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Results for “physiologic variables”

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PubMed1999

Perceptual responses to exercise: the effect of load-awareness on physiological responses during an isometric bout.

To evaluate the effect of awareness of load on cardiovascular and metabolic responses, thirty males were compared in three different loads during upright deadlift isometric exercise, at 25%, 30% and 35% of maximal voluntary contraction for 3 min. Significant differences (P < 0.05) were found from rest to 25%, 30% and 35% for all physiological variables, heart rate (66.5+/-9.0, 104.0+/-12.0, 115.0+/-9.0, and 123.0+/-11.0 beats x min(-1), respectively), and for lactic acid (2.2+/-0.4, 4.6+/-0.7, 5.7+/-1.1, and 6.3+/-1.5 mM x l(-1), respectively). However, no significant differences were revealed between the various conditions when rate-perceived exertion data were analyzed, despite increased absolute loads. These data indicate that the psychological manipulation introduced in this study did not affect physiological responses during isometric exercise, in contrast to that seen during dynamic exercise.

Adult↗

PubMed2002

Post-stress recovery of pituitary-adrenal hormones and glucose, but not the response during exposure to the stressor, is a marker of stress intensity in highly stressful situations.

Acute immobilization in male rats elicited the same ACTH, corticosterone and glucose response as foot shock when measured immediately after stress. However, post-stress recovery of plasma ACTH, corticosterone and glucose levels were delayed in immobilized versus shocked rats. Similarly, stress-induced anorexia was much greater in the former animals. All these data suggest that post-stress speed of recovery of some physiological variables is positively related to stressor intensity and could be used to evaluate it.

Adrenocorticotropic Hormone↗

PubMed1993

Ventilatory threshold and work efficiency during exercise on a cycle and rowing ergometer.

The purpose of this investigation was to determine the effects of increasing specific (rowing ergometer) and non-specific (cycle ergometer) workloads on parameters relating to the ventilatory threshold (Tvent) and work efficiency. When highly trained male rowers were tested using non-specific workloads, their %VO2 max values at Tvent were close to those characteristic of untrained subjects (74.6 +/- 6.2% VO2 max). However, when we tested the same subjects using specific workloads, we recorded values typical of highly trained athletes (85.0 +/- 4.4% VO2 max). For the non-specific exercise on the cycle ergometer, we recorded work efficiency values close to those of untrained subjects (22.8 +/- 2.1%); however, for the specific exercise on the rowing ergometer, we recorded much lower values (16.4 +/- 3.1%). Because of the results of the non-specific submaximal exercise tests, we suggest caution in the interpretation of physiological variables that may be sensitive to training status. The evaluation of Tvent and work efficiency as supplementary parameters during laboratory studies will enable researchers to ascertain the effectiveness of the training process used, as well as indicating the specificity of the loading apparatus.

Adaptation, Physiological↗

PubMed2001

Use of orthoses lowers the O(2) cost of walking in children with spastic cerebral palsy.

PURPOSE: The aim of this study was to assess the effects of hinged ankle foot orthoses (AFO) on the metabolic and cardiopulmonary cost of walking and gross motor skills of children with cerebral palsy (CP). METHODS: Ten habitual users of hinged AFO with spastic diplegic CP (9.01 yr +/- 2.10) participated in the study. Expired gas and heart rate (HR) were measured during sitting and with AFO on and off during steady state treadmill walking at three speeds: 3 km.h(-1), comfortable walking speed (CWS), and 90% of their fastest walking speed (FWS). Comfortable and fastest ground walking speed and Gross Motor Function Measure scores were also assessed with AFO on and off and analyzed with ANOVA. Because not all children could walk at all speeds on the treadmill, an ANOVA was performed on data for children who walked at 3 km.h(-1) and CWS (N = 8 for HR; N = 9 for pulmonary ventilation and metabolic variables) and a t-test on data at 90% of FWS (N = 9 for HR; N = 8 for pulmonary ventilation and metabolic variables). RESULTS: When children wore their AFO net oxygen uptake (L.min(-1), absolute--sitting values) was significantly (P < 0.05) reduced by 8.9% at 3 km.h(-1) and by 5.9% at 90% of FWS. Net pulmonary ventilation (L.min(-1)) was significantly (P < 0.05) lower with AFO on by 10.3% but only at 3 km.h(-1). AFO did not affect net HR (beats.min(-1)) nor the respiratory exchange ratio at any speed, nor any physiologic variable at CWS, nor gross motor skills. CONCLUSIONS: Use of hinged AFO reduces the oxygen and ventilatory cost of walking in children with spastic diplegic CP.

Ankle Joint↗

PubMed2006

Semiquantitative imaging measurement of baseline and vasomodulated normal prostatic blood flow using sildenafil.

The physiologic variability of blood flow to the prostate has not been studied until this time. We report the vasoactive effects of sildenafil and phenylephrine on blood flow of the normal prostate. Sildenafil increases prostate blood flow by approximately 75% and phenylephrine reduces the flow incrementally. Administration of these drugs with dynamic contrast-enhanced magnetic resonance imaging may improve the diagnosis of cancerous tissue because according to the literature, tumor angiogenic vessels lack the vasoactive physiologic response of the normal tissue.

Blood Flow Velocity↗

PubMed2005

Whole-body PET/CT: spectrum of physiological variants, artifacts and interpretative pitfalls in cancer patients.

Accurate diagnosis and staging in oncology is essential in the evaluation of cancer for optimal patient outcome. Conventional imaging techniques, such as computed tomography (CT), rely basically on morphological changes for tumour detection. Clinical experience, however, shows that morphological criteria may be misleading and may not always allow differentiation between benign and malignant lesions. Positron emission tomography (PET) with [F]fluorodeoxyglucose (FDG) is rapidly gaining a critical role in the clinical evaluation of patients with cancer. However, PET lacks anatomical landmarks for topographic orientation, and identification of abnormal glucose metabolic activity in regions close to organs with variable physiological FDG uptake can be difficult. To overcome these difficulties, a combined PET/CT scanner that acquires both functional (PET) and CT images has been recently developed. Proper interpretation of PET (and PET/CT) images requires a thorough understanding of the normal physiological distribution of FDG in the body, along with a knowledge of frequently encountered physiological variations in FDG distribution, and recognition of non-malignant causes of FDG uptake that can be confused with a malignant neoplasm. In addition, because of the utilization of the CT transmission information for the correction of the attenuation of the PET emission data (and for the reconstruction of the PET images), some artifacts may be generated. As a consequence, CT based attenuation correction of PET images may result in erroneous PET/CT interpretations. The aim of this extensively illustrated paper is to demonstrate several potential pitfalls encountered during the interpretation of PET/CT images so that radiologists can avoid false positive diagnoses and recognize inherently non-specific findings on PET/CT images obtained for oncological diagnosis.

Artifacts↗

PubMed2001

Predictors of outcome in severely head-injured children.

OBJECTIVE: Determine variables in the acute care period associated with survival and pediatric intensive care unit (PICU) length of stay (LOS) for children with severe traumatic brain injury. DESIGN: Retrospective cohort. SETTING: Level 1 pediatric trauma center. PATIENTS: Children (0-17 yrs) admitted 1991 to 1995 with nonpenetrating traumatic brain injury and admission Glasgow Coma Scale score of or=14. Predictors of outcome were abstracted, including Pediatric Trauma Score, Glasgow Coma Scale score, Pediatric Risk of Mortality, physiologic variables, computed tomography evidence of brain injury, and neuroresuscitative medications. The fatality rate was 24%. Age and gender were similar between groups (p >or= .1). Survival was independently predicted by 6-hr Glasgow Coma Scale score (odds ratio [OR] 4.6; 95% confidence interval [CI] 2.06-11.9; p < .001) and maximum systolic blood pressure (OR 1.05; 95% CI 1.01-1.09; p < .02). Odds of survival increased 19-fold when maximum systolic blood pressure was >or=135 mm Hg (OR 18.8; 95% CI 2.0-178.0; p < .01). By discharge, 67% of patients had an age-appropriate Glasgow Coma Scale score. Median hospital costs were 8,798 dollars for survivors: only mannitol use independently predicted high cost (odds ratio 4.9; 95% CI 1.2-19.1; p < .01). For survivors, median PICU LOS was 2 days, although 25% had LOS >6 days. Six-hour Glasgow Coma Scale score (OR 0.62; 95% CI 0.48-0.80; p < .001) and mannitol (OR 7.9; 95% CI 2.3-27.3; p < .001) were each independently associated with a prolonged LOS among survivors. CONCLUSIONS: Patients with higher 6-hr Glasgow Coma Scale scores were more likely to survive. Adjusting for severity of injury, survival was associated with maximum systolic blood pressure >or=135 mm Hg, suggesting that supranormal blood pressures are associated with improved outcome. Mannitol administration was associated with prolonged LOS, yet conferred no survival advantage. We suggest reevaluation of blood pressure targets and mannitol use in children with severe traumatic brain injury.

Adolescent↗

PubMed1991

Ventilatory threshold and work efficiency on a bicycle and paddling ergometer in top canoeists.

The purpose of this investigation was to determine the effect of increasing specific (paddling ergometer) and non-specific (bicycle ergometer) work load on the parameters at the ventilatory threshold (VT) and on work efficiency (WE) during increasing exercise ergometry. When highly trained male canoeists were given an unspecific exercise load, the values of %VO2max at VT were close to the values characteristic for an untrained population (72.3 +/- 5.3% VO2max). When the same subjects were given a specific work load, they produced values typical for highly trained athletes (83.4 +/- 2.5% VO2max). Non-specific exercise produced WE values close to those of untrained subjects on the bicycle ergometer (23.3 +/- 2.1%), and when loading is specific, the groups of working muscles are smaller, producing lower WE values (14.7 +/- 3.5%). It was concluded that the responses to submaximal exercise intensities in the case of nonspecific loading suggests caution in the interpretation of physiological variables which may be sensitive to training status. The assessment of VT and WE as supplementary characteristics during laboratory measurements, enables us, along with other parameters, to ascertain not only the effectiveness of the training process used, but also the specificity of a loading apparatus.

Adaptation, Physiological↗

PubMed1994

Physical activity does not account for the physiological response to forced swim testing.

Two experiments were conducted to examine physiological variables associated with the immobility response in the forced swim test. The first study compared the effects of water immersion, treadmill running, and foot shock, and showed that the time-related pattern of reactions to these three conditions, especially those involving lactate, glucose, anion gap (a measure of metabolic acidosis), and carbon dioxide differed significantly. The second study examined the role of food deprivation, and showed that this manipulation does not affect the behavior or physiological response of rats to testing. These results indicate that the physiological changes occurring during the forced swim are not simply due to increased physical activity or stress.

Acid-Base Equilibrium↗

PubMed2006

Steady-state acid-base response at exercise levels close to maximum lactate steady state.

OBJECTIVE: To study acid-base status during a constant-load treadmill test at exercise levels close to the maximum lactate steady-state. DESIGN: Two tests were performed: one maximal and one steady-state at a load corresponding to the mean of the two ventilatory thresholds observed in the first test. SETTING: University Sports Science Laboratory. PARTICIPANTS: Twenty-three male Sports Science students, aged 26.7 (+/- 4.9 SD) years, 176.1 (+/- 6.3) cm in height, and weighing 72.8 (+/- 6.7) kg. MAIN OUTCOME MEASURES: Capillary blood gases, metabolites, electrolytes. RESULTS: Acid-base status variables declined significantly during the maximal test. Lactate concentrations were above the values observed at onset of blood lactate accumulation. All the blood variables did not vary significantly at the various experimental times, except pH values and PCO2 values. Bicarbonate concentration remained constant. Plasma potassium, chlorine and sodium concentration did not increase. CONCLUSION: During a steady-state test at a load corresponding to approximately 80% of VO2max, the acid-base status in capillary blood remained constant even though the lactate concentration was over 4 mmol/L. However, despite the maintenance of a constant acid-base status, other physiological variables did not behave in the same fashion.

Acid-Base Equilibrium↗

PubMed1995

Physiologic response to two endotracheal suctioning techniques in newborn lambs with and without acute pulmonary hypertension.

BACKGROUND: Endotracheal suctioning may cause sudden increases in pulmonary arterial pressure, which can result in hypoxia secondary to right ventricular failure and/or increased right-to-left shunting. An adaptor that allows suctioning without disconnecting the ventilator has been proposed to prevent these problems; however, its efficacy has not been rigorously studied. OBJECTIVE: To examine the physiologic responses to two endotracheal suctioning techniques in newborn lambs with and without acute pulmonary hypertension. METHODS: A repeated-measures design was used to compare two endotracheal suctioning techniques in seven newborn lambs with and without acute pulmonary hypertension. An adaptor was used in the ventilator-controlled technique, making disconnection of the ventilator during suctioning unnecessary. In the bag-controlled technique, the ventilator was disconnected and ventilation was done with a manual resuscitation bag. Physiologic variables, pulmonary and mean arterial pressure, peak inspiratory pressure, mixed venous oxygen saturation, cardiac index, and arterial blood gas values were recorded before, during, and after endotracheal suctioning. RESULTS: Endotracheal suctioning caused a statistically significant systemic hypertensive response in lambs with and without acute pulmonary hypertension, regardless of which suctioning technique was used. No statistically significant changes occurred in pulmonary arterial pressure using either technique. CONCLUSIONS: Use of an adaptor resulted in no differences in the physiologic responses to endotracheal suctioning. However, endotracheal suctioning was easier to perform using an adaptor because no extra equipment or person was needed.

Animals↗

PubMed1989

Conjunctival oxygen tension monitoring in experimental septic shock.

Continuous non-invasive monitoring of conjunctival oxygen tension (PcjO2) versus 'conventional' invasive hemodynamic and oxygen transport variables was evaluated in a porcine model of septic shock induced by a continuous i.v. infusion of E. coli endotoxin over 2 hours. Seventeen pigs under ketamine anesthesia and breathing air spontaneously were investigated. PcjO2, which reflects local oxygen tension at tissue level, correlated significantly at baseline and throughout the septic course with mixed venous oxygen saturation and oxygen utilization coefficient. All these correlations were significant at the 1% level. The corresponding correlations between PcjO2 and cardiac output were significant at the 5% level. A finding of great importance was that changes in PcjO2 preceded major changes in the intermittently measured physiological variables such as SvO2 and cardiac output. We conclude that PcjO2 monitoring is a valuable non-invasive method and which can provide a continuous assessment of the hemodynamic and oxygenation status in experimental septic shock.

Animals↗

PubMed1998

Reproducibility and validity of physiological parameters measured in cyclists riding on racing bikes placed on a stationary magnetic brake.

UNLABELLED: The purpose of this study was: 1) To evaluate the reproducibility of physiological parameters measured during cycle exercise, and 2) To validate the predictive capacity of physiological parameters related to endurance performance. Therefore, physiological variables were measured twice during cycling exercise in a group of seven cyclists. Each cycle exercise session was separated by one week and included progressive submaximal cycling followed by a 5-km time trial. Two and three weeks later, endurance performance was evaluated by calculating average work output during a 50-km time trial (W50km). To simulate cycle performance, the cyclists' private racing bikes were placed on a stationary magnetic brake. No differences were observed between paired physiological observations in the test-retest (P>0.05). The coefficient of variation (CV) was calculated from the differences between test-retest parameters. CV for the maximal oxygen uptake (VO2max), average work output during the 5-km trial (W5km), the calculated work intensity which increased the blood lactate concentration to 2 and 4 mmol/l (W2mM and W4mM) and W50km were 1.9, 2.7, 6.1, 5.9 and 6.3%, respectively, while the 95% confidence interval (CI) showing the expected range for variation in a retest was calculated to be 80 ml.min(-1), 9, 16, 18 and 18 W, respectively. Simple linear regression showed significant correlations between VO2max, W5km, W2mM, W4mM and W50km (r-values: range 0.83-0.98, P<0.01). IN CONCLUSION: 1) Physiological parameters can be reproduced during an exercise test procedure in cyclists riding on racing bikes placed on a stationary magnetic brake, and 2) The validity of VO2max, W5km, W2mM, and W4mM as predictive parameters of endurance was demonstrated.

Adult↗

PubMed1985

Clinical prediction of the adult respiratory distress syndrome.

The use of clinical, physiologic, and laboratory parameters in the prediction or early detection of ARDS has been reviewed. From both a clinical and research standpoint, the ability to identify patients at risk is extremely important. The selection of patients according to predisposing clinical events has been the most successful thus far. The use of physiologic variables and gauges of injury severity have been of limited value, particularly for assessing ARDS risk in the individual patient. Only a handful of the proposed mediators or markers of acute lung injury have been studied prospectively in patients at risk. Of these, factor VIII antigen, lactoferrin, and phospholipase A2 appear the most promising as laboratory tests for selecting patients at risk. In the future it may be possible by using sophisticated statistical analysis techniques to combine important clinical, physiologic, and laboratory information into a numerical ARDS risk index, essentially assigning a probability of ARDS in individual patients.

Blood Platelets↗

PubMed2004

Multicenter trial for the set-up of a MRI quality assurance programme.

Many international protocols related to RMI-QC program are focused on acquisition methods and analysis of several image quality parameters but rarely normality ranges or measurement frequencies are presented. To address this problem we investigated the variability of many magnetic resonance imaging (MRI) systems with the set-up of multicenter trial. The trial was set up to investigate short-and mid-term variability of two fundamental nongeometric image quality parameters: signal-to-noise (SNR) and integral percent uniformity (U%). Ten centers (12 devices) participated to data collection consisting of a three-step-protocol. First, 10 consecutive images of a phantom were collected with a spin echo sequence. As second step the series collection was repeated 24 h later. Finally a single image acquisition was performed twice a week for 5 weeks. The analysis of results allowed us to define a "physiological" variability of +/-3% of the reference level for both parameters and to conclude that a weekly measurement is adequate to detect relevant variations of device performance.

Analysis of Variance↗

PubMed1990

Identification of a coronary-prone profile for business managers: comparison of three approaches to Type A assessment.

This study compares three approaches to Type A assessment for identifying a coronary-prone profile for business managers. The Survey of Work Styles (SWS), a profile measure of the Type A behavior pattern, was compared with the Structured Interview (SI), a categorical measure, and with the Jenkins Activity Survey (JAS) and Framingham Type A Scale, both continuous measures. The blood pressure, heart rate, and cardiac effort of 163 middle-aged male business managers (107 of whom were classified as Type A by the SI) were assessed during the SI. Neither the classification by the SI of the subjects into Type A and non-Type A groups nor Type A1, A2, X, B3, and B4 revealed differences in physiological arousal. Similarly, no relationship was found between physiological variables and Type A behavior that was assessed on a continuum by the JAS or Framingham Type A Scale. When business managers were classified by the SWS according to their pattern of Type A components, however, the results showed that men high on Anger but low on Competitiveness and Job Dissatisfaction had significantly higher levels of systolic blood pressure during the SI. The importance of recognizing individual differences in the expression of Type A behavior when assessing coronary-prone physiological reactivity is discussed.

Adult↗

PubMed2004

Extracellular Brain pH and Outcome following Severe Traumatic Brain Injury.

The ability to measure brain tissue chemistry has led to valuable information regarding pathophysiological changes in patients with traumatic brain injury (TBI). Over the last few years, the focus has been on monitoring changes in brain tissue oxygen to determine thresholds of ischemia that affect outcome. However, the variability of this measurement suggests that it may not be a robust method. We have therefore investigated the relationship of brain tissue pH (pH(b)) and outcome in patients with TBI. We retrospectively analyzed prospectively collected data of 38 patients admitted to the Neurosciences Critical Care Unit with TBI between 1998 and 2003, and who had a multiparameter tissue gas sensor inserted into the brain. All patients were managed using an evidence-based protocol targeting CPP > 70 mm Hg. Physiological variables were averaged over 4 min and analyzed using a generalized least squares random effects model to determine the temporal profile of pH(b) and its association with outcome. Median (IQR) minimum pH(b) was 7.00 (6.89, 7.08), median (IQR) maximum pH(b) was 7.25 (7.18, 7.33), and median (IQR) patient averaged pH(b) was 7.13 (7.07, 7.17). pH(b) was significantly lower in those who did not survive their hospital stay compared to those that survived. In addition, those with unfavorable neurological outcome had lower pH(b) values than those with favorable neurological outcome. pH(b) differentiated between survivors and non-survivors. Measurement of pH(b) may be a useful indicator of outcome in patients with TBI.

Acid-Base Equilibrium↗

PubMed1985

Oxygen in the treatment of spinal cord decompression sickness.

Twenty-five anesthetized dogs were used to find the optimum Po2 for the delayed treatment of spinal cord decompression sickness (DCS). They were instrumented for the measurement of physiological variables and somatosensory spinal evoked potentials (SEP) given an air dive of 15 min at 10 bar (300 ft) and decompressed in under 6 min. At the surface SEP were observed for signs of DCS. Fifteen minutes after cord DCS was observed in the SEP, the dogs were compressed to 5.0 bar breathing one of 5 gas mixtures giving a Po2 of 1.0, 1.5, 2.0, 2.5, or 3.0 bar. At the start of therapy all groups were in a similar physiological state with a similar loss of SEP. Between 40 and 120 min, recovery was significantly different (P less than 0.05) between the groups, most SEP recovery having occurred within 15 min. The treatments ended with 22, 32, 70, 66, and 42% recovery, respectively. It would appear that the optimum Po2 is around 2.0 bar.

Animals↗