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Results for “physiologic variables”

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At least 739 records · Page 41Linked to original sources

PubMed1989

Does chromogranin a respond to short-term mild physiologic challenge?

Plasma chromogranin A, norepinephrine, epinephrine, blood pressure, and heart rate were examined in 51 unmedicated volunteers at rest, in response to postural stimulation, and in response to a mild behavioral stressor. The short-term stressors led to the expected increases in catecholamines, blood pressure, and heart rate; however, chromogranin A was not influenced by these stimuli. Chromogranin A levels were not higher in the hypertensives, nor were they correlated with any of the other physiological variables. Although chromogranin A is coreleased with catecholamines from the sympathoadrenomedullary system, it does not respond to modest short-term postural or psychological stimuli that simultaneously evoke changes in other variables relevant to the sympathetic nervous system.

Adult↗

PubMed1991

Cerebral Doppler studies in the fetus and newborn infant.

The goal of developing reliable commercial Doppler systems for measuring vessel diameter and velocity changes during the cardiac cycle appears to be near. Reaching this goal would enable us to obtain volume-flow information continuously. In animal experiments, continuous measurements of Doppler velocity, pressure, and flow add important insights into hemodynamic measurements. Incorporating Doppler methods in microcirculatory research could also provide a link between the microcirculatory and the macrocirculatory hemodynamic research. Although Doppler methods have been validated, Doppler findings in clinical research (using commercial systems) must be considered at best to reflect qualitative circulatory alterations indicating directions of change. Because of inherent technologic limitations and considerable intersubject and intrasubject variability, direct extrapolation of the numeric findings from one study to the other can lead to misleading conclusions. The Doppler results are also influenced by measurement conditions and equipment settings. However, Doppler-derived information can be used as an adjunct to clinical management in many of the diseases discussed above. As with any physiologic variable, serial measurements probably are of greater value than single measurements. With continued improvement in technology, Doppler methods hold promise of becoming an important adjunct in cerebral hemodynamic monitoring in perinatal-neonatal intensive care units.

Brain Diseases↗

PubMedDate not supplied

Fractals in physiology and medicine.

Nonlinear dynamics, a branch of the basic sciences that studies complex physical systems, offers novel approaches to long-standing problems of physiological form and function. The nonlinear concept of fractals, introduced and developed over the last decade, provides insights into the organization of complex structures such as the tracheobronchial tree and heart, as well as into the dynamics of healthy physiological variability. Alterations in fractal scaling may underlie a number of pathophysiological disturbances, including sudden cardiac death syndromes.

Algorithms↗

PubMed1983

The description and initial evaluation of an intensive live-in program in risk reduction.

Drawing upon the epidemiological, clinical, and behavioral studies suggesting the importance and feasibility of multidisciplinary efforts to reduce levels of risk variables for cardiovascular and other chronic diseases, a short-term live-in intervention program was developed. The program includes efforts to reduce smoking, weight, blood lipids, blood pressure, and stress through improving habits of exercise, nutrition, weight management, and stress control delivered to individuals with varying levels of health risk based on measurable biochemical and physiological variables and medical history. Major changes occurred during the 24-day program in 459 individuals enrolled in the program: 68% of smokers ceased, average cholesterol fell from 240 to 200 mg%, ideal body weight fell from 134 to 129% (82 to 79 kg), systolic blood pressure (BP) fell from 131 to 119 mm Hg, diastolic BP fell from 81 to 73 mm Hg. and reported feelings of general well-being increased. Greater changes were observed in the high-risk groups. Follow-up results at 1 year (48% of patients reporting) for those defined as high risk were a net decrease of 22 mg% in cholesterol, 7 mm Hg in systolic BP, 6 mm Hg in diastolic BP, and 6.8% of ideal body weight; 45% of those smoking at admission were still not smoking at 1 year (32% reporting). For those at lower risk there was a general return of risk levels toward baseline values.

Adult↗

PubMed2004

[Use of corneal pachymetry in ocular hypertension and chronic glaucoma].

Among the numerous corneal variables that may influence the determination of the "true" intraocular pressure (IOP) from applanation tonometry measurements and considering the still non conclusive scientific data on all the different aspects of this topic, the measurement of the central corneal thickness (CCT) may be an interesting diagnosis tool in hypertensive and glaucomatous patients. As far as the physiologic variability of the corneal thickness is considered, the measurement of CCT can potentially become an important confounding variable when measuring applanation tonometry in patients with ocular hypertension. It could also improve the management of patients with normal tension glaucoma and patients with suspicious optic discs. In these three groups, the measurement of CCT may be useful in determining if there is an artefactual error in the IOP measurement due to a thicker (too high) cornea or thinner (too low) cornea. Therefore the IOP corrected by CCT may change or influence a decision to initiate or modify treatment. CCT measurement has also proved to be crucial in patients who have undergone laser refractive surgery.

Chronic Disease↗

PubMed1993

How do we keep in time? Understanding human circadian rhythms.

1. Circadian rhythms tend to have a periodicity of 20-28 hours. Physiological variables such as body temperature, blood pressure, and intraocular pressure show fluctuations over each 24-hour period. 2. Circadian rhythms have an endogenous component produced by a 'clock' inside the body, and an exogenous component produced by our rhythmic lifestyle and environment. 3. An understanding of circadian rhythmicity is relevant to nurses, as variations in physiological parameters may have implications for patient care and treatment. 4. Discussion of circadian rhythmicity and its implications should be included in Project 2000 courses to increase understanding of how we 'keep time'.

Circadian Rhythm↗

PubMed2005

Multimodal brain monitoring in the neurological intensive care unit: where does continuous EEG fit in?

Continuous EEG (cEEG) is a vital component of patient monitoring in the neurologic intensive care unit, allowing the intensivist to diagnose nonconvulsive seizure activity. Though still in its infancy, Fourier-transformed cEEG data are also increasingly being used in ICUs to monitor global cerebral activity and cortical function. In conjunction with other components of multimodality neurologic monitoring, including intracranial pressure, cerebral blood flow, brain tissue oxygen tension monitoring, transcranial Doppler, and microdialysis monitoring, cEEG provides unique data regarding the electrical activity of the brain. The main challenge for clinicians and researchers will be to understand how these different aspects of multimodality monitoring relate to each other, and how physiologic variables such as blood pressure, osmolality, and temperature can be manipulated to optimize cerebral function and tissue survival in the setting of acute injury.

Brain↗

PubMed2005

Evaluation of oral administration of cortisol as a model for prenatal stress in pregnant sows.

OBJECTIVE: To design a treatment that increases plasma corticosteroid concentrations to mimic prenatal stress in pregnant sows. ANIMALS: 24 pregnant sows. PROCEDURE: Sows were assigned to 1 of 4 treatment groups; treatment consisted of twice-daily oral administration of a placebo or 20, 60, or 180 mg of hydrocortisone acetate (HCA)/sow from 7 to 11 weeks of gestation. Blood and saliva samples for determination of cortisol concentrations were obtained hourly on treatment days 3 and 25 and twice weekly for the remainder of the treatment period. The WBC, neutrophil, and lymphocyte counts and concentrations of interleukin (IL)-2 and IL-4 were determined on 4 days during treatment. Litter characteristics were recorded. RESULTS: Plasma and salivary cortisol concentrations were significantly increased in sows that received 60 or 180 mg of HCA (0.30 to 0.37 mg/kg and 0.95 to 1.15 mg/kg, respectively), compared with control sows. Except for the second day of treatment, the number of WBCs and the IL-2:IL-4 ratio did not differ among treatment groups. The neutrophil-to-lymphocyte ratio was significantly higher in sows that received 180 mg of HCA. Gestation duration was significantly shorter in sows that received 180 mg of HCA. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of 60 mg of HCA is suitable to increase plasma and salivary cortisol concentrations in pregnant sows in a controlled manner to concentrations comparable to concentrations detected after psychologic stressors. This model seems to be suitable to study the effects of increased maternal corticosteroid concentrations on young pig behavior, physiologic variables, and development.

Administration, Oral↗

PubMedDate not supplied

The assessment of potential for QT interval prolongation with new pharmaceuticals: impact on drug development.

Few examinations of a single physiological variable can end the development of a putative new pharmaceutical. Prolongation of the electrocardiographic QT interval is one of these tests. Recognizing the removal of several approved and widely used medicines, worldwide regulatory authorities have raised a heightened awareness on the submission of data surrounding the ventricular repolarization process. This review will discuss the anatomy and physiology surrounding the generation of the electrocardiographic QT interval and the consequences of its alteration. In addition, relevant models of preclinical safety and general guidelines for clinical examination in this area are discussed along with the impact of incorporating these assays into the drug development process.

Action Potentials↗

PubMed1999

Asthma severity: histopathologic correlations.

Asthma is a disorder characterized by inflammation of the airways which leads to variable airflow obstruction and symptoms of wheezing, chest tightness, cough, and dyspnea. Decisions concerning the type and intensity of therapy for asthma are generally based on the severity of the disease in a given individual. Guidelines for asthma management classify disease severity on the basis of symptom frequency and intensity as well as the degree of physiological impairment. Because treatment decisions are currently not based on markers of airway inflammation, it is important to know how well the underlying inflammatory pathology correlates with clinical and physiological variables and whether airway inflammation, if undertreated, leads to longer term adverse outcomes such as chronic persistent airway obstruction. Studies of asthma pathology reveal an inflammatory response characterized by infiltration of the airways with eosinophils, mast cells and lymphocytes; disruption of the epithelium; thickening of the reticular basement membrane; and increases in smooth muscle mass. These findings are qualitatively found in mild as well as severe asthmatics, and attempts to draw quantitative correlations between severity and intensity of inflammation have yielded discordant results. Although antiinflammatory therapy with corticosteroids decreases the intensity of the inflammation in association with improved clinical variables, the association is circumstantial and it is unclear which marker of inflammation correlates best with the severity of acute episodes or the severity of the disease in patients who are stable. Problems in relating the underlying pathology to disease severity are largely due to inadequate tissue sampling as bronchoscopically obtained specimens do not permit an evaluation of the outer airway wall or small airways and their surrounding parenchyma.

Journal Article↗

PubMed1992

On cognitive theories and causation in human behavior.

Modern theories of social behavior are based on the largely unquestioned assumption that human activity is determined by cognitive variables. Physiology, environment, and behavior are seen as peripheral to the understanding of cognition, seen as central to the understanding of human nature. This paper argues that these approaches to psychology are essentially metaphorical models of behavior, inadequate as explanatory theories, because they rely on untestable assumptions concerning the centrality to human behavior of hypothetical and unmeasurable cognitive variables. Their lack of precision does not allow for the testing of specific predictions. This paper argues that contemporary cognitive-behavioral and cognitive-social theories cannot be salvaged as explanatory models.

Cognitive Behavioral Therapy↗

PubMed1999

Estimating venous admixture using a physiological simulator.

Estimation of venous admixture in patients with impaired gas exchange allows monitoring of disease progression, efficacy of interventions and assessment of the optimal inspired oxygen fraction. A pulmonary artery catheter allows accurate measurement, although the associated risks preclude its use solely for estimation of venous admixture. Non-invasive methods require assumed values for physiological variables. Many of the required data (e.g. haemoglobin concentration (Hb), base excess, inspired oxygen fraction, arterial oxygen (PaO2) and carbon dioxide (PaCO2) tensions, temperature) are available routinely in the intensive therapy unit. We have compared a typical iso-shunt-style estimation of venous admixture (assuming Hb, base excess, PaCO2 and temperature), and estimation using the Nottingham physiology simulator (NPS), with measured data. When the arteriovenous oxygen content difference (CaO2-CvO2) was assumed to be 50 ml litre-1, the 95% limits of agreement (LA95%) for venous admixture using the NPS were -3.9 +/- 8.5% and using an iso-shunt-style calculation, -6.4 +/- 10.6%. CaO2-CvO2 was 41.1 ml litre-1 in the patients studied, consistent with previous studies in the critically ill. When CaO2-CvO2 was assumed to be 40 ml litre-1, LA95% values were 0.5 +/- 8.2% and -2.1 +/- 10.1%, respectively.

Carbon Dioxide↗

PubMed1999

Physiologic study of pressure point techniques used in the martial arts.

BACKGROUND: Study physiologic changes occurring during "knockouts" produced by application of pressure point techniques during martial arts demonstrations. METHODS EXPERIMENTAL DESIGN: prospective analysis of physiologic variables during and immediately following an acute event. SETTING: martial arts demonstration carried out at a medical center hospital. SUBJECTS: 12 normal volunteers participating in a martial arts demonstration. INTERVENTIONS: application of various pressure point techniques that have been observed to produce states of unresponsiveness in volunteers. MEASURES: continuous ECG and video/EEG monitoring with measurements of blood pressure and oxygen saturation. Qualitative analysis of EEG and ECG recordings and quantitative comparison of heart rate, blood pressure, and oxygen saturation measurements before during and after the period of induced unconsciousness. RESULTS: No significant changes in blood pressure, oxygen saturation, cardiac rate or rhythm, or electroencephalogram are noted during the knockouts produced by application of pressure point techniques. There was only variable inability for subjects to remember words spoken to them during the episode of apparent unresponsiveness. CONCLUSIONS: The mechanism for the state of unresponsiveness produced by application of pressure point techniques is not related to a significant cardiac or pulmonary process. There is no evidence of reduced cerebral blood flow during this time or of other dangerous physiologic changes. The exact mechanism for this phenomenon remains uncertain.

Adult↗

PubMed1986

Intersubject variability in corneal swelling response to anoxia.

A controlled, double-masked, randomized experiment was conducted on 9 human subjects, to determine whether there is an intersubject difference in the corneal swelling response to anoxia. A statistically significant intersubject variability was observed (P less than 0.001), with oedema ranging from a mean of 3.6% to 7.3% following 3 h exposure to humidified nitrogen gas (anoxia). This result supports the hypothesis of previous workers that the intersubject difference in the corneal oedema response to a thick HEMA "stress lens" is due to oxygen deprivation and not some other physiological variable resulting from lens wear.

Adult↗

PubMed1992

Investigating the role of angiotensin II in thirst: interactions between arterial pressure and the control of drinking.

Several lines of evidence suggest that angiotensin II plays a physiological role in the control of thirst. Establishing that, however, has been surprisingly difficult, given our current knowledge about the renin-angiotensin systems in the circulation and the brain and the variety of techniques available to measure and manipulate them. A major problem is that stimulating or blocking the renin-angiotensin system affects several physiological variables simultaneously. Since several of these variables also influence the controls of water intake directly or indirectly, the interpretation of the effect on drinking becomes more difficult. To illustrate the problem and recent developments, this paper describes some of the interactions between the effects of angiotensin II on arterial pressure and thirst, and it shows how they have contributed to the controversy over the physiological role of the peptide.

Angiotensin II↗

PubMed1987

Laser Doppler velocimetry in critically ill patients.

Cutaneous blood flow may be an indirect measure of circulatory function estimated by continuous, noninvasive laser Doppler velocimetry (LDV). It has been postulated that LDV may be a useful monitor of cardiac output changes. To test this hypothesis, LDV was evaluated in 67 critically ill adult patients with simultaneous measurements of cardiac index (CI) and other physiologic variables. Heated and unheated laser probes were utilized. The results indicate that LDV reflects acute directional changes of CI. Further, with the heated laser probe, the magnitude of acute CI change is reflected. However, there are gradual changes over time of LDV which may occur independently of CI or other monitored variables. Hence, absolute LDV values are not predictive of absolute CI values.

Adult↗

PubMed1999

Genetic, environmental and maternal influences on embryonic cardiac rhythms.

The relative roles of an animal's genetic constituents and environmental factors in influencing physiological variables such has heart rate have not been extensively investigated. This paper considers how heart rate patterns in the developing animal can be regulated, and how a combination of 'nature' and 'nurture' may interact to produce discrete patterns of heart rate change during development. The concept of the 'developmental trajectory' is evoked to generate a conceptual framework for how physiological development can be perturbed by environmental factors. Data are provided from three species showing how 'clutch-effects' (the fact that siblings perform physiologically much more similarly than non-siblings) can greatly influence the variance observed when collecting data on heart rate during development. Finally, so-called 'maternal effects', which are the influences on embryos of environmental experiences of the parents, are discussed as potentially confounding effects in the study of the genetic basis for physiological patterns of change during development.

Animals↗

PubMed1986

Man versus beast: pharmacokinetic scaling in mammals.

Land mammals range in size from the 3-g shrew to the 3000-kg elephant. Despite this 10(6) range in weight, most land mammals have similar anatomy, physiology, biochemistry, and cellular structure. This similarity has allowed interspecies scaling of physiologic properties such as heart rate, blood flow, blood volume, organ size, and longevity. The equation that is the basis for scaling physiologic properties among mammals is the power equation Y = aWb, where Y is the physiologic variable of interest, W is body weight, and log a is the y-intercept and b is the slope obtained from the plot of log Y versus log W. Animals commonly used in preclinical drug studies (i.e., mice, rats, rabbits, monkeys, and dogs) do not eliminate drugs at the same rate that humans eliminate drugs; small mammals usually eliminate drugs faster than large mammals. Since drug elimination is intimately associated with physiologic properties that are well described among species, it seems reasonable to surmise that drug elimination can be scaled among mammals. Analysis of drug pharmacokinetics in numerous species demonstrates that drug elimination among species is predictable and, in general, obeys the power equation Y = aWb. Early papers on interspecies pharmacokinetic scaling normalized the x- and y-axes to illustrate the superimpossibility of pharmacokinetic curves from different species. More recently, the x- and y-axes have been left in the common units of concentration and time, and individual pharmacokinetic variables have been adjusted to predict pharmacokinetic profiles in an untested species, usually humans.

Administration, Oral↗