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PubMed1997

Fetal heart rate decelerations precede a decrease in fetal oxygen content.

To determine the relationship between abnormal fetal heart rate (FHR) patterns, fetal oxygen content by reflectance pulse oximetry, and the effects of maternal oxygen administration, 158 intrapartum women consisting of 120 women with normal FHR patterns, and 38 women with varying degrees of variable FHR decelerations were examined. A new reflectance pulse oximetry probe was attached to the fetal forehead to continuously monitor fetal oxygen saturation (SpO2) during labor. Oxygen was administered for 30 min at 5 liters/min by nasal canula in 32 women. No significant change in fetal SpO2 was seen in women with normal FHR patterns, but a significant decline in SpO2 was observed shortly before births. FHR decelerations less than 90 bpm occurred prior to the decline in fetal SpO2. Maternal oxygen administration was effective in increasing fetal SpO2 in fetuses with decreased SpO2 (SpO2 < 50%), but not in fetuses with high SpO2 (SpO2 > 60%). It is concluded that fetal SpO2 exhibits no change during normal labor but significantly declines shortly before birth, that relatively severe variable decelerations (<90 bpm) can decrease fetal SpO2, and that maternal oxygen treatment at 5 liters/min is effective in augmenting fetal oxygen tension in fetuses with decreased oxygen tension.

Female↗
PubMed1999

Resolving competing theories for control of the jamming avoidance response: the role of amplitude modulations in electric organ discharge decelerations.

The algorithm for the control of the jamming avoidance response (JAR) of Eigenmannia has been the subject of debate for over two decades. Two competing theories have been proposed to explain how fish determine the correct direction to shift their pacemaker frequency during jamming. One theory emphasizes the role of time-asymmetric beat envelopes, while the other emphasizes the role of amplitude- and phase-difference computations that arise from the differences in spatial geometry of the electric fields of neighboring fish. In repeating earlier experiments, we found that the decision to raise or lower the pacemaker frequency reliably above or below its resting level depends on the latter process, and that frequency deceleration responses to amplitude modulation appear to be sufficient to explain previous experimental results on which the former theory is based. Specifically, fish of the genus Eigenmannia show differential deceleration responses to asymmetric beat envelopes. The deceleration responses do not require phase modulation and show a sensitivity for amplitude modulation depth and selectivity for amplitude modulation rate comparable with that of JARs that are elicited when amplitude- and phase-difference information is available.

Animals↗
PubMed1977

Cardiac deceleration as an indicator of correct performance.

A within-subjects experiment involving 10 subjects was performed to examine the relationship between the accuracy of judgment of position and cardiac deceleration. The results supported the hypothesis that accurate (correct) performance is accompanied by greater cardiac deceleration than inaccurate performance for those subjects (9 out of 10) who exhibited cardiac deceleration to stimulus onset. The data indicated, however, that the relationship varied with time. Part of this variability appears related to the initial exploratory behavior in which subjects engaged and later reported during the post-experiment interview.

Adolescent↗
PubMed2001

Cardiac deceleration in elite golfers as modified by noise and anxiety during putting.

The relationship between attention and performance in sports has been investigated in numerous studies, often by using indirect measurements such as self reports. Alternatives for studying attentional processes during an event are pro vided by psychophysiological methods. In the present study, cardiac patterns of highly skilled golfers were monitored during the performance of a putting task in both the presence and absence of noise. As a group, the golfers putted as well when noise was present as when it was absent. However, those who scored high on a trait anxiety test showed greater intraindividual variation between putts when noise occurred. More importantly, the players with higher trait anxiety did not show, as expected, pronounced cardiac deceleration prior to putting, as did the players with low trait anxiety scores. Consequently, the present result calls into question the view that cardiac deceleration is associated with superior athletic performance. Furthermore, cardiac deceleration cannot be used as a general measure of attentional processes because interindividual differences in traits, such as anxiety. are probably also important factors to consider.

Adult↗
PubMed1975

Antiaccelerator and decelerator activity of eleven phenothiazine derivatives.

Eleven N-substituted phenothiazine derivatives were studied for their antiaccelerator and decelerator activities on the dog heart. The antiaccelerator activity was determined in heart-lung preparation in dogs. Taking into consideration the percentage inhibition of cardio-acceleration produced by continuous infusion of 3 mug/min of adrenaline, all the drugs except chlorpromazine and 10-butyl-phenothiazine in two experiments caused more than 50 percent inhibition. 10-Propylphenothiazine induced maximum inhibitory effect, i.e. 90.1 percent in a total dose of 20 mg. Two types of effects were observed upon impulse generation in the sinus node. Acceleration was produced by chlorpromazine, 10-cyclopentyl-phenothiazine, prothipendyl, and thiazinamium, which was very short-lived, whereas other drugs produced deceleration. The correlation between antiaccelerator and decelerator properties is rather a close one.

Animals↗
PubMed2001

Acceleration-Deceleration Sport-Related Concussion: The Gravity of It All.

OBJECTIVE: To discuss a newtonian physics model for understanding and calculating acceleration-deceleration forces found in sport-related cerebral concussions and to describe potential applications of this formula, including (1) an attempt to measure the forces applied to the brain during acceleration-deceleration injuries, (2) a method of accruing objective data regarding these forces, and (3) use of these data to predict functional outcome, such as neurocognitive status, recovery curves, and return to play. BACKGROUND: Mild concussion in sports has gained considerable attention in the last decade. Athletic trainers and team physicians have attempted to limit negative outcomes by gaining a better understanding of the mechanisms and severity of mild head injuries and by developing meaningful return-to-play criteria. Mild head injury in sports has become an even greater area of focus and concern, given the negative neurobehavioral outcomes experienced by several recent high-profile professional athletes who sustained repeated concussions. Applying the principles of physics to characterize injury types, injury severity, and outcomes may further our development of better concussion management techniques and prevention strategies. DESCRIPTION: We describe the search for models to explain neuronal injury secondary to concussion and provide an exploratory method for quantifying acceleration-deceleration forces and their relationship to severity of mild head injury. Implications for injury prevention and reduction of morbidity are also considered.

Journal Article↗
PubMed1991

[Significance of heart rate deceleration in pattern recognition tasks].

As strength of foreperiod heart rate (HR) deceleration in reaction time paradigms with a fixed foreperiod has been discussed in terms of activities related to differences in regulations of attentional processes, the present study was concerned with the question of whether this variable also accounts for the variance in the latency of response in two attention-demanding pattern recognition tasks, one of which involved mental rotation. Subjects were required to determine as quickly and as correctly as possible whether a two-dimensional asymmetrical shape was intrinsically identical to a previously presented visual pattern or not, regardless of its rotational position within the picture plane. The first stimulus was always in normal upright position, whereas the probe stimulus could either be rotated or presented in an upright position. The findings of the study are indicative of a reliable relation between anticipatory HR deceleration and reaction time. It was not restricted to detection and response requirements but also held true in the case of additional mental rotation requirements. Strength of anticipatory HR deceleration is therefore interpreted as an indicator of regulations of attentional processes mustered in order to facilitate or to support stimulus detection and response elicitation as well as to prime or to set up the mental structures required in mental rotation. Additional support for this assumption could be found in the analyses of HR changes at the beginning of the response interval.

Adult↗
PubMed1986

Growth decelerations among under-5-year-old children in Kasongo (Zaire). II. Relationship with subsequent risk of dying, and operational consequences. Kasongo Project Team.

The relationship between growth decelerations (in terms of various anthropometric parameters) and death occurring during the subsequent 100 days was studied among under-5-year-old children in Kasongo, Zaire. A significant association, more pronounced for large decelerations, was demonstrated for some anthropometric parameters. The observations provide support for the hypothesis that the frequency of stress due to malnutrition and infection party explains the high mortality. Although the association with mortality is significant, the observation of growth decelerations remains a screening instrument of limited predictive power.

Anthropometry↗
PubMed1985

Relationship between accelerations and decelerations in heart rate and skeletal muscle activity in fetal sheep.

Accelerations in fetal heart rate have been shown to be closely related to fetal body movements and are indicative of well-being in the human fetus. We have examined the association of accelerations and decelerations in heart rate with skeletal muscle activity in 8 fetal sheep between 125 and 145 days' gestation. Accelerations/decelerations were defined as transient increases/decreases in fetal heart rate of greater than or equal to 10 beats/min. lasting for 5 s or longer. For accelerations (n = 1180), the mean duration was 18.8 +/- 1.5 s (SEM) and the mean amplitude was 25.3 +/- 1.2 beats/min; for decelerations (n = 237), the mean duration was 17.4 +/- 1.6 s and the mean amplitude was 18.7 +/- 1.0 beats/min. Electromyograms were recorded from the nuchal muscles and antagonistic muscle groups of the fetal forelimb and hindlimb. Electromyogram activity occurred during 88.4 +/- 2.8% of accelerations and 60.6 +/- 7.7% of decelerations. There was a 36.6% reduction in the number of accelerations following fetal paralysis with gallamine, but no change in their amplitude or duration. It is concluded that accelerations in heart rate are highly associated with skeletal muscle activity in fetal sheep. The majority of these occur as a result of central neuronal output rather than as a consequence of fetal movement.

Animals↗
PubMed1985

Fetal heart rate decelerations after oxytocin infusion in an abdominal pregnancy.

Fetal heart rate (FHR) decelerations during a contraction stress test are recognized as signs of possible uteroplacental insufficiency. Although these decelerations have been described commonly in intrauterine pregnancies, they have not been noted in extrauterine pregnancies. Reported herein are FHR decelerations associated with oxytocin infusion in an extrauterine pregnancy and a discussion of the possible pathophysiologic mechanisms.

Adult↗
PubMed1981

Senile cataracts: evidence for acceleration by diabetes and deceleration by salicylate.

A method is described for determining the natural progression of senile cataracts in humans and whether certain factors accelerate or decelerate this progression. The method consists in plotting the age of the patient against the degree of opacity of the cataract to find the regression relation. A comparison of cataracts from diabetic and nondiabetic patients revealed that diabetes accelerated senile cataract formation, so that there was a difference of 9.6 years in the age of the two groups with more dense cataracts. Plasma tryptophan levels, which are increased in cataract patients, are lowered by acetylsalicylic acid (ASA). In this study ASA decelerated cataract formation in diabetic and nondiabetic patients. Among the nondiabetic patients cataract formation in a group with osteoarthritis was delayed by an average of 10 years. Deceleration of cataract formation resulting from ASA administration may reduce the need for surgical removal of cataracts.

Age Factors↗
PubMed1996

Prognostic relevance of the intrinsic growth deceleration of the first passage xenografts of human renal cell carcinomas.

BACKGROUND: Although successful xenotransplantation of human tumors in nude mice highly predicts prognosis, little is known regarding the biologic background of this correlation. In this study, the relationship between the macroscopic growth pattern of first-generation xenografts of human renal cell carcinomas in nude mice and prognosis was studied. METHODS: Macroscopic growth patterns of the first-generation xenografts of locally confined renal cell carcinomas were analyzed according to the best-fit Gompertz recursion formulas. RESULTS: The parameter "b" of the growth pattern, the measure of the intensity of growth deceleration as a function of tumor growth, strongly predicted prognosis after nephrectomy as a single factor; faster growth deceleration, i.e., lower b values, predicted better prognosis (mean follow-up, 5.2 years; P = 0.000008 for the disease free period and P = 0.000018 for overall survival). It is also the most significant single prognostic parameter among others (including staging and grading) according to a multivariate analysis. CONCLUSIONS: The parameter expressing the Gompertzian macroscopic growth deceleration of the first-generation xenografts of clinically locally confined renal cell carcinomas in nude mice explains the strong prognostic impact of xenotransplantation.

Animals↗
PubMed1999

Intrasaccadic target steps during the deceleration of primary saccades affect the latency of corrective saccades.

This study investigates how visually guided saccades and subsequent corrective saccades are affected by a secondary target step occurring at different times during the primary saccade. Eye movements of human subjects were measured by means of a differential infrared light reflection technique while the subjects performed visually guided saccades to a laser spot in darkness. The target was stepped backward or onward during the targeting saccade. While the intrasaccadic target step did not influence gain, peak velocity or skewness of the primary saccade, it had a significant effect on the subsequent corrective saccade when the secondary target step occurred during the deceleration phase of the primary saccade: the latency of the corrective saccade was significantly increased compared with the one performed under the single-step control condition. This increase also occurred when single target steps were presented randomly intermixed with backward and onward double target steps and even between selected sub-samples of saccades with identical postsaccadic visual error. If the target step occurred early during the primary saccade, the latency of the corrective saccade was not changed. This indicates that visual information sampled during the deceleration phase of a saccade can lead to a cancellation of the normal trigger mode of corrective saccades.

Deceleration↗
PubMed2006

The influence of deceleration forces on ACL strain during single-leg landing: a simulation study.

Anterior cruciate ligament (ACL) injury commonly occurs during single limb landing or stopping from a run, yet the conditions that influence ACL strain are not well understood. The purpose of this study was to develop, test and apply a 3D specimen-specific dynamic simulation model of the knee designed to evaluate the influence of deceleration forces during running to a stop (single-leg landing) on ACL strain. This work tested the conceptual development of the model by simulating a physical experiment that provided direct measurements of ACL strain during vertical impact loading (peak value 1294N) with the leg near full extension. The properties of the soft tissue structures were estimated by simulating previous experiments described in the literature. A key element of the model was obtaining precise anatomy from segmented MR images of the soft tissue structures and articular geometry for the tibiofemoral and patellofemoral joints of the knee used in the cadaver experiment. The model predictions were correlated (Pearson correlation coefficient 0.889) to the temporal and amplitude characteristic of the experimental strains. The simulation model was then used to test the balance between ACL strain produced by quadriceps contraction and the reductions in ACL strain associated with the posterior braking force. When posterior forces that replicated in vivo conditions were applied, the peak ACL strain was reduced. These results suggest that the typical deceleration force that occurs during running to a single limb landing can substantially reduce the strain in the ACL relative to conditions associated with an isolated single limb landing from a vertical jump.

Anterior Cruciate Ligament↗
PubMed2005

Intrapartum repetitive maternal heart rate deceleration pattern simulating nonreassuring fetal status.

Uterine contraction-associated accelerations of the maternal heart rate are considered to reflect both a transient contraction-related increase in cardiac output and endogenous catecholamine secretion. Uterine contraction-associated decelerations of the maternal heart rate are rare and remain unexplained. A young multiparous patient with systemic lupus erythematosus (postrenal transplant for lupus nephropathy-related renal failure) presented in early labor at 39 weeks gestation, prior to elective repeat cesarean section. Intrapartum continuous maternal heart rate monitoring demonstrated repetitive uterine contraction associated decelerations of the maternal heart rate of 60 beats per minute, each lasting 2 minutes, simulating nonreassuring fetal status. Simultaneously depicted fetal heart rate was reassuring. This case demonstrates an unusual marked early intrapartum affect of uterine contractions upon the maternal heart rate. In addition, this case illustrates the potentially dangerous similarity of an intrapartum maternal heart rate to an abnormal fetal heart rate pattern, and emphasizes the importance of correct identification of the maternal and fetal heart rates, respectively.

Cardiotocography↗
PubMed1985

The effect of varied stride rate upon shank deceleration in running.

The purpose of this study was to determine the effects of systematic changes in stride rate and length at a given running speed on the peak shank deceleration (PSD) experienced during ground contact. Data were collected from 10 well-trained subjects as they ran on a treadmill at a pace of 3.8 m s-1 (7-min mile-1). Shank deceleration was measured by a lightweight accelerometer which was tightly attached over the distal medial tibia. High-speed films (200 Hz) were taken from a side view to quantify modifications in sagittal plane movement which might have accompanied the stride rate changes. Five stride rate conditions were randomly presented - 10% slower, 5% slower, normal, 5% faster and 10% faster. Average PSD was computed from 10 steps during each condition and testing was repeated on three different occasions. For each session, PSD observed for each condition was normalized to that observed at the normal stride rate in order to minimize the effects of variations in attachment of the accelerometer between and within subjects. The normalized PSD results at each stride rate tested were - normal = 1.0, 10% slower = 1.09, 5% slower = 1.03, 5% faster = 0.96 and 10% faster = 0.91. Significant differences were found between all these means except normal and 5% slower. The kinematic analysis revealed non-significant results for hip, knee and ankle joint angles at touchdown for the various stride rates. Application of the findings to existing analytical models indicated that, for a given running speed, peak impact forces in the ankle and knee joints decreased as stride rate increased.

Acceleration↗
PubMed1990

Blunt aortic trauma following deceleration in a seven year old.

Aortic injury following deceleration is an uncommon clinical entity in the pediatric population. Flexibility of the thoracic cage and marked tissue elasticity have been hypothesized as critical factors. Unfortunately, the scarcity of this phenomenon can lead to a lowered suspicion. We describe a case of blunt aortic injury following deceleration to raise the index of suspicion for this injury in the pediatric population.

Accidents, Traffic↗