Factors affecting radioactive microsphere measurement of blood flow in pregnant guinea pigs

Comparative blood flow studies were performed in pregnant guinea pigs using radioactive microspheres to test the effects of different sphere sizes on blood flow measurements and the relationship between flows obtained intraoperatively and those performed after 5 days of recovery from anesthesia and surgery. We observed that 1.5% of the cardiac output was shunted through the microcirculation of the carcass, gut, skin and endomyometrium when 15 mu microspheres were used. Intraoperative measurements of heart rate, cardiac output and placental blood flow are significantly lower than measurements made after 5 days recovery. These reductions were ameliorated with the addition of a continuous infusion of isoproterenol and the deletion of atropine from the anesthetic.     

Measurement of bronchial blood flow with radioactive microspheres in awake sheep

Distribution of bronchial blood flow was measured in unanesthetized sheep by the use of two modifications of the microsphere reference sample technique that correct for peripheral shunting of microspheres: 1) A double microsphere method in which simultaneous left and right atrial injections of 15-microns microspheres tagged with different isotopes allowed measurement of both pulmonary blood flow and shunt-corrected bronchial blood flow, and 2) a pulmonary arterial occlusion method in which left atrial injection and transient occlusion of the left pulmonary artery prevented delivery to the lung of microspheres shunted through the peripheral circulation and allowed systemic blood flow to the left lung to be measured. Both methods can be performed in unanesthetized sheep. The pulmonary arterial occlusion method is less costly and requires fewer calculations. The double microsphere method requires less surgical preparation and allows measurement without perturbation of pulmonary hemodynamics. There was no statistically significant difference between bronchial blood flow measured with the two methods. However, total bronchial blood flow measured during pulmonary arterial occlusion (1.52 +/- 0.98% of cardiac output, n = 9) was slightly higher than that measured with the double microsphere method (1.39 +/- 0.88% of cardiac output, n = 9). In another series of experiments in which sequential measurements of bronchial blood flow were made, there was a significant increase of 15% in left lung bronchial blood flow during the first minute of occlusion of the left pulmonary artery. Thus pulmonary arterial occlusion should be performed 5 s after microsphere injection as originally described by Baile et al. (1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Age-related changes in skin blood flow at four anatomic sites of the body in males studied by xenon-133

The normal skin blood flow in healthy subjects consisting of 28 males whose ages ranged from 20 to 72 years was measured by the xenon-133 clearance method at four different sites of the body to determine the presence of any age-related changes. The following results were obtained: Significant age-related changes were observed in the skin blood flow of the deltoid region, anterior chest, dorsum of the hand, and dorsum of the foot. Normal skin blood flow was demonstrated to be highly dependent on age and to significantly decrease with age. Average skin blood flow at these four regions of those 70 years of age decreased by 30 to 40 percent when compared to that of those 20 years of age. The skin blood flow at the deltoid region of healthy subjects was higher by 6.3 ml/100 gm per minute than that of patients in poor condition with cancer of the head and neck.     

Systemic blood flow to sheep lung: comparison of flow probes and microspheres.

Discrepancies exist between experimental measurements of the systemic blood flow to sheep lung by use of microsphere techniques and flow probes on the bronchial artery. In these studies, we simultaneously measured the blood flow through the bronchial artery, using a transit time flow probe, and the systemic blood flow to left lung, using radioactive microspheres. All measurements were made on conscious sheep previously prepared with chronic catheterizations of the left atrium, aorta, and vena cava and a flow probe around the bronchial artery. Inflatable occluder cuffs were placed around the pulmonary and bronchoesophageal arteries. Bronchial artery blood flow in six sheep was 25.3 +/- 5.2 ml/min or 0.4% of the cardiac output. Systemic blood flow to left lung, measured with microspheres, was 54.1 +/- 14.2 ml/min. Calculated systemic blood flow to that portion of sheep lung perfused by the bronchial artery was 127.6 +/- 35.3 ml/min or 1.9% of cardiac output. Occlusion of the bronchoesophageal artery reduced bronchial artery flow to near zero, whereas total systemic blood to the lung was reduced by only 55%. Blood flow to the intraparenchymal cartilaginous airways was reduced 60-90% after occlusion of the bronchoesophageal artery. Sheep, like most mammals, have multiple and complex systemic arterial inputs to the lungs. We conclude that multiple branches of the bronchoesophageal artery provide most but not all of the systemic blood flow to the intraparenchymal cartilaginous airways but that over one-half of the total systemic blood flow to sheep lung comes from sources other than the common bronchial artery.     

Skin blood flow changes in anaesthetized humans: comparison between skin thermal clearance and finger pulse amplitude measurement

The effect of general anaesthesia on skin blood flow in the left hand, measured by a new non-invasive probe using the thermal clearance method was examined. A mercury silastic gauge was placed around the third left finger and the plethysmographic wave amplitude was recorded to measure changes in finger pulse amplitude. Heart rate (HR), mean arterial blood pressure (MABP) and skin temperature were also recorded. General anaesthesia was induced by droperidol and phenoperidine injection and propanidid infusion in eight female patients. Skin thermal clearance, plethysmographic wave amplitude, HR, MABP and skin temperature were 0.40 +/- 0.02 w X m-1 degree C-1, 9 +/- 1 mm, 98 +/- 5 beats X min-1, 12.50 +/- 0.93 kPa and 33.3 +/- 3.4 degrees C respectively. The minimal value of MABP was 9.58 +/- 1.06 kPa, whereas skin thermal clearance, plethysmographic wave amplitude, HR and skin temperature increased to 0.45 +/- 0.02 w X m-1 degree C-1, 29 +/- 3 mm, 110 +/- 4 beats X min-1 and 34.4 +/- 0.4 degrees C. Changes in skin thermal clearance correlated well with plethysmographic wave amplitude. Statistically significant changes in these two parameters occurred before significant change in HR, MABP or skin temperature. The results show that the new non-invasive probe using the thermal clearance method appears to be a useful device for measuring cutaneous microcirculation in anaesthetized humans, and responds more quickly than change in skin temperature, which is a delayed effect of skin blood flow change. Our results also show that the intensity of cutaneous vasodilatation induced by general anaesthesia did not relate to the vascular tone before anaesthesia.     

Estimation of blood flow distribution in skeletal muscle from inert gas washout

A new method is evaluated for the estimation of blood flow-to-volume distribution in skeletal muscle from inert gas washout kinetics. Acetylene washout from the isolated, blood-perfused canine gracilis muscle was measured continuously with a blood gas catheter in combination with a mass spectrometer. The washout curves were transformed to flow-to-volume ratio distributions by means of a 50-compartment model. The algorithm fits the expression for the washout curve derived from the model by a least-squares method with enforced smoothing. The algorithm was evaluated using computer simulations in which artificial washout curves were generated by a multicompartment model with a known flow distribution. A wide range of given flow distributions could be recovered from the simulated data. The data were also analyzed using a linear programming technique. Analysis of the experimental data with the least-squares method showed that there is considerable heterogeneity in the distribution of perfusion in resting gracilis muscle. The distribution is characterized by at least two modes and a single compartment with a very low perfusion-to-volume ratio. Experimental noise made it impossible to obtain feasible flow distributions by means of linear programming.     

Fluorescent microsphere technique to measure cerebral blood flow in the rat

The present protocol describes a method for parallel measurement of cerebral blood flow (CBF) using fluorescent microspheres and structural assessment of the same material. The method is based on the standard microsphere technique, embolizing capillaries proportional to the blood flow, but requires dissolution of the tissue to retrieve the microspheres. To link the blood flow to the tissue morphology we modified the technique to fluorescent microspheres, which are quantified in cryo- or vibratome sections, allowing structural analysis by, for example, immunohistochemistry or standard histology. The protocol takes 8 h 50 min, without pauses, to complete, but additional flow measurements or specific protocols can increase the time needed.     

Heat stress and age: Skin blood flow and body temperature

1. 1. The ability to increase skin blood flow is an important mechanism for transferring heat from the body core to the skin for dissipation.

2. 2. During exercise, skin blood flow is typically 20–40% lower in men and women aged 55 and over (compared with 20–30 years old) at a given body core temperature. Yet criterion measures of heat tolerance (changes in core temperature, heat storage) often show minimal or no age-related alterations. From a series of studies conducted in our laboratory over the past 5 years, the following conclusions can be drawn.

3. 3. When fit healthy older subjects are matched with younger subjects of the same gender, size and body composition, V_O2max, acclimation state, and hydration level, age-related differences in skin blood flow are evident. However, these differences often do not translate into “poorer” heat tolerance or higher core temperatures.

4. 4. The larger core-to-skin thermal gradient maintained by the older individuals allows for effective heat transfer at lower skin blood flows.

5. 5. Furthermore, there is an increased coefficient of variation for thermoregulatory response variables with increasing age.

6. 6. Despite differences in the mechanisms underlying thermoregulation, true thermal tolerance is less a function of chronological age than of functional capacity and physiological health status.

7. 7. While this conclusion is based primarily on cross-sectional studies, it is supported by the results of more recent studies using multiple regression analyses.

8. 8. Implicit in this conclusion is the notion that thermal tolerance, at any age, is a modifiable individual characteristic.

Correlation between 2 methods of measuring cutaneous blood flow: photoplethysmography and xenon 133

Photoplethysmography, cutaneous blood flow measurement by Xenon 133 were carried out before and after resolution by Puva therapy on a lesion and on the symmetrical healthy skin area of 29 psoriatic subjects. The increase of the blood pulsatility and cutaneous blood flows found before treatment, disappears after resolution. The correlation between the two methods is studied.