Clinical physiology (Oxford, England)最新文献

The effect of the degree and speed of tilt on the immediate heart rate reaction measuring cardiac autonomic nerve function was evaluated in nine healthy subjects. The results showed that the tilt angle determined the immediate increase in heart rate. The increase in heart rate was maximal when a 90 degrees tilt was performed. After the immediate increase there was a transient decrease in heart rate after rapid tilts (2-5 s). A rapid 90 degrees tilt is preferred when automatic nerve function should be evaluated from the immediate heart rate response.

Simultaneous assessment of coronary flow and flow-volume relation makes it possible to evaluate the dilatatory responses of coronary vasculature. A new set up of methods for investigation of the coronary circulation was employed to study the nature of the coronary flow and volume responses to dipyridamole in dogs. The turnover rate of coronary blood, the reciprocal value of the mean transit time, can be accurately determined by computer simulation analysis of coronary dye dilution curves. After intravenous dipyridamole (0.5 mg/kg) both coronary turnover rate and electromagnetically assessed blood flow were observed to increase in parallel and to the same degree (+55%). This indicates that no increase in the coronary vascular volume and, accordingly, no significant overall coronary dilatation takes place. The effective coronary blood flow in relation to the myocardial oxygen consumption, i.e. the nutritional flow, and the myocardial oxygen consumption decreased by 25% concomitant to a corresponding fall in myocardial oxygen requirements. Thus, the increase in total coronary flow after dipyridamole is useless for myocardial metabolism, and may properly be denoted as luxury perfusion or throughput flow.

A formula has been derived for the calculation of renal clearance with the use of a single plasma sample. The formula is based on a one-compartment model. A small correction for non-immediate mixing and non-uniform distribution of the tracer was calculated from empirical data. The accuracy in the calculation method depends on how exactly the distribution volume is known and at what time the blood sample is taken. The expected standard deviation in the clearance value was calculated from data of mean value and spread for the distribution volume of 99Tcm-DTPA. In an investigation of 39 subjects with 99Tcm-DTPA, a standard deviation of 5 to 6 ml/min was obtained in comparison with a standard method for clearance calculation. This value is in good agreement with the expected one.

Three techniques for measurement of right (RVEF) and two techniques for left (LVEF) ventricular ejection fraction were evaluated in five dogs. RVEF was measured with a first-pass radionuclide technique using erythrocytes labelled in vitro with Technetium-99m methylene disphosphonate (MDP) and compared with RVEF measured with a thermodilution technique. Thermodilution-determined RVEF was compared with RVEF values measured with cine angiocardiography. LVEF was measured with a radionuclide ECG-gated equilibrium technique and compared with cine angiocardiography. Measurements were performed before and during a continuous infusion of dopamine. There was an excellent correlation between RVEF measured with the first-pass and the thermodilution technique, rs being 0.86, n = 9, P less than 0.01. When RVEF measured with the thermodilution technique was compared with cine angiocardiography rs was 0.75, n = 10, P less than 0.01. LVEF measured with the ECG-gated equilibrium technique correlated well with cine angiocardiography (rs = 0.91, n = 10, P less than 0.01).

To study the transvascular passage of albumin from the plasma to the skin interstitium, suction blisters were developed on the abdominal skin of six young, healthy male volunteers. Fifteen minutes after the blisters had been formed and the suction had been stopped, 125I-albumin was injected intravenously and the disappearance of the tracer protein from plasma was compared to its appearance in blister fluid as a function of time for up to 4 h after the injection. There was a linear increase of blister fluid activity with time after injection and the mean accumulation rate of the six subjects was 0.9 +/- 0.4 (SD)%/h. It is suggested that this figure is a representative measure of the leakage of albumin through the skin microvasculature. In previous studies, a ten-fold higher accumulation rate of albumin was found when the protein tracer was administered intravenously before the suction was induced. This difference was probably due to a suction-induced increase of the filtration gradient across the skin vessels. It is concluded that both methods might be used to obtain a comparative measure of the local rate at which albumin passes from plasma to the interstitial fluid of the skin.

Five different methods were used to evaluate the arterial blood supply to 29 toes from 15 patients with atherosclerotic disease: digital pulse plethysmography, systolic toe blood pressure recording, skin temperature recording, vital capillary microscopy and dynamic fluorescein angiography. An optimal discrimination between legs with and without ischaemic ulcers or gangrene was obtained with the following borderlines: inclination time non-measurable because of very low or no recordable pulse curve, systolic toe blood pressure less than 20 mmHg, skin temperature (after vasodilatation) less than 29 degrees C, capillary stage greater than 3 (indicating the presence of capillary haemorrhages or more advanced changes) and fluorescein appearance time greater than 45 s. The results of the study provide no basis for the opinion that one method is superior to the others in discriminating between arteriosclerotic feet with and without existing skin necrosis.

133Xe washout measurements from locally injected depots in the subcutaneous tissue of the thigh have been performed intermittently by a NaI(Tl) detector placed 15 cm from the depot and a cadmium telluride [CdTe(Cl)] detector fixed to the skin surface above the depot. In 19 experiments, the measurements were performed during rest, before and after bicycling and during circulatory arrest during an occlusion cuff pressure of 240-250 mmHg. The disappearance rates measured by the two detector systems showed a linear correlation (r = 0.934, P less than 0.001). However, the rate constants measured by the CdTe(Cl) detector were an average of 1.48 times the values obtained by the NaI(Tl) detector during a period of 1-4 h after the injection. The coefficient of variation of the proportionality factor is 3.3%. Only the central part of the local depot area is exposed to the CdTe(Cl) detector. Using the NaI(Tl) detector and lead shielding of the peripheral or central part of the depot area, it was demonstrated that the disappearance rates obtained reflect the measuring geometries. The correction itself is therefore due to differences in the measuring geometries of the two detector types, and possibly to diffusion and convection of xenon. For quantitative determination of the subcutaneous blood flow, the disappearance rate constants determined by the CdTe(Cl) detector thus have to be corrected by division with the factor 1.48.

Total body bone mineral (TBBM), measured by dual photon absorptiometry, and local body bone mineral content (BMC), measured by single photon absorptiometry, in both forearms were determined in 49 epileptic patients, 19 receiving phenytoin and 30 receiving carbamazepine, and in 55 controls. A highly significant correlation was found between BMC and TBBM in the patients (r = 0.81, SEE = 10.6%), as well as in the controls (r = 0.78, SEE = 9.9%). Furthermore, the intercepts and the slopes were virtually of the same order. The patients on phenytoin had a mild generalised osteomalacia, independent of method used, whereas the patients on carbamazepine did not have this side-effect. It is concluded that BMC of the forearm can be used as a valid estimate of total body bone mineral in groups of epileptic patients and in normal subjects.