A PC-aided optical foetal heart rate detection system

Safe monitoring of foetal heart rate is a valuable tool for the healthy evolution and wellbeing of both foetus and mother. This paper presents a non-invasive optical technique that allows for foetal heart rate detection using a photovoltaic infrared (IR) detector placed on the mother’s abdomen. The system presented here consists of a photoplethysmography (PPG) circuit, abdomen circuit and a personal computer equipped with MATLAB. A near IR beam having a wavelength of 880?nm is transmitted through the mother’s abdomen and foetal tissue. The received abdominal signal that conveys information pertaining to the mother and foetal heart rate is sensed by a low noise photodetector. The PC receives the signal through the National Instrumentation Data Acquisition Card (NIDAQ). After synchronous detection of the abdominal and finger PPG signals, the designed MATLAB-based software saves, analyses and extracts information related to the foetal heart rate. Extraction is carried out using recursive least squares adaptive filtration. Measurements on eight pregnant women with gestational periods ranging from 35–39 weeks were performed using the proposed system and CTG. Results show a correlation coefficient of 0.978 and a correlation confidence interval between 88–99.6%. The t test results in a p value of 0.034, which is less than 0.05. Low power, low cost, high signal-to-noise ratio, reduction of ambient light effect and ease of use are the main characteristics of the proposed system.     

Improved Doppler ultrasonic monitoring of the foetal heart rate

The Doppler ultrasonic technique for the monitoring of the foetus has been available for well over a decade. It offers a noninvasive assessment of the condition of the foetus and has therefore become an important antenatal technique. However, the foetal heart rate information obtained by this technique is considered to be less precise than that obtained from the foetal e.c.g. The waveforms recorded by the Doppler ultrasonic method are complex and variable and this often leads to difficulty in identifying a reliable and regular measuring point within these waveforms from which to calculate the heart rate. This has resulted in a cautious acceptance of ultrasonically determined foetal heart-rate records. This paper does not dispute the difficulties of interpreting such rate information, but outlines a pair of algorithms for processing and presenting a more accurate and reliable indication of the foetal heart rate determined from the Doppler ultrasonic method. These algorithms calculate a two second average rate from only those intervals which have been determined to be ‘valid’, based on the criterion that they should be within ±10% of the most previous valid interval.     

Heart rate changes with exercise and voluntary heart rate acceleration.

The present study examined the relationship between heart rate (HR) changes accompanying isometric and isotonic exercises and HR changes during attempted voluntary HR acceleration. Substantial cardiac accelerations accompanied both types of exertion, with the isotonic exercise attracting the larger magnitude HR changes. Significant HR increases were also observed during attempted voluntary HR acceleration both with and without feedback; however, feedback prompted larger HR increases than instructions alone. The HR changes accompanying both types of exercise reliably predicted the extent of voluntary HR increase but only for the condition in which feedback was available. This occurred in spite of the absence of observable EMG changes during attempted HR acceleration. Changes in respiration rate during voluntary HR increase were highly correlated with changes in HR. A similar co-variation occurred with the isotonic exercise but was absent with the isometric exercise. The results are discussed in terms of the possible mediational mechanisms underlying voluntary HR acceleration.     

Improvement in Doppler ultrasound human foetal heart rate records by signal correlation

An improved method for the determination of foetal heart rate from Doppler ultrasound signals is described and evaluated. It determines the most probable pulse interval from the recurrence times of multiple echoes generated by each cardiac pulse. The method, when optimised, is shown to offer an improvement over current systems, especially in reduced signal loss.     

Intrinsic heart rate in the dog determined by pharmacologic denervation

Intrinsic heart rate was measured in 19 dogs in 76 experiments after autonomic blockade, using various forms of anesthesia. Measurements were made in conscious dogs (n = 16) and in dogs in neuroleptanesthesia (n = 54) or under pentobarbital sodium (n = 6). Temperature, arterial pH, and blood gases were kept within narrow limits. Adrenergic blockade was achieved by phenoxybenzamine (2 mg X kg-1) and propranolol (2 mg X kg-1, followed by 2 mg X kg-1 X h-1). The parasympathetic system was blocked either by atropine (0.5 mg X kg-1, followed by 0.5 mg X kg-1 X h-1) and hexamethonium (20 mg X kg-1, followed by 10 mg X kg-1 X h-1) or by atropine and bilateral cervical vagotomy. Administration of hexamethonium or vagotomy was needed to block the vagal cardioacceleration unmasked by the administration of muscarinic blocking agents in conscious dogs and in dogs in neuroleptanesthesia. The mean denervated heart rate was 142.8 beats/min. This value is higher than that reported for surgically denervated hearts, the difference very likely reflecting the activity of the intact parasympathetic intrinsic cardiac innervation in surgical preparations. The estimated intraindividual and interindividual SD were 9.7 and 19.4 beats/min, respectively. The highly significant interindividual variation (P less than 0.01) contradicts the concept of an intrinsic heart rate as a practically constant species-dependent quantity.     

Classification of foetal heart rate sequences based on fractal features

Visual inspection of foetal heart rate (FHR) sequences is an important means of foetal well-being evaluation. The application of fractal features for classifying physiologically relevant FHR sequence patterns is reported. The use of fractal features is motivated by the difficulties exhibited by traditional classification schemes to discriminate some classes of FHR sequence and by the recognition that this type of signal exhibits features on different scales of observation, just as fractal signals do. To characterise the signals by fractal features, two approaches are taken. The first models the FHR sequences as temporal fractals. The second uses techniques from the chaos-theory field and aims to model the attractor based on FHR sequences. The fractal features determined by both approaches are used to design a Bayesian classification scheme. Classification results for three classes are presented; they are quite satisfactory and illustrate the importance of this type of methodology.     

Differences in foetal heart rate variability from phonocardiography and abdominal electrocardiography

The agreement of the phonocardiographic method to provide foetal heart rate variability (FHRV) indices equivalent to those derived from abdominal electrocardiography was tested. 15 pregnant women were recruited in order to obtain antepartum foetal phonocardiograms and abdominal electrocardiograms three minutes long. From the respective sound (SS) and electric (RR) time series, typical temporal and spectral indices of FHRV were computed and compared. Means of the SS and RR intervals were not significant (P > 0.05) and these showed a correlation r=0.98. However, the temporal indices, P TOT, HF and LF/HF presented differences (P < 0.05), since SS values were higher. Spectral coherence decreased below 0.5 for frequencies above 0.28 &#45 0.07Hz, where bands resembling maternal and foetal breathing movements were noted. Particularly above 0.28 Hz, temporal and spectral FHRV indices derived from phonocardiography and electrocardiography show differences. Quality of the signal, processing techniques, and maternal and foetal respiratory factors could account to explain these.     

Differences in foetal heart rate variability from phonocardiography and abdominal electrocardiography

The agreement of the phonocardiographic method to provide foetal heart rate variability (FHRV) indices equivalent to those derived from abdominal electrocardiography was tested. 15 pregnant women were recruited in order to obtain antepartum foetal phonocardiograms and abdominal electrocardiograms three minutes long. From the respective sound (SS) and electric (RR) time series, typical temporal and spectral indices of FHRV were computed and compared. Means of the SS and RR intervals were not significant (P> 0.05) and these showed a correlation r=0.98. However, the temporal indices, P(TOT), HF and LF/HF presented differences (P< 0.05), since SS values were higher. Spectral coherence decreased below 0.5 for frequencies above 0.28+ 0.07 Hz, where bands resembling maternal and foetal breathing movements were noted. Particularly above 0.28Hz, temporal and spectral FHRV indices derived from phonocardiography and electrocardiography show differences. Quality of the signal, processing techniques, and maternal and foetal respiratory factors could account to explain these.     

Analgesia produced by vaginal self-stimulation in women is independent of heart rate acceleration

In the present study, the analgesia produced by vaginal stimulation (VS) in women was found to be dissociated from heart rate. The VS-produced analgesia was not accompanied by an acceleration of heart rate. Heart rate acceleration produced by exercise did not result in analgesia. The independence of VS-produced analgesia from this index of autonomic activity is consistent with recent findings in rats.     

Real-time analysis of foetal heart rate patterns using a computer system

The foetal heart rate and uterine contraction curves provide both continuous and real-time information on the foetus. In recent years, attempts have been made to automatically diagnose foetal distress using a computer to provide direct analysis of this information. In the present study, we performed pattern-analysis of the foetal heart rate and uterine contraction curves using a minicomputer on 476 mothers who gave birth at the hospital attached to Hamamatsu University School of Medicine from April 1978 to March 1980. We developed the algorithm for these curves. The algorithm was roughly divided into two groups, original signal process and pattern-recognition algorithms. Following the autocorrelation and noise reduction of original signals, the algorithm was analysed. The algorithmic analysis consisted of the calculation of baseline f.h.r. recognition of deceleration, recognition of uterine contraction, and classification of the deceleration pattern. By using these algorithms, the true diagnostic distribution rate was obtained: early deceleration: 76%, variable deceleration: 88%, late deceleration: 72%, and prolonged deceleration: 81%.     

Pulmonary vasoconstriction and changes in heart rate during asphyxia in immature foetal lambs

1. The effect of changing the composition of pulmonary arterial blood on the pulmonary vasoconstrictor response to asphyxia was studied in immature foetal lambs of ~ 90 days gestation age.

2. When normal foetal carotid arterial blood (withdrawn before asphyxia) was introduced during asphyxia, the pulmonary vasoconstriction was rapidly and wholly relieved as soon as this blood reached the lung. This did not happen when blood was used which had been withdrawn during asphyxia.

3. Conversely introduction into a pulmonary artery of a foetal lamb during recovery, of arterial blood withdrawn during asphyxia, caused an immediate return of pulmonary vasoconstriction.

4. These phenomena could not be explained by the generation of vasodilator agents such as bradykinin, acetylcholine, histamine or isoprenaline.

5. During asphyxia injection of normal foetal arterial blood into the left atrium did not cause pulmonary vasodilatation, but did elicit a large increase in heart rate.

6. Neither the pulmonary vasoconstriction during asphyxia, nor its relief by normal foetal arterial blood, nor the changes in heart rate were affected by previous bilateral vagotomy or administration of atropine or hexamethonium.

7. It was concluded that, in immature foetal lambs, the effect of asphyxia in causing pulmonary vasoconstriction was mainly, if not exclusively, by a local action within the lungs, and that the bradycardia during asphyxia was mainly due to the fall in P_O2 acting locally upon the heart.

     

Computerised electronic foetal heart rate monitoring in labour: automated contraction identification

The foetal heart rate (FHR) response to uterine contractions is crucial to detect foetal distress by electronic FHR monitoring during labour. We are developing a new automated system (OxSys) for decision support in labour, using the Oxford database of intrapartum FHR records. We describe here a novel technique for automated detection of uterus contractions. In addition, we present a comparison of the new method with four other computerised approaches. During training, OxSys achieved sensitivity above 95% and positive predictive value (PPV) of up to 90% for traces of good quality. During testing, OxSys achieved sensitivity = 87% and PPV = 75%. For comparison, a second clinical expert obtained sensitivity = 93% and PPV = 80%, and all other computerised approaches achieved lower values. It was concluded that the proposed method can be employed with confidence in our study on foetal health assessment in labour and future OxSys development.     

Multichannel automatic foetal movement monitoring and classification system

The purpose of this work was to develop a compact, noninvasive and objective tool for foetal movement monitoring and classification. Four tocodynamometers were used as movement transducers and their output signals processed by a minicomputer on which a microprocessor real time compatible algorithm was developed. The algorithm was based on time domain analysis where the parameters, such as averaging intervals and threshold levels were optimised in a trial and error procedure to minimise undetected foetal movements and false detections on a set of nine pregnant women. The detection score was 92·2 per cent when short foetal movements were ignored.     

Thyrolinguofacial trunk arising from the carotid bifurcation determined by cadaver dissection

Knowledge of the arterial variations in the neck region may be of great importance in the diagnosis and treatment of cervical and maxillofacial pathologies. We report on a male cadaver found to have a superior thyroid, lingual and facial artery arising with a common trunk from the relatively high carotid bifurcation on the right side. After branching off the superior thyroid artery, the linguofacial trunk divided in the submandibular region into the lingual and the facial artery. The embryogenesis of such a combination of anomalies is not clear, but the anatomic consequences may have important clinical implications for radiologic examinations and surgical procedures in the regions of the head and neck.     

Cardiac, respiratory and metabolic changes during static exercise and voluntary heart rate acceleration

Various ventilatory and metabolic parameters were monitored in 12 subjects while they performed each of three tasks: Voluntary cardiac acceleration with the aid of continuous heart rate feedback; a static hand-grip exercise at 1/3 maximum voluntary contraction; and a combined task involving both voluntary acceleration and exercise. Task order was counterbalanced across subjects and there were six 30 sec trials of each task. While reliable cardiac accelerations were recorded throughout, they were substantially greater with the combined task. This confirmed previous findings attesting that individuals can voluntarily elevate heart rate above levels induced by standard physical loads. However, the pattern of results for oxygen consumption and carbon dioxide production, with the most substantial increase in both also occurring for combined voluntary acceleration and exercise, suggested that the cardiac elevations superimposed on exercise levels were largely non-specific, i.e. they involved additional energy expenditure. Respiration volume increased during the performance of all three tasks, with the greatest increase again occurring in the combined tasks. The precise respiratory adjustments, in terms of rate and tidal volume, varied subtly among tasks; while all three tasks produced a rise in respiration rate, only the combined task increased tidal volume.     

Association of breathing movements to the variability of heart rate and blood pressure in foetal lambs

Heart rate (HR) variability and arterial blood pressure (BP) variability were analysed as functions of foetal breathing movements (FBMs) by means of power spectral analysis in seven foetal lambs during the third trimester of gestation. No evidence of FBM-related changes, either in mean HR, mean systolic or diastolic arterial pressures, were found. Mean arterial pulse pressure, HR variability, and BP variability increased during FBMs. The increase in BP variability occurred at frequencies higher than 0.35 Hz, i.e. those of FBMs. The increase in HR variability occurred at 0.07-1.0 Hz, i.e. at every frequency band except the lowest one. Thus, the increase in HR variability was not frequency-specifically related to FBMs. During FBMs the periodic variability of HR at frequencies > 0.35 Hz was only 10% of total HR variability. We suggest that the FBM-related changes of BP variability may be mediated by direct peripheral, hydraulic mechanisms. HR changes involve autonomic control systems: the vagal component of baroreflex seems to be relatively insensitive, whereas the very slow vasomotor component of HR variability is dominant.     

Detection of atrial-flutter and atrial-fibrillation waveforms by fetal magnetocardiogram

Two cases of fetal tachycardia are reported: atrial flutter and fibrillation. The waveforms from each case were detected by fetal magnetocardiograms (FMCGs) using a 64-channel superconducting quantum interference device (SQUID) system. Because the magnitude of supraventricular arrhythmia signals is very weak, two subtraction methods were used to detect the fetal MCG waveforms: subtraction of the maternal MCG signal, and subtraction of the fetal QRS complex signal. It was found that atrial-flutter waveforms showed a cyclic pattern and that atrial-fibrillation waveforms showed f-waves with a random atrial rhythm. Fast Fourier transform analysis determined the main frequency of the atrial flutter to be about 7 Hz, and the frequency distribution of atrial fibrillation consisted of small, broad peaks. To visualise the current pattern, current-arrow maps, which simplify the observation of pseudo-current patterns in fetal hearts, of the averaged atrial flutter and fibrillation waveforms were produced. The map of the atrial flutter had a circular pattern, indicating a re-entry circuit, and the map of the atrial fibrillation indicated one wavelet, which was produced by a micro-re-entry circuit. It is thus concluded that an FMCG can detect supraventricular arrhythmia, which can be characterised by re-entry circuits, in fetuses.     

Thyrolinguofacial trunk arising from the carotid bifurcation determined by three-dimensional computed tomography angiography

It is recognized that the branches of the external carotid artery (ECA) can show variation, but the presence of a thyrolinguofacial trunk is extremely rare and always originates from the ECA. We report a case of the thyrolinguofacial trunk arising from the carotid bifurcation (CB) on the left side in a 76-year-old man with advanced tongue cancer, as revealed by three-dimensional computed tomography angiography for vascular mapping of the carotid vessels prior to superselective intra-arterial catheterization. The thyrolinguofacial trunk arose 1.6 mm below the CB from the anterior surface of the left CB. The inner diameter of the thyrolinguofacial trunk at origin was 4.4 mm and the angle between the thyrolinguofacial trunk and CB was 128°. After a 1.7-mm course, the trunk divided into the superior thyroid artery and a linguofacial trunk, the inner diameters of which were 1.5 and 3.4 mm, respectively, at origin. The angle between the two arteries was 88°. After a 9.8-mm course from the bifurcation, the linguofacial trunk divided into the lingual artery and facial artery, the inner diameters of which were 1.8 and 1.9 mm, respectively, at origin. The angle between the two arteries was 61°. It is important to recognize such an anatomic variation of the branches of the ECA prior to superselective intra-arterial catheterization or microsurgical reconstruction for head and neck cancer.