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At least 955 records · Page 53Linked to original sources
PubMed1998

Diastolic filling in human severe sepsis: an echocardiographic study.

OBJECTIVE: To determine if nonsurvivors have a more abnormal pattern of left ventricular relaxation than survivors with severe sepsis. DESIGN: Prospective, observational, cohort study. SETTING: Intensive care unit in a university-affiliated tertiary care hospital. PATIENTS: Twenty-four adults with severe sepsis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Baseline clinical and hemodynamic variables, Acute Physiology and Chronic Health Evaluation (APACHE) II scores and Doppler echocardiographic mitral inflow pattern (analyzed for normalized peak early filling rate [E/VTI, systolic volumes/sec], deceleration time [msec], and early to atrial filling velocity ratio [E/A]). There were seven deaths. The patients did not differ in baseline demographics, inotropic infusions, hemodynamic measurements or ventilatory settings or variables. Nonsurvivors had a more abnormal pattern of left ventricular relaxation (E/VTI, 4.7 [range 3.8 to 5.8] vs. 5.8 [range 3.8 to 8.9], p= .04; deceleration time, 235 [range 209 to 367] vs. 182 [range 155 to 255], p = .002). E/A showed a nonsignificant trend in the same direction (0.9 [range 0.8 to 1.6] vs. 1.2 [range 0.7 to 1.9], p = .12). In a multivariate analysis, deceleration time (p< .004) and APACHE II score (p < .02) were the only independent predictors of mortality. CONCLUSION: Severe sepsis nonsurvivors have a more abnormal echocardiographic pattern of left ventricular relaxation than survivors.

APACHE↗
PubMed1997

Insights into the mechanism of the nitroprusside-induced increase in cardiac output in failing hearts: an attempt at its prediction with Doppler echocardiography.

Increased left ventricular (LV) diastolic pressure is consistently decreased by the administration of nitroprusside; however, nitroprusside-induced changes in cardiac output (CO) vary among patients with failing hearts. Although the variation has been considered to be related to interindividual inhomogeneity of LV diastolic performance, nitroprusside-induced changes in CO are not predictable before drug administration in individual subjects. We attempted to clarify whether nitroprusside-induced changes in CO may be predicted by analysis of the mitral flow velocity pattern in failing hearts. LV diastolic pressure was increased by the combination of the decrease in LV function and the volume expansion, and 15 conditions with LV end-diastolic pressure (EDP) > or =15 mm Hg were obtained in 8 dogs. In each condition, pulsed Doppler mitral flow velocity patterns were recorded simultaneously with hemodynamic variables before and during intravenous nitroprusside infusion. After nitroprusside administration, LV systolic pressure and LVEDP decreased in all dogs, and CO increased in eight conditions but decreased in seven conditions. CO was more likely to increase with administration of nitroprusside, and its change was greater in the conditions in which deceleration time of the early diastolic filling wave before nitroprusside infusion was longer (r = 0.56, p<0.05, n = 15). Better correlation was obtained with multiple-regression analysis, using the deceleration time and peak filling velocity at atrial contraction (r = 0.67, p<0.05, n = 15). The deceleration time correlated with LV dynamic compliance (r = 0.66, p<0.01, n = 30). Analysis of mitral flow velocity patterns may be useful in predicting nitroprusside-induced changes in CO in failing hearts.

Animals↗
PubMed1980

Influence of occiput posterior position on the fetal heart rate pattern.

Fetal heart rate (FHR) recordings of 138 deliveries with the fetus in the occiput posterior position (OPP) are compared with recordings of 138 control fetuses in the occiput anterior position (OAP). The 2 groups are comparable in maternal age, parity, duration of first stage of labor, frequency of nerve blocks for analgesia, and incidence of cord complications. Variable decelerations were significantly more frequent and more pronounced in the OPP group than in the controls. The number of newborns with low Apgar scores was similar in both groups, despite a large number of pronounced decelerations in the OPP group. Possible mechanisms for the origin of variable decelerations in the occiput posterior position are discussed.

Female↗
PubMed2002

Cervical muscle dysfunction in chronic whiplash-associated disorder grade 2: the relevance of the trauma.

STUDY DESIGN: Surface electromyography measurements of the upper trapezius muscles were performed in patients with a chronic whiplash-associated disorder Grade 2 and those with nonspecific neck pain. OBJECTIVE: To determine the etiologic relation between acceleration-deceleration trauma and the presence of cervical muscle dysfunction in the chronic stage of whiplash-associated disorder. SUMMARY OF BACKGROUND INFORMATION: From a biopsychosocial perspective, the acceleration-deceleration trauma in patients with whiplash-associated disorder is not regarded as a cause of chronicity of neck pain, but rather as a risk factor triggering response systems that contribute to the maintenance of neck pain. One of the contributing factors is dysfunction of the cervical muscles. Considering the limited etiologic significance of the trauma, it is hypothesized that in patients with neck pain, there are no differences in muscle activation patterns between those with and those without a history of an acceleration-deceleration trauma. METHODS: Muscle activation patterns, expressed in normalized smooth rectified electromyography levels of the upper trapezius muscles, in patients with whiplash-associated disorder Grade 2 were compared with those of patients with nonspecific neck pain. The outcome parameters were the mean level of muscle activity before and after a physical exercise, the muscle reactivity in response to the exercise, and the time-dependent behavior of muscle activity after the exercise. RESULTS: There were no statistical significant differences in any of the outcome parameters between patients with whiplash-associated disorder Grade 2 and those with nonspecific neck pain. There was only a tendency of higher muscle reactivity in patients with whiplash-associated disorder Grade 2. CONCLUSIONS: It appears that the cervical muscle dysfunction in patients with chronic whiplash-associated disorder Grade 2 is not related to the specific trauma mechanism. Rather, cervical muscle dysfunction appears to be a general sign in diverse chronic neck pain syndromes.

Adult↗
PubMedDate not supplied

Leg tourniquets modify the on-kinetics of oxygen uptake during cycle exercise.

PURPOSE: Obstructive cardiovascular disease decelerates the on-kinetics of the body's oxygen uptake rate (VO2), either by reducing the O2 delivery or by degrading the exercise capacity of skeletal muscle. This study sought to determine whether obstructed blood flow decelerates the on-kinetics of VO2 by reducing O2 delivery. METHODS: Breath-by-breath measurements of VO2 were studied in eight healthy youth (age, 16.5 +/- 0.6 years) during two-legged square-wave exercise on the cycle ergometer. The square protocol was 5 minutes of unloaded exercise followed by an immediate increase to 5 minutes of loaded exercise at 78 +/- 5 W. In the experimental trials, thigh cuffs were inflated 30 seconds before the onset of loaded exercise. Control trials replicated the square-wave exercise with deflated thigh cuffs. RESULTS: The on-kinetics of VO2 were biphasic in the control trial and triphasic in the experimental trial. Experimental VO2 was significantly higher than control values in the final 90 seconds of exercise (P<.05). CONCLUSIONS: The difference between experimental and control VO2 was attributable to inflated thigh cuffs. At no time was experimental VO2 significantly lower than control VO2. The clinical implication of the results is that skeletal myopathy, not reduced blood flow, is essential for decelerating the VO2 on-kinetics of patients with obstructive vascular disease. The warranted conclusion is that square-wave exercise with inflated thigh cuffs stimulates a third phase of VO2 on-kinetics.

Adolescent↗
PubMed2004

Endothelin-1 and cardiac function in anthracycline-treated patients: a 1-year follow-up.

Anthracyclines are widely used chemotherapeutic agents in the treatment of lymphomas known to induce cardiomyopathy in more than 20% of patients. There is increasing experimental evidence that cardiac endothelial cells regulate cardiac performance and that endothelin-1 (ET-1) is a central substance in this regulatory mechanism. Twenty (seven male, aged 20-68 years) patients with Hodgkin's or non-Hodgkin's lymphoma treated with anthracycline were followed-up for 1 year. At baseline, after cessation of anthracycline treatment and at 1 year, the plasma ET-1 level was measured by enzyme-linked immunosorbent assay and cardiac function was estimated by echocardiographic measurement of the ejection fraction, the E/A ratio and the deceleration time. The ET-1 level decreased significantly after therapy (5.47 +/- 3.34 pg/mL versus 3.44 +/- 0.69 pg/mL, P < 0.02), and remained significant at 1 year (3.43 +/- 0.57 pg/mL, P < 0.008). The ejection fraction (57.80 +/- 4.73% versus 48.05 +/- 5.65%, P < 0.0001) and the E/A ratio (1.35 +/- 0.40 versus 1.15 +/- 0.40, P < 0.01) decreased, and the deceleration time (177.00 +/- 44.96 ms versus 209.50 +/- 66.25 ms, P < 0.04) increased significantly after therapy, showing that both systolic and diastolic left ventricular performance were deteriorated. Compared with the baseline, the same significant changes were found at 1 year (ejection fraction, 50.65 +/- 8.87%, P < 0.0007; E/A ratio, 1.10 +/- 0.34, P < 0.003; deceleration time, 223.25 +/- 46.85 ms, P < 0.002). The decrease of the ET-1 concentration might be a result of anthracyclines' direct cytotoxic effect and the decreasing level of ET-1 may play a role in the ejection fraction reduction. The results of 1-year follow-up suggest that, although anthracycline toxicity occurs shortly after treatment, the undesirable effect remains.

Adult↗
PubMed2004

A preliminary study of bottom care effects on premature infants' heart rate and oxygen saturation.

The purposes of this study were to explore (1) the effect of buttock care (BC) on premature infant heart rate (HR) and oxygen saturation (SpO(2)), and (2) the effect of buttock lifting angle during BCs on HR and SpO(2). The study used a repeated measure design. A convenience sample of 11 premature infants in the neonatal intensive care unit (NICU) of a medical center were studied during 30 BC events. The subjects were of a gestational age of less than and 37 weeks, and postnatal age of less than one month, without known congenital abnormalities and without having been treated with sedatives during the study. Infant HR and SpO(2) were measured at a 30-second interval 10 minutes before and during, and 15 minutes after BC. Maximal lifting angles of BCs during the procedure were recorded. Based on the infant's individual responses to BC, 63.3% of BCs induced an increase in HR and a decrease in SpO(2), defined as the change in HR and SpO(2) greater than two standard deviations from the baseline. In addition, 30% of BCs resulted in cardiac decelerations. The extent of the difference found in these change patterns in HR or SpO(2) were all significant (p <.01) and their mean recovery times were longer than 10 minutes. More HR acceleration events occurred as the BC lifting angle exceeded </= 30 degrees, and more HR deceleration events were found as the angle > 30 degrees (p =.035). Buttock care can have a significant impact on premature infant physiological stability. The BC lifting angle may play an important role in HR acceleration or deceleration. Careful observation before and after BC for premature infants is recommended.

Buttocks↗
PubMed2004

Traumatic hematuria in children can be evaluated as in adults.

PURPOSE: Controversy exists regarding whether children who present with blunt abdominal trauma and microhematuria should undergo renal imaging. Adult blunt trauma victims who present without gross hematuria, shock, or significant deceleration or other major associated injuries do not require renal imaging. This study was designed to evaluate whether the criteria for imaging the renal parenchyma in adult blunt trauma victims apply to the pediatric population. MATERIALS AND METHODS: We retrospectively reviewed 720 consecutive pediatric patients with suspected renal trauma to determine mechanism of injury, evaluation and treatment of subsequent injuries. RESULTS: Of the 720 trauma patients with hematuria (mean age 8 years) 334 underwent imaging, and 59 renal injuries were identified (grade I 32, grade II 6, grade III 8, grade IV 12, grade V 1). A total of 11 patients underwent exploration, resulting in 3 nephrectomies (grade IV 2, grade V 1). Renorrhaphy was not necessary and all other cases were managed conservatively. All patients with significant renal injuries experienced either gross hematuria, shock (systolic blood pressure less than 90 mm Hg) or a significant deceleration injury. CONCLUSIONS: The decision to image pediatric trauma cases based on the adult criteria of gross hematuria, shock and significant deceleration injury is appropriate. Among 720 pediatric cases of potential renal injury all would have been identified.

Adolescent↗
PubMed2004

Dynamics of drag and force distributions for projectile impact in a granular medium.

Our experiments and molecular dynamics simulations on a projectile penetrating a two-dimensional granular medium reveal that the mean deceleration of the projectile is constant and proportional to the impact velocity. Thus, the time taken for a projectile to decelerate to a stop is independent of its impact velocity. The simulations show that the probability distribution function of forces on grains is time independent during a projectile's deceleration in the medium. At all times the force distribution function decreases exponentially for large forces.

Journal Article↗
PubMed1979

Studies on protein folding, unfolding and fluctuations by computer simulation. IV. Hydrophobic interactions.

The theoretical model of proteins on the two-dimensional square lattice, introduced previously, is extended to include the hydrophobic interactions. Two proteins, whose native conformations have different folded patterns, are studied. Units in the protein chains are classified into polar units and nonpolar units. If there is a vacant lattice point next to a nonpolar unit, it is interpreted as being occupied by solvent water and the entropy of the system is assumed to decrease by a certain amount. Besides these hydrophobic free energies, the specific long-range interactions studied in previous papers are assumed to be operative in a protein chain. Equilibrium properties of the folding and unfolding transitions of the two proteins are found to be similar, even though one of them was predicted, based on the one globule model of the transitions, to unfold through a significant intermediate state (or at least to show a tendency toward such a behavior), when the hydrophobic interactions are strongly weighted. The failure of this prediction led to the development of a more refined model of transitions; a non-interacting local structure model. The hydrophobic interactions assumed here have a character of non-specific long-range interactions. Because of this character the hydrophobic interactions have the effect of decelerating the folding kinetics. The deceleration effect is less pronounced in one of the two proteins, whose native conformation is stabilized by many pairs of medium-range interactions. It is therefore inferred that the medium-range interactions have the power to cope with the decelerating effect of the non-specific hydrophobic interactions.

Computers↗
PubMed1976

Obstetric history and the heart-rate response of newborns to sound.

Two groups of clinically normal newborns, differing in the number of non-optimal factors in their obstetric history, were compared by measuring heart-rate response to a series of auditory stimuli. There was a significant difference between the groups in the direction of the average heart-rate response. The high risk" group showed more heart-rate acceleration and less deceleration compared with the "low-risk" group. The heart-rate responses were significantly related to the number of non-optimal obstetric conditions and to parity, but not to the maternal pre-delivery medication score. The greater the "risk" at birth, the less was the deceleration; the greater the maternal parity, the less did acceleration occur in response to auditory stimulation. There was no significant difference between the high-risk and low-rsik groups in heart-rate response trends over trials. Both groups showed reliable diminution of deceleration heart-rate response over trials.

Acoustic Stimulation↗
PubMed1989

Effects of a change in tone frequency on the habituated orienting response of the sleeping rat.

EEG arousal and heart rate responses to change in tone frequency following habituation training were studied during slow wave sleep in the rat. Rats were exposed to sequences of 12 tone pulses. Habituation stimuli (trials 1-7) had a frequency of 16 kHz. The frequency of the following (test) trials was changed to either 5, 12, 14, 22, or 40 kHz. Hearing level was held constant for all frequencies. Test trials were repeated five times to study rehabituation. The results indicate that heart rate deceleration is an indicator of the orienting reflex and its magnitude is a positive function of the amount of frequency change of the stimulus. Large frequency changes in either direction relative to the habituation frequency lead to re-evocation of the habituated EEG arousal and heart rate deceleration, with subsequent rehabituation. Small tone-frequency changes do not result in EEG arousal or heart rate deceleration responses that differ from the responses to the habituated frequency. Heart rate acceleration shows neither short-term habituation nor significant reaction to any of the test frequencies.

Animals↗
PubMed1989

Does the heart know what the eye sees? A cardiac/pupillometric analysis of motor preparation and response execution.

Autonomic response measures are well suited for the study of preparation because they allow the analysis of covert aspects of performance. This is illustrated by an experiment in which task-evoked cardiac and pupillary responses were compared during a disjunctive (Go/No Go) reaction task. The motoric demands of the task were varied by manipulating foreperiod length (4 and 8 s) and probability of response (25%, 50%, and 75%). Reaction time increased with foreperiod length and decreased with probability of response. The depth of anticipatory heart rate deceleration was affected only by foreperiod length. Analysis of the beats during, and directly preceding and following the imperative stimulus revealed that interbeat intervals increased with probability of responding and foreperiod duration. The effect of stimulus timing relative to the R-wave of the ECG was also analyzed. Early occurring stimuli prolonged the cycle of their occurrence more than late occurring stimuli. The cycle time effect was somewhat more pronounced for No Go stimuli than for Go stimuli. The subsequent cycle was shorter for early occurring stimuli compared to late stimuli. This effect was stronger for Go compared to No Go trials. Both Go and No Go reactions elicited significant pupil dilations. The No Go dilation peaked earlier than the Go dilation and its amplitude was smaller. Probability of responding affected the latency of the No Go dilation but not that of the Go dilation. The current results justify an interpretation of preparation in terms of a timing mechanism (indexed by heart rate deceleration during the foreperiod) and a mechanism allocating processing resources to stimulus encoding (indexed by cardiac slowing just prior to stimulus occurrence) and response preparation (indexed by continued cardiac deceleration and pupillary dilation).

Adult↗
PubMed1992

Beat-by-beat cardiac responses in normals and schizophrenics to events varying in conditional probability.

Anticipatory cardiac deceleration and poststimulus acceleration were studied in schizophrenic inpatients and controls during performance of a counting task. Reduced cardiac responding has been reported for schizophrenic patients for paradigms using relatively long intertrial intervals. During a relatively fast rate of stimulus presentation (3-s interstimulus interval), changes in cardiac interbeat interval were measured in 20 inpatient male chronic schizophrenics and 18 control volunteers. Subjects counted an infrequent tone which was always followed by at least one frequent tone. Control subjects showed significant anticipatory cardiac deceleration preceding the unpredictable tones, whereas patients did not show a differential cardiac deceleration. Control subjects showed poststimulus acceleration that was inversely proportional to the conditional probability of events, whereas patients exhibited greatly reduced poststimulus acceleration; patterns for both groups resembled findings previously observed for event-related potential and pupillary dilation data. Analysis of cardiac cycle time indicated significant variation in primary bradycardia associated with the delay between stimuli and immediately preceding R-waves in controls (replicating Lacey & Lacey, 1980), with only an immediate bradycardia at stimulus reception for patients regardless of cardiac cycle time. The data reinforce the notion that the manner in which information is used by schizophrenics, as reflected by cardiac responsivity, differs both quantitatively and qualitatively from that of controls.

Acoustic Stimulation↗
PubMed1977

Effects of spontaneous and artificial membrane rupture in labour upon fetal heart rate.

This study reports the effects of spontaneous rupture of membranes and artificial rupture of membranes on fetal heart rate patterns during labour in 87 normal and 25 complicated pregnancies. The incidence of early deceleration patterns following membrane rupture was 6.25 per cent during the first 15 minutes and 1.78 per cent after 45 minutes, regardless of whether the pregnancy was normal or complicated. It is concluded that rupture of membranes does not significantly increase the incidence of early deceleration patterns. However, the occurrence of other heart rate alterations such as late decelerations, loss of beat-to-beat variability, changes in base line and tachycardia, need to be investigated further in larger collaborative studies.

Extraembryonic Membranes↗
PubMedDate not supplied

Effect of cardiac resynchronization therapy on diastolic dysfunction as assessed by transthoracic two-dimensional Doppler echocardiography.

Cardiac resynchronization therapy (CRT) in patients with left ventricular systolic dysfunction and electrical dyssynchrony has been shown to improve morbidity and mortality. Improvement in diastolic dysfunction may contribute to these results. In this retrospective study, the authors assessed the effect of CRT on the E/A ratio and mitral valve deceleration time, which are commonly utilized parameters of left ventricular diastolic function. In 13 patients (aged 62 +/- 11.3 years), the E/A ratio increased from 1.17 +/- 0.58 to 1.49 +/- 0.66 (p = nonsignificant) and the mitral valve deceleration time increased from 178.48+/-57.71 milliseconds to 227.70 +/- 76.18 milliseconds (p = 0.054) post-CRT. In patients without mitral regurgitation, there was a significant increase in E/A ratio, from 1.22 +/- 0.4 to 1.86 +/- 0.47 (p = 0.025), but no significant change in the mitral valve deceleration time post-CRT was observed. These data suggest improvement in diastolic dysfunction as assessed by routine two-dimensional echocardiography in patients who receive CRT devices.

Adult↗
PubMed2002

Subclavian steal syndrome: can the blood pressure difference between arms predict the severity of steal?

BACKGROUND AND PURPOSE: A side-to-side difference in systolic brachial arterial blood pressure is a common finding in subclavian artery stenosis and is frequently used as a screening tool for subclavian steal syndrome (SSS). It was the goal of this retrospective study to investigate the relationship between different vertebral artery waveform types and the side-to-side difference in systolic blood pressure in patients with sonographically proven SSS. METHODS: The records of 1860 patients from the Neuroultrasound Laboratory between January 2000 and December 2000 were screened for the diagnosis of SSS in the final ultrasound report. In all patients, bilateral brachial arterial blood pressure was measured in a sitting position prior to the ultrasound examination. Vertebral artery waveforms were classified as (1) systolic deceleration, (2) alternating flow, and (3) complete reversal at rest. Blood pressure difference as calculated by normal-side blood pressure minus lesion-side blood pressure was compared with the 3 Doppler waveform types. RESULTS: SSS was found in 51 of 1860 (2.7%) ultrasonography studies of 49 patients (17 men, 32 women; mean age 65.3 +/- 10.5 years). Two patients (4%) had bilateral SSS. In 3 patients (6%), SSS was related to an innominate artery stenosis. Waveform analysis showed a completely reversed flow in 16 (31%), an alternating flow in 24 (47%), and a systolic deceleration in 11 (22%) cases. Systolic blood pressure difference was significantly higher in the complete reversal and alternating groups than in the systolic deceleration group (P < .001). CONCLUSION: Brachial systolic blood pressure difference is related to the severity of SSS and can be used as a screening tool for SSS. However, it performed better in severe steal than milder steal phenomena.

Aged↗
PubMed1987

Analysis of linear growth using a mathematical model. I. From birth to three years.

According to the "ICP-growth model" (ICP = Infancy, Childhood and Puberty components), linear growth during the first three years of life can be represented mathematically by a combination of a sharply decelerating Infancy component and a slowly decelerating Childhood component. Growth as measured by supine length is analysed for 191 longitudinally followed healthy infants using this model. The main aim is to devise ICP-based methods for biological and clinical applications. The onset of the Childhood component, which occurs some time between 6 and 12 months of age and is typically abrupt, can be detected on an individual basis. Its starting point probably defines the as yet unknown age at which growth hormone begins to exert a significant influence. The analyses have also revealed some new facets of linear growth. Most infants are found to have a non-linear decelerating Infancy component, free from seasonal influence. Age at onset of the Childhood component is earlier for girls than for boys and is positively related to the magnitude of the Infancy component. During the second year of life the variation in growth rate of the cohort increases. This fluctuation is found to be seasonal and greater for those with late onset of the Childhood component. During the third year of life the growth pattern is stabilized.

Age Factors↗