An improved data display system for fetal heart rate monitoring.

Fetal heart rate (FHR) monitor records, particularly those derived from external sensors, may contain artifactual information closely resembling true FHR patterns. Additional machine-determined information may be used to help discriminate these data. Present commercial systems for indicating potentially artifactual FHR modify the FHR display, and this tends to cause the physician to ignore the absence of data or annoy him by obliterating some useful as well as potentialy useless information. Therefore, we chose to put the information that the data may be artifactual on another channel and allow the physician, rather than the instrument, to modify the interpretation of the FHR as necessary. A computer study was made of the characteristics of FHR beat-to-beat changes during poor signal to determine the most appropriate criteria for indicating when the FHR record is highly likely to be artifactual. Unphysiologic, erratic FHR changes are easily flagged by the presence of 3 serial beat-to-beat changes greater than 25 beats/min. Clinical testing demonstrated that this system allows the physician to better discriminate between valid and invalid data and increases the amount of usable data, particularly in active patients.

Microfilm storage of fetal monitoring records: a practical solution.

Microfilming of fetal monitoring records has, at our institution, been found to be a practical method for storage of recording papers from fetal monitoring. This system permits a reduction of the records by a factor of 20:1 and up to 7.64 hours of fetal monitroing records will fit into a 4 x 6 inch film jacket. This microfilm record can easily be placed into a patient's chart and can thus easily be retrieved.

Automatic detection of fetal movement by Doppler ultrasound during non-stress testing.

A new external fetal monitor, using a defocused, wide-area ultrasound transducer has been devised in order to obtain a more accurate representation of fetal movement during antepartum non-stress testing. The fetal activity Doppler signal is easily distinguished from the fetal heart Doppler and provides an automatic record of fetal movement which is objective and reproducible. In several clinical tests, this new monitor was found to be more sensitive and reliable than either reports of fetal movement from the mother or from a physician palpating the abdomen. This method of automatic detection of fetal activity can improve the accuracy of the non-stress test by providing an additional objective criteria.

Variable range directional doppler and abdominal ECG for FHR monitoring.

Antepartum nonstress fetal heart rate (FHR) monitoring may become a valuable screening tool for all pregnancies. Two methods proposed for an antepartum FHR monitor are examined: abdominal electrocardiogram (AECG) and variable range directional Doppler (RDD). A good quality (detailed, clearcut baseline) RDD FHR record was obtained in 74/75 (99%) examinations, and a good quality AECG record was obtained i31/75 (41%). Each patient was monitored in the supine, lateral and sitting positions. Considering all positions, 76% of the RDD records and 19% of the AECG records were good. The RDD system was efficacious for routine, clinical antepartum FHR monitoring, but the performance of the AECG was too limited for this purpose.

Microprocessor-controlled doppler. A new fetal heart rate monitoring technique.

A new Doppler fetal heart rate (FHR) monitoring system using microprocessor-controlled ranged directional Doppler (RDD) was developed. The instrumentation was evaluated for accuracy and reproducibility of results by computer measurement and statistical analysis of the difference between FHR simultaneously obtained from Doppler and from fetal scalp electrocardiography (ECG) in 20 high-risk patients during labor. During 90% to 93.5% of the monitoring time, Doppler-derived FHR approximated ECG-FHR to within 5 beats per minute (BPM). The FHR records from this monitoring system can provide accurate and reliable external FHR information that may approximate the internal ECG-FHR record to such a degree that the practitioner is offered a reliable, noninvasive alternative to internal fetal monitoring.

Observations in perinatal heart rate monitoring. I. A quantitative method of describing baseline variability of the fetal heart rate.

Simultaneous magnetic tape recordings of fetal scalp ECG, maternal ECG and uterine contractions were obtained from 23 patients in active labor. Computer-derived distributions of beat-to-beat changes were used to develop a simple numerical and graphical description of the long and short-term variability patterns. The visually observed variability may be described by the R-R interval change (beat-to-beat change), which is greater than 90% of the total number of beat-to-beat changes. Thus, the 90th percentile of R-R interval changes quantitatively describes the baseline variability. The variability may be classified as fixed, minimal, moderate or marked, based on this simple calculation. Graphs of cumulative percentage of R-R interval changes provide additional visual information. The effects of meperidine HCl on the observed variability were easily detected and visualized by these methods.

Observations on perinatal heart rate monitoring. II. Quantitative unreliability of Doppler fetal heart rate variability.

Fifty-three fetal heart rate (FHR) tracings obtained by direct ECG monitoring during labor and 24 simultaneous external Doppler FHR tracings were analyzed for the quantitative assessment of baseline FHR variability. The beat-to-beat difference in FHR subsumed by 90% of all beat-to-beat changes within a tracing was taken as the index of variability of that tracing. This index correlated well with the visual assessment of variability for both internal ECG records (Spearman rank correlation coefficient, rs, = 0.71) and external Doppler records (rs = 0.78). However, there was no correlation between the variability index of the Doppler FHR records and that of simultaneous ECG FHR records (r = 0.11, p greater than 0.6). This finding casts doubt on the use of the presence of "normal" FHR variability as a sign of fetal well-being during antepartum FHR monitoring with current Doppler equipment.

Technical aspects of ranged directional doppler: a new doppler method of fetal heart rate monitoring.

A new technique for clarifying the fetal heart Doppler signal (Ranged Directional Doppler) for fetal heart rate (FHR) monitoring has been developed. Ranged Directional Doppler enhances the signals of interest and, in addition, permits a separation of the Doppler signals generated by fast-moving structures of the fetal heart either toward or away from the transducer. The separation of the Doppler signals provides increased clarity and reduced baseline clutter. These Doppler signals may approach the fetal scalp ECG in signal-to-noise ratio, and they may provide a signal that allows more accurate external monitoring of long-term and short-term variability patterns of the FHR.

New instrument developments for fetal pH monitoring.

Recent technical improvements in the ROCHE fetal pH monitor have simplified its use and increased the proportion of useful and accurate recordings. These improvements include electronic changes to reduce static electricity, a new spiral electrode which stabilizes the pH electrode in the fetal scalp, improved incision tools, simplified applicator tools, and a total system for reducing pH electrode handling during calibration.