SEARCH · PubMed Health

Results for “physiologic variables”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 451 records · Page 25Linked to original sources

PubMed1998

Assessment of middle-distance running performance in sub-elite young runners using energy cost of running.

The purpose of this study was to assess the validity of v(amax) as an indicator of middle-distance running performance in sub-elite young runners, v(amax) being defined as the quotient maximal oxygen uptake (VO2max) divided by the net energy cost of running (Cr) on a treadmill at a submaximal running velocity (280 m x min[-1]). The VO2max, ventilatory threshold, v(amax), and Cr were assessed in 39 young male sub-elite runners having only small variations in performance level. The relationship between each variable and running performance (at 1500 m, 3000 m, and 5000 m) was evaluated. A trend toward a negative correlation existed between Cr and performance although this was not significant. The VO2max and v(amax) were significantly related to performance. The v(amax) accounted for around 50% of the variability in performance whereas other physiological variables selected in this study were responsible, at best, for approximately 39%. The results presented in this study suggested that v(amax) was a useful indicator of middle-distance running performance in sub-elite young runners with similar performance levels as well as in top elite athletes.

Adolescent↗

PubMed1997

Declining gonadal function in elderly men.

Ageing in men is accompanied by a progressive decline of gonadal function with, in particular, a decline of total and free testosterone (T) plasma levels resulting in a significant proportion of elderly men over age 60 years presenting with subnormal T levels compared with the levels in young adults. A great interindividual variation in T levels is observed in elderly men, a variability explained in part by physiological variables and differences in life style, while associated acute or chronic diseases may accentuate the age-related decline of T levels. The progressive decrease of plasma T levels has been shown to result from both primary testicular changes and altered neuroendocrine regulation of Leydig cell function. At present, little is known about the clinical relevance of the relative hypoandrogenism of elderly men and there is an urgent need for more longitudinal studies, which may clarify a possible role of decreased T levels in the modulation of the clinical consequences of ageing in men. In view of the lack of relevant controlled clinical trials having careful assessment of the risks and benefits of androgen replacement therapy in elderly men, this treatment should be reserved for selected patients with clinically and biochemically manifest hypogonadism, after careful screening for contraindications.

Aged↗

PubMed1999

Effect of smoking abstinence on the subjective effects of caffeine.

Abstinence from smoking increases blood levels of caffeine and may potentiate the ability of caffeine to increase anxiety, insomnia, etc., during smoking cessation. The present study tested this hypothesis using a wider range of abstinence levels (0, 36 and 84 h), caffeine doses (0, 200 and 400 mg) and subjective effects (31 measures) than prior studies. Fourteen participants were studied using a randomized, within-subjects, double-blind design. Participants were tested on 31 subjective variables, two performance and two physiological variables on five occasions over the 3 h following dosing. Although abstinence and caffeine produced their prototypic effects, only one of the 35 interactions tested was significant and the magnitude of this interaction was small. Although our statistical power was limited, we conclude abstinence from smoking does not change the subjective effects of caffeine in the first days of abstinence. These results and those of prior studies suggest smokers who are trying to stop smoking do not need to change their caffeine intake.

Adolescent↗

PubMed2004

Variable ventilation improves perioperative lung function in patients undergoing abdominal aortic aneurysmectomy.

BACKGROUND: Optimizing perioperative mechanical ventilation remains a significant clinical challenge. Experimental models indicate that "noisy" or variable ventilation (VV)--return of physiologic variability to respiratory rate and tidal volume--improves lung function compared with monotonous control mode ventilation (CV). VV was compared with CV in patients undergoing abdominal aortic aneurysmectomy, a patient group known to be at risk of deteriorating lung function perioperatively. METHODS: After baseline measurements under general anesthesia (CV with a tidal volume of 10 ml/kg and a respiratory rate of 10 breaths/min), patients were randomized to continue CV or switch to VV (computer control of the ventilator at the same minute ventilation but with 376 combinations of respiratory rate and tidal volume). Lung function was measured hourly for the next 6 h during surgery and recovery. RESULTS: Forty-one patients for aneurysmectomy were studied. The characteristics of the patients in the two groups were similar. Repeated-measures analysis of variance (group x time interaction) revealed greater arterial oxygen partial pressure (P = 0.011), lower arterial carbon dioxide partial pressure (P = 0.012), lower dead space ventilation (P = 0.011), increased compliance (P = 0.049), and lower mean peak inspiratory pressure (P = 0.013) with VV. CONCLUSIONS: The VV mode of ventilation significantly improved lung function over CV in patients undergoing abdominal aortic aneurysmectomy.

Aged↗

PubMed2006

Redefining cancer-related asthenia-fatigue syndrome.

BACKGROUND: Asthenia fatigue syndrome (AFS) is a common symptom perceived by patients with cancer and consists of reported pathologic fatigue, poor endurance, and impaired motor and cognitive function. OBJECTIVE: The purpose of this study was to examine the relationship between a traditional measure of AFS, visual analogue scale (VAS) fatigue ratings, and a set of more objective functional and physiologic measures (Dietz oncology classification, C-reactive protein, serum albumin, hemoglobin, body mass index [BMI]), Motor Functional Independence Measure (FIM) Score, Cognitive FIM Score. We hypothesized a relationship could suggest the utility of alternative means of assessing and addressing AFS. METHODS: We retrospectively examined the records of 131 patients admitted to our facility for inpatient rehabilitation because of disability-causing cancer or its treatment. RESULTS: Of our sample, 94.7% (124 cases) indicated at least mild fatigue and 97.7% (128 cases) showed abnormal serum albumin, C-reactive protein, hemoglobin, or BMI. We used multiple regression analysis to examine the relationship between VAS fatigue ratings and the aforementioned set of functional and physiologic variables. The regression explained a significant proportion of the variability in VAS fatigue ratings (F = 2.25, df = 7,123, p = 0.03, R = 0.34, R(2) = 0.11). However, only Motor FIM Score accounted for a significant independent contribution to the variability in VAS fatigue ratings. CONCLUSION: The data indicate physiologic and functional variables may provide an alternative, objective, and reliable operational definition of AFS. Specifically, using Motor FIM Score, as a surrogate for VAS fatigue ratings may be used to measure the efficacy of AFS treatment.

Activities of Daily Living↗

PubMed1990

Correlations between psychological and physiological responses to acute flight phobia stress.

Exposure of phobic subjects to real-life psychological stress may induce a high level of anxiety and be better than laboratory experiments for studies of physiological responses to psychological stress in human research. Therefore, by introducing natural psychological stress, i.e. actual flying in subjects with flight phobia (n = 23), the present study aimed at testing the hypothesis that there is, during mental stress, a direct relationship between the level of anxiety and the responses in the physiological variables blood pressure, heart rate and plasma catecholamines. Plasma adrenaline, heart rate, blood pressure and perceived anxiety measured by three different scales increased highly significantly during flight whereas plasma noradrenaline did not change. No direct relationship was found between the physiological and psychological variables. Thus, the physiological responses to natural psychological stress in terms of phobic anxiety may be definite, but the way the responses are related is less clear.

Adult↗

PubMed2002

Simulate heart rate variability in different physiological conditions.

Heart rate variability is assumed to result from a multiplicative or cascade mechanism based on its multifractal property. Numerical results on the perturbation of the cascade are given to compare HRV under parasympathetic (PNS) and sympathetic (SNS) autonomic blockades. It was found that qualitative change of the HRV multifractal, which was observed in PNS blockade, is due to the change from a multiplicative to an additive mechanism.

Biophysical Phenomena↗

PubMed1992

The role of upper airway anatomy and physiology in obstructive sleep apnea.

Research efforts to date have determined that both anatomic and physiologic variables may contribute to the pathophysiology of OSA. Whether specific factors within either of these two categories will be shown to predominate remains to be seen. Surely, experience with sleep apnea patients teaches us that different variables are important in different OSA patients. However, even those patients who initially appear to have predominantly an anatomic or physiologic cause of their OSA often fail to respond to specific treatment. Treatment failure implies the following: (1) The initial impression of the importance of a given variable was wrong. This may happen in the patient who has a narrow transpalatal airway and fails to respond to uvulopalatopharyngoplasty. In this individual, physiologic variables such as pharyngeal collapsibility or periodic breathing may need to be addressed. Of course, the reverse may occur; patients may be treated pharmacologically for an assumed physiologic mechanism and important anatomic factors may have been overlooked. Our ability to differentiate the importance of these different variables is poor. Therefore, our diagnostic acumen needs further refinement. (2) Of course, it is likely that the proper diagnosis was made, but the therapy chosen was imperfect. In the area of anatomy, investigators are just beginning to try surgical approaches designed specifically for the pharyngeal site of obstruction. In other words, uvulopalatopharyngoplasty is not the best approach for everyone. In physiology, treatments beyond continuous positive airway pressure will be needed. It is hoped that advances in the pharmacology of sleep disorders will establish more convenient and successful therapies. It is likely that OSA is a heterogenous disease process. We must realize that a treatment that helps one patient may not be applicable to the next individual. Through a better understanding of the pathophysiology of OSA, better treatment modalities should be developed, resulting in improved quality of life for OSA patients.

Humans↗

PubMed1995

Extraction of discriminant features in post-cardiosurgical intensive care units.

A linear transformation, based on the Karhunen-Loève expansion, is applied to 13 physiological variables, measured in 200 surgical patients, in order to extract a limited number of features well representative of the differences between normal and high-risk classes of subjects. This transformation may be considered as a mapping from the primitive 13-dimensional space to a lower dimensional one, without severely reducing class separability. The efficacy of both transformed and primitive variables in the separation of normal and high-risk subjects is compared using the error probability, i.e. the probability that a patient is assigned to the wrong class. In particular, its upper bound is evaluated through the Kullback divergence and its estimate is computed, from the available samples, by applying a quadratic classifier. The results obtained show that only two transformed variables are able to present a divergence better than the most effective set of eight primitive variables. In agreement with the divergence criterion, the classifier provides a recognition error lower than 5% and greater than 13% when using the two best transformed and the two best primitive variables, respectively. Even though the new variables do not have a direct physiological meaning, this limitation has been partially overcome by calculating the correlation matrix between transformed and primitive variables. The results presented show that the first two transformed variables are strongly related to the most discriminant primitive ones (i.e. cardiac index, oxygen delivery and arterio-venous oxygen difference). In conclusion, the transformation of variables proposed appears to be extremely attractive for practical applications, since it allows recognition systems to be designed which exhibit both high performance and great simplicity.

Algorithms↗

PubMed1983

The differentiation of individual-specific, stimulus-specific, and motivation-specific response patterns in activation processes: an inquiry investigating their stability and possible importance in psychophysiology.

The role of specific response patterns obtained by means of psychophysiological activation and their temporal stability are meeting with an increasing interest in the literature because of a low correlation between psychophysiological variables and of possible implications with regard to pathogenetic mechanisms in psychosomatic disease. Two empirical studies are presented that were conducted under similar stress conditions (mental arithmetic, free speech, cold-pressor test, blood-taking) and have been monitoring similar activation variables (seven physiological and four or five psychological variables) - one of which using a large sample of 125 students, the other one consisting of 47 students, who were tested three times week- by-week. Findings reveal that substantial proportions of variance in the three-factorial ANOVA (subjects, situations, variables) may be considered on the basis of individual-specific (23-29% for physiological variables, 6-11% for psychological variables), stimulus-specific (5-19% for physiological variables, 1-11% for psychological variables), and motivation-specific (21% for physiological variables, 10% for psychological variables) response patterns. Five evaluation procedures on nominal, ordinal, and interval data levels as well as various definitions of similarity found in the reaction patterns are used in a comprehensive approach to the analysis of specificities. Estimation of variance components, global tests, and individual tests are applied. The results prove to be reliable and rather stable, at least over a period of several weeks. In total, about one fourth of the subjects show a stable individual-specific response pattern on physiological variables. The results are discussed with respect to data and sampling problems as well as to various methods of data analysis.

Adult↗

PubMed1992

Weighting according to location in computer-assisted glaucoma visual field analysis.

In recent years several aids for automated interpretation of visual field data have been suggested. We believed that incorporation of thorough knowledge of normal visual field variability would allow improvements in the performance of such aids since more attention would be paid to field results in areas with low physiological variability. Two visual field models for classification of fields in glaucoma based on comparisons of sensitivity values in the upper and lower hemifields and on analysis of test point clusters with diminished sensitivity were compared. Both models were constructed using logistic regression analysis in 101 normal eyes and 101 eyes with glaucoma. The first, more traditional model assumed Gaussian distributions of deviations from age-corrected normal thresholds and constant variability across the field (non-weighted model). The second model took into account empirically determined variability of pointwise threshold results and of cluster volumes in various visual field regions (weighted model). The two models were subsequently tested on an independent material of 163 normal eyes and 76 eyes with glaucoma. The weighted model gave significantly better classification of the fields in both materials. Accounting for physiological threshold variability can offer significant advantages in the construction of perimetric analysis aids for detection of glaucoma.

Adult↗

PubMed1996

Time series analysis in critical care monitoring.

Time series analysis techniques facilitate statistical analysis of variables in the course of time. Continuous monitoring of the critically ill offers an especially wide range of applications. Several studies from different work groups show that autoregression, integration, moving average (ARIMA) models help to identify pathologic outliers and trends in physiologic variables in surgical critical care. The effect of therapeutic interventions on physiologic target variables has been estimated with interrupted ARIMA models. The time series before the therapeutic intervention were compared to changes under intervention using the same model including an intervention regressor. In most patients clinically relevant therapeutic effects could be statistically identified. Similarly, noneffective therapeutic maneuvers could be detected early, and eventually changes in therapeutic strategy initiated. These techniques appear to be most appropriate with electronic online measurements at short time intervals, e.g., heart rate, invasive pressures, regional oxygenation. But even on the basis of short time series of critical care monitoring variables, ARIMA models can successfully be employed for the analysis of laboratory variables and of therapeutic interventions. Nevertheless, due to high demands for manpower and to statistical methodological limitations, the general use of this methodology in clinical practice apart from controlled clinical studies cannot be recommended today. Nevertheless, time series analysis techniques bear a great potential for clinical applications. Ongoing studies will in the future allow us to apply time series analyses to a wide group of clinical problems. In clinical practice, time series analyses support a more analytical and reproducible approach toward the evaluation of pathologic changes and therapeutic effects in the individual patient. Present research focuses on the development of automatic methods for time series analysis that allow instantaneous statistical analysis at the bedside and algorithms for multivariate time series analysis. This would offer an option to the healthcare professional for a more reliable evaluation of the individual treatment. Therefore, it appears rewarding to invest further efforts into the development of medical time series analysis techniques.

Critical Illness↗

PubMed1992

Taste and food preference changes across the course of pregnancy.

The present study investigates taste and specific food consumption changes across the course of pregnancy. These variables could potentially play a role in excess pregnancy-associated weight gains. Pregnant and postpartum women were asked to consume a series of everyday foods in the laboratory. Consumption and taste perception of each food were measured. In contrast to the self-report literature on cravings and aversions during pregnancy, which emphasizes changes in the first trimester, this study found that women in the second trimester consumed significantly more sweet food, but not salty or non-sweet/non-salty food, as compared with women at any other point in pregnancy. Subjects were restrained eaters, and so possibly refrained from daily consumption of excess sweet foods. This study suggests that psychological variables may interact with behavioral and physiological variables to control food preferences and eating in pregnancy.

Adult↗

PubMed1999

Comparison of exercise tests in French trotters under training track, racetrack and treadmill conditions.

Standardised exercise tests were performed at 2 different tracks and on an uninclined treadmill during the same week to determine the influence of exercise surface on different measured variables such as heart rate (HR), blood lactate concentration, packed cell volume, stride frequency, stride length, gait symmetry and regularity and on different derived physiological variables such as the speed at a HR of 200 beats/min (V200), the speed at a blood lactate concentration of 4 mmol/l (V4), the speed at a maximal HR (VHRmax). Five French Trotters, age 3 years, in training for 3 months prior to the test, performed 3 exercise tests on a training track (Test 1), a racetrack (Test 2) and an uninclined treadmill (Test 3). Test 1 utilised 3 steps each of 3 min at speeds of 490, 560 and 630 m/min. Tests 2 and 3 utilised the same speeds and a fourth step in which the horse was accelerated for 30 s to speed approaching maximal. No significant differences (P < 0.05) were found for the physiological and locomotor variables between the 2 tracks. In contrast, there was a significant difference (P < 0.05) for these variables between the tracks and the treadmill, horses showing lower heart rate and blood lactate response, reduced stride frequency and increased stride length and regularity on the uninclined treadmill. We concluded that this standardised exercise test was repeatable on various tracks even when the surface and geometry vary. In contrast, both physiological and locomotor variables were different when comparing the tracks with the uninclined treadmill.

Animals↗

PubMed1996

Anthropometric variables and muscle properties of Japanese female ballet dancers.

Physiological characteristics of japanese female classical ballet dancers were investigated in comparison with sedentary women of similar age (non-dancers). Subjects were 20 professional female ballet dancers with a mean age of 26.5 +/- 4.4 years (mean +/- SD) and 66 sedentary women with a mean age of 23.7 +/- 3.6 years. Dancers had been trained in ballet classes for 20.4 +/- 2.4 years and had no experience of regular exercises except dance training. Body mass and % body fat measured by under-water weighing method were significantly smaller in the dancers than in the non-dancers. For all extremities, percentage of the muscle in total cross-sectional area calculated by ultra sound apparatus was significantly larger and percentage of the adipose tissue in total cross-sectional area was significantly smaller in the dancers. The maximal isometric and isokinetic force of knee flexors and the maximal isometric force of dorsi flexors (MVC force) were significantly larger in the dancers when the values were divided by body mass of each subject. During 50 repetitions of maximal plantar flexion, the isometric force of the dancers was significantly larger in all repetitions except first and second reps, though no significant difference was observed in MVC force during plantar flexion. It was suggested that the significant differences between the dancers and the non-dancers in some physiological variables might be attributed to the characteristics of dance movements/training.

Adult↗

PubMed1991

Measurement of breathlessness during exercise in asthmatics. Predictor variables, reliability, and responsiveness.

The purpose of this study was to determine the predictor variables for breathlessness and to investigate the criteria of reliability and responsiveness for measuring breathlessness during progressive, incremental exercise on the cycle ergometer. We studied a heterogeneous group of patients with stable asthma (mean +/- SEM age, 46 +/- 4 yr) for four visits at weekly intervals. Predictor variables were determined at the first visit. Nine independent physiologic variables were obtained at each minute during exercise; the Borg rating of breathlessness (range 0 to 10) was used as the dependent variable. The regression model relating the physiologic parameters to the Borg rating of breathlessness was highly significant (model F = 43.4; p = 0.0001). Backward elimination selected the strongest predictors of the Borg rating: peak inspiratory flow (VI); tidal volume (VT)/FVC; frequency of respiration (f); and peak inspiratory mouth pressures (Pm). These four variables explained 63% of the variance in the rating of dyspnea. Each of the four variables exhibited a linear relationship with the Borg rating. Test-retest reliability was assessed by comparing results at the first and second visits. Individual slopes (except for VT/FVC) and intercepts for the four predictor variables versus Borg ratings were highly reliable. The slope for work intensity (watts) and Borg ratings, but not the intercept, was highly reliable. Responsiveness was evaluated by randomly administering inhaled methacholine or inhaled metaproterenol, alternately, at the third and fourth visits to induce acute changes in lung function before exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

LabVIEW: a software system for data acquisition, data analysis, and instrument control.

Computer-based data acquisition systems play an important role in clinical monitoring and in the development of new monitoring tools. LabVIEW (National Instruments, Austin, TX) is a data acquisition and programming environment that allows flexible acquisition and processing of analog and digital data. The main feature that distinguishes LabVIEW from other data acquisition programs is its highly modular graphical programming language, "G," and a large library of mathematical and statistical functions. The advantage of graphical programming is that the code is flexible, reusable, and self-documenting. Subroutines can be saved in a library and reused without modification in other programs. This dramatically reduces development time and enables researchers to develop or modify their own programs. LabVIEW uses a large amount of processing power and computer memory, thus requiring a powerful computer. A large-screen monitor is desirable when developing larger applications. LabVIEW is excellently suited for testing new monitoring paradigms, analysis algorithms, or user interfaces. The typical LabVIEW user is the researcher who wants to develop a new monitoring technique, a set of new (derived) variables by integrating signals from several existing patient monitors, closed-loop control of a physiological variable, or a physiological simulator.

Analog-Digital Conversion↗

PubMed1993

Combined continuous monitoring of systemic and cerebral oxygenation in acute brain injury: preliminary observations.

OBJECTIVE: To continuously evaluate the relationship between global systemic and cerebral oxygenation during temporary profound hypocapnia, which was attempted for prompt management of posttraumatic intracranial hypertension. DESIGN: Prospective, intervention study. SETTING: Neuroscience intensive care unit of a university hospital. PATIENTS: Young adults (n = 21) with acute brain trauma, undergoing routine monitoring of jugular bulb and pulmonary artery oxyhemoglobin saturations, along with other monitoring. MEASUREMENTS AND MAIN RESULTS: In 102 multivariate observations carried out on days 2 and 3 post-trauma, two new physiologic variables were assessed. These variables, systemic-cerebral oxygenation index and the systemic-cerebral ventilatory index, were evaluated in terms of baseline and post-hyperventilation changes. Overall, when intracranial pressure was largely increased, this increase was associated with decreased cerebral oxygen extraction ("luxury perfusion"), and high values of systemic-cerebral oxygenation index. In response to transient profound hypocapnia, the cerebral oxygen extraction normalized (increased), as did the systemic-cerebral oxygenation index (decreased), under most circumstances. The systemic-cerebral ventilatory index showed adequate systemic-cerebral response to hypocapnia in 92 (90.2%) observations. In the remaining ten (9.8%) observations, this response was considered inadequate, but it did not result in abnormal systemic or cerebral oxygenation parameters. CONCLUSIONS: In young adults with severe acute brain trauma who require prompt management of intracranial hypertension, transient profound hypocapnia is effective in lowering the intracranial pressure, as well as in offsetting the cerebral luxury perfusion, while improving or maintaining adequate systemic oxygenation. The systemic-cerebral oxygenation index and the systemic-cerebral ventilatory index are potentially useful, physiologically monitorable variables for the combined assessment of global systemic and cerebral oxygenation in a variety of areas involving physiologic and/or therapeutic approaches.

Acute Disease↗