![]() Where appropriate, periodic accelerations or decelerations can occur. If fetal records are interrupted, either contractions or stress tests define the basal heart rate as the mean heart rate per minute. Under normal conditions, the interval occurring between consecutive cycles changes very slightly.įHR monitoring is performed for a duration that is in the range from 1 to 10 min (3 min at bradycardia) and using these data the tachogram, which shows the heart rate variability over time, is normally computed for diagnosis. Īn FHR registration is based on the acquisition of the heart rate cardiographic curve considering two consecutive cycles. This system responds to changes in fetal vessels to a deeper degree of respiration. In general, FHR monitor cannot directly detect the presence of fetal hypoxia, except for extreme situations, but it is used to detect frequency changes induced by barochemoreceptors in large myocardial vessels. The CTG allows both early diagnoses of uterine disorders and hypoxemic changes that can compromise the fetus growth (e.g., twins or triplets). The FHR monitor device can be a valid and reliable system to monitor cardiac activity at its very beginning, with a high degree of sensitivity. These combine measurements by one tocographic (TOCO) and at least one ultrasound (US) probe usually recorded in the last pregnancy trimester period. It is important to monitor the heart activity as soon as possible and with accurate and reliable systems, especially by using ultrasound technics, in order to timely detect any abnormal behavior (e.g., cardiorespiratory disease).įor fetus heart rate measurement, FHR monitor devices or combined cardiotocography (CTG) monitors are usually adopted. Starting from the 20th week, the fetal heartbeats can be heard without amplification, and the corresponding Fetal Heart Rate (FHR) normally ranges from about 110 to 150 beats per minute (BPM). The fetal heart activity can be monitored from the seventh week using specific devices, such as ultrasound-based ones. Among these, the heart begins to work at the fourth week of life, so, from this stage, the fetus starts to use its own bloodstream. The features of the proposed device make it simple and quick in testing a fetal heart rate monitor, thus providing an efficient way to evaluate and test the correlation capabilities of commercial apparatuses.ĭuring pregnancy, the development of the different organs usually follows phases that start in different weeks. The proposed equipment and testing respect the technical requirements for medical devices. Moreover, the performed tests and measurements show the correct functionality of the developed simulator. This value complies with the technical standard for the accuracy of fetal heart rate monitor devices. The generated frequencies show an error of about 0.5% with respect to the nominal one while the accuracy of the test equipment was within ☓% of the test signal set frequency. The accuracy of the simulated signals was evaluated, and it resulted to be stable and reliable. The simulator was designed to be compliant with the standard requirements for accurate assessment and measurement of medical devices. ![]() In the designed device, a relay element, driven by an electric signal that allows switching at two specific frequencies, is used to simulate the fetus and the mother’s heartbeat. ![]() The design and realization of the device are presented, together with the description of its features and functioning tests. In this paper, a new approach for the periodical testing and the functionality evaluation of a fetal heart rate monitor device based on ultrasound principle is proposed.
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