[Laser-Doppler technique in diseases of peripheral blood vessels].
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Diabetic Angiopathies↗
Biomedical subjects
U Hoffmann
Publications and source records attributed to U Hoffmann.
Inactivation of the fis gene leads to reduced growth rate.
The FIS protein (factor for inversion stimulation) is known to activate the transcription of rRNA and tRNA operons in Escherichia coli. In this report the growth behaviour of a fis bacterium was studied under steady-state conditions and in competition experiments with a wild-type bacterium in a chemostat. The growth rate of the fis bacterium was reduced as compared to that of an isogenic wild-type and this reduction increased linearly with increasing growth rate. A similar result was obtained in competition experiments in a chemostat, with the selection factor increasing linearly with the growth rate.
Carrier Proteins↗
Influence of body position and pre-exercise activity on cardiac output and oxygen uptake following step changes in exercise intensity.
Parallel measurements of breath-by-breath oxygen uptake, cardiac output (Doppler technique), blood pressure (Finapres technique) and heart rate were performed in nine subjects during cycle ergometer exercise in the upright and supine positions. Transients were monitored during power steps starting from and leading to either rest or lower levels of exercise intensity. Oxygen uptake (VO2) and cardiac output kinetics were markedly faster than in all other conditions when exercise was started from rest. In contrast to exercise-exercise on steps, the computed arteriovenous difference in O2 content increased almost immediately in this situation, indicating that not only the additional energy expenditure due to the acceleration of the flywheel but also an increased venous admixture from non-exercising parts of the body contributed to the early kinetics. The off kinetics generally showed a more uniform pattern and did not simply mirror the on transients. The present findings indicate that transitions from rest should be avoided when muscle VO2 kinetics are to be assessed on the basis of VO2 measurements at the mouth.
Adult↗
Dynamic linearity of VO2 responses during aerobic exercise.
The multifrequent pseudorandom binary sequence (PRBS) technique is a useful tool for studying oxygen uptake (VO2) kinetics within the aerobic range. However, the validity of this multifrequent test may be limited by nonlinearities generated by the circulatory and pulmonary system. To check for such nonlinear effects, we compared the frequency responses computed from two PRBS protocols with the results of pure sinusoidal frequencies varying in amplitude and mean values (periods between 50 s and 450 s). According to our results the VO2 frequency response does not seem to depend on the type of testing--PRBS or sine--or the changes within each test, i.e. mean power and power amplitude of the sine tests and the switching frequency of the PRBS. In the range of higher frequencies small differences between the test conditions may have been obscured by the greater scatter of dynamic responses. It was concluded that the VO2 frequency response was quasi-linear for periods down to the least 100 s. However, even in this range nonlinearities can be provoked by rest-exercise transitions, by a varying contribution of lactate or by an insufficient noise reduction.
Adult↗
Laser Doppler technique for the measurement of digital and segmental systolic blood pressure.
A technique is described for measuring digital and segmental systolic blood pressure by laser Doppler fluxmetry. A transparent plastic capsule contains the small sphygmomanometer cuff connected to a Statham manometer. It has a hole for positioning the probe at the very tips of fingers or toes. An advantage of this method over the conventional strain-gauge technique is that it is better suited for determinations at short digits where it is difficult to fix a strain-gauge. Moreover, it allows consecutive pressure and flux measurements at almost identical distal sites without moving the probe. The correlation between the values obtained by the conventional and laser Doppler procedures are excellent. Systolic pressures were determined on 14 extremities of 7 healthy controls and on 20 extremities of 14 patients with intermittent claudication due to peripheral arterial occlusive disease. Measuring sites were the upper arm, forearm, index finger, ankle and big toe. The values agree well with those obtained earlier by the strain-gauge technique.
Aged↗
Percutaneous transluminal angioplasty (PTA) of the deep femoral artery.
Between 1979 and 1988 43 percutaneous transluminal angioplasties (PTA) of the deep femoral artery were performed for treatment of severe claudication (n = 15) or for limb salvage (n = 28). Ateriographically, all patients had a long occlusion of the superficial femoral artery. Additional PTA of significant obstructions in the iliac and common femoral artery were performed in 6 patients of each group. Technical success was achieved in 41 of the 43 procedures (95%). Early clinical success was 60% for claudicants and 68% for patients with limb threatening ischemia. Success rates tended to be higher if additional PTA of the inflow tract was performed (75% versus 61%, n.s.). Patient with a good distal outflow benefited more frequently from PTA if they were treated for limb salvage (p less than 0.05). Within a follow-up period up to 24 months (mean 18.0 months) 5 patients died and one late failure occurred. Life table analysis lasting success in patients dilated for limb salvage, whereas success rate decreased to 48% in claudicants. PTA of the deep femoral artery is a less invasive and efficient treatment particularly for patients with limb threatening ischemia, an appropriate obstruction morphology provided.
Aged↗
A model for studying the distortion of muscle oxygen uptake patterns by circulation parameters.
The transmission of muscle oxygen uptake (VO2) patterns to the pulmonary site is a basically nonlinear process during unsteady state exercise. We were mainly interested in three questions concerning the dynamic relationship between power input and pulmonary VO2 output: 1. To what extent can linear system analysis be applied? 2. What is the relative influence of muscle VO2 on pulmonary VO2 as compared to other parameters such as muscle perfusion kinetics? 3. To what extent does pulmonary VO2 reflect muscle VO2? Investigations were performed by means of a mathematical model including a muscle compartment and two serial, flow-varying time delays. The non-exercising parts of the body were incorporated as one term for perfusion and one for VO2. Parameters were adjusted so as to represent a reference state of aerobic exercise while monofrequent sinusoidal changes in aerobic metabolism were used as forcing signals. The following answers were derived from the simulations: 1. Non-linear distortions of the VO2 signals are negligible provided that analyses are not driven too far into the higher frequency range (periods shorter than about 1 min). 2. Variations of muscle VO2 kinetics have greater effects on pulmonary VO2 than changes of perfusion kinetics or venous volume. This finding applies irrespective of whether or not pulmonary VO2 closely reflects muscle VO2. 3. Small differences in the time constants for muscle perfusion and muscle VO2 are a major prerequisite if pulmonary VO2 kinetics are to be taken as correct estimates of muscle VO2 kinetics. High basal muscle perfusion, small perfusion changes and small venous volumes between muscle and lungs are further factors reducing dynamic distortions of the muscle VO2 signal.
Exercise↗
Role of duplex scanning for the detection of atherosclerotic renal artery disease.
To assess the accuracy of renal artery duplex scanning for the purpose of diagnosing atherosclerotic renal artery stenosis, we compared the findings of renal arteriograms to the results of duplex scanning in 41 patients. Using an increase of renal artery peak systolic flow velocity of greater than 180 cm/sec, duplex scanning was able to discriminate normal from diseased renal arteries with a sensitivity of 95% and a specificity of 90%. Using the principle that blood flow velocity across a stenosis is roughly proportional to the degree of stenosis, it appeared that a ratio of the peak velocity in the renal artery to the aorta (RAR) of greater 3.5 predicted a greater than 60% diameter reduction of that renal artery, which is felt to be a significant stenosis. Forty-eight vessels were classified as having a greater than 60% diameter reduction by arteriography. Using the RAR of greater than 3.5, duplex scanning agreed in 44 renal arteries (sensitivity 92%). In the 26 renal arteries where arteriography showed a less than 60% diameter reduction, duplex scanning agreed in 16 vessels and correctly detected a focal narrowing in nine of the remaining ten vessels. Ten of 11 occluded renal arteries were correctly identified by duplex scanning. Duplex scanning determined the location of the renal artery lesion with an accuracy of 95% (kappa 0.74). Since duplex scanning can accurately demonstrate and locate focal renal artery stenosis, we believe it may become an accurate screening test for renovascular hypertension.(ABSTRACT TRUNCATED AT 250 WORDS)
Aged↗
Evaluation of flux motion in man by the laser Doppler technique.
Analysis of flux motion by the laser Doppler technique in the forefoot of healthy controls and patients with peripheral arterial occlusive disease was performed by establishing computerized frequency histograms. It was found that the low frequency components (1-10 cycles/min) are caused by local vasomotion. The prevalence of high frequency flux waves (15-25 cycles/min) is significantly increased in peripheral ischemia compared to normal conditions. After successful reopening of large arteries by angioplasty the prevalence decreases (p less than 0.001). Preliminary results indicate that these high frequency rhythmic fluctuations might by induced by respiration.
Arterial Occlusive Diseases↗
Intravital detection of skin capillary aneurysms by videomicroscopy with indocyanine green in patients with progressive systemic sclerosis and related disorders.
Conventional capillaroscopy and infrared fluorescence videomicroscopy with indocyanine green were performed at the nailfold in 12 healthy controls and 38 patients with microangiopathy due to systemic sclerosis or related disorders. Saccular aneurysms featuring head and neck (type 1) and aneurysmatic enlargements (type 2) were defined. Microaneurysms were located at the apex or near the apex of capillary loops and were significantly more common in patients than in controls (p less than 0.02 for type 1 and p less than 0.001 for type 2). Combination of the two lesions was found only in patients and appears to be a valuable new diagnostic sign for the presence of microangiopathy. In comparison with conventional capillaroscopy, about twice as many microaneurysms were detected by videomicroscopy with indocyanine green coupling almost completely to plasma proteins. The new technique allows visualization of capillary aneurysms even when filled only by plasma.
Adult↗
[Value of duplex sonography in diagnosis of renal artery stenosis].
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Blood Flow Velocity↗
[Pattern of flow movement in healthy probands and patients with peripheral arterial occlusive disease].
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Aged↗
[Psychosocial problems in patients with chronic osteomyelitis].
52 patients suffering from a chronical bone infection were followed up with a special interest in psychosocial problems. In all cases psychosocial disturbances of different importance were evaluated. Possible causes have to be seen in long time of hospitalisation (average = 304 days), and apparent inadequate enlightenment of patients and in functionally and cosmetically insufficiencies. Conclusions are shown for the management in treatment of chronical bone infections.
Activities of Daily Living↗
[New methods for assessing gastrointestinal blood flow].
Non-invasive tests for evaluation of intestinal blood flow include duplex scanning and laser Doppler flowmetry. Duplex scanning combines ultrasonic imaging with a pulsed doppler unit. By analysing flow curves and changes in Doppler frequency spectra blood flow in the mesenteric arteries and the coeliac trunc can be analysed. Laser Doppler flowmetry is another promising new technique. The fiber optic guides, which conduct laser light to the tissue and carry back-scattered light to a photodetector, can be placed endoscopically on the mucosal surface of the bowel, thus allowing examination of the intestinal mucosal microcirculation.
Blood Flow Velocity↗
Comparison of arterial, end-tidal and transcutaneous PCO2 during moderate exercise and external CO2 loading in humans.
Static relationships between arterial, transcutaneous and end-tidal PCO2 (PaCO2, PtcCO2, PetCO2) as well as the dynamic relationship between PetCO2 and PtcCO2 were studied during moderate bicycle ergometer exercise with and without external CO2 loading. The exercise pattern consisted of 5-min intervals of constant power at 40 W and 100 W and 900 s of randomised changes between these two power levels. The external CO2 loading was achieved by means of controlled variations of inspiratory gas compositions aimed at a constant PetCO2 of 6.5 kPa (49 mm Hg). The PetO2 was regulated at 17.3 kPa (130 mm Hg). Under steady-state conditions all PCO2 parameters showed close linear relationships. PaCO2/PtcCO2 was near to identity while the PetCO2 systematically overestimated changes in PaCO2l No relationship showed a significant influence of the exercise intensity. Transients of PtcCO2 are considerably slower than PetCO2 transients. The dynamic relationship between both parameters was found to be independent of whether internal or external CO2 loadings were applied. It is concluded that the combination of PetCO2 and PtcCO2 measurements allows an improved non-invasive assessment of PaCO2. While PetCO2 better reflects the transients, PtcCO2 can be employed to determine slow changes of the absolute PaCO2.
Adult↗
Ventilatory effects of hypercapnic end-tidal PCO2 clamps during aerobic exercise of varying intensity.
Nine subjects performed a sequence of sustained and randomised changes between 40 W and 100 W on a cycle ergometer while the end-tidal PO2 was kept close to 17.3 kPa (130 mm Hg) by means of a dynamic forcing technique (reference experiment). In a second series inspiratory CO2 was additionally manipulated so as to hold end-tidal PCO2 (PETCO2) near 6.5 kPa (49 mm Hg; 'CO2-clamp' experiment). By this forcing PETCO2 oscillations were attenuated and more evenly distributed over the frequency range. Ventilation (VT) responded to this manoeuvre with an upward trend that could not be ascribed to a slow CO2-response component, changes in metabolic rate or a dissociation of end-tidal and arterial PCO2. VT differences between reference and CO2-clamp experiments were abolished within a 3-min period following the termination of the external CO2 control. The present results suggest that the CO2-H+ stimulus plays a major role in adjusting ventilation when exercise intensity is decreased. The underlying CO2 effect appears to be neither additive nor bi-directionally symmetrical.
Arteries↗
The frequency histogram--a new method for the evaluation of laser Doppler flux motion.
A digital filter system (DFS) was implemented to describe the frequency components of laser Doppler signals. The DFS calculates a frequency histogram on the basis of the prevalence of a certain frequency band during the sample period. This approach seems to be more suitable for the detection of low-power small-amplitude flux motion components recorded by laser Doppler as compared to the commonly used fast Fourier algorithm. Fourier analysis provides an amplitude-relevant frequency spectrum which may overlook relevant frequency components with small amplitude due to low power or short duration. DFS allows better detection of such signals as demonstrated by the initial clinical results of this study evaluating flux motion on the feet of 4 healthy controls and 10 patients with peripheral arterial occlusive disease. Three frequency components are easily distinguished corresponding to low (3.6 +/- 1.5 cycles/minute) and high (18.6 +/- 4.5 cycles/min) frequency flux motion and the pulsatile waves due to cardiac action.
Aged↗