Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “DECELERATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed1982

Fetal heart rate accelerations and late decelerations during the course of intrauterine death in chronically catheterized rhesus monkeys.

The appearance of late decelerations and the disappearance of accelerations in the fetal heart rate were observed during the days that preceded intrauterine fetal death in nine chronically instrumented rhesus monkeys. All nine animals had recovered satisfactorily from the initial surgical procedure, as evidenced by normal biophysical and biochemical parameters. After recovery, all the fetuses had shown accelerations and no late decelerations with spontaneous uterine contractions. The mean duration of the preparations was 16.1 days. The duration of the preterminal observation period varied from 3 to 13 days, during which time no experiments were performed. The fetuses died during labor at a mean gestational age of 143 days. Late decelerations were the first sign of fetal deterioration and occurred with a slight but significant decrease in fetal PaO2 without changes in pH, whereas accelerations in fetal heart rate were still present. The loss of accelerations in fetal heart rate was a later phenomenon and was associated with significant reductions in fetal pH and PaO2.

Animals↗
PubMed1985

Longitudinal measurements of fetal breathing, body movements, heart rate, and heart rate accelerations and decelerations at 24 to 32 weeks of gestation.

Fetal breathing, fetal body movements, fetal heart rate, and fetal heart rate accelerations and decelerations were studied longitudinally in healthy fetuses between 24 and 32 weeks' gestation in the second and third hour following an 800 kcal maternal meal. The expected increase in fetal breathing following a maternal meal was not seen until fetuses were at 30 to 32 weeks' gestation. The number of body movements decreased and the interaction between body movements and fetal heart rate accelerations became more evident as fetuses became older. Fetal heart rate decelerations increased with gestational age, and the relative proportion of total decelerations that were either associated with body movements or were part of a deceleration/acceleration/deceleration complex increased from 24 to 32 weeks' gestation. The data support the hypothesis that gestational age is an important variable to consider when interpreting biophysical measurements in the human fetus at 24 to 32 weeks' gestation. Fetal body movements may be the single most important measurement of fetal health at these gestational ages.

Adult↗
PubMed1991

An unusual cause and treatment of decelerations in fetal heart rate.

Decelerations of severe degree were detected during the monitoring of fetal heart rate at term. Decelerations continued despite the usual maneuvers in patient's position. Examination by ultrasound revealed that a loop of umbilical cord was held and squeezed in the fetal fist. The oxytocin infusion stimulated strong and frequent fetal movements which caused the fetal grip on umbilical cord to release and FHR decelerations to disappear. Induced labor progressed rapidly and within 5 h a healthy term infant was delivered.

Adult↗
PubMed1988

Fetal umbilical artery flow velocity waveforms: prediction of small for gestational age infants and late decelerations in labour.

The relationship between fetal umbilical artery waveform patterns and (a) small for gestational age infants or (b) late fetal heart rate (FHR) decelerations in labour was examined in 205 clinically high-risk pregnancies. All pregnancies were studied using continuous-wave Doppler Ultrasound within 7 days of delivery. Waveforms were analysed by calculating a ratio of peak systolic frequency to end diastolic frequency (A/B ratio). An abnormal Doppler result was defined as being above the 97th centile for gestation from our previously derived normal values. Abnormal Doppler results occurred in only 38% of small for gestational age (SGA) infants and in 70% of those developing late decelerations in labour. Doppler ultrasound is a poor predictor of SGA infants, but may identify a high proportion of cases at risk of developing late FHR decelerations in labour.

Blood Flow Velocity↗
PubMed1986

A comparison of the effects of fixed versus variable foreperiods on anticipatory cardiac deceleration prior to an exercise task in grade school children.

Children's heart rate responses in anticipation of a signalled exercise task were examined. The use of fixed (15 s) vs variable (10, 15 or 20 s) preparatory intervals (PI) was compared. The analysis across all subjects indicated that the children exhibited a stable deceleration immediately prior to the exercise task. A difference was found between the fixed and variable PI's. During the period immediately before the exercise task, those subjects receiving the variable PI exhibited a decrease across trials in the size of the anticipatory heart rate deceleration. The children receiving the fixed PI showed an increase across trials in the size of the deceleration.

Attention↗
PubMed1975

Human Pavlovian decelerative cardiac conditioning based on a respiratory-induced cardiac deceleration as an unconditional reflex.

This study was directed at examining the feasibility of using a respiratory-induced cardiac decelerative reflex as an unconditioned response (UCR) in a Pavlovian conditioning paradigm. Experiment I assessed the reflexive features of the cardiac response under a respiratory procedure which involved 3 sec of exhalation, 4 sec of inhalation, and then 30 sec of breath-holding (BH). The results indicated that the BH onset aspect of this respiratory cycle involved a phasic, large-magnitude cardiac deceleration (27 beats/min) with short latency, fast recruitment, and no indication of habituation over trials. Experiment II examined the feasibility of using BH onset as an unconditioned stimulus (UCS) in a Pavlovian paradigm by presenting an auditory conditional stimulus (CS) 1 sec prior to the instructed BH aspect of the respiratory cycle. A separate control condition involved presenting the CS 10 sec after BH onset which constituted a 'backward' conditioning control. The results indicated that the conditioning group displayed a significant cardiac deceleration on CS-alone test trials (under normal breathing) in contrast to the absence of such an effect for the control group. In brief, the study suggested that a decelerative conditioned response (CR) could be established by using a respiratory-induced cardiac deceleration as a Pavlovian UCS. Potential clinical applications of such a decelerative CR were noted.

Acoustic Stimulation↗
PubMed1994

Doppler-derived mitral deceleration time of early filling as a strong predictor of pulmonary capillary wedge pressure in postinfarction patients with left ventricular systolic dysfunction.

OBJECTIVES: The aim of this study was to investigate the correlations between Doppler-derived transmitral flow velocity variables and pulmonary capillary wedge pressure in patients with severe left ventricular systolic dysfunction. BACKGROUND: Abnormal relaxation and increased chamber stiffness have opposing effects on the left ventricular filling pattern. When both abnormalities are present at the same time, as often occurs in patients with systolic dysfunction, the ability of Doppler recording to assess diastolic function and predict left ventricular filling pressure may be significantly compromised. METHOD: Pulmonary capillary wedge pressure and Doppler transmitral flow velocity profile were simultaneously recorded in 140 postinfarction patients with ejection fraction < or = 35%. RESULTS: Correlation between the ratio of mitral peak flow velocity in early diastole to peak flow velocity in late diastole (E/A ratio) and pulmonary capillary wedge pressure was weak (r = 0.65). Although the specificity of E/A > or = 2 in predicting > or = 20 mm Hg in pulmonary capillary wedge pressure was high (99%), its sensitivity was low (43%). Conversely, a very close negative correlation was found between mitral deceleration time of early filling and pulmonary capillary wedge pressure (r = -0.90). Sensitivity and specificity of < or = 120 ms in deceleration time in predicting > or = 20 mm Hg in pulmonary capillary wedge pressure were 100% and 99%, respectively. CONCLUSIONS: Doppler-derived mitral deceleration time of early filling provides a simple and accurate means of estimating pulmonary capillary wedge pressure that is particularly useful in patients with a normal or normalized mitral flow velocity pattern.

Adult↗
PubMed1994

Variable fetal heart rate decelerations and electrocortical activities.

OBJECTIVE: The purpose of this study was to examine the influence of fetal behavioral states on baroreflex-mediated, variable fetal heart rate decelerations caused by umbilical cord occlusion. STUDY DESIGN: Five chronically instrumented fetal lambs were subjected to intermittent partial umbilical cord occlusion for 1 minute every 3 minutes, lasting 2 hours. Fetal behavioral states determined by electrocorticogram and heart rates by electrocardiogram were monitored continuously during these experiments. RESULTS: The fetuses exhibited an alteration between low- and high-voltage electrocorticogram states. Both the depth and width of the variable fetal heart rate decelerations were greater during high-voltage than during low-voltage electrocorticogram. CONCLUSION: Amplitude and duration of variable fetal heart rate decelerations are affected by fetal behavioral states.

Animals↗
PubMed2003

Cytochrome c decelerates channel kinetics of negatively charged gramicidin due to electrostatic interaction.

The effect of cytochrome c on the kinetic properties of ion channels formed by O-pyromellitylgramicidin (OPg), the negatively charged analogue of gramicidin A (gA), in bilayer lipid membranes was studied by the method of sensitized photoinactivation. The addition of cytochrome c to both sides of the membrane caused substantial deceleration of the photoinactivation kinetics of OPg channels which expose three negative charges to the aqueous phase at both sides of the membrane. By contrast, the gA photoinactivation kinetics was unaltered by the addition of cytochrome c. Based on the sensitivity of the observed effect to the ionic strength of the bathing solution, the cytochrome c-induced deceleration of the OPg photoinactivation kinetics reflecting the increase in the OPg channel lifetime was ascribed to electrostatic interaction of positive charges of cytochrome c with negative charges of OPg that resulted in channel clustering. Formation of clusters of OPg channels was previously inferred to explain the polylysine effect on the OPg channel kinetics. The decelerating effect of cytochrome c on OPg channels was observed only at a high number of OPg channels in the membrane, thus suggesting that the interaction between cytochrome c and the charged transmembrane protein requires sufficiently high negative charge density on the surface of the membrane.

Animals↗
PubMed2002

Polyanions decelerate the kinetics of positively charged gramicidin channels as shown by sensitized photoinactivation.

The effects of different anionic polymers on the kinetic properties of ionic channels formed by neutral gramicidin A (gA) and its positively charged analogs gramicidin-tris(2-aminoethyl)amine (gram-TAEA) and gramicidin-ethylenediamine (gram-EDA) in a bilayer lipid membrane were studied using a method of sensitized photoinactivation. The addition of Konig's polyanion caused substantial deceleration of the photoinactivation kinetics of gram-TAEA channels, which expose three positive charges to the aqueous phase at both sides of the membrane. In contrast, channels formed of gram-EDA, which exposes one positive charge, and neutral gA channels were insensitive to Konig's polyanion. The effect strongly depended on the nature of the polyanion added, namely: DNA, RNA, polyacrylic acid, and polyglutamic acid were inactive, whereas modified polyacrylic acid induced deceleration of the channel kinetics at high concentrations. In addition, DNA was able to prevent the action of Konig's polyanion. In single-channel experiments, the addition of Konig's polyanion resulted in the appearance of long-lived gram-TAEA channels. The deceleration of the gram-TAEA channel kinetics was ascribed to electrostatic interaction of the polyanion with gram-TAEA that reduces the mobility of gram-TAEA monomers and dimers in the membrane via clustering of channels.

Acrylic Resins↗
PubMed1998

Mannan decelerates the clearance of human red blood cells in SCID mouse.

Mannans and its related compounds decelerated human (Hu) red blood cell (RBC)-clearance in severe combined immunodeficiency (SCID) mice by inhibiting erythro-phagocytosis of macrophages. Chimeric SCID mice for Hu-RBC which are generated by repeated transfusions with mature Hu-RBCs are described recently as a model for Plasmodium falciparum infection, though the Hu-RBC clearance in the mice at present is very rapid and the parasitemia in the mice is only erratic. Here, we aimed to study the method to decelerate Hu-RBC clearance in SCID mice, to establish a suitable mouse model for malaria parasites. Yeast and Candida mannans as well as lactoferrin, a glycoprotein containing both oligomannoside- and N-acetyllactosamine-type glycans, decelerated Hu-RBC clearance, but instead other saccharides such as carboxymethyl chitin, N-acetylglucosamine, and D-glucose did not. Yeast mannan and lactoferrin interfered significantly with in vitro Hu-RBC-phagocytosis which was also inhibited by mannopentaose and mannotoriose. D-mannose exhibited a moderate inhibitory activity. N-acetyl-D-glucosamine, however, showed only a slight inhibitory activity, but D-glucose had no inhibitory activity on Hu-RBC phagocytosis. These results may postulate that Hu-RBC clearance in SCID mouse might be mediated by receptor-ligand binding by a macrophage lectin like receptor with mannose specificity.

Acetylglucosamine↗
PubMed1997

Paradoxical sinus deceleration during dobutamine stress echocardiography: description and angiographic correlation.

OBJECTIVES: This report characterizes the paradoxical sinus deceleration occasionally observed during dobutamine stress testing and determines its relation to myocardial ischemia. BACKGROUND: Dobutamine stress echocardiography is widely accepted as a noninvasive tool for evaluating coronary artery disease. With infusion of dobutamine, there is typically a dose-dependent increase in heart rate. However, in some patients, a paradoxical decrease in heart rate has been observed during high dose dobutamine infusion. METHODS: In 181 consecutive patients undergoing both dobutamine stress echocardiography and coronary angiography, electrocardiographic (ECG) data collected during dobutamine infusion were reviewed to identify patients with a decrease in heart rate. The clinical, stress echocardiographic, hemodynamic and angiographic correlates of patients with a decrease in heart rate were reviewed. RESULTS: A decrease in heart rate ranging from 7 to 64 beats/min occurred during high dose dobutamine infusion in 14 patients (8%, 95% confidence interval [CI] 6% to 10%), including 3 in whom a junctional rhythm developed. The decrease was sudden in five patients (36%, 95% CI 13% to 65%) and gradual in nine (64%, 95% CI 35% to 87%). A decrease in blood pressure (12 patients [86%], 95% CI 57% to 98%) with simultaneous chest pain (7 patients [50%], 95% CI 23% to 77%) and nausea (5 patients [36%], 95% CI 13% to 65%) was common. Significant coronary artery disease (> or = 50% diameter stenosis) was present in 8 (57%) of 14 patients (95% CI 29% to 82%). Two patients (14%, 95% CI 2% to 43%) had no clinical, ECG or echocardiographic evidence of ischemia and no significant coronary artery disease by angiography. There was no increased incidence of right coronary artery stenosis in patients with paradoxical sinus deceleration. CONCLUSIONS: Paradoxical sinus deceleration occurs in 8% of patients during dobutamine stress testing. Although most often observed in patients with coronary artery disease, it can occur in the absence of ischemia and coronary artery disease, and in some patients may be due to a vasodepressor reflex.

Aged↗
PubMed1998

Short deceleration time of mitral inflow E velocity: prognostic implication with atrial fibrillation versus sinus rhythm.

The present study retrospectively identified 367 patients who had restrictive physiology as defined by deceleration time < or = 130 msec; 293 were in sinus rhythm (SR) (194 men and 99 women; mean age 64 +/- 14 years) and 74 were in atrial fibrillation (AF) (51 men and 23 women; mean age 72 +/- 11 years; p < 0.001). Both groups had similar underlying diagnoses and no significant difference in Doppler indices (E wave, 96 +/- 23 vs 99 +/- 22 cm/sec in SR and AF, respectively; deceleration time, 116 +/- 12 vs 116 +/- 13 msec; and left ventricular outflow tract time velocity integral, 14.8 +/- 4.8 vs 14.5 +/- 4.4 cm). Left ventricular ejection fraction was significantly lower in SR patients (29% +/- 16% vs 39% +/- 20%; p = 0.0003). There were 120 deaths (41%) in the SR group and 35 (47%) in the AF group (median follow-up for both groups, 2.2 years). Restrictive physiology as defined by Doppler echocardiography (deceleration time < or = 130 msec) appears to predict a similar poor prognosis with AF as with SR.

Aged↗
PubMed2003

Pleural mesothelioma incidence in Europe: evidence of some deceleration in the increasing trends.

OBJECTIVE: To summarize the geographical and temporal variations in incidence of pleural mesothelioma in Europe, using the extensive data available from European general cancer registries, and consider these in light of recent trends in asbestos extraction, use and import in European countries. MATERIAL AND METHODS: The data were extracted from the European Cancer Incidence and Mortality database (EUROCIM). The inclusion criteria was acceptance in Volume VII of Cancer Incidence in Five Continents. Truncated age-standardized rates per 100,000 for the ages 40-74 were used to summarise recent geographical variations. Standardized rate ratios and 95% confidence intervals for the periods 1986-1990 and 1991-1995 were compared to assess geographical variations in risk. To investigate changes in the magnitude of most recent trends, regression models fitted to the latest available 10-year period (1988-1997) were compared with trends in the previous decade. Fitted rates in younger (40-64) and older adults (65-74) in the most recent period were also compared. RESULTS: There was a great deal of geographical variation in the risk of mesothelioma, annual rates ranging from around 8 per 100,000 in Scotland, England and The Netherlands, to lower than 1 per 100,000 in Spain (0.96), Estonia (0.85), Poland (0.85) and Yugoslavia, Vojvodina (0.56) among men. The rank of the rates for women was similar to that observed for men, although rates were considerably lower. Between 1978 and 1987, rates in men significantly increased in all countries (excepting Denmark). In the following 10 years, there was a deceleration in trend, and a significant increase was detectable only in England and France. In addition, the magnitude of recent trends in younger men was generally lower than those estimated for older men, in both national and regional cancer registry settings. CONCLUSIONS: While mesothelioma incidence rates are still rising in Europe, a deceleration has started in some countries. A decrease may begin in the next few years in certain European populations considering the deceleration of observed trends in mesothelioma and asbestos exposure, as well as the recent ban on its use.

Asbestos↗
PubMed1993

Pressure-controlled ventilation versus controlled mechanical ventilation with decelerating inspiratory flow.

OBJECTIVE: To ascertain whether pressure-controlled ventilation offers any advantage with respect to conventional controlled mechanical ventilation with decelerating flow. DESIGN: Prospective, comparative study. SETTING: Intensive care unit. PATIENTS: Eleven consecutive critically ill adult patients. MEASUREMENTS AND MAIN RESULTS: Study of respiratory mechanics and arterial blood gases after 30 mins of pressure-controlled ventilation. Repetition of the same measurements after 30 mins of controlled mechanical ventilation with decelerating flow waveform, with equal tidal volumes, using a commercially available mechanical ventilator. Student's t-test for paired comparisons. A lesser maximum inspiratory flow rate was required for pressure-controlled ventilation (55.7 +/- 16 L/sec) than for controlled mechanical ventilation (72 +/- 2 L/sec) (p < .001). Nevertheless, the peak pressures measured in the orotracheal tubes of the patients were higher in pressure-controlled ventilation (20.4 +/- 3.5 cm H2O) than in controlled mechanical ventilation (18.4 +/- 4.8 cm H2O) (p < .05). This model measured pressure in the inspiratory line, providing erroneous information regarding the behavior of pressures in the airway. The peak pressure measured by the ventilator was significantly higher in controlled mechanical ventilation than in pressure-controlled ventilation and was, in addition, reached at initiation of inspiration in ten of 11 patients with controlled mechanical ventilation, while peak pressure measured in the orotracheal tube was invariably reached at the end of the inspiration, both in pressure-controlled ventilation and controlled mechanical ventilation. The rest of the parameters analyzed, including end-inspiratory pressure, mean pressure, intrinsic positive end-expiratory pressure, and arterial blood gases, showed no differences. The difference between quasi-static compliances almost reached statistical significance (72 +/- 25.4 mL/cm H2O in pressure-controlled ventilation vs. 68.8 +/- 24.3 mL/cm H2O in controlled mechanical ventilation; p = .052). CONCLUSIONS: Our study failed to demonstrate any important difference between pressure-controlled ventilation and controlled mechanical ventilation with decelerating inspiratory flow waveform. The differences in the airway pressures detected by the ventilator are spurious and are due to the place (inspiratory line) where these pressures were measured. The difference between the peak pressure measured in the orotracheal tube has statistical, but not clinical, value and is lower in controlled mechanical ventilation. Based on the limited number of variables we studied and unless the tendency indicated in the quasi-static compliance is demonstrated in the future, we do not believe that pressure-controlled ventilation contributes any uniqueness to the theory or practice of mechanical ventilation.

Adolescent↗
PubMed1992

Fetal middle cerebral artery blood flow during normal active labour and in labour with variable decelerations.

OBJECTIVE: To assess the distribution of fetal blood flow impedance of the umbilical and middle cerebral artery in active uncomplicated labour and in labour complicated by variable decelerations. INTERVENTIONS: Blood flow impedance of the umbilical and fetal middle cerebral arteries was assessed by means of pulsed Doppler ultrasonography and measured by the resistance index (RI) and the systolic/diastolic ratio. SUBJECTS: 35 women at 38-40 weeks gestation admitted to, or monitored in the intrapartum unit. One group of 25 women had a normal active labour, the second group of 10 women were in active labour with moderate variable decelerations. A control group of 25 women--healthy pregnant women at term but not in active labour. All three groups were comparable for maternal age and parity. SETTING: Hospital department of obstetrics and gynaecology, Israel. DESIGN: A prospective descriptive study. RESULTS: There was a 40% reduction in middle cerebral artery blood flow impedance in the two groups of women in active labour compared with the control group. Umbilical blood flow did not differ significantly between the three groups. Fetal middle cerebral blood flow impedance in labour was not significantly different in uncomplicated labours and those complicated by fetal heart rate decelerations. CONCLUSIONS: During active labour, mechanisms that may be unrelated to low fetal blood oxygen content reduce fetal brain blood vessel impedance.

Blood Flow Velocity↗
PubMedDate not supplied

Analysis of umbilical artery flow parameters during fetal variable decelerations using computerized Doppler waveforms.

Umbilical artery velocity waves were obtained by Doppler ultrasonography before, during, and after 20 episodes of fetal heart rate (FHR) variable decelerations (VD) during the active stage of labor in 8 women. During 50% of the VD periods, the umbilical artery resistance flow parameters increased significantly (p < 0.01). The increase in resistance preceded the decrease in FHR in six episodes (30%) of VD (AR-VD group; arterial resistance VD) and did not precede the change in FHR in another ten episodes (50%) of VD (VR-VD group; venous resistance VD). In the AR-VD group the FHR accelerations occurred before the decelerations in only 1 case (17%), while in the VR-VD group FHR accelerations preceded the decelerations in 8 out of the 10 episodes (80%). Using these Doppler studies, it may be possible to differentiate between two groups of VD: AR-VD - which are caused by umbilical artery occlusion and thus preceded by a measurable increase in umbilical artery resistance - and VR-VD - which are not preceded by a measurable increase in umbilical artery resistance and may be caused by fetal hypoxia.

Adult↗
PubMedDate not supplied

Severe variable decelerations and fetal pulse oximetry during the second stage of labor.

OBJECTIVES: The aim of the study was to investigate the usefulness of fetal pulse oximetry in cases of severe variable decelerations in the second stage of labor. METHODS: It is a prospective study including 58 patients. Thirty-eight patients (group A) had a normal uncomplicated labor and 20 patients (group B) developed severe variable decelerations during the second stage of labor. All patients were primiparous with normal pregnancies and had electronic fetal monitoring of labor in conjunction with fetal pulse oximetry. An estimation of fetal pH and base deficit was performed at delivery in all patients. RESULTS: There was no statistically significant difference in relation to maternal age and gestational age between the two groups. Group A patients did not delivered neonates with metabolic acidosis. Six out of 20 (group B) patients delivered neonates with a pH <7.10 despite a fetal pulse oximetry reading of >30%. CONCLUSIONS: It appears that fetal pulse oximetry is not capable of detecting pre-acidotic or acidotic fetuses during the second stage of labor in patients with severe variable decelerations and the management of such patients should be supported by fetal scalp pH when indicated or otherwise the obstetrician should expedite delivery either with assisted operative delivery or cesarean section. Fetal heart rate monitoring was introduced into clinical practice over 30 years ago. It continues to be the predominant method of intrapartum fetal surveillance despite worries about its accuracy and efficacy.

Acidosis↗