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Biomedical subjects

C M Schram

Publications and source records attributed to C M Schram.

5 recordsLinked to original sources
PubMed1994

Artifacts in fetal pulse oximetry: incomplete sensor-to-skin contact.

OBJECTIVE: Our purpose was to investigate apposition of reflectance sensors as a possible source of artifact in fetal pulse oximetry. STUDY DESIGN: A laboratory model was created to examine the effect of varying the distance of a reflectance probe from a subject's finger. The setup used two wavelengths (660 and 940 nm) and pulsatile (AC) and nonpulsatile signals (DC). An investigator's finger was stabilized in a purposely built mold from where the distance between skin and sensors could be varied in 1 mm steps. RESULTS: The AC and DC components of the signal react differently to increasing the distance between sensor and skin. The overall effect is that the ratio [formula: see text] increases with skin to sensor distance, which results in falsely low readings of oxygen saturation. CONCLUSIONS: Poor sensor-to-skin contact in reflectance pulse oximetry may cause false readings despite the presence of good waveforms and hence go unrecognized. Probe and software design needs to be able to identify and exclude such artifact before this technique can become useful for intrapartum fetal monitoring.

Artifacts↗
PubMed1994

Artifacts in fetal pulse oximetry: nonarterial pulsatile signals.

OBJECTIVE: We wished to investigate the effect of caput succedaneum on pulse oximetry readings. STUDY DESIGN: Oxygen saturation was measured by reflection pulse oximetry on various sites of scalps of 18 healthy neonates. The pulse rate obtained from the oximeter was checked against the heart rate from the electrocardiogram to see whether they were in agreement and synchronized. RESULTS: Nonsynchronized saturation values had a much wider range (30 to 97 vs 70 to 98) and a significantly lower mean (70 vs 84) than did synchronized values. Synchronized readings were obtainable in all 18 subjects over the temporal region but in only 39% of cases over the occipital region. Fourteen neonates had caput succedaneum, and in nine (61%) of these synchronized readings were not possible. It was noted that falsely low saturation values can be derived from pulsating waveforms, which have a slower rate than the electrocardiogram rate. CONCLUSIONS: The observed low pulsation rate is either of venous origin or represents modulated transmission of arterial signal through an edematous or congested scalp. This artifact will result in nonarterial oxygen saturation readings, and its exclusion is of importance in the development of pulse oximetry for intrapartum monitoring of the fetus.

Artifacts↗
PubMed1991

Adaptation of pulse oximetry for fetal monitoring during labour.

Application of pulse oximetry to intrapartum monitoring was investigated in 105 women. No adequate reading could be obtained in 44 cases. Two major sources of artifact, related to probe apposition and signal processing, were identified and excluded. The average arterial oxygen saturation from the fetal scalp was 82% (SD 6%), which is higher than has been inferred from pO2 levels. Readings below 60% or the development of an unstable baseline suggest the presence of substantial hypoxia and acidosis.

Adaptation, Physiological↗