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Biomedical subjects

B Oeseburg

Publications and source records attributed to B Oeseburg.

At least 19 recordsLinked to original sources
PubMed1995

The effect of pulsating arteries on reflectance pulse oximetry: measurements in adults and neonates.

OBJECTIVE: The objective of our study was to describe the results from human experiments during normoxia that demonstrate the effect of pulsating arteries on the measured arterial oxygen saturation (SpO2) using a reflectance pulse oximeter sensor. METHODS: In 6 healthy adults and 7 healthy neonates, a Nellcor reflection sensor (FS-10 oxisensor, Nellcor, Inc., Pleasanton, CA) was placed in three different positions: (1) on the forehead, (2) on the temporal area, with the photodiode placed over the superficial temporal artery, and (3) on the temporal area, with the light-emitting diodes (LEDs) placed over the superficial temporal artery. RESULTS: Placement of the sensor in position 2 resulted in a significantly lower SpO2 reading, compared to sensor position 1: 5.8% (p < 0.01) lower for adults and 7.5% (p < 0.01) lower for neonates. Placement of the sensor in position 3 resulted in significantly larger plethysmographic signals, compared to sensor position 1; but, the Spo2 readings were alike. CONCLUSIONS: Pulsating arteries can affect the reliability of reflection pulse oximetry. Depending on the position of the sensor, a falsely low Spo2 value can be observed.

Adult↗
PubMed1995

Arterial oxygen saturation in relation to metabolic acidosis in fetal lambs.

OBJECTIVE: We studied the relationship between preductal arterial oxygen saturation and metabolic acidosis in 18 chronically instrumented fetal lambs (gestational age 119 to 133 days) in two experimental designs. In the first group the onset of metabolic acidosis was determined. In the second group the progression of metabolic acidosis was studied as was the cardiovascular and hormonal changes resulting from hypoxemia. STUDY DESIGN: In nine fetal lambs maternal fraction of inspired oxygen was lowered stepwise by increasing flows of nitrogen delivered into the trachea through a small indwelling catheter (group 1), and in nine fetal lambs maternal blood flow was reduced stepwise by means of a vascular occluder (group 2). RESULTS: Baseline arterial oxygen saturation values ranged from 26% to 67% with normal pH and extracellular fluid base excess values in both groups 1 and 2. In both groups pH and extracellular fluid base excess started to decrease below 30% arterial oxygen saturation, with a progressive decrease below 20% arterial oxygen saturation to an end value for pH of 7.14. In some fetal lambs pH and extracellular fluid base excess decreased initially at 20% to 30% arterial oxygen saturation and then stabilized at the lower level. Fetal heart rate in group 1 increased during hypoxemia from 155 to 179 beats/min. In group 2 baseline fetal heart rate was 153 beats/min and fell with every step change in arterial oxygen saturation but subsequently increased to 172 beats/min by the end of the period of hypoxemia. Baseline values for epinephrine, norepinephrine, dopamine, cortisol, and mean arterial pressure were not related to baseline arterial oxygen saturation levels, and each of these variables was increased at the end of hypoxemia in group 2. CONCLUSION: Preductal arterial oxygen saturation can reach values between 20% and 30% before anaerobic metabolism starts. During the progressive acidosis blood pressure was increased, which can be attributed to a strong rise in catecholamines.

Acidosis↗
PubMed1995

Measurement of the blood supply to the abdominal testis by means of near infrared spectroscopy.

Cryptorchidism is the most common male sexual disorder. In the case of an abdominal testis there is no objective criterion to choose between autotransplantation or orchiopexy after ligation of the spermatic vessels with subsequent development of collateral blood supply. By combining near infrared spectroscopy (NIRS) with pulse oximetry the active testicular blood volume (ATBV) before and after occlusion of the spermatic vessels can be calculated in an animal model. NIRS is a noninvasive continuous optical technique that measures tissue oxygenation and hemodynamics. Ten boars with one non-palpable testis each were selected. The spermatic vessels and vas deferens were separately prepared and atraumatic occluders were placed around the vessels. ATBV was measured before and after occlusion of the spermatic vessels. The calculated ATBV was 18.3 +/- 2.3 ml/100 g of testicular tissue, not corrected by division by the path length factor, accounting for light scattering in the tissue. In 5 of 10 boars no significant ATBV was found after occlusion of the spermatic vessels, suggesting subsequent atrophy. NIRS combined with pulse oximetry provides us with reproducible quantification of ATBV. The method can be used to investigate the viability of a testis after (temporary) occlusion of the spermatic vessels.

Animals↗
PubMed1995

Disturbance of cerebral oxygenation and hemodynamics related to the opening of the bypass bridge during veno-arterial extracorporeal membrane oxygenation.

The objective of this study was to investigate changes of cerebral oxygenation and hemodynamics related to opening of the bypass bridge during veno-arterial extracorporeal membrane oxygenation (ECMO). Ten newborn infants and 12 piglets were studied during opening of the bridge for 10 and 1 s, respectively. Changes in cerebral concentration of oxyhemoglobin (cO2Hb), deoxyhemoglobin (cHHb), (oxidized-reduced) cytochrome aa3 (cCyt.aa3), and blood volume (CBV) were continuously measured by near infrared spectrophotometry. Heart rate, arterial O2 saturation (saO2), and mean arterial blood pressure (MABP) were measured simultaneously. In the piglets, central venous pressure (CVP), intracranial pressure (ICP), and left common carotid artery blood flow (CaBF) were also measured. Opening of the bridge for 10 s in the infants resulted in a significant decrease in MABP, saO2, and cO2Hb, whereas cHHb increased. CBV did not change significantly. In piglets biphasic changes were observed for MABP, CaBF, cO2Hb, and CBV, showing an initial decrease followed by a smaller increase. cHHb and CVP showed reverse biphasic changes. ICP increased but saO2 was unchanged. In all cases heart rate and cCyt.aa3 did not change significantly. Opening of the bridge for 1 s resulted in minor changes in only a few variables. In conclusion, opening of the bridge resulted in a decrease of CBV and cerebral O2 supply due to a decrease of cerebral blood flow, followed by a compensatory increase of cerebral O2 extraction and vasodilatation. The return of oxygenated blood after reclosing resulted in an increase of CBV with overcompensation of cerebral O2 supply.

Animals↗
PubMed1995

Cerebral oxygenation and hemodynamics during induction of extracorporeal membrane oxygenation as investigated by near infrared spectrophotometry.

OBJECTIVE: To investigate cerebral oxygenation and hemodynamics in relation to changes in some relevant physiologic variables during induction of extracorporeal membrane oxygenation (ECMO) in newborn infants. METHODS: Twenty-four newborn infants requiring ECMO were studied from cannulation until 60 minutes after starting ECMO. Concentration changes of oxyhemoglobin (cO2Hb), deoxyhemoglobin (cHHb), total hemoglobin (ctHb), and (oxidized-reduced) cytochrome aa3 (cCyt.aa3) in cerebral tissue were measured continuously by near infrared spectrophotometry. Heart rate (HR), transcutaneous partial pressures of oxygen and carbon dioxide (tcPO2 and tcPCO2), arterial O2 saturation (saO2), and mean arterial blood pressure (MABP) were measured simultaneously. Intravascular hemoglobin concentration (cHb) was measured before and after starting ECMO. In 18 of the 24 infants, mean blood flow velocity (MBFV) and pulsatility index (PI) in the internal carotid and middle cerebral arteries were also measured before and after starting ECMO using pulsed Doppler ultrasound. RESULTS: After carotid ligation, cO2Hb decreased whereas cHHb increased. After jugular ligation, no changes in cerebral oxygenation were found. At 60 minutes after starting ECMO, the values of cO2Hb, saO2, tcPO2, and MABP were significantly higher than the precannulation values, whereas the value of cHHb was lower. There were no changes in cCyt.aa3, tcPCO2, and HR, whereas cHb decreased. The MBFV was significantly increased in the major cerebral arteries except the right middle cerebral artery, whereas PI was decreased in all measured arteries. Cerebral blood volume, calculated from changes in ctHb and cHb, was increased in 20 of 24 infants after starting ECMO. Using multivariate regression models, a positive correlation of delta ctHb (representative of changes in cerebral blood volume) with delta MABP and a negative correlation with delta tcPO2 were found. CONCLUSIONS: The alterations in cerebral oxygenation after carotid artery ligation might reflect increased O2 extraction. Despite increase of the cerebral O2 supply after starting ECMO, no changes in intracellular O2 availability were found, probably because of sufficient preservation of intracellular cerebral oxygenation in the pre-ECMO period despite prolonged hypoxemia. The increase in cerebral blood volume and cerebral MBFV may result from the following: (1) reactive hyperperfusion, (2) loss of autoregulation because of prolonged hypoxemia before ECMO and/or decreased arterial pulsatility, or (3) compensation for hemodilution related to the ECMO procedure.

Brain↗
PubMed1994

The ductus arteriosus, pre- and post-ductal oxygen saturation measurements in fetal lambs.

In the fetus, the arterial oxygen saturation (SaO2) in the ascending aorta is higher than in the descending aorta. We questioned whether this difference over the ductus arteriosus (delta SaO2) would change during hypoxaemia. Therefore, six chronically instrumented fetal lambs (119-126 days of gestation) were studied, by changing the inspired oxygen (FIO2) via a tracheal tube to the ewe. The SaO2 was measured intermittently every 15 min with blood samples obtained from the ascending and descending aorta, and continuously with 2 pulse oximeters at both sides of the ductus arteriosus. delta SaO2 was at a level of 3.4-5.3% and had a tendency to decrease at preductal SaO2 levels of 10-20% and at pH levels below 7.25. The precision of the pulse oximeters, expressed as standard deviation of the differences between sample SaO2 and pulse oximeter SaO2, was around 5.0% for the individual calibration curves. This precision was not enough to show details of the course of delta SaO2 between the blood samples. Our results show that there is no change in delta SaO2 across the ductus arteriosus.

Animals↗
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↗
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↗