Differences In Blood Flow Response Research Articles

OP.8C.08] INTERACTION BETWEEN PERIPHERAL ALPHA-ADRENERGIC RECEPTORS AND NEURONAL NITRIC OXIDE SYNTHASE

Objective: Vascular tone is influenced by release of norepinephrine (NE) from sympathetic nerves and by nitric oxide (NO) released from perivascular neuronal NO synthase (nNOS). nNOS appears a more important physiological determinant of vascular tone than endothelial NO synthase (eNOS), particularly when stimulated by stress. Thus vascular tone is determined mainly by the balance of the two neurally released mediators, NE tending to constrict and NO to dilate vascular smooth muscle. Indirect observations suggest there may be cross-talk between peripheral α-adrenergic receptors and nNOS signalling. Design and method: We therefore examined local forearm vasodilator responses to intra-brachial artery infusion of the non-selective α-adrenergic antagonist phentolamine in the presence and absence of S-methyl-L-thiocitrulline (SMTC), a specific inhibitor of nNOS. Normotensive participants (n = 12, 7 female, mean ± SD age 33 ± 13 years) were studied on two separate occasions in a two-visit single-blind, cross-over study, with each visit separated by at least 7 days. SMTC (0.2 μmol/min, a dose that inhibits vasodilation to mental stress but not to other NO donors or to calcium channel antagonists) on one visit and saline vehicle on the other were co-infused with a rising dose infusion of phentolamine (10, 30 and 100 μg/ml/min). Results: Phentolamine increased forearm blood flow less (from 3.39 ± 0.58 to 6.01 ± 1.10 ml/min/100 ml) when co-infused with SMTC compared to saline vehicle (increase from 3.37 ± 0.45 to 8.74 ± 1.16 ml/min/100 ml, P < 0.05 for difference in blood flow response). Conclusions: These data suggest that peripheral α-adrenergic receptors inhibit nNOS activation, an action likely to potentiate vasoconstrictor responses and to oppose antithrombotic and antiplatelet effects of nNOS-derived NO and which may contribute to nNOS dysfunction in hypertension and in other conditions associated with increased sympathetic activation.

Regional difference in blood flow response to hypercapnia (1106.12)

To investigate whether vascular responses to hypercapnia differ among various blood vessels, we recorded relative changes of mean arterial pressure (MAP) and blood flow values in the middle cerebral artery (MCA), retinal artery (RA), and choroidal vessels (CV) associated with an increase in end‐tidal CO2 pressure (PETCO2) induced by breathing CO2 rich air (5%) for 3 min in 30 healthy males (23.6 ± 0.3 years). PETCO2 and MAP significantly increased from baseline values by 16.5 ± 1.2% and 4.9 ± 1.0%, respectively (P&lt;0.05). Blood flow values in MCA, RA, and CV significantly increased by 11.2 ± 4.9%, 7.6 ± 2.0%, and 18.4 ± 4.5%, respectively (P&lt;0.05). There was a significant inter‐individual correlation in relative changes solely between RA and CV (r=0.47). It was suggested that vascular responses to hypercapnia differ among vessels, even among vessels similarly having vasodilatory response to CO2.

Different lying positions and their effects on tissue blood flow and skin temperature in older adult patients

To report a study to compare the effects of different lying positions on tissue blood flow and skin temperature in older adult patients. This article reports the evaluation of study design and procedures. To reduce risk of pressure ulcers, repositioning of immobile patients is a standard nursing practice; however, research into how different lying positions effect tissue microcirculation is limited. Descriptive comparative design. From March-October 2010, 20 inpatients, aged 65 years or older, were included in the study. Tissue blood flow and skin temperature were measured over bony prominences and in gluteus muscle in four supine and two lateral positions. The blood flow over the bony prominence areas was most influenced in the superficial skin and especially in the 30° lateral position, where the blood flow decreased significantly in comparison with the supine positions. There were significant individual differences in blood flow responses, but no common trend was identified among the patients considered at risk for pressure ulcer development. The study procedure worked well and was feasible to perform in an inpatient population. The lying positions seem to influence the tissue blood flow over the bony prominences in different ways in older adult inpatients, but further study is needed to confirm the results and to make recommendations to clinical practice. The study procedure worked well, although some minor adjustments with regard to heat accumulation will be made in future studies.

Exercise Therapy In Patients With Peripheral Neuropathy

Peripheral neuropathy is a pathology associated with damage to peripheral nerves, especially those of the extremities. Common symptoms of this condition include weakness, numbness, abnormal sensations and pain in feet, legs, arms, and/or hands. A recent literature search concluded there is inadequate evidence to evaluate the effects of exercise on functional ability in people with peripheral neuropathy. PURPOSE The primary objective was to assess the influence of exercise therapy on peripheral blood flow responses, heart rate variability and functional measures in a small sample of individuals with peripheral neuropathy. METHODS Participants engaged in an organized progressive exercise program 3*week for six weeks. The exercise program consisted of a typical walking program (with or without partial body weight support) or Tai Chi. Leg blood flow was evaluated, in both legs, at rest and following 5 minutes of arterial occlusion, using strain gauge plethysmography. Heart rate variability indices included standard deviation (SDNN), and low frequency (LF) and high frequency (HF) powers determined from EKG's obtained during 10 minutes of uninterrupted supine rest. Postural stability was defined as the average sway velocity in varied conditions on a force platform. Dynamic gait capability was defined as the center of pressure motion during walking on a treadmill. RESULTS To this point sixteen individuals (9 Women and 7 Men, Age: 68±7yrs, Height: 167±9cm, and Weight: 85±16kg) completed the exercise program. The program was well tolerated. No apparent differences in blood flow responses between the left and right legs were noted prior to the program. After 6 weeks, systolic blood pressure decreased (Pre: 135±15 Post: 126±14mmHg, p=0.001), whereas reactive hyperemic blood flow (RHBF) increased (Pre: 16.77±8.16 Post: 20.26±6.45ml/100ml/min, p=0.05). Moreover, changes in measures of heart rate variability suggest a favorable shift in autonomic modulation of the heart (Pre: LF/HF: 2.97±2.42 Post: 2.11±2.05, p=0.03). Finally, the changes in RHBF were associated with changes in SDNN (r2=0.39). Measures of postural stability improved significantly, whereas measures of dynamic gait capability only improved in those individuals involved in the walking program. CONCLUSION The results suggest that progressive exercise therapy is well tolerated in patients with peripheral neuropathy and may improve RHBF, HRV and postural stability. Improvements of measures of dynamic gait capability were specific to the modality of training used.

Exercise Therapy In Patients With Peripheral Neuropathy

Peripheral neuropathy is a pathology associated with damage to peripheral nerves, especially those of the extremities. Common symptoms of this condition include weakness, numbness, abnormal sensations and pain in feet, legs, arms, and/or hands. A recent literature search concluded there is inadequate evidence to evaluate the effects of exercise on functional ability in people with peripheral neuropathy. PURPOSE The primary objective was to assess the influence of exercise therapy on peripheral blood flow responses, heart rate variability and functional measures in a small sample of individuals with peripheral neuropathy. METHODS Participants engaged in an organized progressive exercise program 3*week for six weeks. The exercise program consisted of a typical walking program (with or without partial body weight support) or Tai Chi. Leg blood flow was evaluated, in both legs, at rest and following 5 minutes of arterial occlusion, using strain gauge plethysmography. Heart rate variability indices included standard deviation (SDNN), and low frequency (LF) and high frequency (HF) powers determined from EKG's obtained during 10 minutes of uninterrupted supine rest. Postural stability was defined as the average sway velocity in varied conditions on a force platform. Dynamic gait capability was defined as the center of pressure motion during walking on a treadmill. RESULTS To this point sixteen individuals (9 Women and 7 Men, Age: 68±7yrs, Height: 167±9cm, and Weight: 85±16kg) completed the exercise program. The program was well tolerated. No apparent differences in blood flow responses between the left and right legs were noted prior to the program. After 6 weeks, systolic blood pressure decreased (Pre: 135±15 Post: 126±14mmHg, p=0.001), whereas reactive hyperemic blood flow (RHBF) increased (Pre: 16.77±8.16 Post: 20.26±6.45ml/100ml/min, p=0.05). Moreover, changes in measures of heart rate variability suggest a favorable shift in autonomic modulation of the heart (Pre: LF/HF: 2.97±2.42 Post: 2.11±2.05, p=0.03). Finally, the changes in RHBF were associated with changes in SDNN (r2=0.39). Measures of postural stability improved significantly, whereas measures of dynamic gait capability only improved in those individuals involved in the walking program. CONCLUSION The results suggest that progressive exercise therapy is well tolerated in patients with peripheral neuropathy and may improve RHBF, HRV and postural stability. Improvements of measures of dynamic gait capability were specific to the modality of training used.

Forearm beta adrenergic receptor-mediated vasodilation is impaired, without alteration of forearm norepinephrine spillover, in borderline hypertension.

Impaired beta adrenoceptor-mediated vasodilation associated with enhanced sympathetic activity has been reported in established hypertension. We examined whether altered beta adrenoceptor-mediated vasodilation occurs early in the disease process, when structural vascular changes are likely to be less marked, by measurement of forearm blood flow by strain gauge plethysmography after the intraarterial administration of increasing doses of a beta receptor agonist, isoproterenol, in eight subjects with borderline hypertension (BHT) and 13 normotensive (NT) controls. To determine the role of sympathetic activation in the regulation of responsiveness, we measured local sympathetic activity in the forearm by a radioisotope dilution technique. Vasodilation in response to isoproterenol, measured either as changes in forearm blood flow or forearm vascular resistance, was impaired in the BHT group so that flow at the highest dose of isoproterenol (400 ng/min) increased less (15.2 +/- 1.5 ml/100 ml per min) than in the NT group (24.4 +/- 2.4 ml/100 ml per minute) (P < 0.001). Although, systemic norepinephrine spillover was significantly greater in BHT, the difference in blood flow response to isoproterenol was not accounted for by increased local sympathetic activity since forearm norepinephrine spillover at baseline (BHT 1.0 +/- 0.4 ng/min vs. NT 0.64 +/- 0.13 ng/min) and after the administration of isoproterenol 60 ng/min (BHT 5.2 +/- 1.4 ng/min vs. NT 6.0 +/- 1.5 ng/min) and 400 ng/min (BHT 13.5 +/- 2.9 ng/min vs. NT 16.5 +/- 2.7 ng/min) did not differ between the two groups. We therefore conclude that vasodilation in response to isoproterenol is impaired in subjects with BHT and that this impairment is not explained by locally increased basal, or stimulated, sympathetic activity.

Method for the measurement of susceptibility to decubitus ulcer formation.

A method for measuring the susceptibility of a patient to develop decubitus ulcers is described and initially evaluated. It is based on an indirect, noninvasive measurement of the transient regional blood flow response after a test pressure load which simulates the external stimulus for pressure-sore formation. This method was developed to determine the individual risk of a patient and to study the subfactors which contribute to the susceptibility. This would also offer the possibility of evaluating the effect of preventive treatment aimed at reducing the susceptibility. The method was found to discriminate between preselected elderly patients at risk on the one hand, and non-risk patients and healthy young adults on the other hand. No differences in blood flow responses were found between the non-risk elderly patients and the healthy young adults. This suggests that age per se is not a factor in the formation of pressure sores. In the risk group the recovery time after pressure relief was found to be three times as long as the duration of the pressure exercise. This indicates that the recovery time after pressure exercise may be as important as the period of pressure exercise in deducing the risk of developing decubitus ulcers.

Blood flow to different rat skeletal muscle fiber type sections during isometric contractions in situ.

In whole skeletal muscle, peak blood flow is known to correlate with the capacity for oxidative metabolism. Since most mammalian skeletal muscle is comprised of different fiber types whose oxidative potential varies widely, the possibility of heterogeneous blood flow distribution within a given muscle was investigated. An in situ preparation of the rat gastrocnemius-soleus-plantaris muscle group was used and blood flow measured by the radiolabeled microsphere technique. Blood flow at rest averaged 5-6 ml.min-1.100 g-1 in fast-twitch white (FTW) fiber sections, while flows to fast-twitch red (FTR) and slow-twitch red (STR) muscle were 10-12 ml.min-1.100 g-1. Isometric twitch contractions generated large (12-15 times above rest) increases in blood flow to all fiber type sections that tended to decrease at higher frequencies. Tetanic contractions result in greater tension development and higher blood flows in the red fiber sections. The highest blood flow to the FTR section was 300 ml.min-1.100 g-1, a value 3-4-fold greater than the maximum for the FTW fiber section. Peak blood flow to the STR (soleus) was intermediate between the two fast fiber types. Differences in blood flow response between fiber sections could not be dismissed due to measurement artifact. Thus, the capacity for blood flow is fairly proportional to the differences in oxidative capacity among fiber types. Blood flow to the skeletal muscle fiber types of the rat also differed qualitively in response to contractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood flow to different skeletal muscle fiber types during contraction.

Blood flow to fast-twitch red (FTR), fast-twitch white (FTW), and slow-twitch red (STR) muscle fiber sections of the gastrocnemius-plantaris-soleus muscle group was determined using 15 +/- 3-microns microspheres during in situ stimulation in pentobarbital-anesthetized rats. Steady-state blood flows were assessed during the 10th min of contraction using twitch (0.1, 0.5, 1, 3, and 5 Hz) and tetanic (7.5, 15, 30, 60, and 120/min) stimulation conditions. In addition, an earlier blood flow determination was begun at 3 min (twitch series) or at 30 s (tetanic series) of stimulation. Blood flow was highest in the FTR (220-240 ml X min-1 X 100 g-1), intermediate in the STR (140), and lowest in the FTW (70-80) section during tetanic contraction conditions estimated to coincide with the peak aerobic function of each fiber type. These blood flows are fairly proportional to the differences in oxidative capacity among fiber types. Further, their absolute values are similar to those predicted from the relationship between blood flow and oxidative capacity found by others for dog and cat muscles. During low-frequency contraction conditions, initial blood flow to the FTR and STR sections were excessively high and not dependent on contraction frequency. However, blood flows subsequently decreased to values in keeping with the relative energy demands. In contrast, FTW muscle did not exhibit this time-dependent relative hyperemia. Thus, besides the obvious quantitative differences between skeletal muscle fiber types, there are qualitative differences in blood flow response during contractions. Our findings establish that, based on fiber type composition, a heterogeneity in blood flow distribution can occur within a whole muscle during contraction.

Cutaneous Hyperaemia Elicited by Larvae of the Cattle Tick, Boophilus Micro Plus

The responses of skin capillary blood flow (BF) to infestation by larvae of B. microplus have been determined using radioactive microspheres. Larvae were placed in gauze-covered rings glued to the closely clipped skin. In pilot experiments on three Brahman-cross calves which had prior exposure to ticks, BF measurements at intervals up to 25 h post-infestation revealed a continuing increase. 'High' rates of infestation (5000 larvae per ring) elicited up to an 80-fold increase in BF. In four Australian Illawarra Shorthorn (AIS) calves with prior exposure to ticks, BF had increased by 0.5 h post-infestation, it reached a peak at 24 h, and fell markedly by 48 and 75 h. In contrast, two AIS calves without prior tick exposure showed no significant increase in BF until 24 h and this increase continued until observations were terminated at 72 h. BF in the neck area (normally favoured by ticks) increased most in calves of highest resistance to ticks, but the flank area (normally unfavoured) showed no consistent difference in BF response between animals of different tick resistance. It is concluded that skin capillary hyperaemia is triggered by the host's immune response to larval attachment. Within the relatively narrow range of tick resistance in the present animals, the degree of hyperaemia was directly related to level of resistance to the tick in skin regions normally favoured by ticks and therefore it may play a role in determining resistance to ticks.

The effects of hot packs and exercise on local blood flow.

The relative effects on local blood flow of hot packs, mild rhythmical exercise, and a combination of hot packs and exercise were measured by acute venous occlusion plethysmography on ten healthy human subjects. Skin temperature was measured during application of heat. Exercise produced a large, brief increase in blood flow while heat caused a smaller, more prolonged increase resulting in a greater total excess blood flow. Differences in blood flow response appeared to be related to intensity and duration of procedure. The combined effect on blood flow of heat and exercise was additive.