tailieunhanh - Fetal Electrocardiography – part 2

Nghiên cứu này một lần nữa là hoàn cảnh khó khăn bằng cách sử dụng các bộ lọc cung cấp tần số cắt thấp-off và do đó có thể đã bị bóp méo đặc tính sóng P & T. Tuy nhiên, các dữ liệu được sản xuất bằng cách đo khoảng PR | Historical Development 5 The study again was disadvantaged by the use of filters that provided low frequency cut-offs and may therefore have distorted P T wave characteristics. Nevertheless the data produced by measuring the PR interval and the QRS duration are probably valid within the constraints of the methodology and these measurements were related to oxygen saturation in the umbilical venous and arterial blood. Southern reported that diminished oxygen saturation was associated with bradycardia prolonged PR interval which was probably a direct consequence of the fetal heart rate and a widened QRS complex. Changes with the T wave and ST segment were said to be characterised by depression of the ST segment and isoelectric or inverted T waves. In 1956 Sureau produced data using a direct intrauterine electrode in labour but was unable to demonstrate any effects of labour on the FECG. Kaplan and Toyama 1958 used a cardiac catheterisation electrode placed inside the amniotic sac in apposition to the fetus following rupture of the membranes. In 12 cases they were able to define characteristics of the time intervals. These values for the PQ interval differ slightly from those of Southern. Sureau 1956 also published intrapartum recordings of the FECG using a direct application electrode and these three studies represent the major technical advances that occurred in the 1950s and which laid the groundwork for the future of fetal electrocardiography. The rather mixed and conflicting results in these reports highlight the continuing technical problems at that time but they also began to illustrate the difficulties related to signal processing and interpretation that were not really to see resolution for another 20 years. It was however at this stage that the use of this technology began to split into two different pathways. Because early studies on the FECG did not show any obvious and easily discernable changes in the waveform emphasis switched to heart rate which was .