Fetal breathing movements—A comparison of hard copy records produced by M-mode and Doppler ultrasound

Abstract

To precisely measure the events of the fetal breath cycle it is necessary to have an accurate hard copy record. Two approaches to this have been made using either M-mode or Doppler ultrasound. It was the aim of this paper to compare these methods. Hard copy records of fetal breathing movements were produced by simultaneously recording movements of the fetal chest wall with M-mode and frequency spectral analysis of Doppler signals from either the fetal inferior vena cava or umbilical vein. Timing of the onset and end of inspiration was equally recognised by chest wall movement and changes in umbilical vein flow. Augmented flow in the fetal inferior cava began after the onset of “inspiration” and continued into “expiration”. This signal could be used for registering the occurrence of a breath but not for timing. Because of unequal'rotation and distortion of the chest wall, during fetal breathing movements, records of chest wall movement were considered less precise than those from the umbilical vein for timing the events of the fetal breath cycle. The umbilical vein flow velocity sonogram provides an accurate record to allow measurement of “inspiratory” time and total breath movement time.