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PubMed2001

Comparison of transthoracic Doppler echocardiography and natriuretic peptides in predicting mean pulmonary capillary wedge pressure in patients with chronic atrial fibrillation.

The purpose of this study was to assess whether transthoracic Doppler echocardiography and serum natriuretic peptide levels could predict mean pulmonary capillary wedge pressure (PCWP) in patients with chronic atrial fibrillation. We examined mitral flow velocity and pulmonary venous flow (PVF) velocity patterns in 32 patients with chronic atrial fibrillation. Plasma A-type and B-type natriuretic peptide (ANP, BNP, respectively) levels in the peripheral vein were measured. Significant correlations were observed between mean PCWP and the following: peak velocity (r = 0.51) and deceleration time (r = -0.65) of the mitral flow; peak velocity (r = 0.64) and deceleration time (r = -0.80) of the PVF; BNP (r = 0.60); and ANP (r = 0.36). Stepwise multiple linear regression analysis selected PVF deceleration time and mitral flow deceleration time as independent predictors of PCWP. A cutoff value of PVF deceleration time of < or =150 ms and a mitral flow deceleration time of < or =100 ms predicted a mean PCWP of > or =18 mm Hg, with a sensitivity of 100% and 80% and a specificity of 96% and 85%, respectively. In conclusion, PVF deceleration time and mitral flow deceleration time obtained from transthoracic Doppler echocardiography are more accurate predictors of mean PCWP than values obtained with natriuretic peptides in patients with chronic atrial fibrillation.

Aged↗
PubMed2001

[Relationship between computerized cardiotocography and perinatal outcomes].

OBJECTIVE: To analyze the relationship between the parameters of computerized cardiotocography (CTG) and perinatal outcomes. METHODS: Three hundred and eight CTG examination in 190 third trimester pregnancy were performed, 46 cases in antepartum, 262 cases in intrapartum. CTG parameters including: baseline fetal heart rate (BHR), the square root of the mean squared differences (RMSSD), the proportion derived by dividing the number of differences greater than 3 beats/min by the total number (NN50), acceleration (AC), deceleration (DC), amplitude of deceleration (AMP), duration of deceleration from BHR to bottom (T1) and duration from bottom to BHR (T2), the ratio of T2 to T1 (T2/T1), square of deceleration (DS), the ratio of AMP to duration of deceleration (H/T), the ratio of DS to the product of AMP multiplied deceleration duration (S/HT), amplitude of uterine contraction (UTAMP), number of uterine contraction (UTNO), duration of uterine contraction (UTDUR), square of uterine contraction (UTS), the ratio of AMP to UTAMP (HR/HU), the ratio of DS to UTS (SR/SU), the ratio of DS to UTAMP (SR/HU). After childbirth record neonatal Apgar scores, amniotic fluid colour (COL) and volume (VOL), umbilical cord arteria blood gas analysis. RESULTS: (1) The fetal heart rate (FHR) baseline and variability . In antepartum, there were significantly relationship between BHR and Apgar (r = 0.460, P < 0.01), RMSSD and COL (r = - 0.389, P < 0.05), NN50 and COL (r = - 0.368, P < 0.05), RMSSD and actual base excess (ABE) (r = 0.904, P < 0.05), NN50 and ABE (r = 0.919, P < 0.05), AC and ABE (r = 0.943, P < 0.05), BHR and SO2 ( r = - 0.895, P < 0.05). But during intrapartum, there were no significantly relationship between the baseline and variability of CTG with the Apgar scores, the quality and color of amniotic fluid, and the indexes of blood gas analysis of umbilical artery blood. (2) The deceleration of FHR. During antepartum there were significantly relationship between Apgar and AMP (r = - 0.472, P < 0.05), Apgar and H/T (r = - 0.526, P < 0.05), COL and AMP (r = 0.447, P < 0.05), COL and H/T (r = 0.543, P < 0.05) . During intrapartum the relationship of COL and T1 was significant (r = - 0.205, P < 0.05), there were significantly relationship between PH and H/T (r = 0.386, P < 0.05), ABE and H/T (r = 0.367, P < 0.05), Apgar and UTDUR (r = 0.149, P < 0.05), Apgar and UTS (r = 0.148, P < 0.05), PO2 and UTS (r = 0.234, P < 0.05), PO2 and UTNO (r = -0.246, P < 0.05), HCO3 and UTAMP (r = - 0.265, P < 0.05), TCO2 and UTAMP (r = - 0.268, P < 0.05), HCO3 and HR/HU (r = 0.385, P < 0.01), TCO2 and HT/HU (r = 0.385, P < 0.01), ABE and HR/HU (r = 0.323, P < 0.05). CONCLUSIONS: In antepartum, the baseline and variability of FHR play a more important role in predicting prenatal outcome than any other parameters; during intrapartum deceleration become more important, but with the affect by uterin contraction, the ratio of HR/HU may be useful during intrapartum.

Amniotic Fluid↗
PubMed2005

The scaling of information to action in visually guided braking.

Braking to avoid a collision can be controlled by keeping the deceleration required to stop (i.e., ideal deceleration) in the "safe" region below maximum deceleration, but maximum deceleration is not optically specified and can vary as conditions change. When brake strength was manipulated between participants using a simulated braking task, the ratio of ideal to maximum deceleration at brake onset was invariant across groups, suggesting that calibration involves scaling information about ideal deceleration in intrinsic units of maximum deceleration. Evidence of rapid recalibration was found when brake strength was manipulated within participants, and the presence of external forces that affect brake dynamics resulted in biases in performance. Discussion focuses on the role of calibration, internal models, and affordance perception in visually guided action.

Acceleration↗
PubMed1996

Dynamics of the martial arts high front kick.

Fast unloaded movements (i.e. striking, throwing and kicking) are typically performed in a proximo-distal sequence, where initially high proximal segments accelerate while distal segments lag behind, after which proximal segments decelerate while distal segments accelerate. The aims of this study were to examine whether proximal segment deceleration is performed actively by antagonist muscles or is a passive consequence of distal segment movement, and whether distal segment acceleration is enhanced by proximal segment deceleration. Seventeen skilled taekwon-do practitioners were filmed using a high-speed camera while performing a high front kick. During kicking, EMG recordings were obtained from five major lower extremity muscles. Based on the kinematic data, inverse dynamics computations were performed yielding muscle moments and motion-dependent moments. The results indicated that thigh deceleration was caused by motion-dependent moments arising from lower leg motion and not by active deceleration. This was supported by the EMG recordings. Lower leg acceleration was caused partly by a knee extensor muscle moment and partly by a motion-dependent moment arising from thigh angular velocity. Thus, lower leg acceleration was not enhanced by thigh deceleration. On the contrary, thigh deceleration, although not desirable, is unavoidable because of lower leg acceleration.

Adolescent↗
PubMed1979

[Patterns of fetal heart frequency during the second stage of labour and expulsion period--typical patterns, frequency, risk of acidosis and evaluation (author's transl)].

Four patterns of fetal heart frequency with normocardia, two with tachycardia and three with bradycardia are described during the expulsion period. The most frequent patterns are normocardia with decelerations (48%), normocardia with decelerations and final bradycardia (21.1%) and basal bradycardia with decelerations (13.5%). The frequency of acidosis (pH of the umbilical artery less than or equal to 7,200) of these three patterns amounts to 8.3, 24.1 respectively 26.7%. The mean values of pHUA of normocardia with decelerations and final bradycardia, bradycardia, bradycardia with decelerations, tachycardia with decelerations and final bradycardia with prepathologic respectively pathologic Scores (Hammacher's Score, greater than or equal to five points) range from preacidosis to acidosis. Scoring of cardiotocograms seems to be of greater clinical significance than the measurement of deceleration areas.

Acidosis↗
PubMed2002

Doppler-derived left ventricular end-diastolic pressure prediction model using the combined analysis of mitral and pulmonary A waves in patients with coronary artery disease and preserved left ventricular systolic function.

The aim of this study was to analyze the components of mitral and pulmonary A waves and to construct a Doppler-derived left ventricular (LV) end-diastolic pressure (EDP) prediction model based on the combined analysis of transmitral and pulmonary venous flow velocity curves. Combined analysis of transmitral and pulmonary venous flow velocity curves at atrial contraction is a reliable predictor of increased LV filling pressure. The duration of pulmonary and mitral A waves is determined by the sum of respective acceleration and deceleration time. Mitral flow and left upper pulmonary vein flow velocity curves were recorded simultaneously with LVEDP in 40 consecutive patients (aged 59 +/- 8 years) with coronary artery disease and preserved LV systolic function. Differences in all parameters represent values of pulmonary minus those of mitral A wave curve. The difference in deceleration time was the strongest candidate, being included in all models. After redundancy evaluation, we reached the following model: LVEDP = 20.61 + 0.229 x difference in deceleration time (r(2) = 0.80, p <0.001). In the entire study group, the difference in duration and in deceleration time of the A wave was highly correlated with LVEDP (r = 0.79, p <0.001, and r = 0.88, p <0.001, respectively). The entire study group was further divided according to whether LVEDP was above (group I, 20 patients) or below (group II, 20 patients) the median value (15.5 mm Hg). In group I, the difference in duration and in deceleration time correlated well (r = 0.62, p = 0.01, and r = 0.75, p = 0.001, respectively) with LVEDP, whereas in group II only the difference in deceleration time correlated well (r = 0.68, p = 0.005). In patients with coronary artery disease and preserved LV systolic function, the combined analysis of mitral and pulmonary A waves can predict LVEDP. The difference in deceleration time between pulmonary and mitral A waves can reliably evaluate high and normal LVEDP.

Blood Flow Velocity↗
PubMed2000

Exploiting rate-related hysteresis in repolarization alternans to improve risk stratification for ventricular tachycardia.

OBJECTIVES: We sought to study the effect of heart rate acceleration and deceleration on the ability of repolarization alternans (RPA) to stratify ventricular tachycardia (VT) risk. BACKGROUND: Heart rate fluctuations alter arrhythmic propensity, yet it is unclear whether fluctuations, as well as absolute rate, dynamically increase VT risk. We hypothesized that repolarization heterogeneity reflected by RPA would exhibit hysteresis during rising and falling heart rate, which may reflect arrhythmic propensity. METHODS: The RPA magnitude (absolute voltage of alternation [V(alt)] and T-wave alternans ratio [TWAR]) and temporal distribution were determined from the electrocardiogram (ECG) in 60 patients during paced heart rate acceleration from 100 to 150 beats/min, then deceleration to 100 beats/min at electrophysiologic study (EPS). The V(alt) and TWAR thresholds were varied prospectively to generate receiver-operating characteristics (ROC) for the prediction of inducible VT at EPS. RESULTS: Thirty-six patients were induced into VT and 24 were not. Hysteresis of RPA was seen. The V(alt) reached steady-state within 60 beats of each rate transition and was higher in deceleration than in acceleration at matched heart rates. In induced patients, V(alt) rose then fell with heart rate. In noninduced patients, V(alt) was insensitive to acceleration, but rose on initial deceleration. The RPA distributed later within repolarization in induced patients but, on deceleration, moved earlier in both groups. By ROC analysis, V(alt) = 2.6 microV in late repolarization at 120 beats/min provided optimal sensitivity and specificity for VT in acceleration (87.5% and 88.7%, respectively) versus deceleration (80% and 62.5%, respectively; p = 0.004, chi-square test). CONCLUSIONS: 1) Physiologic fluctuations in heart rate may affect the clinical utility of RPA for VT risk stratification; and 2) repolarization dispersion measured by RPA is more exaggerated during deceleration than acceleration at matched heart rates (rate hysteresis).

Adult↗
PubMed2004

Development of cholinergic chronotropic control in chick (Gallus gallus domesticus) embryos.

In chick (Gallus gallus domesticus) embryos, instantaneous heart rate begins to fluctuate with the appearance of rapid, transient decelerations at around the end of the second week of incubation. Previously, it was shown that instantaneous heart rate decelerations were eliminated by administration of atropine and concurrently heart rate baseline was elevated in late embryos. Because the previous study lacked statistical treatment and there has been recent controversy over the development of tonic vagal control of the heart, we reexamine the hypothesis that transient decelerations of instantaneous heart rate are mediated by vagus nerve and the vagal tone begins to appear at around the end of the second week of incubation. Atropine administration tests were conducted for sixty-seven 11- to 14-day-old and 18-day-old embryos in total. Heart rate decelerations appeared sporadically in three out of ten 12-day-old embryos, but the difference of mode heart rate before and after administration of atropine was not significant. Seven out of nine 13-day-old embryos and all nine 14-day-old embryos showed heart rate decelerations and the difference of mode heart rate before and after atropine administration was significant. In late (18-day-old) embryos, magnitude and frequency of instantaneous heart rate decelerations further increased with additional appearance of transient, irregular accelerations. Administration of varying doses of atropine completely eliminated the heart rate decelerations and elevated the heart rate baseline more markedly than in young embryos, indicating the maturation of vagal tone late in incubation.

Animals↗
PubMed1996

Comparison of volume control and pressure control ventilation: is flow waveform the difference?

OBJECTIVE: To examine the hypothesis that a decelerating inspiratory flow waveform is responsible for improvements in gas exchange during pressure control ventilation for acute lung injury. DESIGN: Prospective, controlled, crossover study. MEASUREMENTS AND MAIN RESULTS: Twenty-five patients with acute lung injury requiring mechanical ventilation with a positive-end expiratory pressure > or = 10 cm H2O, ventilator frequency of > or = 8 bpm, inspired oxygen concentration of > or = 0.50, peak inspiratory pressure > or = 40 cm H2O, and requiring sedation and paralysis were studied. Patients were ventilated at a tidal volume of 10 mliters/kg, respiratory frequency was set to maintain a pH > 7.30 and PaCO2 < 50 mm Hg, and positive end-expiratory pressure (PEEP) set to maintain Pao2 > 70 mm Hg or Sao2 > 93% with an Fio2 < or = 0.50. In random sequence, ventilator mode was changed from volume control with a square flow waveform, pressure control ventilation with a decelerating flow waveform, or volume control ventilation with a decelerating flow waveform. Tidal volume, minute ventilation, and airway pressures were continuously measured at the proximal airway. After 2 hours of ventilation in each mode, arterial and mixed venous blood gases were drawn and cardiac output determined by thermodilution. Dead space to tidal volume ratio was determined from mixed expired gas concentrations and Paco2. During volume control ventilation with a square flow waveform, Pao2 was decreased (75 +/- 11 mm Hg vs. 85 +/- 9 mm Hg and 89 +/- 12 mm Hg), p < 0.05, and peak inspiratory pressure was increased (50 +/- 9 cm H2O vs. 42 +/- 7 cm H2O and 39 +/- 9 cm H2O) p < 0.05 compared to volume control with a decelerating flow waveform and pressure control ventilation. Mean airway pressure was also lower with volume control with a square flow waveform (17 +/- 4 cm H2O vs. 20 +/- 4 cm H2O and 21 +/- 3 cm H2O) compared to volume control with a decelerating flow waveform and pressure control ventilation. There were no differences in hemodynamic parameters. CONCLUSIONS: Both pressure control ventilation and volume control ventilation with a decelerating flow waveform provided better oxygenation at a lower peak inspiratory pressure and higher mean airway pressure compared to volume control ventilation with a square flow waveform. The results of our study suggest that the reported advantages of pressure control ventilation over volume control ventilation with a square flow waveform can be accomplished with volume control ventilation with a decelerating flow waveform.

Adult↗
PubMed2004

Fetal heart rate changes associated with uterine rupture.

OBJECTIVE: To identify fetal heart rate characteristics of patients with uterine rupture compared with successful vaginal birth after cesarean (VBAC) controls. METHODS: This is a case-control study. Obstetric records of patients at the University of Washington Medical Center and Swedish Medical Center were reviewed for cases of uterine rupture. Entry criteria included operative confirmation of the diagnosis, gestational age beyond 24 weeks, presence of one or more prior low transverse uterine incisions, and availability of fetal heart tracings. Each case was matched with 3 controls randomly selected from a pool of successful VBAC deliveries at the same institution within 1 year. Three blinded independent examiners then examined fetal heart tracings. Each tracing was rated for the presence of fetal tachycardia, mild or moderate variable decelerations, severe variable decelerations, late decelerations, prolonged decelerations, fetal bradycardia, and loss of uterine tone in both the first and second stages of labor separately. RESULTS: Of the 48 uterine ruptures identified, 36 met inclusion criteria. These were matched with 100 controls. Cases showed significantly increased rates of fetal bradycardia than controls in the first stage (P <.01) and second stage (P <.01). No significant differences were noted in rates of mild or severe variable decelerations, late decelerations, prolonged decelerations, fetal tachycardia, or loss of uterine tone. CONCLUSION: Fetal bradycardia in the first and second stage is the only finding to differentiate uterine ruptures from successful VBAC patients. LEVEL OF EVIDENCE: II-2

Adult↗
PubMed1997

Gender Differences in Mitral Inflow Parameters of Doppler Echocardiography.

BACKGROUND: Doppler echocardiographic parameters are useful in understanding cardiac function. Previous studies have evaluated the physiologic effects of heart rate, body position, and age on left ventricular (LV) Doppler inflow variables. OBJECTIVE: The aim of this study was to investigate the effect of gender on LV Doppler inflow variables. METHODS: A complete echocardiographic study was performed in the left lateral position on 25 male and 25 female normal subjects. The Doppler variables, of E and A wave velocities, acceleration and deceleration times of the E wave velocity, and cardiac chamber dimensions were measured. RESULTS: The aortic root size (3.2 +/- 0.4 vs 2.8 +/- 0.4 cm, P = 0.002), LV end systolic (2.8 +/- 0.3 vs 2.5 +/- 0.5 cm, P = 0.03), and LV end diastolic dimensions (5.0 +/- 0.4 vs 4.5 +/- 0.6 cm, P = 0.003) were larger in men compared to women. E wave deceleration time (233 +/- 40 vs 197 +/- 37 msec, P = 0.002) was longer in men compared to women. Using univariate analysis, deceleration time of the E wave was correlated with heart rate (P = 0.001), maximal A wave velocity (P = 0.007), acceleration time of the E wave (P = 0.01), LV systolic dimension (P = 0.03), maximal E wave velocity (P = 0.04), LV diastolic dimension (P = 0.06), and height (P = 0.07). E/A ratio, body surface area, age, weight, and left atrial dimension had no significant correlation with the deceleration time of the E wave. In the multivariate model, heart rate (P = 0.001) had the most significant (inverse) correlation with deceleration time of the E wave. CONCLUSIONS: In this cohort of subjects, there were significant differences in LV systolic and diastolic measurements and Doppler measurements of deceleration time of the E wave between men and women. The differences in Doppler measurements between men and women are most likely affected by the higher heart rate in women. Therefore, when interpreting deceleration time of the E wave, the effect of heart rate should be considered.

Journal Article↗
PubMed1996

Motor unit activity during human single joint movements.

1. To explore the neural control of single joint movements in humans, the activity of 47 motor units in triceps brachii muscle was recorded during elbow flexion and extension movements. Movements were performed with different but changing deceleration magnitudes, while the acceleration magnitude was kept constant, to determine the relationship between motor unit activity and the acceleration and deceleration characteristics of single joint movements. 2. The number of motor unit action potentials was found to vary with the magnitude of the movement deceleration. In addition the duration of the discharge of a motor unit was found to parallel the duration of the acceleration phase of the movement, when the acceleration duration was varied while acceleration magnitude was kept constant. 3. Approximately half of the recorded motor units in triceps brachii were active both in the initiation and in the termination of the extension movements. However, motor units were identified that participated in specific phases of the movement (i.e., either during the 1st agonist or 2nd agonist burst of muscle activity) depending on the magnitude of the acceleration or deceleration. 4. During flexion movements, when the triceps muscle served as an antagonist, approximately half of the motor units were recruited only when the magnitude of the flexion deceleration was large. Further, this deceleration magnitude was larger than that evident during the extension movements in which the motor unit discharged. 5. The findings of this study demonstrate that the nervous system activates the same motor units whether the muscle is functioning as an agonist or antagonist so as to control the characteristics of acceleration and deceleration of single joint movements.

Acceleration↗
PubMed1984

The genesis of the third and fourth heart sounds. A pressure-flow study in dogs.

To examine the mechanism of mitral flow deceleration in diastole and its potential influence on the genesis of third (S3) and fourth (S4) heart sounds, we simultaneously recorded left atrial and left ventricular pressures (micromanometers), mitral flow velocity (electromagnetic catheter-tip flow velocity meter), and internal and external phonocardiograms in 25 open-chest dogs. Diastolic time intervals, transmitral pressure gradients (planimetry), maximum mitral flow velocity, and acceleration and deceleration of flow were measured under different loading conditions. It was found that deceleration of mitral flow in early and late diastole is always caused by a negative transmitral pressure gradient. After volume loading, diastolic pressures, positive (forward) and negative (backward) transmitral pressure gradients, and acceleration and deceleration of flow increased, and an S3 or S4 appeared (20:25 dogs). These sounds occurred during the phase of flow deceleration and could be recorded from the chest wall, inside the left ventricle, and directly from the epicardial surface of the freely exposed left ventricular wall. After balloon occlusion of the inferior vena cava (17:25 dogs), the opposite changes were observed and gallop sounds disappeared. The results indicate that the left ventricular pressure rise in response to filling reverses the transmitral pressure gradient and decelerates flow. Deceleration of inflow by the left ventricular wall in early and late diastole may represent a key mechanism in the genesis of S3 and S4.

Animals↗
PubMed2007

Feeding, fins and braking maneuvers: locomotion during prey capture in centrarchid fishes.

Locomotion is an integral aspect of the prey capture strategy of almost every predatory animal. For fishes that employ suction to draw prey into their mouths, locomotor movements are vital for the correct positioning of the mouth relative to the prey item. Despite this, little is known regarding the relationships between locomotor movements and prey capture. To gain insights into how fishes move during prey capture and the mechanisms underlying deceleration during prey capture, I measured the fin and body movements of largemouth bass, Micropterus salmoides, and bluegill sunfish, Lepomis macrochirus. Using a high-speed video camera (500 frames s(-1)), I captured locomotor and feeding movements in lateral and ventral (via a mirror) view. Largemouth bass swam considerably faster than bluegill during the approach to the prey item, and both species decelerated substantially following prey capture. The mean magnitude of deceleration was significantly higher in largemouth bass (-1089 cm s(-2)) than bluegill (-235 cm s(-2)), and the timing of maximum deceleration was much later for largemouth bass (30.3 ms after maximum gape) than bluegill (6.7 ms after maximum gape). Both species employed their pectoral, anal and caudal fins in order to decelerate during prey capture. However, largemouth bass protracted their pectoral fins more and faster, likely contributing to the greater magnitude of deceleration in the species. The primary mechanism for increased deceleration was an increase in approach speed. The drag forces experienced by the fins and body are proportional to the velocity of the flow squared. Thus, the braking forces exerted by fins, without any change in kinematics, will increase exponentially with small increases in swimming speed, perhaps allowing these fishes to achieve higher braking forces at higher swimming speeds without altering body or fin kinematics. This result can likely be extended to other maneuvers such as turning.

Animals↗
PubMed1976

[Influence of umbilical cord entanglement on fetal heart rate].

Umbilical cord entanglement was found in 34% of 555 women in labour. One loop of cord around the neck of the fetus was seen in 29% of the women and two or more loops in 5%. Cardiotocograms of these patients were examined for abnormal heart rate patterns. Cord involvement did not influence the incidence of basal bradycardia or tachycardia, early or late decelerations, loss of beat-to-beat variation or acceleration patterns. Variable decelerations, however, were seen in 23% of the patients with cord entanglement and in 7% without cord involvement. This difference is statistically significant (P less than 0.001). Subclassification of variable deceleration into different grades according to the amplitude of the deceleration, demonstrated the presence of cord involvement in 50% of the patients with moderate variable decelerations. This incidence rose to 65% when severe variable decelerations were demonstrated and to 75% when decelerations had increased during labour. Low Apgar scores at 1 and 5 minutes occurred 2 and 3 times more often, respectively, when cord involvement was present.

Adolescent↗
PubMed2000

Baselines for three-dimensional perception of combined linear and angular self-motion with changing rotational axis.

The laws of physics explain many human misperceptions of whole-body passive self-motion. One classic misperception occurs in a rotating chair in the dark: If the chair is decelerated to a stop after a period of counterclockwise rotation, then a subject will typically perceive clockwise rotation. The laws of physics show that, indeed, a clockwise rotation would be perceived even by a perfect processor of angular acceleration information, assuming that the processor is initialized (prior to the deceleration) with a typical subject's initial perception - of no rotation in this case. The motion perceived by a perfect acceleration processor serves as a baseline by which to judge human self-motion perception; this baseline makes a rough prediction and also forms a basis for comparison, with uniquely physiological properties of perception showing up as deviations from the baseline. These same principles, using the motion perceived by a perfect acceleration processor as a baseline, are used in the present paper to investigate complex motions that involve simultaneous linear and angular accelerations with a changing axis of rotation. Baselines - motions that would be perceived by a perfect acceleration processor, given the same initial perception (prior to the motion of interest) as that of a typical subject - are computed for the acceleration and deceleration stages of centrifuge runs in which the human carriage tilts along with the vector resultant of the centripetal and gravity vectors. The computations generate a three-dimensional picture of the motion perceived by a perfect acceleration processor, by simultaneously using all six interacting degrees of freedom (three angular and three linear) and taking into account the non-commutativity of rotations in three dimensions. The resulting three-dimensional baselines predict stronger perceptual effects during deceleration than during acceleration, despite the equal magnitudes (with opposite direction) of forces on the subject during acceleration and deceleration. For a centrifuge run with the subject facing tangentially in the direction of motion, the deceleration baseline shows a perception of forward tumble (pitch rotation) beginning with ascent from the earth, while the acceleration baseline does not have analogous pitch and vertical motion. These results give a three-dimensional explanation for certain puzzling acceleration-deceleration perceptual differences observed experimentally by Guedry, Rupert, McGrath, and Oman (Journal of Vestibular Research, 1992.). The present analysis is consistent with, and expands upon, previous analyses of individual components of motion.

Acceleration↗
PubMed2005

[Clinical analysis of continuous electronic fetal heart rate monitoring for preterm small for gestational age during labor].

OBJECTIVE: To investigate the clinical value of continuous electronic fetal heart rate (FHR) monitoring for preterm small for gestational age (PSGA) during labor. METHODS: Three hundred and three pregnant women who had inevitable preterm labor at 32 - 36 weeks' gestation because of premature rupture of membrane or unknown cause underwent continuous electronic FHR monitoring during labor from Jan 2002 to May 2004. In total, 78 newborns were preterm small for gestational age (PSGA, PSGA group) and 225 newborns were preterm appropriate for gestational age (PAGA, PAGA group). The cardiotocography (CTG), outcome of labor, and cases with combined umbilical cord abnormality of both groups were analysed retrospectively. RESULTS: The number of cases with pure U type variable deceleration of PSGA group and PAGA group was respectively 24 (30.8%) and 10 (4.4%) (P < 0.01). The number of cases of U type variable deceleration accompanied with other abnormal CTG of both groups was respectively 10 (12.8%) and 1 (0.4%) (P < 0.01). Of PSGA group, the rate of cesarean section and forceps among cases of pure U type variable deceleration was lower than that of cases with U type variable deceleration accompanied with other abnormal CTG (20.8% vs 60.0%, P < 0.05. While, the rate of umbilical cord abnormality (44.1%) among 34 cases with U type variable deceleration was higher compared with that (20.5%) among 44 cases without U type variable deceleration (P < 0.05). CONCLUSIONS: U type variable deceleration is the characteristic FHR graph of PSGA during labor and is not the sign of fetal distress when not accompanied with other abnormal CTG.

Adult↗
PubMed1989

[Study on intracardiac blood flow with color flow mapping in human fetus--the reverse flow at tricuspid valve in human fetus during labor].

This study was performed to determine the relation among the reverse flow signal of tricuspid valve, fetal heart rate pattern and uterine contraction. The blood flow signal through the tricuspid valve was continuously recorded with color flow mapping and direct fetal electrocardiogram as well as uterine contraction in 17 human fetuses during labor. Gestational ages ranged from 36 to 41 weeks. No fetus had a congenital heart anomaly. The detection rate of the reverse flow signal at the tricuspid valve was 100% in variable deceleration, 33% in late deceleration, 5% in normocardia and none in early deceleration. In investigation of the time relation between the reverse flow signal and variable deceleration, the reverse flow signal started after the onset of the recovery phase of deceleration. The tricuspid reverse flow, which was observed in variable deceleration, was caused by an increase in the venous return when cord compression disappeared at the onset of the recovery phase of variable deceleration.

Echocardiography, Doppler↗