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Results for “physiologic variables”

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At least 595 records · Page 33Linked to original sources

PubMed2006

Preliminary findings of proton magnetic resonance spectroscopy in occipital cortex during sleep deprivation.

Proton magnetic resonance spectroscopy ((1)H MRS) has revealed biochemical alterations in various psychiatric disorders. Changes in brain metabolites may be caused not only by the disease's progression or response to treatment, but also by physiological variability. The aim of this study was to use (1)H MRS to assess the effects of specific short-term physiological states on major metabolites. Eight healthy women underwent (1)H MRS at the beginning and end of a 40-h period of sleep deprivation. The ratios of N-acetyl-aspartate (NAA), total creatine (tCr), and choline-containing compounds (Cho) to water (H(2)O) were determined from the occipital cortex during both baseline and photic stimulation conditions. During sleep deprivation, NAA/H(2)O decreased by 7% and Cho/H(2)O by 12%. Photic stimulation had no effect on the measured metabolites in the alert state, but in the sleep-deprived state the level of Cho/H(2)O increased during neuronal activation. The results suggest that NAA/H(2)O and Cho/H(2)O may depend on the state of alertness.

Adult↗

PubMed1996

Spectral analysis of short term R-Tapex interval variability during sinus rhythm and fixed atrial rate.

Analysis of heart rate variability has been proven useful in stratifying post myocardial patients at risk and in evaluating autonomic dysfunction. Recently augmented inter-lead variability of the QT interval has been associated with increased mortality as a result of arrhythmia and proposed as a marker of dispersion of ventricular repolarization. As the duration of the QT interval is largely dependent upon the length of the preceding cardiac cycle it is tempting to analyse whether neural mechanisms might also directly exert additional modulation. Using autoregressive algorithms we therefore analysed RR and R-Tapex interval variabilities in 15 normal subjects during sinus rhythm and in six patients with a fixed atrial rate. In controls mean R-Tapex interval and variance measured on the vector magnitude were, respectively, 245 +/- 6 ms and 5.1 +/- 0.7 ms2. Spectral analysis of R-Tapex indicated the presence of two spectral components which corresponded to the low and high frequency components of heart rate variability. In R-Tapex variability, high frequency (44 +/- 4 nu) was predominant over low frequency (29 +/- 4 nu). During controlled respiration, a manoeuvre associated with enhanced vagal modulation of sinus node, there was a further increase in high frequency (58 +/- 4 nu) whereas during tilt the low frequency component of R-Tapex variability became predominant (57 +/- 6 nu). In patients with a fixed atrial rate, variance was extremely low (3 +/- 0.9 ms2) and only a respiration-related high frequency component was recognizable in spectral analysis of RR and R-Tapex variabilities. This component was likely to depend upon mechanically induced changes in cardiac vector orientation. These data indicate that during sinus rhythm short-term R-Tapex interval variability is characterized by the same rhythmical components present in RR variability. However, the presence of a very low variance and of only a high frequency component in patients in whom the physiological variability of sinus node is abolished by atrial pacing. suggests that neural modulatory mechanisms do not exert a direct effect on the length of the R-Tapex interval.

Adult↗

PubMed2006

Performance of the Yo-Yo Intermittent Recovery Test by elite professional and semiprofessional rugby league players.

The purpose of this study was to assess the performance of elite rugby league players by using the Yo-Yo Intermittent Recovery Test. Fifty players were recruited to the study during preseason and were classified as professional (P) or semiprofessional (SP). All performed the level 1 Yo-Yo Intermittent Recovery Test. Total distance achieved was taken as the performance index. Physiological (heart rate and blood lactate) correlates of performance were also assessed. Results showed that P players achieved a greater total distance than did SP players (p > 0.05). End heart rates did not differ significantly (p < 0.05). Semiprofessional players had significantly lower end blood lactate values than did P players (p < 0.05). Relationships between test performance and physiological variables were not significant (p > 0.05). These findings showed that P and SP players performed the test at a comparable level. Physiological indices indicated that performance was near maximal. The test is considered a useful measure of intermittent high-intensity performance for rugby league players.

Adult↗

PubMed1999

Change in quality of life after lung volume reduction surgery.

BACKGROUND: Lung volume reduction surgery has been reintroduced for treatment of severe emphysema. Goals of this surgery are to decrease dyspnea, increase exercise tolerance, and improve quality of life. OBJECTIVES: To describe the effect of lung volume reduction surgery on overall quality of life, disease severity, dyspnea, and functional status during the first 12 months after surgery. METHODS: Data were collected for 20 patients (mean age, 63 years; 15 men) before and 3, 6, and 12 months after lung volume reduction surgery. Disease severity was determined by percentage of forced expiratory volume in 1 second (compared with established norms); functional status, by a 6-minute walk test; dyspnea, by scores on a visual analog scale; and overall quality of life, by scores on the Quality of Life Scale. RESULTS: Scores on the Quality of Life Scale and distance walked increased significantly after surgery, and these increases were maintained at 6 and 12 months, respectively. Percentage of forced expiratory volume in 1 second increased significantly 3 months after surgery, but changes at 6 and 12 months were not significant. Changes in dyspnea ratings were not significant. No pattern of correlations among study variables was significant. CONCLUSIONS: Quality of life and functional status are improved after lung volume reduction surgery. Because none of the physiological variables were related to changes in quality of life, alternative explanations for these improvements must be explored in future studies.

Analysis of Variance↗

PubMed1999

Music: an intervention for pain during chest tube removal after open heart surgery.

BACKGROUND: Pain associated with chest tube removal is a major problem for patients who undergo open heart surgery. Because this pain is short-lived, timing the administration of pharmacological agents for pain relief is difficult and is therefore done inconsistently. OBJECTIVE: To examine the effect of music as an intervention for pain relief during chest tube removal after open heart surgery. METHODS: In an experimental design, 156 subjects (mean age, 66 years; 69% men) were randomly assigned to 1 of 3 groups: control, white noise, or music. All subjects preselected the type of music they preferred hearing. Ten minutes before the chest tube was removed, the patient's heart rate and blood pressure were measured, the patient rated pain intensity by using a numeric rating scale, and the prerecorded audiotape of music was begun. The patients rated their pain again immediately after chest tube removal and 15 minutes later. Physiological variables were assessed every 5 minutes until 15 minutes after the chest tubes were removed. RESULTS: Self-reported pain intensity, physiological responses, and narcotic intake after chest tube removal did not differ significantly among the 3 groups. CONCLUSIONS: Although the findings were not statistically significant, most subjects enjoyed listening to the music, and therefore the use of music as an adjuvant to other therapies may be an appropriate nursing intervention.

Adult↗

PubMed2004

Relationships among attention deficit hyperactivity disorder, induced labor, and selected physiological and demographic variables.

We investigated whether events associated with physiological maternal and fetal stress during the birth process were associated with diagnosis of attention deficit hyperactivity disorder (ADHD), alone or in combination with demographic variables. We gathered data through maternal responses to a 17-item questionnaire. Sex, mother's educational level, mother's age at delivery, interval between the beginning of labor and birth, and presence or absence of complications during the delivery process accounted for 42% of the variance in the diagnostic (ADHD) category. The model correctly classified 87% of the non-ADHD group (n = 90) and 48% of the children with ADHD (n = 40), for an overall correct classification rate of 75%. A differential effect for sex was indicated, but a low number of females in the diagnostic category limited meaningful analysis. Maternal age at delivery and maternal education level emerged as the strongest predictors, with the exception of sex, of ADHD in the full model.

Age Factors↗

PubMed1999

Inhospital cardiac arrest: pre-event variables and nursing response.

This retrospective study examined the medical records of 100 patients who experienced an in-hospital cardiopulmonary arrest. The purposes of this study were to identify pre-arrest physiologic changes that may have occurred in the patient and to determine whether physician notification time, physiologic variables, patient location, and the presence of an electrocardiogram (ECG) monitor before the arrest affected the resuscitation outcome. The results showed that assessment variances were present in most patients before the arrest and also were recognized by the nursing staff. Implications for practice include formation of quality improvement screening tools to assess the patient's pre-arrest status, development of competency tests that include scenarios involving changes in a patient's physiologic parameters, staff education, and evaluation of current nursing policies for obtaining vital signs and assessments.

Adult↗

PubMed1994

Stability of cardiovascular responses across subjects and situations: a systematic approach.

This study describes the reproducibility of behaviorally elicited cardiovascular response patterns, 111 subjects were studied over a 1-year interval. Physiological variables recorded were heart rate, systolic and diastolic blood pressure, and respiratory rate. Test-retest stability coefficients were calculated and compared with the results of a study with a 3-day interval between test sessions. The physiological data are depicted in a four-dimensional data box (subjects, situations, replications, variables), and the variance components of the factors and their interactions are estimated. Some of the interaction components are associated with specificity principles and with temporal stability. To comprehensively describe special aspects of stability, measures for stability were generated (concerning subjects, situations, or both), adopting basic ideas from the covariance partitioning approach. The stability measures were compared with simple test-retest reliability coefficients and with generalizability coefficients, and systematic relationships between the stability measures are discussed.

Adolescent↗

PubMed2006

Mathematical model for the estimation of hemodynamic and oxygenation variables by tissue spectroscopy.

This article presents a quasistatic, compartmental model of tissue-level hemodynamics and oxygenation that leads to a set of formulas, which is suitable to calculate important physiological variables from the mean tissue concentration and saturation of hemoglobin, measured by tissue spectroscopy. Dimensioned quantities are represented relative to their baseline value in the equations (relative value = perturbed/baseline). All model parameters are non-dimensional. The model is based and extends on a number of previous works: previous models of similar aim and scope are consolidated, and every critical assumptions and approximations are treated explicitly; extensions include for example the incorporation of the Fahraeus-effect and the separate estimation of the volume changes of the arterial and the venous compartments. The information content of spectroscopic data alone is shown to be valuable, but limited: the relative venous volume, the oxygen extraction fraction and the relative cellulovascular coupling (defined as the ratio of blood flow and oxygen consumption) can be calculated from these data, if the alterations in arterial blood volume are negligible. The number of variables estimated by the derived formulas can be increased if local blood flow is measured simultaneously: in this case, the relative arterial and venous volume and resistance, the oxygen extraction fraction, and the relative oxygen consumption can be determined. Given that this model considers arterial blood pressure, saturation and hematocrit as its inputs, when measured, the model becomes applicable in such conditions as hyper- or hypotension, hypoxic hypoxia, hemodilution and hemorrhage, where these variables do change. The estimation of the changes in arterial resistance can be applied to estimate the extent of an autoregulatory response.

Blood Pressure↗

PubMed2006

[Circadian rhythm variability in arterial blood pressure].

Summary Chrono-biology consists of the scientific study of biological rhythms and their underlying mechanisms. This study is based on the certainty that for many physiological variables these exists a reproducible pattern in the time of maximum and minimum values. The study of circadian rhythm variations on biological parameters which affect numerous pathologies permits one to foresee rhythmical cycles and to synchronize pharmacological rules to make it possible to obtain improvements in patients' responses. Knowing the circadian rhythm in hypertensive patients brings data related to the prognosis and is a basic tool to introduce the concept of a chronological administration of medicines in providing antihypertensive treatment; this is chronotherapy.

Blood Pressure Monitoring, Ambulatory↗

PubMedDate not supplied

The effects of music interventions on anxiety in the patient after coronary artery bypass grafting.

OBJECTIVE: To examine the influence during the early postoperative period of selected nursing interventions on mood and anxiety of patients undergoing heart surgery. DESIGN: Prospective, repeated measures, quasiexperimental, random assignment. SETTING: The cardiovascular intensive care and progressive care units of a midwestern community hospital were used as the setting for this study. PATIENTS: Ninety-six patients who underwent elective, heart bypass surgery; the mean age of the subjects was 67 years, with an age range of 37 to 84 years. Most subjects were men (n = 65, 68%). OUTCOME MEASURES: Physiologic measures of anxiety and mood include blood pressure and heart rate. Additional measures included the use of Spielberger's state-trait anxiety inventory (STAI) and patient verbal ratings of both mood and anxiety with use of a numeric rating scale (NRS). INTERVENTION: Patients were randomly assigned to one of three groups: (1) music therapy, (2) music-video therapy, or (3) scheduled rest group. Subjects in the groups received their assigned 30-minute intervention at two episodes on postoperative days 2 and 3. Subjects had physiologic measures of blood pressure and heart rate measured immediately before the intervention and at 10-minute intervals throughout the intervention. Mood and anxiety were evaluated by having subjects use a NRS (i.e., 0 to 10) to give rating of mood and anxiety immediately before and after each session. Anxiety was further measured with the STAI. A baseline measure of STAI was taken before surgery; patients also completed the "state" anxiety tool before the intervention session on postoperative day 2 and on completion of the session on postoperative day 3. RESULTS: With use of an analysis of covariance (ANCOVA), subjects' mood ratings showed significant improvement in mood among subjects in the "music intervention" group after the second intervention when controlling for the preintervention rating of mood, F(2, 87) = 4.33, p = 0.016. However, no significant differences were reported for anxiety ratings as measured by the NRS and state anxiety instruments. With use of repeated measures analysis of variance (ANOVA), there were no significant interactions between the intervention groups and time for any of the physiologic variables. However, there were significant main effects over time for heart rate and systolic and diastolic blood pressure, which indicated a generalized physiologic relaxation response. CONCLUSIONS: Although none of the three interventions was overwhelmingly superior, the overall response by all intervention groups demonstrated a generalized relaxation response. It is also important to note that there was reduced anxiety and improved mood within all three groups.

Adult↗

PubMedDate not supplied

Serum levels of prolactin, growth hormone, and cortisol in burn patients: correlations with severity of burn, serum cytokine levels, and fatality.

In this study, we measured serum prolactin (PRL), cortisol, growth hormone, interleukin (IL)-1beta, IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor-alpha in patients admitted with small-to-moderate burn injuries. Serum samples were obtained at the time of admission from 49 adult male burn patients with ages ranging from 18 to 91 years and TBSA ranging from 0.001 to 60%. The levels of serum PRL, IL-8, IL-6, and IL-1beta correlated positively with the TBSA, whereas only serum IL-8 levels correlated positively with fatality. Each of these factors were increased at least 2-fold at the higher burn severity. Not surprisingly, there was a large degree of variability in the hormone and cytokine levels in this patient population, which presumably reflects individual levels of stress, as well as other physiological variables. We also studied relationships between serum hormone levels and serum cytokine levels in this context. Linear regression analysis revealed a significant positive correlation between the serum PRL level and the levels of IL-10, IL-6, and IL-8. These results indicate that PRL responds to burn injury at early time points and that a subset of cytokines are involved in the early response to burn injury.

Adolescent↗

PubMed2006

The presence of emphysema further impairs physiologic function in patients with idiopathic pulmonary fibrosis.

BACKGROUND: Emphysema, especially in the upper lobes, is frequently observed in association with idiopathic pulmonary fibrosis (IPF). However, the combination of emphysema plus IPF has received little attention. OBJECTIVE: To investigate the additional functional impairment from emphysema in IPF patients. METHODS: Twenty-one patients (mean age 66 y, 20 men) (Group I) who had both IPF (mean 35% of total lung volume) and emphysema (mean 14% of total lung volume) were compared to a group of 21 subjects who had IPF but no emphysema (Group II). The groups were matched for (among other criteria) the total extent of disease. Pulmonary function tests, Medical Research Council dyspnea score, 6-min walk test, and radiographic extents of both IPF and emphysema were obtained for each patient. The Composite Physiologic Index was calculated. In the total population (n = 42), the independent contributions of IPF and emphysema to several physiologic variables were investigated by using stepwise multiple regression analysis. RESULTS: Despite the limited extent of emphysema, Groups I and II had similar physiologic impairment. Only residual volume and total lung capacity were significantly higher in Group I. According to stepwise multiple regression analysis, the extent of IPF and either the presence or the extent of emphysema in the total population were independent and significant predictors of dyspnea score, 6-min walk test, P(aO2), forced expiratory volume in the first second (FEV(1)), forced vital capacity (FVC), FEV1/FVC, the diffusing capacity of the lung for carbon monoxide, carbon monoxide diffusing capacity adjusted for alveolar volume (gas-transfer coefficient), and residual volume. The Composite Physiologic Index was closely related to the extent of IPF (r = 0.65, p < 0.0001) and to the dyspnea score (rho = 0.59, p < 0.0001). CONCLUSIONS: In former smokers with IPF, the presence and the extent of emphysema have a profound influence on physiologic function in terms of both further impairment and confounding effects.

Adult↗

PubMed1986

[Psychophysiological reactivity in relation to type A behavior].

This relationship was examined in 77 healthy men. Stress reactivity in the 26 Type A was not more increased than in the 12 Type B men for the cardiovascular variables (heart rate, pulse transit time, finger vasoconstriction and blood pressure), but for body movement, EMG, respiration frequency. Body movement and EMG were the best predictable physiological variables for the Type A behavior pattern, and this mainly in the two speech tests.

Adult↗

PubMed2006

Effects of gender on physiological responses during submaximal exercise and recovery.

PURPOSE: This investigation was conducted to compare the physiological responses of men and women, both during and following an exercise bout at the same relative submaximal intensity. METHODS: Ten untrained men (20.7+/-0.5 yr, 178.4+/-2.3 cm, 79.6+/-4.8 kg; mean+/-SE) and 10 untrained women (20.3+/-0.3 yr, 163.8+/-2.2 cm, 59.5+/-2.1 kg) cycled for 30 min at 60-65% of their predetermined peak oxygen uptake. Physiological variables were measured before exercise, at 15 and 30 min of exercise, and at 5 and 15 min postexercise. For each variable of interest, a two-way repeated-measures of analysis was used to assess the main effects of gender and time, along with potential interactive effects. RESULTS: Our data revealed that for many variables including HR, relative HR (% peak value), mean arterial pressure, and rectal temperature, men and women responded similarly both during exercise and throughout the recovery period. In contrast, significant (P<or=0.05) gender-related differences were noted for RER, plasma lactate, systolic blood pressure, and plasma volume shifts. In each of those variables, values displayed by men during exercise were significantly greater than those observed among women. However, with the exception of plasma lactate, those gender-related differences did not persist into recovery. CONCLUSION: During exercise of the same relative submaximal intensity, some physiological parameters responded likewise in young men and young women, whereas others did not. Among those variables that demonstrated significant gender-related differences, all but one (plasma lactate) were obscured within 5 min of postexercise recovery.

Adult↗

PubMed2003

The effect of metabolic fuel availability on thermoregulation and torpor in a marsupial hibernator.

The physiological signal for torpor initiation appears to be related to fuel availability. Studies on metabolic fuel inhibition in placental heterotherms show that glucose deprivation via the inhibitor 2-deoxy-D-glucose (2DG) initiates a torpor-like state, whereas fatty acid deprivation via mercaptoacetate (MA) does not. As previous studies using inhibitors were limited to quantifying body temperature in placentals, we investigated whether inhibition of glucose or fatty acids for cellular oxidation induces torpor in the marsupial hibernator Cercartetus nanus, and how the response of metabolic rate is related to body temperature. Glucoprivation initiated a torpor-like state in C. nanus, but animals had much higher minimum body temperatures and metabolic rates than those of torpid food-deprived animals and arousal rates were slower. Moreover, 2DG-treated animals were thermoregulating at ambient temperatures of 20 and 12 degrees C, whereas food-deprived torpid animals were thermo-conforming. We suggest that glucoprivation reduces the hypothalamic body temperature set point, but only by about 8 degrees C rather than the approximately 28 degrees C during natural torpor. Reduced fatty acid availability via MA also induced a torpor-like state in some C. nanus, with physiological variables that did not differ from those of torpid food-deprived animals. We conclude that reduced glucose availability forms only part of the physiological trigger for torpor initiation in C. nanus. Reduced fatty acid availability, unlike for placental heterotherms, may be an important cue for torpor initiation in C. nanus, perhaps because marsupials lack functional brown adipose tissue.

Adaptation, Physiological↗

PubMed2004

Flow control with hydrogels.

With the advent of the genomic revolution and the sequencing of the human genome complete, the majority of pharmaceuticals under development are proteins. Consequently, new techniques to more effectively administer these new protein therapeutics need to be developed. One method that is gaining popularity in the research community involves the use of responsive hydrogel actuators for flow control in drug delivery devices. Responsive hydrogels are materials able to undergo a volume change in response to a stimulus from their local environment. The following paper overviews recent advances made using hydrogel actuators for flow control such as resistance based valves, hydrogel jacket valves, hybrid hydrogel membrane valve, electrically triggered valves, and biomimetic valves. Also reviewed are several hydrogel flow control systems such as a flow sorter and pH-regulation system. The chemistry of the hydrogel actuators can be tweaked to allow physiological variables to trigger the volume expansion of the hydrogel actuators as demonstrated by several glucose sensitive hydrogel valves reviewed below. Therefore, the door to physiological feedback controlling the infusion rate in a drug delivery device is opened and has the potential to revolutionize protein pharmaceutical drug delivery.

Drug Delivery Systems↗

PubMed2002

Calcium bioavailability in relation to bone health.

A well established stable isotope technique exists for measuring calcium absorption from single foods and meals, but the long term effects of calcium on bone health cannot be assessed from acute bioavailability studies. Bone health depends primarily on the degree of mineralization, measured as bone mineral density (BMD), and phenotypic variations depend on genetic and environmental factors including calcium supply. Since almost all retained calcium is used for bone mineralization and remodeling, BMD can be used as a long-term (> six months) marker of dietary calcium bioavailability. However, BMD is a very insensitive marker of calcium bioavailability, so its use in dietary intervention studies is restricted to periods of significant bone growth or loss. Biochemical markers of bone metabolism may be used to predict the overall bioavailability of dietary calcium over a shorter time period (> four weeks), but they have a high coefficient of variation, so may not be appropriate for some dietary intervention studies. A group of European laboratories is currently developing an alternative approach using a long-lived radioisotope (41Ca) to label bone calcium and to directly measure the rate of calcium loss from urinary excretion data. The efficiency of calcium absorption is inversely related to intake; whole body balance of the mineral is dependent on rates of absorption and excretion and limited by calcium-binding substances in the gut. Dietary data and indirect measures of bone health indicate that bioavailability is important when habitual intakes are low, especially during periods of bone growth or loss. Further research is required to quantify the effects of major dietary modulators of calcium balance on bone health and to understand their relationship with genetic and physiological variables.

Biological Availability↗