Biomedical subjects
Publications and source records attributed to T Stokke.
The exact separation of in- and expired gas during mechanical ventilation is not possible by means of common breathing valves. This will lead to substantial errors in determination of several lung function tests. In the present paper it is shown, how to obtain exact separation by means of a PEEP-valve and an exhalation valve.
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The continuous arteriovenous haemofiltration (CAVH) is a simple, safe, inexpensive and personnel-saving method for treatment of uremic patients. Since the introduction of the CAVH in 1977, far more than 200 patients have been treated by this method in our hospital. In the present paper the method and our experiences during the clinical application are presented. The haemofilter is placed in an extracorporal shunt between the A. and V. femoralis. Cannulation of these vessels is performed by means of a modified Seldinger technique using commercially available catheter. During haemofiltration, heparin is infused into the arterial blood line at a rate of 10 IU/kg . h. The filtrate is totally or partially replaced by nutrition solutions, enteral or parenteral, and by a potassium-free Ringer's lactate i.v. solution, according to the required fluid balance. In most cases the filtrate-substitution rate will be high enough to compensate renal failure, and thus conventional dialysis methods will not be necessary. Clinical experience to date allows the following conclusions: optimal control of water and electrolyte balance; unlimited parenteral nutrition, continuous fluid withdrawal better tolerated than intermittent withdrawal by means of dialysis; low risk of local bleeding with skilled puncture technique of the femoral vessels. Low dose continuous heparin administration into arterial blood line is sufficient for extracorporal anticoagulation. Saving of expenses: No investment costs for machines; specially trained dialysis personnel superfluous.
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A simple method for determination of the functional residual capacity (FRC) during artificial ventilation by inert gas dilution using a rebreathing technique is described. The measurements can be made during various techniques of mechanical ventilation (eg. PEEP, IMV etc.). Myorelaxation is not required. This technique was used to assess the volume of a lung model (actual volume: 3670 ml) with the result of repeated measures being 3686 +/- 29 ml. Duplicate measurements in artificially ventilated pigs showed a coefficient of variation of +/- 3.2%. In artificially ventilated patients FRC was determined both with this technique and with a reference method, giving a difference of 111 +/- 55 ml (p less than 0.001). The errors in measurements of FRC by this method are small, and as the measurement requires a minimum of time and the apparatus is simple, the method is accurate and yet simple enough to be used on a routine basis in the intensive care unit. Even high risk patients are not disturbed by this technique. The method has the advantage that it can easily be learned by nurses and paramedical personal.
Pulmonary diffusing capacity may be determined by rebreathing techniques using various test gases. The errors caused by functional inhomogenities are smaller with the rebreathing method than those found in the single-breath technique. However, until now there have been some disadvantages to the clinical application of the rebreathing technique. In the present paper, a modification of the rebreathing technique suggested by Piiper, Scheid, Meyer and Adaro (1975 and 1976), in which pulmonary diffusing capacity for carbon monoxide, DCO(RB), is measured, has been applied to intubated and anesthetised patients. Measurements were performed in 39 surgical patients with healthy lungs during artificial ventilation and narcosis. Under these conditions all patients had a DCO(RB) greater than or equal to 75 ml/min . kPa (10 ml/min.torr). The coefficient of variation for duplicate measurements was +/- 4.2%. In the same patients DCO-single-breath-measurements, DCO(SB), were also made. There was a significant (p less than 0.0001) correlation between DCO(RB) in artificially ventilated, anaesthetised patients in a supine position and DCO(SB) for spontaneously breathing, awake patients in a sitting position. A linear regression analysis of the data showed the DCO(SB) was related to DCO(RB) in the following manner: DCO(SB) = 1.62DCO(RB) = 4.44 (ml/min.torr) (r = 0.71, n = 39). The mean value of DCO(RB) was 53.4% of the mean value of DCO(SB). This difference may be due to the combination of different techniques used and different conditions during the measurements (reduced FRC, difference in F1O2 etc.). The histogramm of the distribution of DCO(RB) had a similar form to that of DCO(SB). The modified method has a high reproducibility and can easily be performed as a bed-side test without disturbance to patients with an endotracheal tube.
Pulmonary artery chatheterisation by means of flow-directed balloon-tipped catheters has proved a valuable aid in assessing haemodynamic parameters of critically ill patients. Serious complications are reported to be uncommon. On postmortem examination of 8 patients, in whom flow-directed balloon-tipped catheters were employed, and whose catheters were dissected in situ, there were 5 instances of non-bacterial thrombotic endocarditis (NBTE) and 4 of focal valvular bleeding. This is a much more frequent incidence of valvular lesions than has been reported previously. The pathogensis of NBTE is briefly disicussed, and attention is drawn to potential long-term complications. We suppose that valvular diseases of the right side of the heart will gain in significance due to the increasing use of flow-directed balloon-tipped pulmonary artery catheters.
It may be concluded from our results to date, that arteriovenous hemofiltration is an accurate and reliable method for the management of fluid balance in patients resistant to diuretics. Early use of this method may improve the prognosis of intensive-care patients by decongestion or dehydration of lungs, reduction of cardiac pre-and after-load and unrestricted infusion therapy for prevention of catabolism. In addition, the method has been shown to be useful for compensation of uremia and particularly for hypernatremia. The fact that this method requires no investment costs might be of particular interest to many intensive-care units which cannot afford expensive hemodialysis or hemofiltration machines.
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The amount and composition of lipid in 129 walls of jaw cyst and 18 pieces of cyst contents was determined by thin-layer chromatography. The proportions of the fractions (i.e. phospholipid, free cholesterol, cholesteryl ester, triglyceride, free fatty acids) were compared with corresponding values (collected from the literature) from the superficial layers of normal and atherosclerotic aortas. The amounts of total lipid and of the fractions were comparable. Concomitant with an increasing amount of lipid, there was a rise in the ratio: total cholesterol/phospholipid. In the aortic lesions this increase of cholesterol was due to a rise in the fraction of cholesteryl ester. In the cyst material, the increase was due to a rise in the free cholesterol. A possible explanation is discussed.
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A method for the preparation of HeLa cell plasma membrane ghosts is described. The purity of the plasma membrane fraction was examined by phase contrast and electron microscopy, by chemical analysis, and by assay of marker enzymes. Data on the composition of the plasma membrane fraction are given. It was observed that the distribution pattern of 5'-nucleotidase activity among the subcellular fractions differed from that of ouabain-sensitive ATPase. In addition, the specific activity of 5'-nucleotidase did not follow the distribution of the membrane ghosts. Thus, this enzyme would seem unsuitable as a plasma membrane marker. A complete balance sheet for marker enzyme activities during the fractionation is necessary for the calculation of increase in specific activity because the activities of both 5'-nucleotidase and ouabain-sensitive ATPase might change during the fractionation procedures.
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