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I . A new method has been used to measure mean gastric transit time. 2. This method, based on the absorption of n4Na from the proximal small bowel, is simple, non-invasive 3. The mean transit time was increased by adding mar gum to a test meal.4. There was a significant correlation between mean gastric emptying time and a subjective measure of and can be used at the bedside. . satiety.A simple, cheap and non-invasive method of measuring gastric emptying would be useful in both physiological research and clinical practice. Research into factors influencing gastric emptying has been performed using nasogastric aspiration, which may influence the results of the investigations. Non-invasive tests have been developed in which the subject consumes a meal labelled witb a non-absorbed radioactive tracer whose passage through the stomach is followed using a gamma camera or rectilinear scanner (Tothill et al. 1978).We have developed a simple method for measuring gastric emptying which depends on outflow detection, as distinct from residual detection (Zierler, 1965) and utilizes the fact that sodium is rapidly absorbed by the proximal small bowel after passing through the stomach (Love et al. 1973). The appearance of ingested Na in the blood can therefore provide a measure of the transit time through the stomach. The apparatus is relatively simple, and can be used at the bedside.The most accurate assessments of hunger are probably those based on analogue rating scales (Silverstone, 1975) and gastric emptying may influence hunger (Hunt et al. 1975). METHODTwelve over-weight in-patients were studied. Their mean age was 36 (SD f 15.7) years, mean weight 90.6 (SD f 141) kg, and percentage lean body mass (assessed by measurement of whole body potassium) 6 0 1 (~~f 6 -5 ) yo. The patients had become experienced in the use of visual analogue scales for assessment of hunger and desire to eat for a minimum of 7 d before the administration of the gastric emptying tests.After an overnight fast the patients were given 200 g of a milky drink. The drink had the composition of one of the test meals shown in Table I. On a subsequent occasion the patients received a second test meal and the order of the meals was chosen by tossing a coin. All three meals were similar in taste.The low-energy meal and the high-energy meal were compared in nine pairs of trials and the low-energy meal and the low-energy meal with guar gum were compared in seven pairs of trials. The relatively short half-life of "Na (13 h) made it impossible to carry out more than two measurements with one weekly delivery of isotope so only four patients were available for all three measurements. The viscosities of the test meals were estimated at 37"

suMMARY The nuclear probe was used for measuring left ventricular function in 11 normal subjects and the results compared with those using a digital gammacamera. The probe was then used to measure left ventricular function in patients with coronary artery disease during dynamic exercise and stress atrial pacing. The ability of the probe to detect changes induced by glyceryl trinitrate was also evaluated in separate parallel studies. In the 11 normal subjects there was a good correlation between the left ventricular ejection fraction measured by the gammacamera and the nuclear probe both at rest and during exercise. Exercise increased this value by at least 5% in all normal subjects during measurements with both the gammacamera and the nuclear probe. The mean (SD) difference was -0 3% (2.60) at rest and 2.3% (5 02) at peak exercise. Both exercise and pacing produced angina in the patient group and the mean (SEM) value fell from 52% (3.5) to 28% (2.6) and from 46% (5-1) to 34% (3.2) respectively. Glyceryl trinitrate prolonged the exercise and pacing times, and the corresponding falls in ejection fraction were significantly reduced.The non-imaging nuclear probe is a cheap and portable instrument capable of assessing left ventricular function in patients with cardiac disease. It is designed for high count rate acquisition over a short period of time and can thus provide both beat to beat and summated left ventricular time activity curves suitable for quantitative analysis. It therefore has important advantages in the clinical setting and during controlled interventions compared with the gammacameras.In patients with stable coronary artery disease angina pectoris is provoked by an imbalance between myocardial oxygen supply and demand. Electrocardiographic ST segment depression, a decrease in left ventricular ejection fraction, and the appearance of segmental wall motion abnormalities may all occur during episodes of myocardial ischaemia. Radionuclide angiography has been used extensively to study these changes in left ventricular function using both equilibrium blood pool and the first pass techniques. '

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