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 505 records · Page 28Linked to original sources

PubMed2002

Acute effects of maternal smoking on fetal-placental-maternal system hemodynamics.

OBJECTIVE: To study acute hemodynamic alterations in the fetal-placental maternal system immediately after maternal exposure to nicotine. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Adult↗

PubMed1992

Biological variability of lipoproteins and apolipoproteins in patients referred to a lipid clinic.

We determined the physiological variability of total cholesterol, high- (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, and apolipoproteins A-I and B in fasting blood samples from patients referred to the Johns Hopkins Lipid Referral Clinic. Samples were taken on each of three occasions during baseline evaluation visits before the patients were treated. The median physiological coefficients of variation (CVp) were as follows: total cholesterol, 5.0%; triglycerides, 17.8%; HDL cholesterol, 7.1%; LDL cholesterol, calculated from the previous three measurements, 7.8%; and apolipoproteins A-I and B, 7.1% and 6.4%, respectively. There were no significant differences in CVp between children (less than or equal to 18 years) and adults (greater than 18 years) for any of the measurements. On the basis of our findings, single measurements in serial samples taken on three occasions suffice to establish the patients' usual values with the following precisions (+/- 1 CV): total cholesterol, +/- 4%; triglycerides, +/- 11%; HDL cholesterol, +/- 8%; LDL cholesterol, +/- 6%; and apolipoproteins A-I and B, +/- 7%.

Adolescent↗

PubMed1978

Forty-one variables following thoracotomy in calves.

Seven calves underwent thoracotomy to study the response of 41 physiologic variables over a 14 day post-operative period for comparison to a recent series of left ventricular bypass pump implants. The experimental protocols were identical to the pump implant protocols except that the sham operated animals did not receive antiplatelet or anticoagulant drugs and the pumps were not implanted. Of the 41 variables studied, 13 changed significantly during the post-operative period. Heart rate, hematocrit, whole blood hemoglobin, and fibrinogen concentration decreased, while fibrinogen survival, stroke volume, cardiac output, arterial blood pH, pCO2 and pO2, plasma sodium concentration, and urinary excretion rates of sodium and potassium increased from the first or second to the fourteenth post-operative day. Heart rate and hematocrit also decreased in the recent series of 18 animals in which left ventricular bypass pumps were implanted. The decrease in heart rate is toward the unoperated control value as the calves recover from the operative stress. The decrease in hematocrit is probably the result of daily removal of blood for the physiologic studies because there was no evidence of hemorrhage or red blood cell destruction.

Animals↗

PubMedDate not supplied

Selection of variables from maximum expiratory flow-volume curves.

Various methods are in use for estimating physiological variables from maximum expiratory flow-volume curves, and some of these are recommended by international bodies for use on adults. We have compared eight such methods in 433 adolescents aged 12-16 years. The mean values of expiratory flows, FVC and FEV1 by each method differed less than 6% from those obtained by the method recommended by the ATS, except for MEF25, where differences between methods were substantially larger. The mean within-individual coefficients of variation of FVC and FEV1 did not differ between methods and improved from about 3.1 to 2.6% and 2.7 to 2.3% respectively when using 5 instead of 3 acceptable curves. For expiratory flows, the coefficients of variation ranged between 4.2 and 9.4% and improved slightly but not consistently when using more than 3 acceptable curves. Reproducibilities were systematically poorer when flows were derived from one "best" FVC manoeuvre. It is concluded that taking more than 3 acceptable blows is not cost-effective, even in inexperienced adolescents. An envelope method and maximum composite curve from FVC reproducible within 5% from the largest one are recommended for use with teenagers.

Adolescent↗

PubMed2002

Early immunoneutralization of calcitonin precursors attenuates the adverse physiologic response to sepsis in pigs.

OBJECTIVE: The 116 amino acid prohormone procalcitonin and some of its component peptides (collectively termed calcitonin precursors) are important markers and mediators of sepsis. In this study, we sought to evaluate the effect of immunoneutralization of calcitonin precursors on metabolic and physiologic variables of sepsis in a porcine model. DESIGN: A prospective, controlled animal study. SETTING: A university research laboratory. SUBJECTS: 30-kg Yorkshire pigs. INTERVENTIONS: Sepsis was induced in 15 pigs by intraperitoneal instillation of a suspension of cecal content (1 g/kg animal body weight) and a toxinogenic Escherichia coli solution (2 x 10(11) colony-forming units). During induction of sepsis, seven pigs received an intravenous infusion of purified rabbit antiserum, reactive to the aminoterminal portion of porcine prohormone procalcitonin. Another eight control pigs received an intravenous infusion of purified nonreactive rabbit antiserum. For all 15 animals, physiologic data (urine output, core temperature, arterial pressure, heart rate, cardiac index, and stroke volume index) and metabolic data (serum blood urea nitrogen and creatinine, arterial lactate, and pH) were collected or recorded hourly until death at 15 hrs. MEASUREMENTS AND MAIN RESULTS: In this large-animal model of rapidly lethal peritonitis, serum calcitonin precursors were significantly elevated. Amino-prohormone procalcitonin-reactive antiserum administration resulted in a significant improvement or a beneficial trend in a majority of the measured physiologic and metabolic derangements induced by sepsis. Specifically, arterial pressure, cardiac index, stroke volume index, pH, and creatinine were all significantly improved, while urine output and serum lactate had beneficial trends. Treated animals also experienced a statistically significant increase of short-term survival. CONCLUSIONS: These data from a large-animal model with polymicrobial sepsis demonstrate the salutary effect of early immunoneutralization of calcitonin precursors on physiologic and metabolic variables. Immunologic blockade of calcitonin precursors may offer a novel therapeutic approach to human sepsis.

Animals↗

PubMed1990

A Monte Carlo simulation of range for an invasive impedance respiration monitor.

One method of rate responsive pacing utilizes an analog of minute ventilation as the input to the rate control algorithm. A measure of the intravenous impedance along the pacing catheter is a convenient means of determining minute ventilation. Design of the impedance converter requires a knowledge of the range of DC and AC impedance signals. During normal and deep breathing, 116 AC measurements were taken from 34 Electrophysiology (EP) patients and 31 DC measurements were taken from 13 EP patients. The patient data produced skewed distributions with a normal AC mean of 0.45 +/- 0.40 ohms p-p, a deep AC mean of 2.0 +/- 1.6 ohms and a DC mean of 44 +/- 13 ohms. An eight variable static model was derived from prior work. Five of the physiological variables were chosen from established clinical ranges, one geometrical variable was chosen from prior work and two were selected by matching the statistics of a Monte Carlo analysis of the model with the statistics of the patient data. The blood resistivity was obtained from prior work. A simulation of 1000 measurements produced a normal breathing range of 0 to 2.24 ohms, a deep breathing range of 0 to 9.6 ohms and a DC range of 19 to 100 ohms.

Algorithms↗

PubMed1999

Differential effects of aging on heart rate variability and blood pressure variability.

Previous studies investigating autonomic cardiovascular control in elderly persons usually included analysis of R-R interval but not of blood pressure variability. "Physiological" blood pressure rise during the aging process was not accounted for as a possible confounding factor. This study was designed to characterize the relationship between age and short-term heart rate (HR) and blood pressure (BP) variability, independently of the "physiological" rise in BP associated to aging. The study was carried out in 65 "normotensive" (BP< or =140/80 mm Hg) healthy subjects, ranging in age from 18 to 80 years. BP and HR were recorded at rest with a Finapres device. Low-frequency (LF = 0.066 to 0.129 Hz) and high-frequency (HF = respiratory peak +/-0.05 Hz) components of HR and BP variability were assessed using fast-Fourier spectral analysis. Transfer-function analysis between systolic BP and HR variability permitted the calculation of the gain of baroreflex sensitivity. Significant results of this study include a continuous and linear decline with age of normalized LF spectral power of HR in the standing position and of normalized HF spectral power of HR during paced breathing. No correlation was found between age and BP variability, except for LF diastolic BP spectral power in the standing position. The baroreflex gain was negatively correlated with age. The effect of aging on autonomic nervous system cardiac control is progressive and continuous throughout an 18-80 years age range. Although the aging process diminished HR variability and diastolic BP variability, it had no influence on systolic BP variability.

Adolescent↗

PubMed1991

Automated real-time data acquisition and analysis of cardiorespiratory function.

Microcomputer generation of an automated record without complexity or operator intervention is desirable in many circumstances. We developed a microcomputer system specifically designed for simplified automated collection of cardiorespiratory data in research and clinical environments. We tested the system during possible extreme clinical conditions by comparison with a patient simulator. Ranges used were heart rate of 35-182 beats per minute, systemic blood pressures of 65-147 mmHg and venous blood pressures of 14-37 mmHg, all with superimposed respiratory variation of 0-24 mmHg. We also tested multiple electrocardiographic dysrhythmias. The results showed that there were no clinically relevant differences in vascular pressures, heart rate, and other variables between computer processed and simulator values. Manually and computer recorded physiological variables were compared to simulator values and the results show that computer values were more accurate. The system was used routinely in 21 animal research experiments over a 4 month period employing a total of 270 collection periods. The file system integrity was tested and found to be satisfactory, even during power failures. Unlike other data collection systems this one (1) requires little or no operator intervention and training, (2) has been rigorously tested for accuracy using a wide variety of extreme patient conditions, (3) has had computer derived values measured against a standardized reference, (4) is reliable against external sources of computer failure, and (5) has screen and printout presentations with quick and easily understandable formats.

Computer Systems↗

PubMed1988

Assessment of biological age by principal component analysis.

A method of assessing biological age by the application of principal component analysis is reported. Healthy individuals (462) randomly selected from about 6000 men who had taken a 2-day health examination were studied. Out of the 30 physiological variables examined in routine check-ups, 11 variables were selected as suitable for the assessment of biological age based on the results of factor analysis and the physiological meaning of each test. This variable set was then submitted to principal component analysis, and the 1st principal component obtained from this analysis was used as an equation for assessing one's biological age. However, the biological age calculated from this equation is expressed as a score, so the estimated score was transformed to years (biological age) using the T-score idea. The biological age estimated by this method is practically useful and theoretically valid in contrast with the multiple regression model, because this approach eliminates and overcomes the following 2 big problems of the multiple regression model: (1) the distortion of the individual biological age at the regression edges; and (2) a theoretical contradiction in that a perfect model will merely be predicting the subject's chronological age, not his biological age.

Adult↗

PubMed2003

Evaluating several sources of variability for standard and SWAP visual fields in glaucoma patients, suspects, and normals.

PURPOSE: To quantify factors affecting test-retest variability of threshold measurements over a series of 3 serial visual fields (VF). DESIGN: Prospective comparative observational study. PARTICIPANTS: Forty-one normals, 10 suspects and 35 stable glaucoma patients. METHODS: All subjects performed 3 standard and 3 short-wavelength automated perimetry (SWAP) VFs. At each VF location, severity (defined as age-corrected total deviation) and test-retest variability (TRV), defined as the standard deviation of 3 serial threshold values, were calculated. A multiple regression model (constructed separately for standard VF and SWAP) incorporated 13 factors: severity, location, eccentricity, study group, diagnosis, superior versus inferior hemifield, nasal versus temporal hemifield, one-versus-two thresholds, age, mean pupil size, pupil size variability, between-subject variation, and residual variation. MAIN OUTCOME MEASURES: Variability in threshold sensitivity VF values. RESULTS: Mean TRV (+/- standard deviation) for normal, suspect and glaucoma eyes, respectively, was: 1.28 +/- 0.87, 1.53 +/- 1.04 and 2.20 +/- 1.79 dB for standard VF, and 1.87 +/- 1.35, 1.86 +/- 1.24 and 2.68 +/- 1.85 dB for SWAP. The contribution of each factor to the model for standard VF and SWAP (SWAP in parentheses) were: severity 15.5% (6.9%); location 2.7% (4.1%); eccentricity 1.1% (0.64%); diagnosis 2.9% (5.9%); "superior versus inferior" hemifield 0.17% (1.7%); "nasal versus temporal" hemifield 0.06% (0.02%); one-versus-two thresholds 0.04% (0.16%); age 0.1% (0.06%); mean pupil size 0.59% (0.1%); pupil size variability 3.2% (2.8%); between-subject 8.0% (13.5%) and residual variation 61.0% (66.6%). Excluding between-subject and residual variation, the 11-factor model was able to account for less than one third of the variability seen in both standard VF and SWAP. CONCLUSIONS: Severity of defect and between subject variation exerted the largest effect on TRV. However, even if all 11 factors could be adjusted for, it would reduce the magnitude of TRV by only 30%. More work is needed to reduce the remaining variability inherent in psychophysical testing and to better understand the intrinsic physiological variability present both in healthy and diseased eyes. It is possible that a larger number of VFs used for the calculation of TRV might further reduce the magnitude of the remaining variability found in this study.

Adult↗

PubMed2001

Genetic analysis of autonomic reactivity to psychologically stressful situations.

We present the results of a behavioural genetics study on response profiles of autonomic measures (heart rate, blood pressure, and galvanic skin level), under ecologically valid, stressful conditions. Where response profiles of different physiological variables are the object of study, and when daily life stressors are taken into account (Turner and Hewitt, Annals of Behavioral Medicine, 14 (1992) 12-20), autonomic responsiveness to psychological stressors is thought to be an inherited trait. The participants were 100 female twin pairs, 57 monozygotic and 43 dizygotic twin pairs. Participants watched eight films with a stressful social content while autonomic measures were continuously recorded. Results show that the heritability coefficients of response profiles of autonomic measures are almost twice as high as that of single variables. The results further show that genes exert their influence on physiological behaviour not only directly, but also indirectly, by influencing the idiosyncratic relation between a person and his environment.

Adolescent↗

PubMed1998

Association of factor VII protein concentration with lifestyle factors.

Several studies have demonstrated that changes in fasting levels of factor VII coagulant activity (FVII:C), a thrombotic risk marker, are due to changes in FVII protein concentrations (FVII:Ag). Consequently, studies on FVII now often include measurements of FVII:Ag. The present cross-sectional study examined the association between several behavioural variables (body mass index, physical activity, tobacco or alcohol consumption) or physiological variables (total cholesterol, HDL-cholesterol, triglycerides, glucose, insulin, fibrinogen, resting pulse, systolic blood pressure, bleeding time) and FVII:Ag in 439 51-y-old Danish men. In the multivariate analyses, body mass index (BMI), low physical activity, total cholesterol, short bleeding time, and insulin showed an independent positive association with FVII:Ag. The strongest independent association with FVII:Ag was found for total cholesterol. These results suggest that blood lipids are major determinants of FVII:Ag, but that other lifestyle factors such as insulin, BMI and physical activity can also influence FVII:Ag. Furthermore, the association between FVII:Ag and bleeding time suggests an effect of FVII or the FVII pathway on primary haemostasis.

Adult↗

PubMed1997

Circulating antioxidants as determinants of the rate of biological aging in pigtailed macaques (Macaca nemestrina).

The effect of antioxidant activity on the rate of biological aging was studied in 39 pigtailed macaques (Macaca nemestrina) 7-30 years of age. Scores of seven antioxidant compounds (vitamins C and E, carotenoids, urate, bilirubin, ceruloplasmin, and albumin) were combined to produce an antioxidant variable (AOx) that was tested for correlation with a second composite variable, rate of biological aging (RBA). RBA was formed from seven physiological variables that met a stringent set of criteria as biomarkers of aging. Potential effects of disease on RBA and AOx were excluded by experimental design and by statistical control using a composite index of disease (Dis) that was based on four measures of clinical history and pathology. The study produced three salient findings: (1) there was a significant inverse relation between AOx and RBA (i.e., animals that had high AOx scores had low RBA scores and vice versa); (2) the relation was independent of Dis effects, and (3) there was no significant relation between AOx and Dis independent of RBA (i.e., the correlation between AOx and Dis was dependent on the correlation of AOx with RBA). These results further validated the RBA variable as a measure of the rate of biological aging and supported the concept that antioxidant activity influences both the rate of biological aging and vulnerability to disease.

Aging↗

PubMed2005

Impact of admission hyperglycemia on hospital mortality in various intensive care unit populations.

OBJECTIVE: Hyperglycemia in intensive care unit patients has been associated with an increased mortality rate, and institutions have already begun tight glucose control programs based on a limited number of clinical trials in restricted populations. This study aimed to assess the generalizability of the association between hyperglycemia and in-hospital mortality in different intensive care unit types adjusting for illness severity and diabetic history. DESIGN: Retrospective cohort study. SETTING: The medical, cardiothoracic surgery, cardiac, general surgical, and neurosurgical intensive care units of the University of Maryland Medical Center. PATIENTS: Patients admitted between July 1996 and January 1998 with length of stay > or = 24 hrs (n = 2713). INTERVENTIONS: On intensive care unit admission, blood glucose and other physiologic variables were evaluated. Regular measurements were taken for calculation of Acute Physiology and Chronic Health Evaluation III scoring. Patients were followed through hospital discharge. Admission blood glucose was used to classify patients as hyperglycemic (> 200 mg/dL) or normoglycemic (60-200 mg/dL). The contribution of hyperglycemia to in-hospital mortality stratified by intensive care unit type and diabetes history while controlling for illness severity was estimated by logistic regression. MEASUREMENTS AND MAIN RESULTS: The adjusted odds ratios for death comparing all patients with hyperglycemia to those without were 0.81 (95% confidence interval, 0.37, 1.77) and 1.76 (95% confidence interval, 1.23, 2.53) for those with and without diabetic history, respectively. Higher mortality was seen in hyperglycemic patients without diabetic history in the cardiothoracic, (adjusted odds ratio, 2.84 [1.21, 6.63]), cardiac (adjusted odds ratio, 2.64 [1.14, 6.10]), and neurosurgical units (adjusted odds ratio, 2.96 [1.51, 5.77]) but not the medical or surgical intensive care units or in patients with diabetic history. CONCLUSIONS: The association between hyperglycemia on intensive care unit admission and in-hospital mortality was not uniform in the study population; hyperglycemia was an independent risk factor only in patients without diabetic history in the cardiac, cardiothoracic, and neurosurgical intensive care units.

APACHE↗

PubMed1997

False-positive behavior with the dP/dt sensing pacemaker: a rare complication of a physiological sensor.

As with "nonphysiological" devices, sensors that directly measure physiological variables have the potential to measure unexpected signals and for the physiological parameter being measured to respond in an unexpected manner. We present the case of a dP/dt sensing pacing system that functioned normally for 2 months and then developed upper rate behavior due to the sensing of a high frequency artifact on the pressure recording. Our case and others cited reinforce the need for future physiological rate responsive pacemakers to incorporate a second sensor to provide for backup rate response in cases of inappropriate rate response.

Aged↗

PubMed2003

Risk factors for predicting mortality in a surgical intensive care unit in the year 2000.

OBJECTIVE: To determine the mortality and risk factors of mortality in a surgical intensive care unit (SICU), King Chulalongkorn Memorial Hospital. DESIGN: Review of retrospective data. SETTING: a SICU of a tertiary-care academic medical center. PATIENTS: Out of a total of 546 patients admitted to SICU during a one year period (January 1, 2000 - December 31, 2000), 458 (83.9%) had complete medical data which were analyzed. MEASUREMENTS AND MAIN RESULTS: One hundred and ninety-three variables of 6 categories of patients' characteristics, chronic disease, acute illness, physiologic variables, therapy and miscellaneous were studied. Univariate and multivariate analyses were used. The SICU and hospital mortality was 8.1 and 14.6 per cent, respectively. Multivariate logistic regression analysis identified seven variables as independent risk factors for mortality (p < 0.05): chronic renal failure (adjusted odds ratio [AOR], 7.5; 95% CI, 3.0 to 19.0; p = 0.000), coma (AOR, 11.7; 95% CI, 2.4 to 57.4; p = 0.002), Staphylococcus aureus infection (AOR, 15.4; 95% CI, 1.6 to 147.6; p = 0.018), diagnosis of systemic inflammatory response (AOR, 2.9; 95% CI, 1.2 to 7.1; p = 0.017), mechanical ventilation (AOR, 11.2; 95% CI, 2.0 to 61.4; p = 0.005), having received adrenaline (AOR, 7.1; 95% CI, 2.3 to 22.2; p = 0.001) and diuretic (AOR, 3.3; 95% CI, 1.4 to 8.1; p = 0.008). Besides weight (AOR, 0.9; 95% CI, 0.9 to 1.0; p = 0.002) and having received H2-blocker (AOR, 0.2; 95% CI, 0.1 to 0.5; p = 0.001) were two independent protective factors for mortality. CONCLUSION: Knowing the risk factors of SICU mortality will help physicians to improve patient care, educate patients and their families, optimize ICU resource planning and may decrease health care costs.

Academic Medical Centers↗

PubMed2004

The effects of a 12-week group exercise programme on physiological and psychological variables and function in overweight women.

OBJECTIVES: The aim of this study was to investigate the effect of a 12-week functional exercise programme on overweight women. METHODS: Twenty-six subjects (n=13 exercisers, n=13 controls) aged (mean+/-SD) 63 (+/-4) years completed the study. The exercise sessions were carried out twice each week for 12 weeks. The variables measured were body mass, body mass index, skin-fold thickness, resting blood pressure, total blood cholesterol, chair rise, timed 'up and go' test, 20-m walk,lifting a 1- and a 2-kg bag on to a shelf, stair walking, 'sit and reach' flexibility test, Life Satisfaction Index and Physical Self-perception Profile for Older Adults. The exercise sessions consisted of 40-min sessions during which the subjects performed aerobic and strength exercises. RESULTS: Paired analyses showed that body mass, body mass index, blood pressure (systolic and diastolic values), 'up and go' time, time to complete a 20-m walk, time to lift a 1- and a 2-kg bag with both the right and left arms onto a shelf, and stair climbing-total time and ascent time-decreased significantly in the exercise group. Also, the exercise group improved their Life Satisfaction Index score significantly compared with the control group. CONCLUSIONS: The results indicate that a functional exercise programme has the potential to improve performance in a number of physiological variables and functional activities in overweight women. The exercise programme enhanced life satisfaction.

Aged↗

PubMed1993

Using maximal and submaximal aerobic variables to monitor elite cyclists during a season.

The purpose of this study was to identify sensitive physiological indicators for monitoring the progress in training state of elite cyclists throughout a training and competition season. Seven elite male cyclists performed maximal oxygen consumption (VO2max) tests and submaximal tests on three or four different occasions during their training and competition season. The submaximal test consisted of three successive 16-min bouts at 150, 200, and 250 W interspersed with rest periods between each load. Pedalling rate varied progressively from 50-120 rpm. Results showed that maximal heart rate (HR), ventilation (Ve), gross mechanical efficiency (MEG), and VO2max did not change during the season. Moreover, ventilation threshold (VT) did not change during the season, nor did HR, Ve, and VO2 at VT. However, changes were found in physiological variables during the submaximal test. HR decreased significantly during the season, as did VO2 (P < 0.05) for a standardized workload. On the other hand, at the higher power outputs (200 W and 250 W) MEG increased during the season. These results suggest that VO2max may not be a good indicator of enhanced capacity in elite cyclists. Rather, a standardized efficiency test during which submaximal variables such as HR, VO2, and MEG are monitored might be a more sensitive indicator of the progress in the training state of elite male cyclists during a training and competition season.

Adaptation, Physiological↗