in forearm skin, whereas Uv/Ue was not load-dependent in either site. Uv/Ue remained constant with age in both test sites, whereas Ur/Uf was significantly lower in post-menopausal women in both forearm and vulvar skin. In vulvar, but not in forearm skin, Uv/Ue was significantly correlated with body height which may be an indicator of mechanical connective tissue properties. Viscous deformation plays a lesser role and biological elasticity is decreased in vulvar compared to forearm skin. Despite differences in mechanical parameters at both sites, age-related changes seem to be similar.

Adult↗

Inhibitory action of forearm flexor muscle afferents on corticospinal outputs to antagonist muscles in humans.

1. To find out whether muscle afferents influence the excitability of corticospinal projections to antagonist muscles, we studied sixteen healthy subjects and one patient with a focal brain lesion. 2. Using transcranial magnetic and electrical brain stimulation we tested the excitability of corticomotoneuronal connections to right forearm muscles at rest after conditioning stimulation of the median nerve at the elbow. Somatosensory potentials evoked by median nerve stimulation were also recorded in each subject. 3. Test stimuli delivered at 13-19 ms after median nerve stimulation significantly inhibited EMG responses elicited in forearm extensor muscles by transcranial magnetic stimulation, but did not inhibit responses to electrical stimulation. In contrast, magnetically and electrically elicited responses in forearm flexor muscles were suppressed to the same extent. 4. The higher the intensity of the test shocks, the smaller was the amount of median nerve-elicited inhibition. Inhibition in extensor muscles was also smaller during tonic wrist extension, or if the induced electrical stimulating current in the brain flowed from posterior to anterior over the motor strip rather than vice versa. Test responses evoked by magnetic transcranial stimulation in the first dorsal interosseous and in brachioradialis muscles were not inhibited after median nerve stimulation at the elbow. Stimulation of digital nerves failed to inhibit motor potentials in extensor muscles. 5. Test stimuli delivered at 15 and 17 ms after radial nerve stimulation significantly inhibited EMG responses elicited in forearm flexor muscles by magnetic transcranial stimulation. 6. In the patient with a focal thalamic lesion, who had dystonic postures and an absent N20 component of the somatosensory-evoked potentials but normal strength, median nerve stimulation failed to inhibit magnetically evoked responses in forearm extensor muscles. 7. We propose that activation of median nerve muscle afferents can suppress the excitability of cortical areas controlling the antagonist forearm extensor muscles acting on the hand. The inhibitory effect occurs at short latency and might assist spinal pathways mediating reciprocal inhibition by contrasting the co-activation of antagonistic pools of corticospinal cells.

Adult↗

Effect of local warming on forearm reactive hyperaemia.

Measurement of minimal vascular resistance has proved useful in quantifying structural changes in regional circulations. Accurate measurement of minimal vascular resistance requires full relaxation of all resistance vessels within the region under examination. The usual procedure in humans involves the measurement of maximal forearm blood-flow following 6-10 min of forearm ischaemia. We conducted this study to find whether forearm skin was fully vasodilated by this procedure. Peak forearm blood-flow was measured by plethysmography in six healthy subjects following 10 min of ischaemia while the arm was at a neutral temperature (33 degrees C) and while the arm was locally warmed to 42 degrees C. Peak reactive hyperaemia blood-flow was significantly elevated by local heating (P less than 0.001) to 79.6 ml 100 ml-1 min-1 from a value of 50.2 ml 100 ml-1 min-1 during normothermia. Peak reactive hyperaemia blood-flow in the contralateral unheated forearm showed no significant change between the two periods of ischaemia (P greater than 0.05). These findings were confirmed in four subjects by laser Doppler velocimetry, which gives a linear index of skin blood-flow. In normothermic conditions, this index rose to 0.89 V following 10 min of ischaemia and to 1.26 V with local warming to 42 degrees C (P less than 0.001). Ischaemia plus local warming did not cause a further significant rise in this index of skin blood-flow (1.35 V, P greater than 0.05). These data suggest that 10 min of ischaemia during normothermia is insufficient to relax fully cutaneous resistance vessels and that maximal forearm blood-flow is underestimated by this procedure.

Adult↗

Effect of intermittent compression of upper arm veins on forearm vessels in patients with end-stage renal disease.

Native arteriovenous fistula is the best vascular access for chronic hemodialysis. Primary and long-term success depends, in part, on the state of arteries and veins at the time of the operation. The aim of our study was to investigate the effects of intermittent compression of upper arm veins on forearm vessels in patients with terminal renal disease. The study group was composed of 16 chronic hemodialysis patients who performed daily intermittent compression of the upper arm without vascular access by elastic band (Eschmarch). Ten chronic hemodialysis patients were included in the control group, which performed no specific activity. Forearm measurements were obtained at the beginning of the study and 4 and 8 weeks later during the course of intermittent compression of the upper arm veins. The forearm circumference and maximal handgrip strength were measured. The artery measures, including endothelium-dependent vasodilatation and forearm vein variables, were obtained by ultrasonography measurements. The forearm circumference, maximal handgrip strength, and artery variables, including endothelium-dependent vasodilatation, remained unchanged. The basal venous diameters (2.29 +/- 0.19 mm at the beginning, 2.46 +/- 0.19 mm after 4 weeks, and 2.53 +/- 0.18 mm after 8 weeks) were significantly increased in the study group. The distensibility of veins was preserved in the study group. There were no significant changes in the control group. Our study demonstrated that daily intermittent compression of the upper arm veins increases the forearm vein diameter and preserves the distensibility of veins in patients with end-stage renal failure.

Adult↗

Instability in human forearm movements studied with feed-back-controlled muscle vibration.

1. Frequency-modulated vibration was applied to the elbow flexor and extensor tendons to produce reflex movements of the forearm in normal subjects. The modulating (command) signal caused equal and opposite deviations from the 40 Hz carrier frequency so that when flexor vibratory frequency increased, extensor frequency decreased, and vice versa. 2. It is argued that the movements resulted largely from the reflex action of muscle spindle primary afferents whose firing frequency had been 'taken over' and modulated by the vibration. 3. Bode plots relating forearm movements to command signal (modulating) frequency showed the transfer function of the Ia afferent-CNS-muscle-load system to have a low-pass filter characteristic. The phase lag of movement on command increased progressively with command signal frequency, exceeding 180 deg at 3-4 Hz. 4. The transduced forearm movements were fed back to provide the command signal to the vibrators (and thus indirectly to the spindle afferents) via a filter mimicking the dynamic responsiveness of muscle spindle primary endings. Our aim was to 'break into' the reflex arc, and re-route it so that we could artificially vary the gain without significantly altering the dynamics of the pathway. 5. Nearly all subjects developed forearm oscillations (tremor) when the gain exceeded a threshold value. Subjects varied widely in their threshold, though for a given subject the threshold remained fairly constant from day to day. The results suggest that reflexly active individuals may not have a large safety margin with respect to forearm instability. 6. The frequency range of the oscillations observed in seven subjects was 3-8 Hz. The frequencies depended upon the level of flexor-extensor co-contraction, and increased from 3 to 5 Hz at 10% co-contraction to 5-8 Hz at 100% co-contraction. An analysis of the mechanical impedance of the arm provided estimates of tremor frequencies consistent with these results. 7. These unexpectedly low tremor frequencies led us to propose that it may be erroneous to expect stretch reflexes to contribute to forearm tremor in the range 8-12 Hz (e.g. physiological and 'enhanced' physiological tremors). Rather, their contributions should be sought in the range 3-8 Hz (e.g. pathological tremors such as those of Parkinson's and cerebellar disease).

Action Potentials↗

Forearm blood glucose testing in diabetes mellitus.

AIMS: To compare the accuracy and acceptability of capillary blood glucose testing from the forearm with finger prick testing in diabetic children. METHODS: Blood glucose measurements from samples taken from the forearm and the finger were compared in an outpatient setting from 52 children and adolescents with diabetes mellitus aged 6-17 years. Opinions on forearm sampling were collected by questionnaire. RESULTS: Blood glucose results obtained from forearm sampling correlated well with results from the finger measured by the Yellow Springs Instrument analyser. Error grid analysis showed that 100% of measurements were clinically acceptable; 61% of children reported that forearm testing was painless and 19% that it was less painful than finger prick testing. CONCLUSION: Forearm testing is an acceptable alternative to finger prick testing for blood glucose measurement in children and adolescents.

Adolescent↗

Isokinetic profile of wrist and forearm strength in elite female junior tennis players.

BACKGROUND: In tennis, injuries to the elbow and wrist occur secondary to the repetitive nature of play and are seen at increasingly young ages. Isokinetic testing can be used to determine muscular strength levels, but dominant/non-dominant and agonist/antagonist relations are needed for meaningful interpretation of the results. OBJECTIVES: To determine whether there are laterality differences in wrist extension/flexion (E/F) and forearm supination/pronation (S/P) strength in elite female tennis players. METHODS: 32 elite female tennis players (age 12 to 16 years) with no history of upper extremity injury underwent bilateral isokinetic testing using a Cybex 6000 dynamometer. Peak torque and single repetition work values for wrist E/F and forearm S/P were measured at speeds of 90 degrees/s and 210 degrees/s, with random determination of the starting extremity. Repeated measures analysis of variance was used to determine differences between extremities for peak torque and single repetition work values. RESULTS: Significantly greater (p<0.01) dominant arm wrist E/F and forearm pronation strength was measured at both testing speeds. Significantly less (p<0.01) dominant side forearm supination strength was measured at both testing speeds. CONCLUSIONS: Greater dominant arm wrist E/F and forearm pronation strength is common and normal in young elite level female tennis players. These strength relations indicate sport specific muscular adaptations in the dominant tennis playing extremity. The results of this study can guide clinicians who work with young athletes from this population. Restoring greater dominant side wrist and forearm strength is indicated after an injury to the dominant upper extremity in such players.

Adolescent↗

Role of mechanical and psychosocial factors in the onset of forearm pain: prospective population based study.

OBJECTIVE: To determine the aetiology of forearm pain. In particular to determine the relative contribution of (a) psychological factors, features of somatisation, and health anxiety and behaviour, (b) work related mechanical factors, and (c) work related psychosocial factors in the onset of forearm pain. DESIGN: 2 year prospective population based cohort study, with retrospective assessment of exposures at work. SETTING: Altrincham, Greater Manchester. PARTICIPANTS: 1953 individuals aged 18-65 years. OUTCOME MEASURES: Forearm pain of new onset. RESULTS: At follow up, 105 (8.3%) participants reported forearm pain of new onset lasting at least one day in the past month. Among these, 67% also reported shoulder pain, 65% back pain, and 45% chronic widespread pain. Increased risks of onset were associated with high levels of psychological distress (relative risk 2.4, 95% confidence interval 1.5 to 3.8), reporting at least two other somatic symptoms (1.7, 0.95 to 3.0), and high scores on the illness behaviour subscale of the illness attitude scales. The two work related mechanical exposures associated with the highest risk of forearm pain in the future were repetitive movements of the arm (4.1, 1.7 to 10) or wrists (3.4, 1.3 to 8.7), whereas the strongest work related psychosocial risk was dissatisfaction with support from colleagues or supervisors (4.7, 2. 2 to 10). CONCLUSIONS: Psychological distress, aspects of illness behaviour, and other somatic symptoms are important predictors of onset of forearm pain in addition to work related psychosocial and mechanical factors. Misleading terms such as "cumulative trauma disorder" or "repetitive strain injury," implying a single uniform aetiology, should be avoided.

Adult↗

Unilateral posterior parietal lobe lesions disrupt kinaesthetic representation of forearm orientation.

OBJECTIVE: To apply the lesion method to assess neuroanatomical substrates for judgments of forearm orientation from proprioceptive cues in humans. METHODS: Participants were 15 subjects with chronic unilateral brain lesions and stable behavioural deficits, and 14 neurologically normal controls. Subjects aligned the forearm to earth fixed vertical and trunk fixed anterior-posterior (A-P) axes ("straight ahead"), with the head aligned to the trunk and with head and shoulder orientations varied on each trial. RESULTS: Most subjects with posterior parietal lobe lesions made larger variable errors than controls in aligning the forearm to the earth fixed vertical axis and the trunk A-P axes, whether the head was held upright or oriented in different positions. Lesion subjects and controls made similar constant errors for aligning the forearm to gravitational vertical. Variable error magnitude correlated positively with greater lesion volume of right and left superior parietal lobules (SPL), but not with lesions in other brain areas. Larger variable errors for aligning the forearm to the trunk fixed A-P axis were also correlated with the volume of SPL lesions, but constant error magnitude correlated with larger volume lesions in premotor areas, inferior parietal lobules, and posterior regions of the superior temporal gyri, but not with SPL lesion volume. CONCLUSIONS: The findings suggest that the right and left superior and inferior parietal lobules, posterior superior temporal gyri, and premotor areas play a role in defining higher level coordinate systems for specifying orientation of the right and left forearm.

Adult↗

The effects of forearm rotation on three wrist measurements: radial inclination, radial height and palmar tilt.

The purpose of this study was to evaluate and quantify the effects of forearm rotation on radial inclination, radial height and palmar tilt. Seventeen arms, nine cadaveric and eight volunteer, were examined using a radiolucent device that allowed for the controlled rotation of each arm. Lateral and posterior-anterior X-rays were taken at 5 degrees increments which were then measured by two physicians using standardised protocol. The results revealed that all three measurements were significantly affected by forearm rotation with forearm supination increasing the apparent measurements and forearm pronation decreasing the apparent measurements. This relationship was well characterised by linear trend modelling such that forearm pronation of 10 degrees decreased the apparent radial inclination, radial height and palmar tilt by 2.8 degrees , 1.6 mm and 4.4 degrees , respectively. This study demonstrates that forearm rotation is an important factor in the accurate evaluation of wrist measurements, and that slight rotation of the wrist during radiographic imaging may significantly alter management decisions given established surgical criteria.

Adult↗

Independent stimulation of glucose metabolism and Na+-K+ exchange by insulin in the human forearm.

Insulin promotes potassium uptake into skeletal muscle by stimulating the activity of the Na+-K+ pump. To test whether insulin-induced glucose and potassium uptake are linked processes in vivo, we used the perfused forearm technique in healthy volunteers. Local hyperinsulinemia (125 +/- 11 microU/ml for 100 min) induced a net uptake of glucose and potassium (4.79 +/- 0.61 and 0.76 +/- 0.22 mumol.min-1.100 ml-1 of forearm volume, respectively). When an intra-arterial ouabain infusion (0.72 microgram.min-1.100 ml-1, producing local levels of approximately 0.5 mM) was superimposed on the insulin infusion, potassium uptake was blocked (0.026 +/- 0.190 ml.min-1.100 ml-1, P less than 0.02), and glucose uptake was decreased (to 3.31 +/- 0.34 mumol.min-1.100 ml-1, P less than 0.03). The latter change was explained by a 30% fall in forearm blood flow (from 2.95 +/- 0.10 to 2.01 +/- 0.18 ml.min-1.100 ml-1, P less than 0.001). To separate out the effect of blood flow, in another series of studies forearm blood flow was clamped by co-infusing propranolol and phentolamine (7 and 8 micrograms.min-1.100 ml-1, respectively). Under these conditions of fixed flow (7.0 +/- 0.8 ml.min-1.100 ml-1), ouabain still abolished the stimulatory effect of insulin on potassium uptake but had only a small (and statistically insignificant) effect on forearm glucose extraction (from 20 +/- 2 to 16 +/- 2%, P = N>). We conclude that in human forearm muscle ouabain inhibits Na+-K+ exchange and depresses insulin-induced glucose uptake via an adrenergic-mediated limitation of blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Effects of insulin on whole body and forearm leucine and KIC metabolism in type 1 diabetes.

To investigate whole body rates of appearance (Ra) and forearm metabolism of leucine and alpha-ketoisocaproate (KIC) in type 1 diabetes, before and after insulin administration, seven diabetic subjects were studied in the postabsorptive state with primed-constant infusions of L-[4,5-3H]leucine and [1-14C]KIC, and forearm arterial deep-venous catheterization. This combined technique allowed the selective quantitation of the two processes regulating forearm leucine and KIC metabolism (release and uptake) that may occur simultaneously. Before insulin (arterial plasma glucose, 284 +/- 24 mg/dl; leucine, 215 +/- 24 mumol/l; KIC, 42 +/- 3 mumol/l) forearm leucine and KIC release exceeded uptake slightly but significantly (P less than 0.05). During a 180-min insulin infusion, arterial glucose (144 +/- 27 mg/dl) and leucine concentrations (130 +/- 15 mumol/l) decreased (P less than 0.05 or less vs. base line) toward normal, whereas KIC did not change (33 +/- 4 mumol/l, NS). However, no net uptake of either leucine or KIC across the forearm was detected at any time point. In contrast, a significant net release of these substrates occurred throughout the insulin infusion. By the end of the hormone administration, whole body leucine and KIC Ra decreased 17 and 33%, respectively (P less than 0.01). However, forearm uptake and release of leucine and KIC did not significantly change with respect to base line. The fraction of whole body leucine released from estimated total muscle mass did not change (54 to 48%, NS) before vs. after insulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Interaction of local and reflex thermal effects in control of forearm blood flow.

We measured forearm blood flow (ABF) bilaterally on six subjects during 15-min periods of leg exercise and the first 10 min of recovery. One forearm (control) was kept at about 33 degrees C skin temperature in all experiments. In experiments at ambient temperature (Ta) of 15 degrees C, the other arm (experimental) was kept at about 26, 33, and 40 degrees C, respectively, during three successive cycles of exercise and recovery. ABF in the 26 degrees C forearm was linearly related to and averaged 42% of control. The relation of ABF in the 40 degrees C forearm to control ABF showed a bend at control ABF of 4-5 ml X 100 ml-1 X min-1. Below the bend, experimental ABF average 213% of control. Above the bend, experimental ABF averaged 5.09 ml X 100 ml-1 X min-1 above control. In four subjects, after heating the experimental forearm to 40 degrees C, we measured ABF for 25-30 min at rest in Ta of both 15 and 25 degrees C. At 25 degrees C Ta, ABF in the heated forearms rose gradually, but control ABF showed little change. At 15 degrees C Ta, the effect on ABF of local heating to 40 degrees C was much reduced, apparently due to reflex vasoconstrictor signals.

Adult↗

Postural cardiovascular reflexes: comparison of responses of forearm and calf resistance vessels.

Simultaneous measurements were made of changes in vascular resistance in the forearm and calf in response to moving from supine to sitting or to head-down tilt. The subjects were healthy male volunteers, 21-63 yr. Blood flows were measured by venous occlusion plethysmography using mercury-in-Silastic strain-gauges. The gauges were maintained at the same level relative to the heart during the postural changes. Arterial blood pressure was measured by auscultation; heart rate was counted from the plethysmograms. Changing from supine to sitting caused a decrease in forearm blood flow from 4.13 +/- 0.14 to 2.16 +/- 0.19 ml.100 ml-1.min-1. Corresponding calf flows were 4.21 +/- 0.32 and 4.40 +/- 0.59 ml.100 ml-1.min-1. There was no change in mean arterial blood pressure, and heart rate increased by 8.0 +/- 1.5 beats/min. Arrest of the circulation of both legs with occlusion cuffs on the thighs before sitting, to prevent pooling of blood in them, reduced the degree of forearm vasoconstriction. Neck suction (40 Torr) during sitting, to oppose the decrease in transmural pressure at the carotid sinuses, inhibited the vasoconstriction. During a 30 degrees head-down tilt, there was a dilatation of forearm but not of calf resistance vessels. A Valsalva maneuver caused a similar constriction of both vascular beds. Thus, when changes in vascular resistance in forearm and calf are compared, the major reflex adjustments to changes in posture take place in the forearm.

Adult↗

In vivo thermal conductivity of the human forearm tissues.

The effective thermal conductivities of the skin + subcutaneous (keff skin + fat) and muscle (keff muscle) tissues of the human forearm at thermal steady state during immersion in water at temperatures (Tw) ranging from 15 to 36 degrees C were determined. Tissue temperature (Tt) was continuously monitored by a calibrated multicouple probe during a 3-h immersion of the resting forearm. Tt was measured every 5 mm from the longitudinal axis of the forearm (determined from computed-tomography scanning) to the skin surface. Skin temperature (Tsk), heat loss (Hsk), and blood flow (Q) of the forearm, as well as rectal temperature (Tre) and arterial blood temperature at the brachial artery (Tbla), were measured during the experiments. When the keff values were calculated from the finite-element (FE) solution of the bioheat equation, keff skin + fat ranged from 0.28 +/- 0.03 to 0.73 +/- 0.14 W.degrees C-1.m-1 and keff muscle varied between 0.56 +/- 0.05 and 1.91 +/- 0.19 W.degrees C-1.m-1 from 15 to 36 degrees C. The values of keff skin + fat and keff muscle, calculated from the FE solution for Tw less than or equal to 30 degrees C, were not different from the average in vitro values obtained from the literature. The keff values of the forearm tissues were linearly related (r = 0.80, P less than 0.001) to Q for Tw greater than or equal to 30 degrees C. It was found that the muscle tissue could account for 92 +/- 1% of the total forearm insulation during immersion in water between 15 and 36 degrees C.

Adipose Tissue↗