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Biomedical subjects

T C Jansen

Publications and source records attributed to T C Jansen.

11 recordsLinked to original sources
PubMed1987

Pulse oximetry and transcutaneous oxygen tension in hypoxemic neonates and infants with bronchopulmonary dysplasia.

The reliability of pulse oximetry and transcutaneous oxygen tension (tcPO2) was investigated in hypoxemic neonates and older infants with chronic hypoxemia due to bronchopulmonary dysplasia (BPD). It was found that during severe hypoxemia (tcPO2 less than 40 mmHg and saturation less than 80%) pulse oximetry showed a better correlation with arterial saturation than tcPO2 with arterial oxygen tension. During mild hypoxemia and normoxemia (tcPO2 40-90 mmHg and saturation 80-95%) tcPO2 and pulse oximetry both showed a good correlation with arterial values. Above 95% saturation and a corresponding tcPO2 of 70-120 mmHg, the correlation between arterial and transcutaneous PO2 was better than that between pulse oximetric and arterial saturation. Computer recording and analysis of tcPO2 and pulse oximetry improves the quality of both noninvasive oxygenation parameters in older infants with BPD.

Birth Weight↗
PubMed1987

Multichannel recording and analysis of physiological data using a personal computer.

A flexible data acquisition system was designed for an Apple IIe computer. For implementation, we used a microcomputer capable of recording 4 channels simultaneously with a selectable sample rate; this information was saved on a floppy disc and the recordings could be evaluated later. This evaluation is accomplished by reproducing the analog signals on display and calculating a histogram after deleting artefacts in the signal.

Blood Gas Monitoring, Transcutaneous↗
PubMed1987

Human gaze stability in the horizontal, vertical and torsional direction during voluntary head movements, evaluated with a three-dimensional scleral induction coil technique.

The stability of gaze in three dimensions (horizontal, vertical and torsion) was measured with a new type of scleral search coil in eight emmetropic observers. Subjects held the head still or oscillated it at 0.16-0.67 Hz (amplitude about 10 deg) in the horizontal, vertical or torsional plane while fixating a point target at optical infinity. Veridical gaze and head coordinates were calculated with full correction for non-linear goniometric relations and for cross-coupling artifacts due to misalignments of the coil on the eye. The amount of gaze instability in the horizontal and vertical direction was virtually identical. With the head still, in either of these directions the mean standard deviation of gaze position (inclusive saccades) was about 7 min arc; mean non-saccadic retinal image speeds were 20-30 min arc/sec. During head oscillation these values increased to about 16 min arc and 1 deg/sec; a mean of about 2.5% of the head motion remained uncorrected by the compensatory eye movements. These findings agree well with our earlier results for the horizontal plane; the effect of the corrections was relatively small because the adventitious cross-coupling of horizontal and vertical to torsional head movements proved to be usually smaller than 10%. However, the corrections were important when head torsion was deliberately produced. Gaze stability in the torsional plane was considerably inferior to that in the horizontal and vertical plane. With the head held still, the mean SD of torsional gaze position was about 17 min arc; mean torsional non-saccadic retinal image speed was about 46 min arc/sec. Gain of the torsional compensatory eye movements was frequency dependent and rose from about 0.26 in static conditions (0 Hz) to about 0.42 at 0.16 Hz and 0.64 at 0.67 Hz. Accordingly, position instability and speed of the retinal image in torsion were about an order of magnitude larger than in the horizontal and vertical direction.

Eye Movements↗
PubMed1985

Human ocular counterroll: assessment of static and dynamic properties from electromagnetic scleral coil recordings.

Static and dynamic components of ocular counterroll as well as cyclorotatory optokinetic nystagmus were measured with a scleral search coil technique. Static counterroll compensated for about 10% of head roll when the head was tilted to steady positions up to 20 deg from the upright position. The dynamic component of counterroll, which occurs only while the head is moving, is much larger. It consists of smooth compensatory cyclorotation opposite to the head rotation, interrupted frequently by saccades moving in the same direction as the head. During voluntary sinusoidal head roll, cyclorotation compensated from 40% to more than 70% of the head motion. In the range 0.16 to 1.33 Hz, gain increased with frequency and with the amount of visual information. The lowest values were found in darkness. The gain increased in the presence of a visual fixation point and a further rise was induced by a structured visual pattern. Resetting saccades were made more frequently in the dark than in the light. These saccades were somewhat slower than typical horizontal saccades. Cyclorotatory optokinetic nystagmus could be induced by a patterned disk rotating around the visual axis. It was highly variable even within a same subject and had in general a very low gain (mean value about 0.03 for stimulus velocities up to 30 deg/s). It is concluded that cyclorotational slip velocity on the retina is considerably reduced by counterroll during roll of the head, although the residual cyclorotation after the head has reached a steady position is very small.

Biomechanical Phenomena↗
PubMed1984

Effects of experimental head compression on transcutaneous scalp PO2 in fetal lambs.

Equatorial compression of the fetal head is known to occur during labor; its effect on trancutaneous scalp PO2 (PtCO2) was investigated in acute experiments in four fetal lambs. Fetal PtCO2, and oxygen tension (PaO2) and flow in a carotid artery were continuously measured. Equatorial head compression was obtained by inflating a cuff around the fetal head. A strong relationship was shown to exist between PtCO2 and PaO2 values in the normoxemic and hypoxemic fetus. Stepwise compression of the fetal head resulted in a PtCO2 of zero at cuff pressures of 40 to 50 mmHg. Laborlike fetal head compression with an intensity of 50 to 70 mmHg and a duration of one minute resulted in a 30 to 60% fall in PtCO2. Fetal PaO2 remained stable in all experiments. The present findings indicate that values of PtCO2 during fetal head compression do not reflect fetal arterial oxygen tension. This questions the reliability of transcutaneous PO2 monitoring as a method of intrapartum surveillance.

Animals↗
PubMed1979

Nocturnal gastric drip feeding in glucose-6-phosphatase deficient children.

UNLABELLED: Six patients with glucose-6-phosphatase deficiency were treated for 12 hr at night with gastric drip feeding (GDF), containing soy milk plus glucose, dextrimaltose, and starch. An alarm system (thermistor), connected to the gastric tube, was devised in case of displacement of the tube by the child. The effects of GDF were as follows. Base deficit and lacticaciduria decreased, but did not normalize. Serum cholesterol levels tended to normalize, but serum triglycerides remained elevated. The hepatic and extrahepatic components of plasma lipoprotein lipase were measured separately 5 and 40 min after iv heparin injection. Hepatic triglyceride lipase activities which were subnormal to normal increased to the lower normal range. Extrahepatic lipoprotein lipase activities, though increasing after GDF, remained abnormally low. Catch-up growth occurred in all four growth-retarded children. The pronounced liver enlargement of the five patients, not previously treated with GDF, decreased markedly. SPECULATION: Nocturnal GDF in glucose-6-phosphatase deficient children, suppresses the tendency for hypoglycemia and acidosis which are causes for stress, catabolism, and anorexia. By suppressing these factors, GDF promotes anabolism and caloric intake, thus accounting for the catch-up growth seen in the patients with growth retardation.

Child↗
PubMedDate not supplied

Quantification of left-to-right shunts using a PO2-electrode cardiac catheter.

A rapid, simple and low-cost method is presented for intracardiac left-to-right shunt quantification in children with congenital heart disease. The percentage of shunt is calculated from data obtained by continuous PO2 measurement during oxygen inhalation, using a nondisposable intravascular PO2-electrode cardiac catheter. These values are compared with those obtained by the dye-dilution method (correlation coefficient r = 0.89) and the Fick method (correlation coefficient r = 0.98). The PO2 measurement proved reliable for small, medium, and large sized shunts.

Adolescent↗