The effect of body heating and cooling on the ankle and toe systolic pressures in arterial disease

Although changes in body temperature alter limb blood flow, little information exists on the effect of body heating and cooling on systolic pressures in limbs with arterial disease. Ten patients with stable claudication were studied. Mean ankle systolic pressure index during body cooling (0.79 +/- 0.04) exceeded (p less than 0.01) both the value during routine test (0.69 +/- 0.03) and during heating (0.65 +/- 0.04). The individual, paired difference in ankle systolic pressure index between cooling and heating exceeded 0.15 in seven limbs and between cooling and routine test in five. Mean toe systolic pressure index during heating, but not during cooling, was lower than during routine test (p less than 0.01). There was no significant difference in the mean toe systolic pressure index between heating and cooling. However, compared with heating, toe systolic pressure index increased with cooling in 12 limbs and decreased in eight, including three with loss of measurable pressure. The paired difference in toe systolic pressure index between cooling and heating exceeded 0.15 in 10 limbs and between cooling and routine test in eight; whereas between heating and routine test the paired difference was within 0.15 in all but three limbs. The results indicate that changes in body temperature have significant effects on distal pressures in arterial disease. Preliminary warming in routine tests should improve reproducibility.

Effect of temperature on digital systolic pressures in lower limb in arterial disease

BACKGROUND

Toe pressures correlate with the chances of healing of skin lesions and with the risk of amputation and mortality. They are not affected by incompressibility of the tibial vessels, which may render ankle pressures inaccurate and reflect the overall arterial obstruction down to the digits. Digital pressures, however, may be affected by temperature.

METHODS AND RESULTS

Measurements under routine laboratory conditions were compared with those at controlled temperatures in 77 limbs with arteriosclerosis obliterans. The desired local temperatures were attained by perfusing water through the cuffs for 7 minutes before the measurements while the flow was interrupted by a tourniquet to allow equilibration of the toe and water temperatures. Mean toe pressure of 34 +/- 4 mm Hg at 10 degrees C was significantly lower (p less than 0.001) than the values during routine measurements (57 +/- 4 mm Hg) and at 30 degrees C (69 +/- 4 mm Hg). The pressure at 30 degrees C was 10 +/- 3 mm Hg higher than during routine measurements when initial digit temperature was below 30 degrees C (p less than 0.01) but not when it was higher. Measurements at 3 degrees C increments from 27 degrees C to 39 degrees C showed progressive increase in pressure (p less than 0.01).

CONCLUSIONS

Pressures at 36 degrees C and 39 degrees C were the highest but were not significantly different from each other. When toe temperature is low under routine conditions, the measured pressure may be falsely low, probably because of an effect on the main digital arteries that leads to delayed opening during deflation of the cuffs. Measurements at warm local temperature will increase the accuracy of the assessment of the severity of the arterial obstruction and may improve prediction of spontaneous healing of skin lesions.

The effect of cooling on toe systolic pressures in subjects with and without Raynaud's syndrome in the lower extremities

The effect of changes in local and body temperature on the toe systolic pressures was studied in 20 subjects with and 30 without Raynaud's syndrome in the toes. The pressures were significantly lower in the group with Raynaud's syndrome under all experimental conditions (P less than 0.01). The pressures were significantly lower during body cooling than during body warming in both groups (P less than 0.01). The mean decrease with body cooling was 58 mmHg in the group with Raynaud's syndrome and 24 mmHg in the control subjects (P less than 0.01). During body cooling pressures fell to less than 30 mmHg in 70% of subjects with Raynaud's syndrome and in 3% of the controls. Local cooling from 30 to 10 degrees C during body cooling resulted in a significant mean decrease in pressure of over 40 mmHg in both groups (P less than 0.01) and the pressure fell below 30 mmHg in over 90% of the group with and in 26% of those without Raynaud's attacks. The results indicate the importance of body cooling and local temperature in the mechanism of vasospasm in the toes. They are also relevant to the diagnosis of Raynaud's syndrome in the lower limbs and have implications for the testing of patients with arteriosclerotic occlusion since erroneously low pressure values could be obtained in tests when the feet are cold.

Walking ability and ankle systolic pressures: observations in patients with intermittent claudication in a short-term walking exercise program

Walking ability and limb hemodynamics were studied in 56 patients with intermittent claudication in an exercise program. Patients walked 1 hour 3 times a week for 3 to 6 months. Ankle and brachial pressures were measured at rest and after a standard walk, and walking ability on the treadmill and during free walking was determined. Average maximal distance on the treadmill increased from 0.59 to 1.00 km after training (p less than 0.0001). Also, after training 84% of patients were able to walk continuously more than 2 km without severe discomfort. The attained walking ability of individual patients could not be predicted from pressure measurements. Small pressure changes after training suggested that factors other than increased development of collateral vessels were important in determining walking ability. Practically useful walking ability was achieved in patients with aortoiliac and femoropopliteal arterial obstruction in the presence or absence of coronary disease and in patients taking beta-blockers. The results indicate that walking exercise is a valuable treatment for many patients with claudication who are not candidates for arterial reconstruction.

A case study of the Tenwek hospital community health programme in Kenya

Tenwek mission hospital, situated in the west-central highlands of Kenya, initiated a community health programme in 1984. This paper describes the major features of the programme and assesses the impact on a number of health and family planning practices after 3 years of implementation. Comparison of the results in the programme areas with the baseline survey and with control areas show significant changes in several indicators. It is concluded that Tenwek hospital demonstrated the impact a hospital can have on health of communities by effectively moving into community-based health care.

Apparent finger systolic pressures during cooling in patients with Raynaud's syndrome

Despite considerable research, the mechanisms responsible for the vasospasm associated with Raynaud's syndrome are not well understood and there is no reliable diagnostic test. In the present studies, measurements of systolic pressure in locally cooled fingers were used to address these issues. We found that local cooling produced a marked decrease or loss of the apparent finger systolic pressure in patients with Raynaud's syndrome in whom a standardized vasoconstriction had been induced by body cooling. Abnormal responses were encountered in 109 of 125 patients with secondary Raynaud's syndrome, in 21 of 37 patients with primary Raynaud's disease or the syndrome of uncertain cause, and in two of 63 subjects without symptoms of Raynaud's. These data suggest a high accuracy of the test in patients with secondary Raynaud's syndrome and lower accuracy in those with disease of primary or uncertain cause. We studied responses of systolic pressures to alterations in body and local temperatures in fingers with and without low pressures secondary to proximal arterial obstruction. Our data show that although local cooling has a small independent effect that increases vascular tone: (1) sympathetic vasoconstriction induced by body cooling is necessary to produce vasospasm and often produces it without local cooling, (2) high local temperature (30 degrees C) protects from vasospasm, and (3) low finger blood pressure predisposes to it. Delayed opening of the vessels observed after sudden deflation of blood pressure cuffs suggests that abnormal responses of finger systolic pressure to cold represent combined effects of high vascular tone, delayed opening, and local blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Training to vasodilate in a cooling environment: a valid treatment for Raynaud's phenomenon?

While many reports indicate that voluntary modification of skin temperature is possible and may be useful in the treatment of Raynaud's phenomenon, little attention has been paid to the ecological validity of training skin temperature increases when a considerable amount of vasodilation of digital vessels may already exist (room temperature, 22-24 degrees C). Patients with Raynaud's vasospastic attacks may benefit from learning to avoid attacks when they are impending by voluntarily vasodilating the vessels of their digits under conditions when vasoconstriction has begun. The results in 14 patients with primary and secondary Raynaud's phenomenon indicated that (a) patients learned to voluntarily increase digital skin temperatures in a "cooling" environment during documented vasoconstriction, and (b) there was a 31% decrease in the occurrence of vasospastic attacks following such learning. These data suggest that a new methodology may be useful in the biofeedback treatment of Raynaud's phenomenon, but further research is needed to determine the specific mechanism(s) involved, and the limits to its usefulness.

Preferred conformational state of the N-terminus section of a bovine growth hormone fragment (residues 96-133) in water is an omega loop

The solution structure of a 38-amino-acid-residue, biologically active fragment of bovine growth hormone (bGH96-133) was investigated with a combined nuclear magnetic resonance (NMR) and computer modeling approach. With the distance geometry program DISGEO and distance constraints derived from nuclear Overhauser enhancement (NOE) experiments, it was found that residues Ser-100 to Tyr-110 circumscribe and omega-loop, a recently categorized feature of nonregular secondary protein structure.

Collapse and viscoelasticity of diseased human arteries

A laboratory study of the hydrostatic collapse of diseased tibial arteries demonstrated hysteresis in the pressure-flow behaviour which resembled that seen in the stress-strain relations of the arterial tissue. The pressures at which the vessels collapsed were found to be considerably lower than expected on the basis of theoretical elastic models. Also, the pressures at which the vessels reopened were consistently lower than the pressures at which they collapsed. These findings were explained on the basis of viscoelasticity. The difference between collapse and opening pressure may provide insight into the mechanical properties of vessels, and a clue to errors in non-invasive measurements of blood pressure which depend upon collapse of arteries.

A mobile internal medicine clinic

The Denver Veterans Administration Medical Center (DVAMC) established a mobile internal medicine clinic (MediVAn) to provide access to primary care for veterans living more than fifty miles from the center and to study the costs of such an outreach program. A fully equipped van staffed by an internist visited four Colorado cities weekly for scheduled appointments. In the first two years of operation there were 4,655 visits by 766 veterans with a mean age of 56 years, with 3.9 diagnoses, and receiving 3.0 medicines. The cost per MediVAn visit was $68, compared with $67 per outpatient visit at DVAMC. We conclude that a mobile medical clinic is a convenient method of delivering primary care over distances and is comparable in cost to outpatient hospital visits.

Arterial auscultation in peripheral vascular disease

Bruits between epigastrium and popliteal fossae were found in 63% of 309 patients with arterial obstruction and in 7% of 149 patients without obstruction. In the former group, ankle systolic pressure at rest was abnormal in 85% of limbs with bruits, indicating a hemodynamic abnormality. In the majority of limbs with bruits and normal pressures at rest, an abnormal pressure response to exercise suggests that auscultation is useful in detection of even milder arterial lesions. Auscultation, after exercise and during compression of arterial branches distal to the bruits, may unmark stenotic lesions that do not produce audible bruits at rest and may localize bruit-producing lesions. This study indicates that peripheral auscultation is a valuable technique for assessing the arterial system in individual patients and for screening population groups.

The effect of age on the unfolding of elastin lamellae and collagen fibers with stretch in human carotid arteries

We measured folding of elastin lamellae and collagen fibers in human carotid arteries and correlated the results with the elastic properties of the vessels. Specimens cut into circumferential strips were stretched to various degrees, fixed, and stained for elastin and collagen. Folding was measured on photographic projections. Elastin lamellae unfolded quickly with initial stretch. In old vessels they did not straighten as much as in the young suggesting that the content of the interlamellar space may interfere with the unfolding. Collagen fibers straightened more during stretch in stiffer older vessels than in the young, already at low degrees of stretch. Young's modulus at extension of 5% appeared to correlate with unfolding of elastin lamellae in young extensible vessels. The modulus correlated significantly with unfolding of collagen fibers at extensions of 15% and greater, and the slope of the regression of the modulus on folding increased with stretch. Our findings provide for the first time morphologic evidence for the role of elastin lamellae in the determination of the elastic properties at low extensions, for the importance of collagen fibers in increasing stiffness with further stretch, and for the relationship between increased stiffness with age and the earlier recruitment of the collagen fibers.

Finger systolic pressures and skin temperatures in severe Raynaud's syndrome: the relationship to healing of skin lesions and the use of oral phenoxybenzamine

Systolic pressures and skin temperatures were studied in 23 patients with severe Raynaud's syndrome who were given oral phenoxybenzamine. There was a relationship between the measurements and the severity of the disease. Statistically significant correlation was found between the measurements and the time for healing of skin lesions. The chances of early healing are high when digital systolic pressure exceeds 55 mm Hg, the branchial-finger pressure difference is less than 50mm Hg, and the maximal difference among fingers less than 30 mm Hg. Early healing is also likely when finger temperature of 10 degree C or more above room temperature is achieved during "reflex" heating and the difference in temperature among fingers is less than 4 degree C. Therefore, the measurements are of value in the determination of prognosis. Rest pain, local tenderness, trophic skin changes, and vasospastic phenomena improved in the majority of patients soon after beginning treatment with phenoxybenzamine. Some side effects, usually minor, were common but with doses not exceeding 50 mg used in this study they were usually not trouble-some and the drug was tolerated well. Phenoxybenzamine is a valuable drug in the treatment of patients with severe vasospastic disease.

Voluntary increase in finger temperature in man in a cooling environment

To test whether man can increase voluntarily skin temperature in a cool environment, 14 subjects (age 15--51) were studied. They came once or twice a week for five to eight sessions of 1 h. The room temperature of various sessions varied from 21.2 to 15.6 degrees C. Temperatures of six fingers were recorded using thermocouples. During trials to increase temperature, subjects were shown a dial indicating temperature of an index finger and were instructed to try to warm their hands. The trials were begun when skin temperatures were stable or were falling, indicating that vasoconstriction was occurring. They were preceded and followed by a rest period. The differences between changes in temperature during the trials and the rest periods were significant for the group of 14 subjects (p less than 0.01). In 10 subjects with individually significant results, differences between the trial and rest periods averaged 5.0 degrees C for 'the best' and 3.9 degrees C for 'the worst' finger. The maximum temperatures during the trials averaged 30.9 +/- 1.0 degrees C (mean +/- SE) in 'the best' finger. During later sessions, subjects were able to increase temperatures without seeing the dial. The results indicate that humans are able to increase voluntarily cutaneous finger blood flow in a cool environment.

Effect of age, cardiovascular disease, and vasomotor changes on transmission of arterial pressure waves through the lower extremities

Pressure waves were recorded by indwelling needles in the femoral and foot arteries. At the foot the systolic and pulse pressures were greater and the dicrotic wave more prominent. These changes during transmission increased during vasoconstriction and decreased during vasodilatation. The ratio of the distal to femoral pulse pressure (amplification) increasing from 1.13 +/- 0.05 during body heating to 1.47 +/- 0.06 during body cooling (P less than 0.01), and from 1.14 +/- 0.10 during infusion of trimethaphan to 1.42 +/- 0.02 during cooling (P less than 0.05). Amplification was also significantly greater following inhalation of amyl nitrite and during and after Valsalva maneuver. Greater pulse pressure at the foot paralleled greater amplitude of individual harmonics. Phase velocities decreased with increasing frequency and tended to level off at a value similar to the foot-to-foot pulse wave velocity. The findings are consistent with peripheral reflections of the waves which increase during vasoconstriction. In the absence of procedures that elicit vasoconstriction or vasodilatation, amplification averaged 1.35 +/- 0.03 in control subjects less than 35 years of age and 1.24 +/- 0.06 in older subjects (P less than 0.05). Amplification also did not differ significantly between control subjects and patients with hypertension or ischemic heart disease. In the absence of pronounced vasodilatation or encroachment on the lumen by atherosclerotic plaques, systolic and pulse pressures at the foot should be higher than in proximal pulses. These findings provide a firm basis for interpreting measurements of distal systolic pressures by using blood pressure cuffs when examining patients with occlusive arterial disease in the extremities.

Digital systolic pressures in the lower limb in arterial disease

Systolic pressures were measured by using pneumatic cuffs on the second toe, ankle, and arm. In the absence of clinically evident peripheral vascular disease, digital pressure expressed as a percentage of the brachial pressure averaged 87% and was not significantly different in older normal persons, patients with hypertension, diabetes mellitus, or coronary artery disease from that in young normal subjects. Digital pressures were decreased in patients with arteriosclerosis and thromboangiitis obliterans, or Raynaud's phenomena. Mean digital pressures correlated well with clinical and angiographic findings. In arteriosclerosis obliterans digital pressures in the limbs with claudication averaged 43% of the brachial pressure, and in patients with rest pain or skin lesions, or both, 21%. The ankle-to-toe pressure difference was increased in the majority of patients with thromboangiitis obliterans and in some diabetics with arteriosclerosis obliterans. The results indicate that digital pressure expressed as percentage of brachial pressure is a good index of the severity of the overall occlusive process, whereas the ankle-to-toe pressure difference may provide a useful index of the disease in the small distal arteries.

Systolic pressures in the extremities of man with special reference to the toes

Systolic pressures have been studied extensively in the fingers but not in the toes. We measured systolic pressures in the toes, fingers, ankles, and wrists of young normal subjects during body heating and cooling. Systolic end points were determined during deflation of pneumatic cuffs by detecting either the appearance of oxyhemoglobin in the skin using a spectroscope, or the increase in the volume of the part using a strain gauge plethysmograph. Toe and finger pressures were higher during vasoconstriction than during vasodilatation (p < 0.001), whereas the ankle-to-toe and wrist-to-finger gradients were higher during vasodilatation (p < 0.005), These changes in pressures and gradients with change in vasomotor state are probably due to alterations in flow through the arteries of the hand and foot and the associated changes in the utilization of pressure energy. Finger pressures were higher than toe pressures during both vasomotor states (p < 0.025). This was only partly explained by the difference in hydrostatic pressure (toes higher than fingers with respect to heart in supine position). The tendency for gangrene to develop in the toes may be related in part to their lower pressures.