The information content of Doppler ultrasound signals from the fetal heart

Knowledge of the content of Doppler ultrasound signals from the fetal heart is essential if the performance of fetal heart rate (FHR) monitors based upon this technology is to be improved. For this reason instrumentation was constructed to enable the simultaneous collection of Doppler audio signals and the transabdominal fetal ECG (for signal registration), with a total of 22 recordings being made with an average length of around 20 minutes. These data demonstrate the transient nature of the Doppler audio data with wide variations in the signal content observable on a beat-to-beat basis. Short-time Fourier analysis enabled the content of the Doppler signals to be linked to six cardiac events, four valve and two wall motions, with higher frequency components being associated with the latter. This differing frequency content together with information regarding the direction of movement that can be discerned from Doppler signals provided a potential means of discriminating between these six events (which are unlikely to all contribute to the Doppler signal within the same cardiac cycle). Analysis of 100 records showed that wall contractions generate the most prominent signals, with atrial contraction recognisable in all records and ventricular wall contraction in 95% (although its amplitude is only around 30% of that of the atrial signal). Valve motion, with amplitudes between 15 and 25% that of the atrial wall signal, were visible in 75% of records. These results suggest means by which the six events that contribute to the Doppler signal may be distinguished, providing information that should enable an improvement in the current performance of Doppler ultrasound-based FHR monitors.     

Automatic detection of ultrasonic Doppler signal episodes resulting from fetal breathing movements

A method for automatic detection of fetal breathing movements has been proposed, based on the time-frequency structure of the corresponding continuous wave ultrasonic Doppler signals. The method uses spectral analysis of the envelope of the directional Doppler signal and cross-correlation analysis of both directional envelopes. Detection rule comprises the following criteria: presence of the peak in the envelope spectrum and of the adequate signal level in the frequency range corresponding to the fetal breathing rhythm, the peak value and the position limits of the peak of the cross-correlation coefficient of the both directional envelopes. The effect of the criteria setting on the rule performance and the tradeoff between the specificity and sensitivity was investigated. The rule is most sensitive to the threshold value of the cross-correlation coefficient of the envelopes. The limits of the position of this peak are crucial for the distinction between the breathing episodes and hiccups. The optimal settings of the criteria, resulting in average sensitivity and specificity exceeding, respectively, 0.70 and 0.80, are proposed.     

Breathing frequency changes at the onset of stepping in human infants

Breathing frequency increases at the onset of movement in a wide rage of mammals including adult humans. Moreover, the magnitude of increase in the rate of breathing appears related to the rate of the rhythmic movement. We determined whether human infants show the same type of response when supported to step on a treadmill. Twenty infants (ages 9.7 +/- 1.2 mo) participated in trials consisting of sitting, stepping on the treadmill, followed by sitting again. Breathing frequency was recorded with a thermocouple, positioned under one naris and taped to a soother that the infant held in his/her mouth. A video camera, electrogoniometers, and force platforms under the treadmill belts recorded stepping movements. We found that the rate of breathing changed at the beginning of stepping. Most surprisingly, we found that when infants stepped at a frequency slower than their breathing frequency in sitting, the breathing frequency decreased. Average breathing frequency during stepping was positively correlated with stepping frequency. There was no evidence of entrainment between stepping and breathing. In conclusion, the rapid change in breathing frequency at the beginning of movement is functional in infants. The direction and magnitude of change in breathing is associated with the leg movements.     

Differences between motion-direction perception and unspecific motion perception in the human knee joint

Perception has commonly been seen as a conscious performance. Thus, regarding proprioception in some publications, it has been proposed that the term is properly used only when subjects are able to report on the direction as well as presence of imposed movements. Consequently, detections of movements without movement-direction perception have not been accepted as perceived, since these detections were regarded as unspecific. Unspecific sensation has been suggested to precede perception. From this "two-state model", it follows that threshold values should be lower for unconscious unspecific perception than for conscious specific perception. The aim of the present study was to test this suggested dichotomy. Proprioception was compared in unspecific detection trials (only the occurrence of a movement had to be detected, not its direction) and direction-specific detection trials (the occurrence of a movement of a specific direction had to be detected). Two types of specific detection trials and two types of unspecific detection trials were studied. Pairs of threshold values were determined, regarding amplitude detection using different angular velocities and regarding velocity detection using different angular displacements, for flexion and extension. Our results showed that, independent of each other, both threshold paradigms (amplitude detection and velocity detection) revealed the same perception characteristics. In specific detection paradigms, the proprioceptive thresholds were two times lower than in unspecific detection paradigms. Thus, movements of a particular type could be detected more easily than movement per se. The suggested "two-state model" might, therefore, not be appropriate in describing proprioceptive perception.     

全方向M型心动图中非功能运动的分离和修正

由于受到血液的冲击和周围肌肉的牵拉,B超探测到的心脏运动包含了功能性和非功能性两种运动,由此获得的心动波形图不能准确反映心脏的功能。首先采用改进的Canny算法并辅以改进的径向灰度搜索算法提取左心室短轴轮廓,然后使用基于傅里叶描述子的运动提取方法和质心主轴法获取心脏的非功能性运动,并从复合运动中剔除非功能性运动。基于该方法得到的心动曲线消除了心动波形图中的多线、偏移和被平滑等现象,经修正后的采样方向线能够跟随心脏特定结构的各方向平移,没有出现心动曲线随非功能运动位移和特征点失落等情况,可更准确地反映心脏结构特定部位的功能性运动。     

Measurement of fetal movements using multichannel ultrasound pulsed Doppler: Autorecognition of fetal movements by maximum entropy method

Changes in fetal movements indicate biophysical conditions and functional development. The precise evaluation of fetal movements in clinical medicine requires the development of a continuous automated monitoring technique. A basic study of the measurement of fetal movements was carried out by modifying the Doppler ultrasound module of a cardiotocograph to produce low-frequency Doppler signals and five simultaneous outputs at various depths. These outputs represent displacement inside tissue at the various depths. Signal processing was executed on a 32-bit computer with a high-accuracy displacement estimation technique using the arctangent method. Results showed successful tracking of minute movements, such as fetal breathing movements (FBM), while rejecting other movements derived from maternal breathing etc. Using spectral analysis by the maximum entropy method (MEM), fetal movements were classified in three groups (FBM, fetal gross movements (FGM) and fetal heart movements (FHM)), based on the character of their special peak frequencies. The order of movement recognition was first FGM, then FBM and lastly FHM. FBM were more successfully recognised by MEM than by conventional B-mode observation methods. Small body movements were difficult to recognise as FGM by MEM in some cases. Although further studies are required for clinical application, it appears that automated assessments of fetal movements should be possible with this technique.     

Ontogeny of fetal movements in the guinea pig

Assessment of fetal motility is an approach to evaluate the development and function of the nervous system before birth. Reference values for the time of first occurrence and the incidence of normal fetal movements are indispensable for studies in which prenatal motor activity is applied as a model to study the central and peripheral nervous systems. Studies on fetal motility have been performed in a few species, particularly in the human. The aim of the present study is to describe the ontogeny of fetal motility in the guinea pig, a precocious polytocous species.After a pilot study to establish procedures for repeated ultasonographic scanning of guinea pigs, 10 domesticated animals were scanned (5.0 or 7.5 MHz convex transducer) at 2-4 day intervals between day 24 and 63 of gestation (term age 68 days). Per animal two selected fetuses were each scanned for 15 min. Images were stored on videotape and analyzed off-line for the first onset, presence and quality of fetal movement patterns, and quantity of sideway bendings, general movements, breathing movements and periods of fetal rest.Twenty-five different movement patterns could be characterized, 6 emerging at the onset of motor activity were performed only temporarily. The very first fetal movement was observed on day 24 gestational age, and subsequently most other movements developed during a period of only 5 days. Interfetal difference in onset of the frequently occurring sideway bendings, general movements, and front and hind limb movements was only 2 days. Sideway bendings and general movements co-existed during days 29 to 43. There were developmental trends in the course of pregnancy. Sideway bendings increased rapidly between 24 and 30 days and declined hereafter. General movements and fetal breathing increased during midpregnancy and declined towards parturition. Conversely, fetal rest was observed for approximately 60% of time at midgestation and a marked increase was found towards parturition. There were no significant differences in developmental trend of the various movement patterns between individual fetuses.Fetal motility in the guinea pig followed a specific temporal pattern, like in the human, but at a different time scale. The present quantitative data will enable functional investigations into the role of the neuromuscular system. They may also facilitate studies on the effect of environmental influences, such as stress, drugs, toxic substances, and food conditions, on fetal neurobehavioural development in this species.     

Recording fetal breathing movements with a passive transducer based on an inductive principle

A new transducer has been developed, based on an inductive principle, for recording fetal movements and sounds. The compliance of this transducer, the INductive PHOno-sensor (INPHO), can be matched to that of the maternal abdomen to provide an optimal transfer of displacement between maternal abdomen and transducer. In this manner it is possible to detect fetal breathing movements by digital filtering of the INPHO signal in a frequency band between 0·5 and 2·0 Hz. Singular breathing movements can be detected and this was verified by real time ultrasound imaging. The INPHO transducer shows a flat (±1·5 dB) frequency response between 0·2 and 200 Hz. The signal-to-noise ratio of the transducer system is better than 95 dB, and enables very weak movements and sounds to be detected. Spectral analysis of the processed signal shows that modulation of fetal breathing by maternal breathing takes place. The measuring setup allows for the quantitative assessment of fetal respiratory sinus arrythymia.     

Recording and processing of fetal movements and sounds obtained with the Inpho inductive transducer

A recently developed transducer based on an inductive principle allows recording of fetal displacement signals on the maternal abdominal wall. The transducer is a relatively passive device, in contrast to commonly applied ultrasound transducers. This permits long-term observation of fetal movements and sounds. The bandwidth of the system is DC −200 Hz (±3dB), and signal-to-noise ratios of more than 96 dB have been measured in a laboratory setup, whereas in the practical situation a signal-to-noise ratio of 78 dB has been established. The transducer has been applied to study fetal respiratory sinus arrhythmia, which means that fetal breathing movements have to be extracted from the transducer's output. This proved possible by digital filtering of the displacement signal as detected by the transducer. The transducer has also been applied in a study where the signal-to-noise ratio of fetal heart sounds as a function of location of the fetus and position of the transducer on the maternal abdominal wall has been studied. It proved possible to adequately record fetal heart sounds for measurement of fetal heart rate. Also uterine activity could be recorded using the sensor's DC output.     

Prostaglandins are responsible for the inhibition of breathing observed with a placental extract in fetal sheep

We have previously observed that the infusion of a placental extract inhibits breathing movements in fetal sheep, suggesting that a placental factor may be responsible for the inhibition of fetal breathing. Our preliminary results suggested that a small peptide or a substance bound to a peptide was likely responsible for this inhibition. Since prostaglandins are found in high concentrations in the placenta, it is possible that they may be responsible for the inhibition of breathing observed with the placental extract. We hypothesized that if prostaglandins were the active factors in the placental extract, then inhibition of the production of placental prostaglandins should eliminate the activity of the extract. We infused untreated and indomethacin/ASA-treated placental extracts into the carotid artery of eight chronically instrumented fetal sheep continuously over 3 h. The concentration of all prostaglandins measured in the untreated placental extracts were significantly higher than in the indomethacin/ASA-treated extracts. Only the infusion of the untreated placental extract induced a significant decreased in the incidence of fetal breathing. Fetal plasma prostaglandins increased significantly only with the infusion of the untreated placental extracts. These findings suggest that the inhibition of breathing observed with the placental extract is likely related to prostaglandins.     

Heart sound and lung sound separation algorithms: a review

Breath and cardiac sounds are two major bio sound signals. In this, heart sounds are produced by movement of some body parts such as heart valve, leaflets and the blood flow through the vessels, whereas lung sounds generates due to the air in and out flow through airways during breathing cycle. These two signals are recorded from chest region. These two signals have very high clinical importance for the patient who is critically ill. The lung functions and the cardiac cycles are continuously monitored for such patients with the help of the bio sound signal captured using suitable sensing mechanism or with auscultation techniques. But these two signals mostly superimpose with each other, so the separation of these heart sound signals (HSS) and the lung sound signals (LSS) is of great research interest. There are so many different techniques proposed for this purpose. In this paper, a study is carried out on different algorithms used for the separation of HSS from LSS, and also the results of major four separation algorithms are compared.     

Immobilization effect of air-injected blanket (AIB) for abdomen fixation

A new device for reducing the amplitude of breathing motion by pressing a patient's abdomen using an air-injected blanket (AIB) for external beam radiation treatments has been designed and tested. The blanket has two layers sealed in all four sides similar to an empty pillow made of urethane. The blanket is spread over the patient's abdomen with both ends of the blanket fixed to the sides of the treatment couch or a baseboard. The inner side, or patient side, of the blanket is thinner and expands more than the outer side. When inflated, the blanket balloons and effectively puts an even pressure on the patient's abdomen. Fluoroscopic observation was performed to verify the usefulness of AIB for patients with lung, breast cancer, or abdominal cancers. Internal organ movement due to breathing was monitored and measured with and without AIB. With the help of AIB, the average range of diaphragm motion was reduced from 2.6 to 0.7 cm in the anterior-to-posterior direction and from 2.7 to 1.3 cm in the superior-to-inferior direction. The motion range in the right-to-left direction was negligible, for it was less than 0.5 cm. These initial testing demonstrated that AIB is useful for reducing patients' breathing motion in the thoracic and abdominal regions comfortably and consistently.     

Effects of an opioid on respiratory movements and expiratory activity in humans during isoflurane anaesthesia

Opioids increase abdominal muscle activity during anaesthesia. We proposed that opioid activity during anaesthesia would change chest wall size and movement, and contribute to ventilation. Using an optical system to measure chest wall volume, we studied 10 patients during isoflurane anaesthesia, first under the influence of an opioid and then after reversal with naloxone. Measurements were made during quiet breathing and with carbon dioxide stimulation. Airway occlusion pressure was measured to assess inspiratory and expiratory muscle activity. Chest wall volume decreased with the onset of spontaneous breathing, and decreased further when breathing was stimulated by carbon dioxide. Reversal of opioid activity increased chest wall volume. Breathing movements were predominantly abdominal. Opioid action affected the timing and amplitude of breathing but the pattern of abdominal movement was not affected. Since opioids augment abdominal muscle action during expiration, the unchanged pattern of movement can be attributed to both diaphragm and abdominal activity displacing the abdominal wall reciprocally, in the inspiratory and expiratory phases of the respiratory cycle, respectively.     

产前超声筛查胎儿心脏畸形结果分析

目的 探讨胎儿心脏畸形超声系统检查检出率、超声检查最佳时机及漏诊情况。方法 2013年1月~2016年8月51290例孕早、中、晚期孕妇,依据中国医师协会《产前超声检查指南(2012)》标准与要求进行筛查胎儿心脏畸形。结果 超声产前检出胎儿心脏畸形263例,检出率为5.13‰,各年间胎儿心脏畸形检出率比较,差异无统计学意义(P＞0.05)。孕早期、中期、晚期胎儿心脏畸形检出率分别为1.25‰、7.71‰、5.13‰,三个孕周间胎儿心脏畸形检出率比较,差异有统计学意义（P＜0.05）;孕早期胎儿心脏畸形检出率与孕中期比较,孕晚期胎儿心脏畸形检出率与孕中期比较,孕早期胎儿心脏畸形检出率与孕晚期比较,差异有统计学意义（P＜0.05）。超声产前漏诊9例,漏诊率为3.31％。结论　近年佳木斯市胎儿心脏畸形发病率处于稳定,略有上升的趋势,胎儿心脏畸形的最佳检查时间为孕中期。     

The mechanoreceptors of the costo-vertebral joints

1. Unitary recording in the thoracic dorsal roots of mechanoreceptor discharges from the costo-vertebral joints was carried out in the cat and rabbit. Criteria for the identification of costo-vertebral joint mechanoreceptors were established.2. The majority of rib joint mechanoreceptors are slowly adapting and fifty-three such receptors were studied. Five rapidly adapting receptors were also identified.3. The responses of these receptors have been correlated with rib position and movement. The slowly adapting receptors gave a monotonic response to different rib positions. 72% showed an increase of discharge rate with displacements towards expiratory rib positions.4. In response to manually imposed rib movements slowly adapting joint mechanoreceptors gave a dynamic response which was directly related to the velocity of the movement and adapted within 2 sec. The movements of breathing produced a corresponding alteration of the discharge frequency of the slowly adapting receptors.5. Slowly adapting receptors were localized to the capsule of the costo-transverse joint by probing. They responded to increased intra-articular pressure with an increase of discharge rate and were silenced by intra-articular lignocaine, 0.4%.6. Rapidly adapting joint mechanoreceptors responded to rib movement with a brief burst of discharges.7. The rib joint mechanoreceptors signal rib joint position, and the direction and velocity of rib movement. It is suggested that these afferent discharges provide the basis for the perception of respiratory movements of the chest. The significance of these receptors to the ;sense of effort' resulting from a resistance to breathing is discussed.     

Phase-dependence of breathing and finger tracking movements during normocapnia and hypercapnia

The coordination between breathing and other motor activities usually implies that the respiratory rhythm has become entrained by the rhythm of the simultaneous movement. Our hypothesis was that by increasing the respiratory drive, e.g. by hypercapnia, we would be able to reduce the subordination of breathing to other movements and, on the other hand, enhance effects of breathing on those movements. We investigated interactions between breathing and finger flexion movements in a visually controlled step-tracking procedure which allowed us to distinguish the mutual effects and to detect the dependence of these effects on the phase-relationship between breathing and movement. In contrast to our hypothesis, we found no large increase of the respiratory influences on finger movements during hypercapnia. A noteworthy difference to normocapnia was a shortening of the finger flexion time during the final stage of expiration which was associated with an increased frequency of coincidence between the end of flexion time and the transition from expiration to inspiration. On the other hand, the response of breathing to the finger movement increased when the tracking signal was presented at the beginning of inspiration. The results of the study disproved our hypothesis and demonstrated that, during hypercapnia, breathing can be even more susceptible to influences originating from motor control. Thus, they are in agreement with the findings of a previous study that the coordination between breathing and rhythmic limb movements becomes closer during hypercapnia.     

Local subcutaneous and muscle pain impairs detection of passive movements at the human thumb

Activity in both muscle spindle endings and cutaneous stretch receptors contributes to the sensation of joint movement. The present experiments assessed whether muscle pain and subcutaneous pain distort proprioception in humans. The ability to detect the direction of passive movements at the interphalangeal joint of the thumb was measured when pain was induced experimentally in four sites: the flexor pollicis longus (FPL), the subcutaneous tissue overlying this muscle, the flexor carpi radialis (FCR) muscle and the subcutaneous tissue distal to the metacarpophalangeal joint of thumb. Tests were conducted when pain was at a similar subjective intensity. There was no significant difference in the ability to detect flexion or extension under any painful or non-painful condition. The detection of movement was significantly impaired when pain was induced in the FPL muscle, but pain in the FCR, a nearby muscle that does not act on the thumb, had no effect. Subcutaneous pain also significantly impaired movement detection when initiated in skin overlying the thumb, but not in skin overlying the FPL muscle in the forearm. These findings suggest that while both muscle and skin pain can disturb the detection of the direction of movement, the impairment is site-specific and involves regions and tissues that have a proprioceptive role at the joint. Also, pain induced in FPL did not significantly increase the perceived size of the thumb. Proprioceptive mechanisms signalling perceived body size are less disturbed by a relevant muscle nociceptive input than those subserving movement detection. The results highlight the complex relationship between nociceptive inputs and their influence on proprioception and motor control.     

呼吸频率检测技术研究现状

在机体代谢中,呼吸是至关重要的。定期监测呼吸情况,能尽早发现并预防呼吸系统以及心脑血管等方面的病变。目前,呼吸检测技术主要分为接触式和非接触式两大类。这两种检测技术各有优缺点,其中接触式检测方法能简单并快捷地测量数据,而非接触式检测方法则是利用某些技术手段通过无创测量获取人体的数据。本文对呼吸检测技术的研究现状进行了阐述,并结合各个新技术的现有产品,分析了呼吸检测技术的适用范围及未来的研究方向。     

The role of the central chemoreceptor in causing periodic breathing

In a previous publication (Fowler et al., 1993), we reduced the classical cardiorespiratory control model of (Grodins et al., 1967) to a much simpler form, which we then used to study the phenomenon of periodic breathing. In particular, cardiac output was assumed constant, and a single (constant) delay representing arterial blood transport time between lung and brain was included in the model. In this paper we extend this earlier work, both by allowing for the variability in transport delays, due to the dependence of cardiac output on blood gas concentrations, and also by including further delays in the system. In addition, we extensively discuss the physiological implications of parameter variations in the model; several novel mechanisms for periodic breathing in clinical situations are proposed. The results are discussed in the light of recent observational studies.