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B Oeseburg

Publications and source records attributed to B Oeseburg.

At least 91 records · Page 5Linked to original sources
PubMed1988

Human whole-blood O2 affinity: effect of CO2.

The proton Bohr factor (phi H = alpha log PO2/alpha pH), the carbamate Bohr factor (phi C = alpha log PO2/alpha log PCO2), the total Bohr factor (phi HC = d log PO2/dpH[base excess) and the CO2 buffer factor (d log PCO2/dpH) were determined in the blood of 12 healthy donors over the whole O2 saturation (SO2) range. All three Bohr factors proved to be dependent on SO2, although to a lesser extent than reported in some of the recent literature. At SO2 = 50% and 37 degrees C, we found phi H = -0.428 +/- 0.010 (SE), phi C = 0.054 +/- 0.006, and phi HC = -0.488 +/- 0.007. The values obtained for phi H, phi C, and d log PCO2/dpH were used to calculate phi HC. Calculated and measured values of phi HC proved to be in good agreement. In an additional series of 12 specimens of human blood we determined the influence of PCO2 on phi H and the influence of pH on phi C. At SO2 = 50%, phi H varied from -0.49 +/- 0.009 at PCO2 = 15 Torr to -0.31 +/- 0.010 at PCO2 = 105 Torr and phi C from 0.157 +/- 0.015 at pH = 7.80 to 0.006 +/- 0.009 at pH = 7.00. When on the basis of these data a second-order term is taken into account, a still slightly better agreement between measured and calculated values of phi HC can be attained.

Carbon Dioxide↗
PubMed1987

Calibration of a practical haemoglobinometer.

A practical instrument for routine haemoglobinometry (HemoCue) was compared with the reference haemiglobincyanide (methaemoglobincyanide (HiCN] method. The precision of the routine method was adequate, but a systematic error of about -3.5% was found. As this resulted from errors in the procedure for coupling the haemoglobinometer read-out to the reference HiCN method, we drew up an improved calibration procedure for practical haemoglobinometers to ensure comparability of results with the reference method. After recalibration according to these rules, the HemoCue system proved to be accurate to within +/- 1.5%.

Calibration↗
PubMed1987

Intravascular pH-ISFET, a method of the future.

Since blood pH reflects the metabolic state as well as the functioning of the respiratory and circulatory systems, it appears to be one of the vital parameters that should be continuously monitored. The point to point measurement of pH by sampling has limitations, since results are available after some time only. A continuous pH signal is necessary in rapidly changing situations such as often occur during intensive treatment. The application of ion-selective field-effect transistor (ISFET) technology to intravascular pH measurement seemed attractive since these devices offer a short response time, are suitable to miniaturization and fabrication in large quantities, and have a low output impedance. The system was tested in dog experiments. Two to four pH-ISFET catheters were tested simultaneously in each dog. Arterial samples for blood-gas analysis with a Radiometer ABL2 system were taken during periods in which plasma-pH was stable. Clinical trials were performed in patients who were admitted to the intensive care unit after coronary artery bypass grafting. Testing the pH-ISFET system in dogs (N = 12) and comparing it with ABL2 measured samples (n = 132 with a pH range of 6.72-7.86), resulted in a delta pH (ISFET-ABL2) of 0.016 +/- 0.024 pH with a maximum deviation of 0.06. The clinical trials proved that the system is well-suited for monitoring intravascular pH in critically ill patients.

Animals↗
PubMed1985

Fetal subcutaneous scalp PO2 and abnormal heart rate during labor.

Intrapartum fetal heart rate and subcutaneous scalp PO2 were continuously measured with a combined electrocardiogram-PO2 needle electrode in 34 patients. The incidence of fetal heart rate abnormalities increased significantly with decreasing subcutaneous PO2, from 0.8% of the 10-minute periods in which subcutaneous PO2 was greater than or equal to 25 mm Hg to 53% of the periods in which subcutaneous PO2 was less than 10 mm Hg.

Electrodes↗
PubMed1984

Human whole-blood oxygen affinity: effect of carbon monoxide.

Oxygen dissociation curves (ODC) were recorded in the presence of carboxyhemoglobin fractions (FHbCO) up to 60%. The gradual shift to the left of the ODC at increasing amounts of HbCO was reflected in a gradual fall in the half-saturation pressure of the remaining Hb and was accompanied by a gradual change in the shape of the ODC to a hyperbolic one. The H+ factor (delta log PO2/delta pH) was determined over the entire oxygen saturation (SO2) range at three different FHbCO levels (14, 30, and 52%). At FHbCO = 14 and 30% and for the SO2 range 20-90%, the H+ factor vs. SO2 curve was not significantly different from that in the absence of HbCO. At FHbCO = 52%, however, the value found for the H+ factor (-0.55) was appreciably more negative than in the case of blood containing less than 1% HbCO (-0.44), and there was no dependence on SO2. Comparison of measured and calculated ODCs at varying HbCO fractions showed, for FHbCO less than or equal to 50%, that measured and calculated ODCs coincide over the greater part of the SO2 range. For FHbCO greater than 50%, the measured ODC was situated to the left of the calculated one over the entire SO2 range. We conclude that the heme-heme interaction for CO is appreciably larger than for O2 only for FHbCO greater than 50%, whereas for FHbCO less than 50% there is virtually no difference.

Capillary Permeability↗
PubMed1984

Human whole-blood oxygen affinity: effect of temperature.

phe effect of temperature changes on human whole-blood O2 affinity was measured in the blood of six healthy donors over almost the entire O2 saturation (SO2) range (1-99%). The results showed that temperature has no influence on the shape of the O2 dissociation curve, implying that the temperature coefficient (delta log PO2/delta T) is independent of SO2. Simultaneous measurements of the total (proton) Haldane factor (delta[HbH]/[delta HbO2]) at the five temperatures under study (22, 27, 32, 37, and 42 degrees C) revealed that this factor depends on temperature. The liberation of protons from hemoglobin appeared to be linear with respect to changes in SO2. We therefore conclude that the (proton) Bohr factor (H+ factor) is dependent on temperature over the entire SO2 range in the same way as previously described for SO2 = 50%. The exothermic oxygenation reaction in whole blood was accompanied by a heat evolution (delta HO2) of 42.7 kJ/mol (monomeric) hemoglobin.

Female↗
PubMed1982

Oxygen dissociation curves for whole blood, recorded with an instrument that continuously measures pO2 and sO2 independently at constant t, pCO2, and pH.

We describe a method for recording oxygen dissociation curves for whole-blood specimens. The blood sample is placed in a thermostated measuring chamber, and pO2 and SO2 are measured continuously by polarography and by reflectometry, respectively. During the recording of an oxygen dissociation curve, the pO2 and SO2 signals are stored in a data-acquisition system, while pH, pCO2, and temperature are kept constant. Determination of precision and error discussion indicated that the coefficient of variation (CV) of the determination of the oxygen dissociation curve is mainly determined by the error in the measurement of SO2. The overall CV of pO2 values belonging to the lower, mid-, and upper parts of the SO2 range is estimated to be about 2.6, 3.1, and 2.1%, respectively. In practice the measurements are about 30% more precise than estimated. With our method, the fixed-acid-induced Bohr effect (H+ factor) can be determined over the entire SO2 range with much greater precision than hitherto.

Blood Gas Analysis↗
PubMed1982

Determination of interdependent ligand effects on human red cell oxygen affinity.

Human whole blood oxygen affinity was determined as P50, i.e. PO2 for oxygen saturation (SO2) = 0.5, in a new system which allows the measurement of SO2, PO2 and pH continuously and independently, with control of PCO2 and temperature. The influence of pH on P50 expressed as the H+ factor (delta log P50/delta pH)PCO2 was measured under conditions of varying PCO2, temperature and concentration of 2,3-diphosphoglycerate (2,3-DPG), resulting in a set of data expressing second-order inter-ligand interactions. The H+ factor appeared to be only slightly dependent on PCO2. Similarly, the CO2 factor (delta log P50/delta log PCO2)pH shows only a minor dependence on pH. The H+ factor in linearly related to the temperature: at 17 degrees C and 42 degrees C the H+ factor is about -0.53 and -0.36, respectively. Likewise, the temperature factor (delta log P50/delta T)PCO2,pH is linearly related to pH. A pilot study on the effect of varying intra-erythrocytic 2,3-DPG concentrations on the oxygen affinity showed that a very low 2,3-DPH/Hb4 ratio apparently does not influence the H+ factor. A high ratio, however, seems to lower the H+ factor considerably.

2,3-Diphosphoglycerate↗
PubMed1981

Subcutaneous oxygen tension in the fetal scalp during labour continuous monitoring with a needle electrode.

Continuous intrapartum PO2 recordings were made in 25 fetuses, using a needle electrode that measures PO2 in the subcutaneous (sc) tissue of the scalp or the breech. This small electrode is combined with a spiral ECG electrode and can be easily applied in early labour. One hour after application of the electrode in the early first stage, a mean fetal scPO2 of 29.4 +/- 7.5 mm Hg was found. In the course of labour, scPO2 gradually fell to a mean value of 22.2 +/- 5.6 mm Hg, recorded just before the onset of bearing down contractions, and stabilised in the second stage of labour. ScPO2 values of less than 20 mm Hg were not recorded for a longer period except in one case of severe fetal distress. The relation between scPO2 just before delivery and cord arterial PO2 revealed a coefficient of correlation of 0.85. In general, scPO2 appeared higher than tcPO2 as described in the literature. This is ascribed to the different technique of measurement: the needle electrode measures in the deeper layers of the scalp, whereas the tc electrode is supplied with oxygen form the more superficial capillaries, where blood flow is more liable to be affected by mechanical factors.

Electrodes↗
PubMed1981

Influence of variations in pH and PCO2 on scalp tissue oxygen tension and carotid arterial oxygen tension in the fetal lamb.

A description is given of the effect of hypercapnic acidaemia and hypocapnic alkalaemia on scalp tissue PO2 as measured with a subcutaneous needle-electrode and a transcutaneous electrode in 6 fetal lambs. The experiments were carried out under general anaesthesia with the fetus kept in utero. Hypocapnia was induced by hyperventilating the ewe and hypercapnia was achieved by administering extra CO2 to the ewe. Fetal carotid arterial, subcutaneous and transcutaneous PO2 were continuously recorded, and fetal and maternal arterial pH and arterial PCO2 were determined from blood samples taken at short intervals. In each experiment the H+ Bohr factor of fetal and maternal blood was measured. During hypocapnic alkalaemia, there was a fall in all fetal PO2 levels, whereas a marked rise was observed during hypercapnic acidaemia. The variations in fetal PO2 observed in vivo even exceeded the variations due to the H+ Bohr effect (measured in vitro). This was due to small variations in fetal carotid arterial oxygen saturation, which tended to fall during hypocapnic alkalaemia and to rise during hypercapnic acidaemia. The results of these findings strongly suggest that tissue PO2, as measured with the subcutaneous and transcutaneous electrodes, is dependent on the H+ Bohr effect. This adds to the uncertainty as to the value of subcutaneous and transcutaneous PO2 monitoring during labour as an early warning system for impending fetal asphyxia.

Animals↗
PubMed1981

A multi-wavelength spectrophotometric method for the simultaneous determination of five haemoglobin derivatives.

A method is described by which the concentration of deoxyhaemoglobin, oxyhaemoglobin, carboxyhaemoglobin, haemoglobin and sulfhaemoglobin in a human blood sample is determined by passing the haemolysate without air contact through a coarse filter and subsequently measuring the absorbance at lambda = 500, 569, 577, 620 and 760 nm. The ensuing set of equations is solved by matrix calculation with the aid of a simple computer program. The method has been tested by comparing it with conventional methods for the determination of the various haemoglobin derivatives separately.

Carboxyhemoglobin↗
PubMed1981

Determination of hemoglobin derivatives with IL 282 CO-oximeter as compared with a manual spectrophotometric five-wavelength method.

Hemoglobin derivatives as determined with the IL 282 CO-Oximeter correlated well with results by a manual five-wavelength method, which in turn had been checked against established methods for one or two derivatives. Measurement of total hemoglobin yielded almost identical results with both methods. As for oxyhemoglobin, carboxyhemoglobin, and hemiglobin, agreement between the two methods was fair. Although the IL 282 CO-Oximeter has not been constructed for the determination of sulfhemoglobin, it appeared that the instrument can still give a strong indication as to the presence of this hemoglobin derivative. Results from the IL 282 for fetal human blood should be used with caution, especially because of the possibility of falsely high HbCO readings.

Autoanalysis↗
PubMed1980

Continuous intra-arterial pH measurement.

A flexible glass electrode catheter with a diameter of 3 mm has been developed for pH measurement in the arterial system of dogs. In combination with a galvanically isolated amplifier, an undisturbed pH signal could be obtained from the aorta. The system was fast enough to truly record pH changes synchronous with respiration and was shown to be insensitive to variations in blood flow velocity. Good agreement was found between pH catheter readings nd pH values of simultaneously taken arterial samples as measured with a conventional capillary glass electrode.

Animals↗