Changes In Physiological Variables Research Articles

Dynamic changes of CBF, CMRO 2, OEF, CMR glc, CBV and ADC during neuronal suppression due to hypothermia

The objective of this study was to test that hypothermia improves the outcome of an acute ischemic stroke. In order to test the hypothesis that hypothermia (32 °C) improves the outcome by effecting the global cerebral reduction of oxygen consumption when the blood flow is already low, we investigated the sequential changes of physiological variables during hypothermia using positron emission tomography (PET) and diffusion-weighted magnetic resonance imaging (DW-MRI) in pigs. The cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO 2) decreased significantly to within 50% of the baseline in 3 and 5 h as functions of time, thereby lowering the viability threshold of the brain tissue. The oxygen extraction fraction (OEF) was significantly elevated to 140% of the baseline in 4 h, indicating a reduction in the driving pressure of oxygen delivery in response to the reduced metabolic need, and then it gradually returned so that it was once again level with the baseline. The cerebral metabolic rate of glucose (CMR glc), the cerebral blood volume (CBV), and apparent diffusion coefficient (ADC) decreased to 75%, 72% and 80% of the baseline after 6 h of hypothermia in response to the lowered metabolism for maintenance of cellular integrity, and the diminution of intracranial pressure. The results of ischemia show that rapid cooling of the brain to 32 °C significantly increases the survival of tissue at risk.

Acute Effects of Maternal Smoking on Fetal-Placental-Maternal System Hemodynamics

To study acute hemodynamic alterations in the fetal-placental maternal system immediately after maternal exposure to nicotine. This is a noncontrolled experimental study involving 21 pregnant smoking women, randomly selected, with uncomplicated pregnancies and without risk factors for fetal heart disease. Patients underwent ultrasound and fetal echocardiography before and after smoking a cigarette. They were asked to abstain from smoking for 12 hours before the study. The mean nicotine content of the cigarettes used in the study was 0.5mg of nicotine and 6mg of carbon monoxide. The average number of cigarettes smoked per a day prior to the study was 9.67. Gestational age ranged between 18 and 36 weeks. The mean maternal heart rate was elevated (P<0.001) as was the mean fetal heart rate (P=0.044). Maternal systolic blood pressure (P=0.004) and diastolic blood pressure (P=0.033) were also elevated after smoking. A decrease occurred in the systolic/diastolic ratio in the right uterine artery (P=0.014) and in the left uterine artery (P=0.039). The other hemodynamic variables remained unchanged. Cigarette smoking can cause changes in physiologic variables of fetal-placental circulation, but it does not change fetal cardiac function, in the dose of nicotine and its components used in this study. The decrease in systolic/diastolic ratio in the uterine arteries is probably related to a dose-dependent nicotine pattern.

Six-month patient outcomes in a preventive cardiology center.

More effective ways to improve lifestyle behaviors need to be developed. Two hundred forty adult patients at a preventive cardiology clinic were randomly assigned to receive either one or five sessions of behavioral instruction to improve cardiovascular risk behaviors. Results for 102 patients from 6-month follow-up data revealed few significant differences between the two groups. However, in the two groups combined, there were significant reductions in total calories, percent of calories from total fat, percent of calories from saturated and monounsaturated fat, and dietary cholesterol. Reductions were also found in systolic blood pressure, triglycerides, body mass index, and weight. In multiple regression analyses, changes in physiologic variables were primarily associated with baseline and demographic characteristics. Changes in total calories, percent of calories from polyunsaturated fat, and walking were predicted by changes in social support or knowledge. Although most patients improved, the intensity of behavior change instruction was not related to the amount of change in cardiovascular risk factors. (c) 2001 by CHF, Inc.

The effects on patient well‐being of music listening as a nursing intervention: a review of the literature

• A review of the therapeutic potential of music listening as a nursing intervention was performed.• It revealed that evidence from a variety of fields and clinical specialities existed, including the use of music in critical care environments, surgical settings, dental surgery applications, mental healthcare, pain control, and generally for the control of anxiety and promotion of relaxation.• Due to a number of reasons, including the variety of dependent variables that were measured and methodological issues such as the use of small sample sizes, it is difficult to form any firm conclusions.• Tentatively, the research seems to indicate that there often appear to be positive changes in physiological variables measured, although these changes are not consistent, nor are they always statistically significant.• More confidence can be placed in research that examines psychological variables, as a consistent positive impact on certain measures has been found.

Physiological responses to cycling for 60 minutes at maximal lactate steady state.

Changes in physiological variables during a 60-min continuous test at maximal lactate steady state (MLSS) were studied using highly conditioned cyclists (1 female and 9 males, aged 28.3 +/- 8.1 years). To determine power at MLSS, we tested at 8-min increments and interpolated the power corresponding to a blood lactate value of 4 mmol/L. During the subsequent 60-min exercise at MLSS, we observed a sequential increase of physiological parameters, in contrast to stable blood lactate. Heart rate drifted upward from beginning to end of exercise. This became statistically significant after 30 min. From 10-60 min of exercise, a change of +12.6 +/- 3.2 bpm was noted. Significant drift was seen after 30 min for the respiratory exchange ratio, after 40 min for the rate of perceived exertion using the Borg scale, and after 50 min for % VO(2)max/kg and minute ventilation. This slow component of VO(2)max may be the result of higher recruitment of type II fibers.

Endotoxin priming of the cyclooxygenase-2-thromboxane axis in isolated rat lungs.

Enhanced prostanoid generation has been implicated in vascular abnormalities occurring during endotoxemia and sepsis, and the lung is particularly prone to such events. Prostanoids are generated from arachidonic acid (AA) via cyclooxygenase (COX)-1 or -2, both isoenzymes recently demonstrated to be expressed in different lung cell types. Upregulation of COX may underlie the phenomenon that endotoxin [lipopolysaccharide (LPS)]-exposed lungs show markedly enhanced vasoconstrictor responses to secondarily applied stimuli (priming). Isolated rat lungs were perfused with a physiological salt buffer solution in the absence and presence of 1.5% rat plasma and exposed to different concentrations of LPS (1,000 or 10,000 ng/ml) during a 2-h priming period. No change in physiological variables was noted during this period, although enhanced baseline liberation of both thromboxane (Tx) A(2) and PGI(2) as well as of tumor necrosis factor (TNF)-alpha was evident compared with that in control lungs in the absence of LPS. LPS priming caused a significant elevation in AA-induced pulmonary arterial pressure, ventilation pressure, and lung weight gain. Concomitant increased levels of TxA(2) were found in the buffer perfusate. All changes were largely suppressed by three selective, structurally unrelated COX-2 inhibitors (NS-398, DUP-697, and SC-236) in both buffer- and buffer-plasma-perfused lungs. Anti-TNF-alpha neutralizing antibodies were ineffective under conditions of buffer perfusion. In the presence of plasma components, manyfold augmented TNF-alpha generation was noted, and anti-TNF-alpha antibodies significantly suppressed the increase in ventilation pressure but not in the vascular pressor response and lung edema formation. We conclude that the propensity of LPS-primed lungs to respond with enhanced vasoconstriction, edema formation, and bronchoconstriction to a secondarily applied stimulus proceeds nearly exclusively via COX-2 and increased Tx formation, with TNF-alpha generation being involved in the change in bronchomotor reactivity in the presence of plasma constituents. In context with recent immunohistological investigations, LPS-induced upregulation of the COX-2-thromboxane synthase axis in vascular and bronchial smooth muscle cells is suggested to underlie these events.

Late steroid therapy in primary acute lung injury.

To investigate the effect of steroid treatment in the late phase of primary acute lung injury (ALI) with special emphasis on pneumococcal pneumonia. Retrospective study. Multidisciplinary intensive care unit (ICU) in a university hospital. Of 31 patients with primary ALI requiring mechanical ventilation for more than 10 days, 16 were treated with methylprednisolone and 15 served as controls. Steroid and control groups were comparable regarding demographic data, APACHE II score, Multiple Organ Dysfunction Score (MODS), and PaO2/FiO2-ratio on admission to ICU. The mean start of steroid therapy was 9.7 days after establishment of respiratory failure, and values for control patients were registered on day 10. The PaO2/FiO2 ratio improved significantly within 3 days after the start of steroid therapy, and MODS and C-reactive protein decreased concurrently. No differences in mortality, in length of ICU stay, or in length of mechanical ventilation were detectable. In a subgroup analysis, for patients with Streptococcus pneumoniae pneumonia, beneficial change in physiological variables was evident. In patients with primary ALI, steroid therapy, started 10 days after the start of mechanical ventilation, improves gas exchange and is associated with a decrease in multiorgan dysfunction.

Randomised controlled trial of eutectic mixture of local anaesthetics cream for venepuncture in healthy preterm infants

AIMTo assess the safety and efficacy of EMLA cream (eutectic mixture of local anaesthetics) used to induce surface anaesthesia for venepuncture in healthy preterm infants.METHODSNineteen infants, median gestational age 31...

Signal Extraction Technology

Signal Extraction Technology

Signal Extraction Technology

Signal Extraction Technology

Circadian variation in sports performance.

Chronobiology is the science concerned with investigations of time-dependent changes in physiological variables. Circadian rhythms refer to variations that recur every 24 hours. Many physiological circadian rhythms at rest are endogenously controlled, and persist when an individual is isolated from environmental fluctuations. Unlike physiological variables, human performance cannot be monitored continuously in order to describe circadian rhythmicity. Experimental studies of the effect of circadian rhythms on performance need to be carefully designed in order to control for serial fatigue effects and to minimise disturbances in sleep. The detection of rhythmicity in performance variables is also highly influenced by the degree of test-retest repeatability of the measuring equipment. The majority of components of sports performance, e.g. flexibility, muscle strength, short term high power output, vary with time of day in a sinusoidal manner and peak in the early evening close to the daily maximum in body temperature. Psychological tests of short term memory, heart rate-based tests of physical fitness, and prolonged submaximal exercise performance carried out in hot conditions show peak times in the morning. Heart rate-based tests of work capacity appear to peak in the morning because the heart rate responses to exercise are minimal at this time of day. Post-lunch declines are evident with performance variables such as muscle strength, especially if measured frequently enough and sequentially within a 24-hour period to cause fatigue in individuals. More research work is needed to ascertain whether performance in tasks demanding fine motor control varies with time of day. Metabolic and respiratory rhythms are flattened when exercise becomes strenuous whilst the body temperature rhythm persists during maximal exercise. Higher work-rates are selected spontaneously in the early evening. At present, it is not known whether time of day influences the responses of a set training regimen (one in which the training stimulus does not vary with time of day) for endurance, strength, or the learning of motor skills. The normal circadian rhythms can be desynchronised following a flight across several time zones or a transfer to nocturnal work shifts. Although athletes show all the symptoms of 'jet lag' (increased fatigue, disturbed sleep and circadian rhythms), more research work is needed to identify the effects of transmeridian travel on the actual performances of elite sports competitors. Such investigations would need to be chronobiological, i.e. monitor performance at several times on several post-flight days, and take into account direction of travel, time of day of competition and the various performance components involved in a particular sport. Shiftwork interferes with participation in competitive sport, although there may be greater opportunities for shiftworkers to train in the hours of daylight for individual sports such as cycling and swimming. Studies should be conducted to ascertain whether shiftwork-mediated rhythm disturbances affect sports performance. Individual differences in performance rhythms are small but significant. Circadian rhythms are larger in amplitude in physically fit individuals than sedentary individuals. Athletes over 50 years of age tend to be higher in 'morningness', habitually scheduling relatively more training in the morning and selecting relatively higher work-rates during exercise compared with young athletes. These differences should be recognised by practitioners concerned with organising the habitual regimens of athletes.

C-fos Expression in Fetal and Maternal Suprachiasmatic Nucleus (SCN) in the Sheep

Circadian rhythms (CR) are changes in physiological variables with a period close to 24 h., synchronized by environment signals. The fetal sheep presents CR of plasma prolactin and cerebospinal fluid vasopressin at 135 days of gestational age (GA, term 147 days) In adults, CR are driven by the SCN. We investigated whether the maternal and fetal sheep SCN behave as circadian oscillators. To that effect, we measured expression of c-fos (marker of cellular activity) at 135 days's GA in the SCNs of 6 maternal sheep and their fetuses (n=9) at 1200h (day) and 2400h (night). The sheep. were sacrificed with pentobarbitone and the fetuses were delivered by hysterotomy. The maternal and fetal brain were perfused with 4% paraformaldehyde in phosphate buffer 0.1 M, pH 7.4. The brains were removed, post-fixed and the SCN cut in 40μm frozen sections. Alternated sections were stained with cresyl violet of with anti-Fos antibody (Oncogene Science), developed with avidin-biotin and diaminobenzidine. We measured the density of Fos immunoreactive (Fos +) neurons bys mm2 in the SCN. Result were mean ± SE; ANOVA.

Intrahospital transport of critically ill pediatric patients

To determine the frequency of adverse events during intrahospital transport; to determine the requirement of therapeutic interventions during transport; to test the hypothesis that adverse events that occur during intrahospital transport are due to the transport process itself; and to determine the factors that predict the occurrence of adverse events and the requirement of major therapeutic interventions during transport. A two-phase study in which data were prospectively collected. In phase I, we examined the occurrence rate of adverse events, the requirement for therapeutic interventions, and the factors that predicted adverse events and the requirement of therapeutic interventions. In phase II, we tested the hypothesis that adverse events during transport were due to the transport process itself. A 250-bed university children's hospital with a 50-bed intensive care unit (ICU). Phase I of the study consisted of one hundred and eighty intrahospital transports in 139 patients. These transports included patients who were transferred: a) to the ICU from the operating room, emergency department, or the general ward; b) from the ICU to the operating room; and c) from the ICU for diagnostic or therapeutic procedures. Phase II of the study consisted of 89 transports in 85 patients. None. Vital signs and oxygen saturation were measured before and during transport. In phase I, there were no adverse events in 23.9% of transports. There was a significant change in at least one physiologic variable in 71.7% of transports, and at least one equipment-related mishap in 10% of transports. At least one major intervention was performed in 13.9% of transports in response to physiologic deterioration or an equipment-related mishap. There were no arrests or deaths during transport. The requirement for a major procedure was 34.4% in mechanically ventilated patients vs. 9.5% in nonventilated patients. Logistic regression analysis showed that both pretransport Therapeutic Intervention Scoring System and the duration of transport were significantly associated with the requirement of a major intervention and physiologic deterioration, while only the duration of transport was associated with an equipment-related event. The age of the patient and the number of escorts accompanying the transport did not affect the frequency of adverse events. Before transport in phase II study patients, no patient became hypothermic, the changes in physiologic variables were always < 20%, and there was no change > or = 5% in oxygen saturation. Hypothermia occurred in 11.2% of transports. A > or = 20% change in heart rate (15.7%), blood pressure (21.3%), and respiratory rate (23.6%) was seen only during transport. A > 5% change in oxygen saturation (5.6%) was seen only during transport. Serious physiologic deterioration occurs during intrahospital transport of critically ill children. Severity of illness and the duration of transport are associated with the occurrence of adverse events during transport. The team composition and equipment required on transport must be commensurate with the pretransport severity of illness and the anticipated duration of transport.

Auditory steady-state response, upper facial EMG, EEG and heart rate as predictors of movement during isoflurane-nitrous oxide anaesthesia

We have studied the relationship between patient movement and changes in the auditory steady-state evoked potential, upper facial muscle electromyogram (FEMG), electroencephalographic-zero crossing frequency (EEG-ZCF) and heart rate during emergence from anaesthesia. Twelve healthy patients underwent surgery during stable isoflurane-nitrous oxide-oxygen anaesthesia without neuromuscular block. After skin closure, anaesthesia was discontinued abruptly while mechanical ventilation was continued until the patient moved. The magnitude of change in each physiological signal was evaluated in decibels (dB). Both the auditory steady state evoked potential and FEMG showed significant increases in amplitude during the last 5-min period before movement (6.1 and 10.7 dB, respectively). EEG-ZCF increased rapidly after anaesthesia was discontinued (2.5 dB) but there was no further increase in activity before movement. Heart rate did not change before movement. The use of the decibel transformation offers a promising method of displaying and interpreting changes in physiological variables during anaesthesia.

Rate‐responsive pacemakers and anaesthesia A consideration of possible implications

A new generation of pacemakers has been developed in recent years which adjust the pacing rate according to changes in physiological variables. The selected parameters are affected during physical activity that involves an increased heart rate in healthy humans. The variables include body movements, QT interval, breathing, temperature, myocardial contractility, oxygen saturation and changes in blood pH which may be influenced during general anaesthesia, and can lead to unphysiological, high, pacing rates. It is important to be familiar with the pacemaker and its functions before administration of anaesthesia in order to prevent complications. Rate-responsive pacemakers in such situations should be programmed to exclude the rate-responsive function.

An investigation of the partial reinforcement extinction effect in humans and corresponding changes in physiological variables

Human subject’s heart rate and skin conductance were monitored during periods of acquisition and extinction. During acquisition, subjects received either 100% or 50% reinforcement for correct responses. The behavioral data indicated that subjects exposed to partial reinforcement were more persistent than subjects exposed to continuous reinforcement. Significant increases in skin conductance were observed at the start of acquisition and extinction, but there were no differences between the two reinforcement groups. These data are reviewed with respect to Amsel’s frustration-mediation hypothesis of persistence.

Physiology of the circadian timing system: predictive versus reactive homeostasis.

Since Cannon first formulated the concept of homeostasis 60 years ago, attention has been focused on the corrective responses initiated after the steady state of the organism is perturbed. In this lecture it is argued that the concept of homeostasis should be extended to include the precisely timed mechanisms of the circadian (and circannual) timing system which enables organisms to predict when environmental challenges are most likely to occur. A mature understanding of homeostasis should encompass both "reactive" responses to changes in physiological variables which have already occurred and the "predictive" responses initiated in anticipation of predictably timed challenges. Such predictive responses have particular value because they enable physiological mechanisms to be utilized immediately, even if they involve a delay of several hours, by activating them at a suitable time in advance of a probable challenge. However, conflicts may often occur between predictions and reality. Examples from sleep-wake behavior, thermoregulation, blood volume homeostasis, and the regulation of potassium balance show that predictive responses often compromise the effectiveness of reactive homeostatic mechanisms even to the point of risking the survival of the organism. It must be concluded that the day-night cycle of the natural environment has played a fundamental role in shaping the evolutionary development of homeostatic mechanisms because of the dominating predictability of diurnal changes in illumination, temperature, food availability, and predator activity.

The time-course of alcohol induced changes in self-rating-scales of mood (author's transl)

Alcohol was administered in a dose of 0.77 g per kg bodyweight to 16 healthy male subjects in a cross-over-design. A study was made of a number of psychological and physiological variables to determine the modifications that accompany the alcohol-induced changes in the orienting response to an auditory stimulus. Five determinations were made at intervals following a dose of alcohol and five in a control session when no alcohol was given. The results obtained for the psychological variables (self-ratings of the intensity of intoxication and the degree of being startled by the first stimulus; and self-assessment of mood) show alcohol to have stimulant as well as depressant effects. Some of the variables show stimulant effects, mainly at the beginning of the absorption phase, whereas other variables show depressant effects, both in the absorption phase and the postabsorption phase. Changes in physiological variables (such as parameters of electrodermal activity and of the heart rate response) support these findings. The simultaneous presence of both stimulant and depressant effects is pointed out as well as the difficulties in describing these findings in terms of a unidimensional model of activation.