Clinical physiology (Oxford, England)
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The present investigation was undertaken in order to study (1) the difference in arterial (Ca) and venous (Cv) concentration of [51Cr]EDTA (ethylenediaminetetraacetate) after a single intravenous injection, (2) the impact of different physiological variables on this difference, and (3) the error introduced in the measurement of renal plasma clearance and total plasma clearance by using venous blood samples instead of arterial. In 13 patients with GFR ranging from 29 to 150 ml min-1, Ca was higher than Cv immediately after the injection. After mean 38 min (range 12-82 min) the two curves crossed, and 180-300 min post-injection (p.i.) Cv was 5.9% higher than Ca (range 0.5-13.9%, P less than 0.001). ⋯ Plasma clearance determined by venous and arterial blood samples does not differ significantly as long as the concentration is followed from the time of injection and a long period is applied. When simplified plasma clearance techniques are used, different results may be obtained from venous and arterial samples. The simplified techniques using venous blood samples--which usually include some empirical corrections--should be sufficiently reliable in daily clinical practice provided the forearm blood flow is reasonably high, e.g. exposure to cold should be avoided.
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Comparative Study
Total lung capacity measured by body plethysmography and by the helium dilution method. A comparative study in different patient groups.
The helium dilution method is known to underestimate the total lung capacity (TLC) in patients with poorly or non-ventilated areas in the lungs. The standard plethysmographic method has been reported to overestimate TLC in patients with severe airway obstruction. ⋯ In patient groups with moderately obstructed airways (n = 23), severely obstructed airways (n = 20), or emphysema (n = 19), there were no significant average differences, although in two patients in the emphysema group the plethysmographic values were considerably larger than those obtained by helium dilution. We conclude that the gas dilution methods and plethysmography with a pressure-compensated volume displacement plethysmograph gave estimates of TLC which agreed even in patients with airway obstruction or emphysema, except in patients with very severe lung disease.
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Comparative Study
QT and QT-peak interval measurements. A methodological study in patients with subarachnoid haemorrhage compared to a reference group.
To study the properties of QT and QT-peak intervals, ECGs were compared between 56 consecutive patients who were suffering from subarachnoid haemorrhage (SAH) and 50 reference subjects. The routine QTc interval was compared to the mean QTc from all of the 12 leads with identifiable U waves and to the mean QT-peakc. The interval between peak and end of T(Tp-Te) was subsequently calculated. ⋯ In conclusion, the routine QTc measurements, without reference to an identified U wave, may result in falsely prolonged estimates of cardiac repolarization time. In this respect the mean QT-peakc may provide additional information. In the majority of patients the prolonged mean QTc was dependent on a disturbed rate-dependent function (prolonged mean QT-peakc) while some patients had an increased asymmetry of the repolarization process within the myocardium (prolonged Tp-Tc).
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The relationships between portal hypertension and spleen enlargement, in patients with liver cirrhosis, are not clearly defined; as well as those between splenic haemodynamics and portal hypertension. In 25 cirrhotics with spleen enlargement and portal hypertension and in seven controls, the following parameters were determined: estimated splenic volume (ESV) from the radiographic view of the spleen, according to Blendis, Williams and Kreel (1969), specific splenic blood-flow (SSBF), total splenic blood-flow (TSBF), porto-hepatic gradient (PHG), specific splenic resistance (SSR) and total splenic resistance (TSR). ⋯ Neither TSBF nor TSR were found to be correlated to the level of portal hypertension, as estimated by PHG or by oesophageal varices. It is concluded that, in patients with liver cirrhosis and spleen enlargement, splenomegaly is likely to be the consequence of pulp hyperplasia and not of passive congestion, and that increases in splenic blood-flow do not contribute significantly to portal hypertension.