Skin Capillary Blood Flow Research Articles

Isolated circulatory response to intravenous administration of the ACE inhibitor enalaprilat.

The isolated vascular effects of intravenous administration of the angiotensin converting enzyme (ACE) inhibitor enalaprilat were investigated. Thirty male patients undergoing cardiopulmonary bypass (CPB) were studied. According to a randomized sequence, 0.04 mg kg-1 enalaprilat (low-dose, n = 10), 0.08 mg kg-1 (high-dose, n = 10) enalaprilat or saline solution as placebo (control group, n = 10) was given as an i.v. bolus during CPB. Changes in mean arterial pressure (MAP) and venous reservoir (RV) of the extracorporeal circulation were studied as indices of arterial resistance and venous capacitance. Mean arterial blood pressure (MAP) and peripheral vascular resistance (SVR) were significantly more reduced in the high-dose enalaprilat group (MAP: -36 mm Hg after 9 min; SVR: -836 dyn s cm-5) than in the low-dose group (MAP: -13 mm Hg after 10 min). Volume of the reservoir (RV) decreased in both enalaprilat treated groups indicating additional (dose-dependent) venous pooling effects of the substance (low-dose: -300 ml; high-dose: -520 ml; control group: -100 ml). Skin capillary blood flow measured by laser Doppler flowmetry (LDF) increased after injection of 0.04 mg kg-1 enalaprilat, whereas it decreased significantly when MAP fell markedly in patients treated with high-dose enalaprilat. I.v. enalaprilat had dose-dependent vasodilating properties in the arterial and venous vessel system indicating reduction in pre- and afterload. Microcirculation in both enalaprilat treated groups improved as long as reduction in blood pressure was not limited.

Capillary blood flow to the skin of forearm in cirrhosis.

In liver cirrhosis a hyperkinetic circulatory state is frequently observed as a consequence of an arterial or even a venous peripheral vasodilatation with secondary increase in cardiac output. Indirect evidence suggests that, in liver disease, the manifestation of warm hands, capillary pulsation, or palmar erythema may also relate to such a state by way of an increased skin blood flow. The purpose of the present study has been to directly assess capillary skin blood flow in liver disease through the clearance of a locally injected radioactive substance. The study was performed in 24 patients with different liver diseases, including 14 Child class II cirrhotics, and in 9 control subjects. A small volume of Na 131I solution was injected at the volar surface of the forearm, and radioactive counts were recorded continuously for ten seconds every minute for up to twenty minutes. The best fit line of the disappearance rate was determined by the least square method, and both its T/2 and an estimated blood flow parameter were calculated. The T/2 of isotope disappearance rate was 4.54 +/- 0.71 and 4.38 +/- 0.68 minutes in cirrhotics and controls, respectively. Similarly, estimates of skin blood flow (mL/min/100 g tissue) were 7.82 +/- 1.28 in the cirrhotic patients, not significantly different from those in both patients with mixed liver diseases (7.6 +/- 2.86) and control subjects (8.06 +/- 1.04). Parameters of skin blood flow were also invariant in respect to the various etiologies of liver disease. Thus, the present findings indicate that capillary skin blood flow is not affected by the hyperdynamic circulatory changes occurring in liver cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of insulin infusion on capillary blood flow in the diabetic neuropathic foot.

The effect of a short-term improvement in glycaemic control induced by insulin infusion on foot skin capillary blood flow was previously unknown. In seven Type 2 (non-insulin-dependent) diabetic subjects with neuropathy capillary blood flow was measured in the great toe nailfold by television microscopy. An estimate of arteriovenous shunt flow was obtained simultaneously in the pulp of the great toe by laser Doppler flowmetry. After omission of oral hypoglycaemic therapy for 24 h mean blood glucose was 15.7 +/- 0.7 (SEM) mmol l-1. A priming infusion of 0.1 U kg-1 of insulin was given intravenously over 15 min, followed by a variable rate insulin infusion adjusted to steadily reduce blood glucose avoiding hypoglycaemia. At the end of the study blood glucose was reduced to 6.9 +/- 0.7 mmol l-1 (p less than 0.001). During the insulin infusion, capillary blood velocity increased by 28.8% (p less than 0.05), and the diameter of the capillary erythrocyte column increased from 7.6 +/- 0.2 to 9.2 +/- 0.3 micron (p less than 0.01). Thus during the insulin infusion, the calculated capillary flow increased to 226 +/- 36% above basal values (p less than 0.01). Laser Doppler flow did not change significantly, suggesting that during insulin infusion skin blood flow is redistributed with an increase in capillary flow relative to arteriovenous shunt flow.

RETRACTED: THE ROLE OF ENOXIMONE IN CARDIAC SURGERY

After cardiopulmonary bypass (CPB), some patients may require circulatory support. This study examined the role of the phosphodiesterase-III inhibitor, enoximone, in cardiac surgery. Eighty patients selected by chance were allocated randomly to two groups: 40 patients received enoximone 1.0 mg kg-1 approximately 10 min before weaning from CPB and 40 served as a control group. Additional pharmacological therapy (adrenaline, noradrenaline, nitroglycerin) was given, when necessary, by anaesthetists who were not involved in the study. In addition to standard monitoring, skin capillary blood flow was assessed using a laser Doppler technique before, during and after CPB until 2 h after the end of the operation. In the period after bypass, cardiac index was always significantly greater in the enoximone than in the control group. Systemic and pulmonary vascular resistance were less in the enoximone-treated patients, indicating a reduction in right and left ventricular wall stress. Oxygen consumption in the enoximone patients was significantly greater after CPB, whereas intrapulmonary shunting was comparable in the two groups. In comparison with baseline values, skin capillary blood flow in the enoximone patients was always greater than that in the control group. In comparison with the control patients, significantly fewer enoximone patients needed adrenaline, and in a smaller dose, even 2 h after operation, whereas more enoximone patients required noradrenaline therapy for a short period. We conclude that the use of enoximone before weaning from CPB improved overall cardiac function, reduced the need of catecholaminergic inotropic support, and provided increased organ perfusion up to 2 h after operation.

An evaluation of skin capillary blood flow determinations in neonates using a computerized videophotometric method

Dynamic capillaroscopy has been shown to give valid measurements of skin capillary blood flow in adults. The aim of this investigation is to evaluate the accuracy of the method when applied to studies in newborn infants. A computerized videophotometric technique was used to measure the skin capillary blood cell velocity (CBV) and the capillary erythrocyte column diameter at 64 standardized locations in 16 nailfold capillaries in five subjects. To estimate the method's reliability, we calculated the coefficient of variation (CV = 1 SD/mean × 100%) for repeated measurements at each location. The CV for CBV determinations was found to be 3.4% (0.9–13%) and the corresponding value for capillary diameter measurements was 6.7% (0.5–12%) (median and range). Although the CBV and diameter values were found to vary along the course of the capillary, the volume flow of blood cells was assumed to be the same in simultaneously studied but different sections of the capillary. The paired CBV and diameter observations were therefore used to calculate blood cell flow values at an average of four different intracapillary locations. To estimate the method's validity, the CV for these repeated flow calculations was determined and found to be 7.5% (3.2–26%). We conclude that the age-specific characteristics in neonates, mainly a high hematocrit and short, irregular skin capillary loops, do not limit the feasibility and accuracy of videophotometric microscopy for dynamic microcirculatory studies in neonates.

Laser Doppler measurements of skin blood flow before, during, and after lumbar sympathetic blockade in children and young adults with reflex sympathetic dystrophy syndrome.

Changes in the skin capillary blood flow (SBF) and temperature before, during, and 1 hour after unilateral lumbar paravertebral sympathetic blockade (LSB) were studied simultaneously with laser Doppler flowmetry and thermometry in patients with reflex sympathetic dystrophy syndrome. The baseline flow measurements in the toes on the affected limb were significantly lower than in the contralateral limb (p less than 0.01). During LSB, a 10-fold increase in SBF was detected within 4 minutes after injection of a local anesthetic agent when the sympathetic blockade was effective; an increase of more than 1 degrees C in the skin temperature occurred within 11 minutes. Measurements 1 hour after blockade showed an 18-fold (mean) increase in SBF in the toes (p less than 0.0001) and a 2-fold (mean) increase in SBF in the thighs (p less than 0.001). There was a significant decrease in the skin blood flow in the contralateral toes after the sympathetic blockade (p less than 0.01). We conclude that laser Doppler flow measurements can be used to detect immediate onset of sympathetic blockade in patients under general anesthetic or conscious sedation.

Augmentation of Transmidline Skin Perfusion and Viability in Transverse Rectus Abdominis Myocutaneous (TRAM) Flaps in the Pig

The aim of this experiment was to design a clinically relevant TRAM flap in the pig and to use this flap model to study the effectiveness of preoperative ligation of the dominant vascular pedicle in augmentation of muscle and skin capillary blood flow and skin viability in the TRAM flap. This TRAM flap model was based on the deep inferior epigastric vascular pedicle, with the center of the transverse skin paddle attached to the underlying rectus abdominis muscle at the superior end of the muscle and extending bilaterally from its attached muscle. The transverse skin paddle (8 x 30 cm) included a contralateral and ipsilateral random portion of skin. This flap model was based on the deep inferior epigastric rather than the superior epigastric vascular pedicle because the deep inferior epigastric vascular pedicle is the smaller of the two in the pig and augmentation of its blood supply by ligation of the dominant superior epigastric vascular pedicle resembles more closely the clinical situation. It was observed that ligation of the dominant superior epigastric vascular pedicle 14 days prior to raising the TRAM flap significantly (p less than 0.05; n = 5) increased the total muscle and skin capillary blood flow and skin viability in the transverse skin paddle compared with the sham-operated control (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Discrimination of capillary and arterio-venular blood flow in skin by laser Doppler flowmetry

The scattering and absorption of light by tissue and blood is wavelength dependent; the tissue penetration of green light (lambda = 543.5 nm) is about 60 per cent of that of red light (lambda = 632.8 nm) but the absorption of green light by blood is about 20 times greater than for red light. The effect of this difference has been studied by observing the responses of skin blood flow to heat and weal, measured by laser Doppler flowmetry at the two wavelengths. By using time autocorrelation function analysis (ACF) of the scattered light measured, low and high frequency components have been associated with capillary and larger vessel flow, respectively. The comparison of ACF from scattered green and red light has shown that measurements cannot be interpreted by only considering light penetration depth through a homogeneous tissue. Light absorption and multiple scattering by blood at the individual microvessel level, blood rheology and vessel morphology are parameters which are considered for greater attention.

Efficacy of intravenous infusion of prostacyclin (PGI 2) or prostaglandin E 1 (PGE 1) in augmentation of skin flap blood flow and viability in the pig

The dose-response effects of 6-h intravenous infusion of PGI 2 (0, 5, 10, 25 or 75 ng/kg/min) or PGE 1 (0, 25, 50, 100 or 300 ng/kg/min) on skin hemodynamics and viability were studied in 4 × 10 cm random pattern skin flaps (n=24) raised on both flanks of the pig. Infusion of PGI 2 or PGE 1 was started immediately after intravenous injection of a loading dose 30 min before skin flap surgery. PGI 2 infusion significantly (P<0.05) increased the total skin flap capillary blood flow at the dose of 10 ng/kg/min, compared with the control. However, the distance of blood flow along the skin flap from the pedicle to the distal end, i.e. perfusion distance, was not increased. Consequently, the length and area of skin flap viability was also not significantly increased. The effect of PGI 2 infusion on skin blood flow was biphasic. Specifically, higher doses (≥ 25 ng/kg/min) of intravenous PGI 2 infusion produced no beneficial effect on the skin flap capillary blood flow. PGI 2 infusion at the dose of 10 or 75 ng/kg/min did not significantly increased plasma renin activities or plasma levels of norepinephrine compared with the control, therefore the biphasic effect of PGI 2 on skin flap blood flow was not related to circulating levels of norepinephrine or angiotensen. Intravenous infusion of PGE 1 did not produce any therapeutic effect on the skin capillary blood flow in the random pattern skin flaps at all doses tested. At the dose of 300 ng/kg/min, the mean arterial blood pressure was 17% lower (P<0.05) than the control, but the skin capillary flow still remained similar to the control. It was concluded that intravenous infusion of PGI 2 or PGE 1 was not effective in augmentation of distal perfusion or length of skin viability in the porcine random pattern skin flaps. Drug treatment modalities for prevention or treatment of skin flap ischemia is discussed.

Quantitative measurement of sympathetic neuropathy in patients with diabetes mellitus

Vasoconstriction occurs in the skin capillary blood flow of the healthy subject when posture changes from supine to standing. Using frequency analysis of the optical photoplethysmograph signal, a statistically significant difference ( P<0.01) may be demonstrated between supine and standing positions in the lower frequency band (0.01–0.5 Hz) in the foot of normal subjects. This allowed us to develop a simple index: sympathetic power band change (SPBC). Patients with diabetes mellitus often suffer from degeneration in the sympathetic nervous system. This impairs the normal vasoconstrictor response to standing. We have applied the SPBC ‘blind’ to a group of diabetic patients. Such patients may be divided into three groups according to their SPBC indices: normals with SPBC> 2.6 (group A), intermediates with 2.6 ⩾ SPBC ⩾ 0.26 (group B) and poor with SPBC < 0.26 (group C). All patients with retinopathy were in group C and five out of the six patients with electrophysiologically confirmed peripheral neuropathy were in group C. Frequency analysis of the photoplethysmograph signal has produced an index of sympathetic tone change when subjects move from supine to standing position. The application of this index to patients with diabetes mellitus shows some patients to have sympathetic vascular tone failure.

Arteriovenous Shunting and Regional Blood Flow in Myocutaneous Island Flaps

In eight pigs, total blood flow, regional capillary blood flow distribution, and arteriovenous (AV) shunting were studied during the first 4 postoperative hours after elevation of a myocutaneous rectus abdominis island flap. Capillary blood flow and AV shunting were measured using radioactive microspheres before flap creation and 1 and 4 hours after surgery. Total blood flow, measured continuously as venous outflow, increased in the first postoperative hour (p less than 0.05). Elevation of the flap caused a slight decrease in skin capillary blood flow (p less than 0.05), whereas muscular capillary blood flow increased (p less than 0.01). AV shunting accounted for 50 percent of the total flap blood flow, whereas it was negligible in the abdominal wall prior to flap elevation. Thus stalk blood flow, skin appearance, and skin temperature may be poor indicators of nutritional capillary perfusion. However, the clinical and nutritional consequences of these findings remain to be established.

Effects of 5-Hydroxytryptamine on Capillary and Arteriovenous Anastomotic Blood Flow in the Human Hand and Forearm and in the Pig Hind Leg

The effects of intraarterially infused serotonin (5-HT) on capillary and arteriovenous anastomotic (AVA) blood flow were investigated in the hand and forearm of 19 healthy volunteers, and in the hind leg of six anesthetized pigs using radioactive microspheres with a diameter of 15 microns. The 5-HT2-receptor antagonist ketan-serin was used in an attempt to identify the receptors involved. None of the drugs in the doses used induced systemic hemodynamic effects. Low doses of 5-HT significantly increased forearm blood flow with a maximum response at the dose of 1 ng/kg/min (68 +/- 14%, p less than 0.05), whereas only at the highest dose of 80 ng/kg/min was a net decrease in forearm blood flow measured (-28 +/- 6%, p less than 0.05). Conversely, finger blood flow was not influenced by the lower doses of 5-HT, whereas a major reduction was observed at the highest dose (-90 +/- 3%). Ketanserin increased both total forearm blood flow and AVA blood flow. The drug blunted the constrictor response to 5-HT in the forearm but only slightly attenuated this response in the finger. The percentage AVA blood flow in the human hand and forearm was not influenced by an infusion of 5-HT at 80 ng/kg/min alone. However, after pretreatment with ketanserin, which itself increased the AVA component, this dose of 5-HT significantly reduced AVA flow. In the pig, total femoral blood flow was not influenced by 5-HT, but AVA blood flow was significantly reduced and capillary skin blood flow increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical Augmentation of Skin Blood Flow and Viability in a Pig Musculocutaneous Flap Model

A porcine rectus abdominis musculocutaneous (TRAM) flap model was designed and validated in nine pigs. This TRAM flap was based on the deep inferior epigastric (DIE) vessels with an 8 x 18 cm transverse skin paddle at the superior end of the rectus abdominis muscle. The model was subsequently used to test our hypothesis of surgical augmentation of flap viability by vascular territory expansion. Specifically, we observed that ligation of the superior epigastric (SE) vessels at 4, 7, 14, and 28 days (N = 6 to 8) prior to raising the TRAM flaps significantly increased (p less than 0.05) the length and area of the viable skin in the transverse skin paddles of the treatment flaps compared with the contralateral shammanipulated control flaps. This significant increase in skin viability was seen to be accompanied by a significant increase (p less than 0.05) in skin and muscle capillary blood flow in the treatment TRAM flaps compared with the controls (N = 9). The mechanism of vascular territory expansion is unclear. We postulate that hypoxia resulting from the ligation of the superior epigastric vessels prior to the flap surgery may play a role in the triggering of the deep inferior epigastric artery to take over some of the territory previously perfused by the superior epigastric artery. This would then increase the skin and muscle capillary blood flow in the transverse paddle when the TRAM flap was raised on the deep inferior epigastric vascular pedicle.

Leech Therapy and Bleeding Wound Techniques to Relieve Venous Congestion

Temporary restoration of capillary skin blood flow can be established by using leeches or by the creation of a dermal wound and the promotion of continued bleeding from the wound site in a flap with venous occlusion. An increasing restoration of capillary flow occurred with initial application of the leech and tended to exceed other techniques of restoring flow. However, all techniques of exsanguination, including leech therapy, restored very low perfusion over a two-hour course of therapy for a volume of tissue simulating a distal finger replant. The temporary increase in flap perfusion with a single leech application was greatest during the feeding activity of the leech and tapered off after the leech was satiated, to approximate flows achieved with local heparin injection and a punch wound.

Transitory postural vasomotor dysfunction in the finger after short term hand vibration.

The transitory effects of hand vibration (ah, w = 3.16 m/s2 during three minutes) on postural vasomotor functions of skin capillary blood flow rate in the finger were studied by the local 133xenon washout technique in ten men with vibration induced white finger (VWF), nine men professionally exposed to hand-arm vibration but without finger symptoms (HAV), and eight male controls (MC). The following postural vasomotor functions were measured: (a) the vasomuscular, non-neurogenic autoregulation, tested by raising the finger 20 cm; (b) the local venoarteriolar vasoconstrictor axon reflex, tested by lowering the finger 40 cm; and (c) the central sympathetic vasoconstrictor reflex elicited by central baroreceptors and tested by changing the body posture from supine to sitting upright. Before short term vibration the vasoconstriction elicited by central baroreceptors was increased in VWF (p less than 0.01) and normal in HAV (p greater than 0.10). The local axon reflex and the autoregulation functioned normally in VWF and HAV (p greater than 0.30). Three minutes after vibration, autoregulation was abolished and the functions of the central and local sympathetic vasoconstrictor reflexes were equally impaired in all three groups (p less than or equal to 0.01). All three vasomotor functions were completely restored 60 minutes after vibration in MC (p greater than 0.10) and also 30 minutes after vibration in one male control (p greater than 0.20). The results indicate a hyperreactivity of the central sympathetic nervous system in VWF, and a transitory, impaired function of digital arterioles after short term vibration in all groups.

Effect of Capsulectomy on the Hemodynamics and Viability of Random-Pattern Skin Flaps Raised on Expanded Skin in the Pig

Skin flaps constructed on expanded skin usually include the underlying capsular tissue. It has been hypothesized that capsulectomy may jeopardize the viability of the expanded skin flap. The experiments reported herein were designed to test this hypothesis. Specifically, we studied the hemodynamics and viability of random-pattern skin flaps (8 X 20 cm) raised on delayed bipedicle flaps (group A) and on expanded skin pockets with capsulectomy at the time of flap elevation (group B) or with intact underlying capsular tissue (group C). Each group was randomly assigned to each flank in 16 pigs. Skin pockets were expanded by inflation of subcutaneous silicone tissue expanders with sterile saline (299 +/- 7 ml; X +/- SEM) over a period of 3 weeks. At the end of this period, the bipedicle flaps were constructed. Eight days later, random-pattern skin flaps were raised on bipedicle flaps and skin pockets. The length and area of skin flap viability, judged by the fluorescein dye test performed 1 day postoperatively, were not significantly different (p greater than 0.05) among groups A, B, and C (n = 31 to 32). There also were no significant differences (p greater than 0.05) in total skin capillary blood flow measured 1 day postoperatively (A = 2.6 +/- 0.4, B = 2.4 +/- 0.4, and C = 2.7 +/- 0.6 ml/min per flap; n = 15 to 16) and in skin viability assessed 7 days postoperatively (A = 74 +/- 2, B = 75 +/- 2, and C = 76 +/- 2 percent; n = 16) among delayed skin flaps and skin flaps raised on expanded skin pockets with or without capsulectomy. The results of this flap viability study were confirmed in 5 minipigs in a separate experiment. We conclude that capsulectomy did not have a detrimental effect on the hemodynamics and viability of random-pattern skin flaps raised on expanded skin. Furthermore, we hypothesize that skin flaps raised on expanded skin are similar to delayed skin flaps in that the skin blood flow is optimally augmented; therefore, the capsular tissue does not add significant blood supply to the overlying skin.

Clinical television microscopy.

The technique of television microscopy is the only available technique for the direct quantitative measurement of skin capillary blood flow. Television microscopy has applications in both research and clinical practice, and has attracted considerable interest from clinical groups attempting to study capillary blood flow. The critical requirements for a functioning system are difficult to ascertain from the published literature. The aim of this article is therefore to describe the individual components of a television microscope system, outline the current methods of analysis and briefly describe some of the clinical applications of television microscopy.

Direct measurement of capillary blood flow in the diabetic neuropathic foot.

The two major components of the microcirculation in the diabetic neuropathic foot have been examined in detail. Nutritive capillary blood flow was measured directly using the non-invasive technique of television microscopy, applied to the toe nailfold. Arteriovenous shunt flow was assessed using the technique of laser Doppler flowmetry, applied to the toe pulp. Fourteen diabetic patients with peripheral and autonomic neuropathy, 11 with no clinical evidence of neuropathy and 14 normal subjects were studied. Laser Doppler flowmetry (predominantly arteriovenous shunt flow) was increased more than three-fold (p less than 0.01) in the diabetic patients with neuropathy compared to control subjects, (median 3.57, interquartile range 2.00-5.32 volts vs median 0.93, interquartile range 0.47-2.36 volts, respectively). There was no evidence of skin capillary closure. The calculated capillary blood flow (erythrocyte flux) was significantly increased in the diabetic neuropathic patients compared to control subjects (median 76.4, interquartile range 34.4-109.8 picolitres/s vs median 23.2, range 8.0-44.8 picolitres/s, p less than 0.01). This study demonstrates that foot skin capillary blood flow is increased in diabetic patients with neuropathy. There is, therefore, no evidence to support the supposition that capillary ischaemia, either secondary to a "capillary steal phenomenon" or "advanced microangiopathy", is a feature of diabetic neuropathy under resting conditions.

Capillary blood cell velocity in full-term infants as determined in skin by videophotometric microscopy.

In order to study the neonatal microcirculation, the capillary hemodynamics in skin was investigated in 43 full-term infants 2-7 days after birth. The nailfold capillaries of the thumb were visualized by means of television microscopy and the capillary blood cell velocity (CBV) was videophotometrically quantified in 107 microvessels. The skin temperature, mean arterial blood pressure, and heel puncture hematocrit were measured simultaneously to evaluate any relation with the CBV. The mean CBV in all infants was 0.38 +/- 0.21 mm/s, with a range of 0.04 to 1.2 mm/s in individual capillaries. There was no correlation between CBV and skin temperature (27-33 degrees C), mean arterial blood pressure (44-68 mm Hg), or postnatal age. However, a significant correlation was found between the log CBV and the skin prick hematocrit (r = -0.64, p less than 0.001). It is concluded that the mean CBV during the 1st wk of life is not significantly different from the capillary velocity reported in adults. Normal variations in skin temperature and mean arterial blood pressure, as well as age differences 2-7 days after birth, do not significantly influence the neonatal skin capillary blood flow. However, the hematocrit is of major importance for skin capillary perfusion in the newborn infant.

Effects of tobacco smoke inhalation on capillary blood flow in human skin.

To measure the effects of tobacco smoke inhalation on capillary blood flow in human skin, 20 female tobacco smokers consented to smoke three cigarettes with nicotine levels of 0.50, 0.98, and 1.90 mg per cigarette, each on a separate occasion. Measurements of blood flow velocity and vascular diameter were made along the venous limb of capillaries within the nailfold skin of the third finger via videomicroscopy before and for 5 min after the smoking of each cigarette. Capillary blood flow (CBF) was calculated as a product of capillary cross-sectional area and flow velocity. Resting pre-smoke CBF for all experiments combined averaged 4.7 X 10(4) mu 3/sec. All three cigarettes elicited a significant reduction in CBF with the maximal effect within the first 2 min of the post-smoke period (p less than or equal to .05). Respective CBF values during this time averaged 3.6, 3.4, and 2.7 mu 3/sec for the low-, medium-, and high-nicotine cigarettes. Although the data suggested a downward trend in CBF with increasing nicotine levels, the post-smoke values were not significantly different among the three cigarettes. It is concluded that acute tobacco smoke inhalation reduces CBF in human skin, but the effect is not related to the nicotine content of the cigarettes. The changes in cutaneous CBF observed with tobacco smoking are less compared to reported effects of smoke inhalation on total digital blood flow.