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Biomedical subjects

B Oeseburg

Publications and source records attributed to B Oeseburg.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effects of repeated indomethacin administration on cerebral oxygenation and haemodynamics in preterm infants: combined near infrared spectrophotometry and Doppler ultrasound study.

The objectives of this study were to evaluate the effect of repeated indomethacin administration on cerebral oxygenation in relation to changes in cerebral blood flow velocity (CBFV) and other relevant physiological variables. Fourteen preterm infants with patent ductus arteriosus were studied during three subsequent indomethacin bolus administrations with intervals of 12 and 24 h. Changes in concentration of oxyhaemoglobin (cO2Hb), deoxyhaemoglobin (cHHb) and oxidized cytochrome aa3 (cCyt.aa3) in cerebral tissue and changes in cerebral blood volume (CBV) were measured by near infrared spectrophotometry; changes in mean CBFV in the internal carotid artery were measured by pulsed Doppler ultrasound. Simultaneously heart rate, transcutaneous pO2 and pCO2, arterial O2 saturation and blood pressure were measured. All variables were continuously recorded until 60 min after indomethacin administration. Within 5 min after each indomethacin administration, significant decreases in CBFV, CBV and cO2Hb and cCyt.aa3 were observed which persisted for at least 60 min, while cHHb increased or did not change at all. There were no changes in the other variables recorded. These data demonstrate that indomethacin administration is accompanied by a reduction in cerebral tissue oxygenation due to decreased cerebral blood flow. Therefore, low arterial oxygen content, either caused by low arterial O2 saturation or by low haemoglobin concentration, may be a contraindication for indomethacin treatment in preterm infants.

Blood Flow Velocity↗
PubMed1994

Properties of the venous vascular system in the lower extremities of individuals with paraplegia.

The purpose of this study was to examine the properties of the venous vascular system in the lower extremities of individuals with long-standing paraplegia (PP). The venous volume variations (VVV), the venous capacity (VC), the venous emptying rate (VER) and the venous flow resistance (VFR) were measured in the left calf of 14 male PP and 12 male able-bodied subjects (ABS) by means of strain-gauge occlusion plethysmography. VVV and VC were significantly lower in PP compared to ABS, -45% and -50% respectively. Both groups showed a similar resting venous pressure in the calf (PP = 24.4 mmHg; ABS = 19.6 mmHg). VER was significantly lower (-60%) and hence VFR was significantly higher (+75%) in PP compared to ABS. This study demonstrates that the venous vascular properties in the legs of individuals with paraplegia have changed, i.e. a decrease in venous distensibility and capacity and an increase in venous flow resistance. This is most probably the result of vascular adaptations to inactivity and muscle atrophy rather than the effect of a non-working leg-muscle pump and sympathetic denervation.

Adult↗
PubMed1994

Cardiac output determined by the CO2 rebreathing method during arm exercise.

Since arm exercise affects the respiratory muscles the CO2 rebreathing method for determining cardiac output (Q) has to be evaluated during arm exercise. The purpose of this study was (1) to compare three different methods of determining arterial CO2 tension (PaCO2) during arm exercise, (2) to verify the linearity of the relationship between Q and oxygen uptake (VO2) during arm exercise, and (3) to investigate whether the CO2 rebreathing method according to Collier can determine accurately Q during arm exercise. Sixty male subjects performed arm-cranking exercise at 20%, 40% and 60% of their individual maximal load. Carbon dioxide output (VCO2) was measured by gas exchange measurement, and mixed venous CO2 tension (PvCO2) was determined from the CO2 rebreathing plateau at each exercise level. PaCO2 was estimated in three different ways: (A) by the modified Bohr formula for dead space, (B) by an arterialized blood sample from the hyperaemic ear-lobe, and (C) by the end-expiratory CO2 tension. A, B, and C were used to calculate Qa, Qb and Qc, respectively. The Pearson's correlation coefficient was high (P < 0.01) among the three different ways of estimating PaCO2. The Q-VO2 relationship proved to be linear (P < 0.01). The Q-values showed a good agreement with the direct Fick measurements, and were in the same range compared to other results obtained by dye dilution, electrical impedance cardiography and the exponential CO2 rebreathing method during arm exercise. In conclusion, the CO2 rebreathing method appeared to be accurate to determine Q during submaximal arm exercise.

Adult↗
PubMed1993

Do we use the right entry criteria for extracorporeal membrane oxygenation in congenital diaphragmatic hernia?

In a retrospective review we analysed alveolar-arterial oxygen difference (AaDO2) as an entry criterion for extracorporeal membrane oxygenation (ECMO) in neonates with several forms of acute respiratory insufficiency. Although for meconium aspiration syndrome, respiratory distress syndrome, sepsis, and idiopathic pulmonary hypertension of the newborn we found values in accordance with the literature, patients with congenital diaphragmatic hernia (CDH) met 80% mortality criteria with significant lower AaDO2 values. Several patients died before ever reaching usual entry criteria for ECMO, because serious lung deterioration makes AaDO2 values unreliable. Awaiting classical ECMO entry criteria for patients with CDH may at least partially explain the lower survival rate for ECMO in CDH.

Extracorporeal Membrane Oxygenation↗
PubMed1993

Effect of fetal hemoglobin on the determination of neonatal cerebral oxygenation by near-infrared spectroscopy.

Near-infrared spectroscopy has been applied to the study of cerebral oxygenation and hemodynamics in the newborn. Fetal Hb is present in high concentrations in these infants. Because spectral absorption curves in the near-infrared range for fetal Hb are not identical to those for adult Hb, there is a potential for the measurements to be affected. This possibility has not previously been investigated. A quantitative analysis of cerebral oxygenation was undertaken in six newborn infants. The analysis used near-infrared spectroscopy multiplier coefficients derived from the absorption coefficients of both fetal and adult deoxygenated and oxygenated Hb. The results of both analyses were compared. It was concluded that the error in near-infrared spectroscopy analysis of neonatal cerebral oxygenation arising from the use of absorption coefficients derived from adult Hb is inconsequential, even in the presence of high concentrations of fetal Hb.

Adult↗
PubMed1993

Cardiovascular responses in persons with paraplegia to prolonged arm exercise and thermal stress.

The purpose of this study was to investigate cardiovascular responses in subjects with paraplegia (P) during prolonged upper body exercise in a hot environment. In addition, the effect of the level of the lesion on cardiovascular regulation of persons with paraplegia was studied. Four P with lesions between T2-T6 (P1), five P with T7-T8 lesions (P2), four P with lesions between T9-T12 (P3), and 10 control subjects (C) performed 45-min arm-cranking exercise at 40% of the individual peak power output, in a climatic room at 35 degrees C with a 70% relative humidity. From the 15th to the 45th min, cardiac output (Q) and oxygen uptake (VO2) remained unaltered in all subjects, except a significant decrease of Q in P1. Stroke volume (SV) decreased significantly in both P (-20%) and C (-18%) during the test. Heart rate (HR) increased in compensation for P2 (56%), P3 (65%), and C (55%), whereas HR in P1 did not increase significantly. Hemoglobin concentration changes, representing total plasma volume changes, increased significantly in P2, P3, and C but not in P1. Weight loss and sweat rate increased relative to the sensate skin area and, thus, to the level of the spinal cord lesion (P < 0.01). In conclusion, P with lesions below T6 are able to maintain a stable Q by increasing HR to compensate for the declining SV during exercise in a hot environment. P with lesions above T6 cannot fully compensate for the reduction in SV by an increase in HR, therefore, Q declines.

Adult↗
PubMed1992

Cardiovascular responses in paraplegic subjects during arm exercise.

The purpose of this study was to examine cardiovascular responses during arm exercise in paraplegics compared to a well-matched control group. A group of 11 male paraplegics (P) with complete spinal cord-lesions between T6 and T12 and 11 male control subjects (C), matched for physical activity, sport participation and age performed maximal arm-cranking exercise and submaximal exercise at 20%, 40% and 60% of the maximal load for each individual. Cardiac output (Qc) was determined by the CO2 rebreathing method. Maximal oxygen uptake was significantly lower and maximal heart rate (fc) was significantly higher in P compared to C. At the same oxygen uptakes no significant differences were observed in Qc between P and C; however, stroke volume (SV) was significantly lower and fc significantly higher in P than in C. The lower SV in P could be explained by an impaired redistribution of blood and, therefore, a reduced ventricular filling pressure, due to pooling of venous blood caused by inactivity of the skeletal muscle pump in the legs and lack of sympathetic vasoconstriction below the lesion. In conclusion, in P maximal performance appears to have been limited by a smaller active muscle mass and a lower SV despite the higher fc,max. During submaximal exercise, however, this lower SV was compensated for by a higher fc and, thus at the same submaximal oxygen uptake, Qc was similar to that in the control group.

Adult↗
PubMed1992

The effect of an anti-G suit on cardiovascular responses to exercise in persons with paraplegia.

The purpose of this study was to determine whether external pressure on legs and abdomen could prevent venous blood pooling in persons with paraplegia and thus positively affect their cardiovascular responses to arm exercise. To investigate this, five male subjects with paraplegia (P), with complete lesions between T6 and T12, and five male control subjects who were wheelchair bound (C) (due to a chronic lower extremity disability), performed submaximal arm-cranking exercise at 20%, 40%, and 60% of their maximal power output (Wmax), with and without an antigravity (anti-G) suit inflated to 52 mm Hg (1 psi). For P, higher preexercise systolic pressure (127 vs 117 mm Hg) was seen with the anti-G suit. At 40 and 60% Wmax, significantly lower heart rates (at 40% = 5.7%; at 60% = 10.6%) at similar cardiac outputs were seen for P with an anti-G suit. Although not significant, P also demonstrated higher stroke volumes at 40% (4.8%) and 60% (5.0%) Wmax with external pressure. For C, no differences in preexercise blood pressure or cardiovascular responses at all three exercise levels were seen with or without the anti-G suit. These data suggest that an inflated anti-G suit is able to prevent venous blood pooling and offers hemodynamic benefits in persons with paraplegia during submaximal arm-cranking exercise. In addition, this study reports a possible alternative to hosiery or functional neuromuscular stimulation that could be applied to all subjects with spinal cord injuries regardless of type or duration of the lesion or of muscle-atrophy.

Adult↗
PubMed1989

Reliability of the determination of whole-blood oxygen affinity by means of blood-gas analyzers and multi-wavelength oximeters.

Determination of the oxygen affinity of human whole blood with the help of blood-gas analyzers and multi-wavelength oximeters is compared with an accurate method for recording hemoglobin oxygen dissociation curves (Clin Chem 1982;28:1287-92). P50 (oxygen tension at half saturation; So2 = 50%) and Hill's n (delta log [So2/(1-So2)]/delta log Po2) were determined in blood of 24 healthy donors. Three slightly different procedures were used for determination of P50 on the basis of Po2, pH, Pco2, and So2 measured with each of four different blood-gas analyzer/oximeter combinations. These methods were not able to discriminate between high and low values for P50 within the normal reference interval, but never failed to detect the high oxygen affinity of blood stored for 12 days, reflected in low values of P50. The methods thus proved suitable for detecting clinically significant deviations in oxygen affinity such as occur in patients with, e.g., abnormal hemoglobins, anemias, or carbon monoxide poisoning. Determination of Hill's n by these methods did not produce useful results.

Adult↗
PubMed1989

Definition and notation of hemoglobin oxygen saturation.

Oxygen saturation (SO2) should not be confused with oxyhemoglobin fraction (FHbO2). As automated multiple wavelength photometers may yield both SO2 and FHbO2, care should be taken that only SO2 is used in checking the results of pulse oximeters. Arterial SO2 is the quantity aimed at by pulse oximeters. Although the accuracy of the measurement may be less than that of the analysis of an arterial blood sample in vitro, the measured quantity remains SO2. Using a special symbol, like SpO2, obscures this fact and should be discouraged.

Hemoglobins↗