Diaphragmatic activity and lung liquid flow in the unanesthetized fetal sheep.

For some time it has been suggested that breathing movements are made "in utero" and recently measurements of tracheal pressure and lung liquid flow in chronic fetal preparations have led to the hypothesis that rapid changes in these parameters are the result of respiratory muscle activity. To test this hypothesis diaphragmatic electrical activity was measured in seven chronic unanesthetized fetal sheep preparations and correlated with lung liquid flow and tracheal pressure. Diaphragmatic activity led to a fall of tracheal pressure and movement of a small volume of lung liquid into the lung. After the activity ceased, tracheal pressure returned to normal and flow diminished to zero or was directed out of the lung. The breathing pattern was unassociated with the net movement of lung liquid out of the lung. A histogram of the interval between breaths revealed a changing pattern of activity throughout gestation. The pattern was significantly altered after premature delivery of one animal with a respiratory problem. These observations provide evidence that respiratory muscles are active "in utero" and that the pattern of activity changes throughout gestation.     

Maternal perception of fetal motor activity.

A technique using real-time ultrasound for comprehensive recording of fetal motor activity was used in 20 subjects in the third trimester of pregnancy. Maternal awareness of fetal movement correlated with the number of fetal parts contributing to the movement but not with maternal parity or obesity, gestational age, placental site, or duration of the fetal movement. Some subjects recorded fetal breathing, passive fetal displacement, and Braxton Hicks''s contractions as fetal movement. Most of our subjects were consistent and accurate in their perception of major fetal movements, but a few were inconsistent and one was completely unaware of major fetal movements. These results suggest that kick counts kept by most mothers will be accurate. Low counts of fetal movement should be an indication for fetal monitoring by other means and not, unconfirmed, for intervention.     

Upper airway resistances in fetal sheep: the influence of breathing activity

Fetal breathing movements (FBM) and lung liquid volume are known to affect lung development, but little is known about mechanisms controlling movement of liquid through the upper respiratory tract (URT). Therefore we measured resistances of the URT in 8 unanesthetized fetal sheep during late gestation while FBM were monitored from pressures in the lower trachea or from electromyogram of respiratory muscles. URT resistance to liquid flow toward the amniotic sac increased from 3.5 +/- 1.9 Torr X ml-1 X min during episodes of FBM to 21.1 +/- 5.7 Torr X ml-1 X min during apnea. Laryngeal resistance during apnea was greater (P less than 0.001) than supralaryngeal resistance in each of six fetuses in which URT resistance was partitioned. Fetal paralysis abolished the increase in laryngeal resistance to efflux that was previously related to the high-voltage electrocortical state and apnea. We were unable to quantify URT resistance to fluid movement toward the lungs because the larynx acted as a valve, permitting flow toward the lungs only in the presence of FBM. The supralaryngeal portion of the URT also apparently acts as a valve, normally preventing the entry of amniotic fluid into the pharynx. These findings help to explain our earlier observations that efflux of liquid from the fetal lungs is greater during episodes of FBM than during apnea.     

Automated Software Analysis of Fetal Movement Recorded during a Pregnant Woman’s Sleep at Home

Fetal movement is an important biological index of fetal well-being. Since 2008, we have been developing an original capacitive acceleration sensor and device that a pregnant woman can easily use to record fetal movement by herself at home during sleep. In this study, we report a newly developed automated software system for analyzing recorded fetal movement. This study will introduce the system and compare its results to those of a manual analysis of the same fetal movement signals (Experiment I). We will also demonstrate an appropriate way to use the system (Experiment II). In Experiment I, fetal movement data reported previously for six pregnant women at 28-38 gestational weeks were used. We evaluated the agreement of the manual and automated analyses for the same 10-sec epochs using prevalence-adjusted bias-adjusted kappa (PABAK) including quantitative indicators for prevalence and bias. The mean PABAK value was 0.83, which can be considered almost perfect. In Experiment II, twelve pregnant women at 24-36 gestational weeks recorded fetal movement at night once every four weeks. Overall, mean fetal movement counts per hour during maternal sleep significantly decreased along with gestational weeks, though individual differences in fetal development were noted. This newly developed automated analysis system can provide important data throughout late pregnancy.     

A Wearable System for In-Home and Long-Term Assessment of Fetal Movement

Objectives: This paper presents a novel wearable system for in-home and long-term fetal movement monitoring on a reliable and easily accessible basis.Material and methods: The system mainly consists of four accelerometers for fetal movement signal acquisition, a microcontroller for signal processing and an Android-based device interacting with the microcontroller via Bluetooth Low Energy (BLE), providing the mother with information related to the fetal movement in an intelligible way.Results: The proposed system can deliver reliable results with a specificity of 0.99 and a sensitivity of 0.77 for fetal movement time series signal classification.Conclusion: The proposed wearable system will provide a good alternative to optimize the use of medical professionals and hospital resources, and has potential applications in the field of e-Health home care. Besides, the fetal movement acceleration signals acquired with volunteers (pregnant women) help establish an initial database for future medical analysis of sensor-recorded fetal behaviors.     

Combined one- and two-dimensional ultrasound system for monitoring fetal breathing movements.

A combined one- and two-dimensional ultrasonic system for monitoring respiratory movements in the human fetus has been developed. A real-time cross-sectional image of the fetal chest at the level of the fetal heart can be obtained, and a time motion recording of fetal respiratory movements can then be written on a strip-chart recorder. Combining the features of one-dimensional and two-dimensional systems produces an accurate means of investigating fetal breathing movements.     

Nonlinear behavior of human respiratory movement during different sleep stages

To investigate the nonlinear properties of respiratory movement during different sleep stages, we applied an algorithm proposed by Grassberger and Procaccia to calculate the correlation dimension in rapid eye movement and non-rapid eye movement sleep. We also tested for nonlinearity in respiratory movement by comparing the correlation dimension for the original data with that for surrogate data. The study population included eight healthy volunteers. We recorded respiratory movement and the sleep electroencephalogram for 8 h. The correlation dimension for respiratory movement was 3.28+/-0.19 (mean +/- SD) during rapid eye movement sleep, 2.31+/-0.21 during light sleep (stage I) and 1.64+/-0.25 during deep slow-wave sleep (stage IV). Thus, the correlation dimension differed significantly by sleep stage (p < 0.001): it was least during stage IV sleep and greatest during REM. The correlation dimension for the original data also differed from that for surrogate data, confirming nonlinearity in original data. The results suggest that the nonlinear dynamics of respiratory movement in sleep changes with sleep stage, presumably due to the information processing by the cerebral cortex. The increased correlation dimension for respiratory movement in REM sleep may be related to increased cortical information processing associated with dreaming.     

Doppler ultrasound and fetal activity.

The possibility that Doppler ultrasound, as used in routine fetal monitoring by external cardiotocography, might stimulate fetal activity was investigated. A mean increase in fetal activity of over 90% was found, as judged by the fetal movement count.     

Effect of asphyxia on respiratory activity in fetal sheep

Hypoxia in fetal sheep depresses respiratory activity. To determine if this effect is counterbalanced by hypercarbia we studied the effects of two levels of asphyxia produced by occlusions of the maternal uterine artery. Moderate asphyxia (PaO2 16.8 +/- 1.6 (SEM) PaCO2 48.9 +/- 1.0 torr) produced no changes in the percent time fetal breathing movements occupied each hour which ranged from 25.6 +/- 7.0 to 32.4 +/- 6.2%. However, a more marked asphyxia (PaO2 12.0 +/- 0.3, PaO2 57.0 +/- 1.6) resulted in a decrease in fetal respiratory activity to 8.7 +/- 3.7% during the first hour. This depression was sustained over the next 2 h but by the 5th hour breathing had returned to 26.2 +/- 7.3%. We concluded that hypercarbia can offset the respiratory inhibition of acute moderate hypoxia, but not that of a more marked lowering of PaO2 in fetal sheep. Severe asphyxia causes an initial inhibition of respiration which is followed by a return to normal respiratory activity.     

NONLINEAR BEHAVIOR OF HUMAN RESPIRATORY MOVEMENT DURING DIFFERENT SLEEP STAGES

To investigate the nonlinear properties of respiratory movement during different sleep stages, we applied an algorithm proposed by Grassberger and Procaccia to calculate the correlation dimension in rapid eye movement and non-rapid eye movement sleep. We also tested for nonlinearity in respiratory movement by comparing the correlation dimension for the original data with that for surrogate data. The study population included eight healthy volunteers. We recorded respiratory movement and the sleep electroencephalogram for 8 h. The correlation dimension for respiratory movement was 3.28 ± 0.19 (mean ± SD) during rapid eye movement sleep, 2.31 ± 0.21 during light sleep (stage I) and 1.64 ± 0.25 during deep slow-wave sleep (stage IV). Thus, the correlation dimension differed significantly by sleep stage (p < 0.001): it was least during stage IV sleep and greatest during REM. The correlation dimension for the original data also differed from that for surrogate data, confirming nonlinearity in original data. The results suggest that the nonlinear dynamics of respiratory movement in sleep changes with sleep stage, presumably due to the information processing by the cerebral cortex. The increased correlation dimension for respiratory movement in REM sleep may be related to increased cortical information processing associated with dreaming. (Chronobiology International, 18(1), 71–83, 2001)     

Proliferation,differentiation and ciliary beating of human respiratory ciliated cells in primary culture

Summary The growth, differentiation, ciliary beating pattern and frequency of human respiratory ciliated cells in primary culture were studied by scanning and transmission electron microscopy and by videomicroscopy. The epithelial cells were obtained as outgrowth from explants of adult nasal polyps. When the explants were grown on type-I and type-IV collagen substrates in a standard serum-free, hormone-supplemented medium, a high percentage of ciliated cells (range 29±5% to 37±6%) was present within 2 days of culture. After 5 days of culture, the percentage of ciliated cells near the explant was 51±5%. Most of the cultured ciliated cells (85%) were characterized by individual cilia showing a coordinated movement during the beat cycle and a beating frequency (13.3±1.3 Hz) similar to that reported in vivo. In the other 15% of the ciliated cells, the dyskinetic cilia were aggregated into clumps and characterized by a rigid and planar bending movement and a lower (P<0.01) beating frequency (10.7±1.4 Hz). It is suggested that the latter type of cell, already described during fetal development, might be an intermediate type of ciliated cell which appears temporarily during the surface respiratory epithelial differentiation.     

吗啡对鸡胚胎发育的影响

目的：研究吗啡对胎动、心率、孵化率、孵化时间、雏鸡体重等的影响。方法：以气室给药的方式给鸡胚注射吗啡,记录胎动、心率、孵化率、孵化时间、雏鸡体重。结果：吗啡可以缩短雏鸡的孵化时间,降低雏鸡的孵化率,并导致雏鸡出现运动障碍;20mg／kg吗啡剂量和12—16胚龄的给药时间,鸡胚孵化率最高,残疾率最低;吗啡导致胚胎心率加快,胎动减少（P〈0．05）。结论：吗啡对胚胎发育有损伤作用,损伤程度与吗啡剂量和给药时间有关。     

Adaptation of laser-Doppler flowmetry to measure cerebral blood flow in the fetal sheep.

The purpose of this study was to devise a means to use laser-Doppler flowmetry to measure cerebral perfusion before birth. The method has not been used previously, largely because of intrauterine movement artifacts. To minimize movement artifacts, a probe holder was molded from epoxy putty to the contour of the fetal skull. A curved 18-gauge needle was embedded in the holder. At surgery, the holder, probe, and skull were fixed together with tissue glue. Residual signals were recorded after fetal death and after maternal death 1 h later. These averaged <5% of baseline flow signals, indicating minimal movement artifact. To test the usefulness of the method, cerebral flow responses were measured during moderate fetal hypoxia induced by giving the ewes approximately 10% oxygen in nitrogen to breathe. As fetal arterial PO(2) decreased from 21.1 +/- 0.5 to 10.7 +/- 0.4 Torr during a 30-min period, cerebral perfusion increased progressively to 56 +/- 8% above baseline. Perfusion then returned to baseline levels during a 30-min recovery period. These responses are quantitatively similar to those spot observations that have been recorded earlier using labeled microspheres. We conclude that cerebral perfusion can be successfully measured by using laser-Doppler flowmetry with the unanesthetized, chronically prepared fetal sheep as an experimental model. With this method, relative changes of perfusion from a small volume of the ovine fetal brain can be measured on a continuous basis, and movement artifacts can be reduced to 5% of measured flow values.     

Use of real-time B-mode ultrasound for pregnancy diagnosis and measurement of fetal growth rate in captive bottlenose dolphins (Tursiops truncatus)

Real-time ultrasonography was used to detect pregnancy in 4 captive bottle-nose dolphins. Pregnancy was readily confirmed from around the 4th month of gestation by imaging fetal fluids and fetal movement. Periodic examination permitted monitoring of the viability of the fetuses by observation of their heart beat and movement, and serial measurements of skull diameter (occipito-frontal axis) and thoracic diameter was possible. A growth curve for these measurements was plotted.     

Analysis of respiratory neuronal activity in fetal sheep.

We developed a new method to monitor fetal medullary respiratory neurons utilizing a two-stage approach. At 129-133 days of gestation, sheep were anesthetized, and a window was placed over the area of the fourth ventricle. After a recovery period of 3-5 days, the fetus was exteriorized into a saline bath under maternal spinal anesthesia, and the head was connected rigidly to a stereotaxic frame. Microelectrodes were inserted into the area of the nucleus tractus solitarius during rapid-eye-movement sleep, and extracellular recordings of 223 respiratory neurons were analyzed: 76% were inspiratory, 9% expiratory, and 15% phase spanning, as classified by visual and computer correlation to diaphragmatic activity. More detailed analysis of 100 neurons was done to assess the respiratory component (eta 2) by use of a modification of the method developed by Orem and Dick (J. Neurophysiol, 50: 1098-1107, 1983). With use of cohorts of 25 breaths, fetal respiratory neurons were found to frequently change their phase relationship to diaphragmatic activity. The eta 2 statistic of fetal respiratory neurons was not a stable characteristic but changed over time. This could be a reflection of an immature central respiratory system before birth or the lack of major sensory inputs.     

Experimental studies on equine herpesvirus type 1 infections.

The EHV-1 viruses of fetal origin grew better and had a wider tissue culture host range than those isolated from horses with respiratory diseases. Comparisons of a fetal isolate (F/304) and a respiratory disease isolate (R/NM-3) in partly immune horses showed that the F/304 virus infected horses more readily, grew better in the nasopharynx, was more likely to cause abortion, and was excreted to a greater extent into the environment.     

Status and reaction to anoxia of rat fetuses developing in conditions of placental insufficiency

Significant adverse correlation of the fetus mass and the degree of its hydration was noted at term in rats with placental insufficiency induced by ligation of about 40% of preplacental vessels on the 16th day of gestation. Disorders revealed in transplacental water-salt metabolism are apparently of some importance for the pathogenesis of fetal growth retardation. Even moderate retardation alters fetal respiratory activity in anoxia, which is associated with the changes in the function of respiratory centres and neuromuscular abnormalities.     

Fetal movements during late gestation in the pig: A longitudinal ultrasonographic study

Repeated ultrasonographic observation of fetal movements was used to distinguish movement patterns and to investigate the rate of occurrence and temporal organisation of these patterns (rest-activity cycles) during the last three weeks of gestation in the pig.By means of transabdominal ultrasonography with a 3.5 MHz linear array transducer, motility in ten different fetuses (one per sow) was studied. Six (median; range 4-6) 1 h recordings were made per fetus at 3-5 day intervals. Fifty-five 1 h recordings were available for analysis. The occurrence of fetal general movements (GM), isolated head (HM), forelimb movements (LM), and rotations (ROT) was analysed from video tapes. For each movement pattern, the trend in occurrence over time was assessed by multilevel analysis. The temporal association between different movement patterns was studied by calculation of the kappa value.ROT occurred very infrequently and showed no particular trend over time. GM, HM, and LM showed a significant decreasing trend towards parturition (P < 0.01). Total fetal activity (i.e., the sum of the four movement incidences) declined from an average of 25% of recording time to 9% over the last three weeks of pregnancy. Periods of fetal quiescence gradually increased with progressing gestation (P < 0.05). There was no evidence of concordant association between the periods of rest and activity of GM, HM, and LM or of improved temporal linkage between these movement patterns with time.Fetal bodily activity decreases towards parturition mainly due to prolonged periods of rest. Fetal movement patterns show rest-activity cycles, but each pattern appears to cycle independently from the other throughout late gestation. The present results of spontaneous fetal movements in the pig provide reference data for future studies of fetal activity under different zootechnical conditions or pharmacological interventions.     

Drug-induced changes in fetal breathing activity and sleep state

Drugs reported to stimulate fetal breathing (FB) were injected into a femoral vein of near-term fetal lambs during rapid eye movement (REM) and non-REM (NREM) sleep. The primary response to NaCN, 0.25-0.5 mg, a dose which did not flatten the electrocorticogram, was a brief burst of gasping in any sleep state. When injected during REM sleep, NaCN caused the cessation of spontaneous FB and the onset of gasping. Stimulation of FB was observed infrequently. Caffeine (10 mg) and doxapram (3 mg) frequently caused an immediate change in sleep state or arousal. The incidence of FB increased concomitantly with a change to REM sleep or wakefulness (W), but FB still ceased with the onset of NREM sleep. When administered during an episode of spontaneous FB during REM sleep, both caffeine and doxapram caused stimulation of the frequency and depth of breathing. Pilocarpine (4 mg) caused arousal and gasping followed by prolonged vigorous breathing that was dependent on intact carotid sinus nerves. Indomethacin (120 mg over several hours) did not affect sleep states but induced FB in both NREM and REM sleep. In summary, in the fetus the primary effect of NaCN is to suppress spontaneous FB and induce gasping and the effects of pilocarpine, caffeine, and doxapram are intimately related to sleep states or arousal. Indomethacin causes the conversion from episodic fetal to continuous postnatal-type breathing. These data indicate the importance of assessing fetal state of consciousness in interpreting the respiratory response to drugs.     

Electrical activity of phrenic nerve and diaphragm in utero.

Phrenic nerve activity, diaphragmatic EMG, and tracheal or pleural pressure changes were recorded in a chronic fetal sheep preparation. Three patterns of fetal phrenic nerve activity were observed: 1) a single burst; 2) irregular nonrhythmic bursts; and 3) prolonged rhythmic activity, seen only prior to fetal death. The total recording time was 54.53 h and the total duration of phrenic nerve activity was 65.34 min (2.16%). When an inactive period was defined as the absence of phrenic nerve activity for 60 s or more, active periods occupied 44.7% of the total time. Phrenic nerve activity was present in all fetuses and 97.5% of the time was coupled with diaphragmatic EMG. Both diaphragmatic EMG and intrapulmonary pressure changes occurred in the absence of phrenic nerve activity. In three fetal animals both phrenic nerves were transected. Tracheal pressure changes were seen which were not coupled with corresponding intrauterine pressure changes. Thus, changes in fetal tracheal pressure or diaphragmatic EMG do not necessarily represent the output of the fetal respiratory center. This study suggests that the fetal respiratory center is active in utero, but this activity is minimal and has a different pattern that that present after birth.