Indicator-dilution curves were recorded by oximiieters at tlme ears anld the right radial artery following the injection of Evans blue (T 1824) into the superior vena cava and pulmonary arteries of 37 subjects who had no evidence of cardiovascular disease. The variability and ranges of various time and concentration components of these dilution curves are presented. These values can be used as standards of reference in the interpretation of abnormal dilution curves. Some of the factors responsible for the variability of these values in healthy subjects are assessed and discussed.T HE RECORDING of concentration-time curves at a peripheral arterial site following injection of an indicator into the heart and great vessels provides a valuable tool for the study of normal and abnormal circulation. Its increasing use in diagnostic and research laboratories attests to its efficacy. When this technic is used, it is desirable to have a normal standard of reference with which the values obtained from individual subjects can be compared. The present cominunication reports the values and the variability of various time and concentration coinponents derived from indicator-dilution curves recorded during catheterization of the right side of the heart in a series of healthy human 1)ei Imgs. METHODS AND SUBJECTSThe right side of the heart was catheterized by the methods previously described,"'2with the subjects resting in the supine position. They had a light meal prior to the study and were given as premedication 30 lug. of codeine sulfate and 100 ing. of secobarbital sodium at the beginning of the procedure. Evans blue (T 1824) *5 was used as the indicator. Ten milligrams of the dye in 2 iml. of solution was injected into the superior vena eava, main pulmonary artery, right pulmonary artery, or left pulmonary artery. The subjects The Mayo Foundation, Rochester, Minnesota, is a part of the Graduate School of the University of Yinnesota.were breathing 100 per cent oxygen during the recording of the dilution curves, in order to avoid interference due to fluctuations in the oxygen saturation of arterial blood.Dye-dilution curves were recorded photographically by means of ear oximneters placed on one or both ears and a euvet oximueter connected to a, 20-gage needle in the right radial artery. The sensitivity of the system was such that dye concentrations of 1 ing. per liter gave a deflection of 0.4 to 0.7 cmn. for the radial artery curves and 0.2 to 0.8 em. for the ear oximeter curves. Time components of the curves recorded by the euvet oximneter were corrected for the volume of the instrument between the tip of the arterial needle and the middle of the detecting photocell. The time taken for dyed blood to travel from the needle tip in the artery to the detecting element was calculated fromm the volume of this "dead space" and the flow rate of blood withdrawn through the cuvet s stem. This time correction was then subtracted from the appropriate time components of the dilution curve. The dead space and physical dimensions of the o...

Oxygen saturation of arterial and central venous blood was measured continuously during the Valsalva mnaneuver in patients with and without intracardiac defects. The majority of patients with atrial septal defects and patients with ventricular septal defects and high right ventricular pressure showed a sharp decrease in saturation of radial artery blood shortly after the inaneuver. These changes were not recorded accurately by ear oximnetry. The patients with shunts uniformly showed a rapid increase in saturation of pulmonary artery blood during the initial period of increased airway pressure. This effect was not observed in patients without shunts.