Doppler Audio Signal Analysis as an Additional Tool in Evaluation of Umbilical Artery Circulation

Abstract

Purpose To investigate the predictive capacity of a new method for sound spectrum analysis of Doppler signals recorded from the umbilical artery in high-risk pregnancies.

Material and Methods The retrospective study comprised 127 pregnant women with various pregnancy complications between 23 and 39 gestational weeks. Umbilical artery blood flow velocity waveforms were recorded with Doppler ultrasound and characterized by pulsatility index (PI) and blood flow class (BFC). Doppler audio signals were stored on a digital video recorder and the sound frequency at the energy level 15 dB below its peak (MAX_peak-15 dB) was estimated off-line. The prediction of probability for composite adverse pregnancy outcome (operative delivery for fetal distress, admission to neonatal intensive care unit, perinatal death) was evaluated using the area under the curve (AUC) of the receiver operating characteristics (ROC) curve.

Results With increasing umbilical artery BFC, the MAX_peak-15 dB frequencies decreased (p < 0.0001) and the PI increased (p < 0.0001). The ROC AUCs for adverse outcome for MAX_peak-15 dB and for PI were 0.842 and 0.836 (p = 0.88), respectively. For the combination of MAX_peak-15 dB and PI, the corresponding AUC was 0.894, significantly higher than that of PI (p < 0.03) and of MAX_peak-15 dB (p < 0.05).

Conclusion Umbilical artery Doppler sound spectrum analysis might be a useful supplement to PI in the clinical evaluation of fetoplacental circulation.

Zusammenfassung

Ziel Die Untersuchung des prädiktiven Werts einer neuen Methode der Tonspektrum-Analyse von Dopplersignalen der Nabelschnurarterie in Hochrisikoschwangerschaften.

Material und Methoden Die retrospektive Analyse beinhaltete 127 Schwangere mit unterschiedlichen Komplikationen zwischen der 23. und 39. Schwangerschaftswoche. Die Wellenformen der Blutflussgeschwindigkeit wurden mittels Dopplersonografie aufgenommen und durch den Pulsatilitätsindex (PI) und die Blutflussklasse (BFC) charakterisiert. Die Doppler-Tonsignale wurden auf einem digitalen Videorekorder gespeichert und als Off-Line wurde die Tonfrequenz mit einem Energieniveau von 15 dB unterhalb dessen Gipfel (MAXpeak–15 dB) veranschlagt. Die Vorhersage für einen kombinierten schlechten Ausgang der Schwangerschaft (operative Entbindung aufgrund fetaler Notlagen, Einweisung in eine neonatologische Intensivstation, perinatale Sterblichkeit) wurde mittels der „area under the curve“ (AUC) der ROC-Kurve (ROC) bewertet.

Ergebnisse Mit steigender Nabelarterien-BFC sanken die MAX_peak–15dB-Frequenzen (p = 0,0001) und der PI stieg an (p = 0,0001). Bei schlechtem Ausgang betrugen die AUCs der ROC für den MAX_{peak–15 dB} 0,842 und für den PI 0,836 (p = 0,88). Bei der Kombination von MAX_{peak–15 dB} und PI war die entsprechende AUC mit 0,894 signifikant höher, als bei PI (p < 0,03) und MAX_{peak–15 dB} (p < 0,05) alleine.

Schlussfolgerung Die Doppler-Tonsignal-Analyse der Nabelschnurarterie stellt neben dem PI eine nützliche Ergänzung für die klinische Bewertung der fetoplazentalen Durchblutung dar.

Key words

ultrasound Doppler - doppler audio signal - blood velocity waveform - umbilical artery - pregnancy

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