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Results for “physiologic variables”

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PubMed1987

Spinal cord extracellular microenvironment. Can the changes resulting from trauma be graded?

It is now clear that alternatives are available to the standard method of producing spinal injury with the Allen drop technique. We have shown that small groups of animals with predictably consistent mechanical injury descriptors can now be produced for studies of this type. These groups can easily be selected to have minimal or maximal injury results, depending upon this series of mechanical descriptors. In addition, important physiological variables seem to show acute recovery patterns consistent with recovery of function in chronic animals. Since marginal injuries are likely to be more responsive to pharmacological or surgical intervention, a sensible approach would be to design studies in which animals are close to, but not at, some degree of injury from which they will spontaneously recover. Shifts of the acute physiological, chronic behavioral, or histopathological recovery curves would then indicate the potential therapeutic index of different interventions. Only in this way can significant advances be made in the selection of protocols for human trials.

Animals↗

PubMed2005

The Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) weight loss project: Rationale and design.

This paper outlines the rationale and design of the Study of the Effects of Diet on Metabolism and Nutrition (STEDMAN) weight loss project, in which detailed biologic profiling of three hundred and fifty obese individuals (body mass index (BMI): 30-50 kg/m(2)) will be conducted as they lose weight via seven distinct interventions. These profiles will be compared to those of fifty normal, healthy, control participants (BMI: 18.5-24.9 kg/m(2)). The interventions include the following: Roux-en-Y gastric bypass surgery, dietary interventions of differing macronutrient composition and diverse pharmacologic interventions. Outcome variables include eight conventional metabolites and CRP measured by standard clinical chemistry techniques, twenty hormones of energy balance and fuel homeostasis measured by radioimmunoassay (RIA) or by enzyme-linked Immunosorbent assay (ELISA), ten pro- and anti-inflammatory cytokines measured using Luminex xMAP technology, one hundred and one intermediary metabolites measured by targeted mass-spectrometry-based methods, and physiologic variables such as body composition measured by dual energy X-ray absorptiometry (DEXA), air displacement plethysmography, and abdominal computerized tomography (CT), insulin sensitivity measured by intravenous glucose tolerance test (IV-GTT) and metabolic rate measured by indirect calorimetry. Results from this study will expand our knowledge of the biology of obesity and weight regulation and may lead to targeted strategies for its treatment and control.

Adolescent↗

PubMed1992

Analysis of the association between marital relationships and health problems: an interactional perspective.

This article reviews the evidence for a relationship between 3 types of marital variables (marital status, marital adjustment, and marital interaction) and health problems (etiology, course/outcome/treatment) as well as the effect that health problems have on marriage. The mechanisms responsible for these associations also are evaluated. The evidence suggest that marital variables affect health status but that the effect is indirect and nonspecific. The major explanatory model, the stress/social support hypothesis, has provided a broad conceptual framework rather than testable hypotheses. The results of the review suggest, however, that sufficient evidence exists for researchers to focus on exploring specific explanations. A hypothetical model is presented that includes interpersonal, intrapersonal, psychological, and physiological variables. This model is intended as a blueprint for exploration as well as a summary of available evidence.

Female↗

PubMed2003

The effects of prior incremental cycle exercise on the physiological responses during incremental running to exhaustion: relevance for sprint triathlon performance.

It is common for the physiological working capacity of a triathlete when cycling and running to be assessed on two separate days. The aim of this study was to establish whether an incremental running test to exhaustion has a negative effect after a 5 h recovery from an incremental cycling test. Eight moderately trained triathletes (age, 26.2 +/- 3.4 years; body mass, 67.3 +/- 9.1 kg; VO2max when cycling, 59 +/- 13 ml x kg x min(-1); mean +/- s) completed an incremental running test 5 h after an incremental cycling test (fatigue) as well as an incremental running test without previous activity (control). Maximum running speed, maximal oxygen uptake (VO2max) and the lactate threshold were determined for each incremental running test and correlated with the average speed during a 5 km run, which was performed immediately after a 20 km cycling time-trial, as in a sprint triathlon. There were no significant differences in maximum running speed, VO2max or the lactate threshold in either incremental running test (control or fatigue). Furthermore, good agreement was found for each physiological variable in both the control and fatigue tests. For the fatigue test, there were significant correlations between the average speed during a 5 km run and both VO2max expressed in absolute terms (r = 0.83) and the lactate threshold (r = 0.88). However, maximum running speed correlated most strongly with the average speed during a 5 km run (r = 0.96). The results of this study indicate that, under controlled conditions, an incremental running test can be performed successfully 5 h after an incremental cycling test to exhaustion. Also, the maximum running speed achieved during an incremental running test is the variable that correlates most strongly with the average running speed during a 5 km run after a 20 km cycling time-trial in well-trained triathletes.

Adaptation, Physiological↗

PubMed1989

Experimental investigation of stress-inducing properties of system response times.

System response times are regarded as a major stressor in human-computer interaction. In two earlier studies short (2s) and long (8s) response times were found to have differential effects on psychological, subjective, and performance variables, but results did not favour either response time. Therefore, in another laboratory study with 48 subjects in four independent groups working at a stimulated computer workplace, system response times of 2, 4, 6 and 8s were introduced in the same error detection task as used before, during 3 training and 5 working trials of 20 min each, and the same physiological, subjective and performance measures were obtained. There were no global effects on physiological variables, possibly due to low work load as a result of missing time pressure, but subjective and performance variables clearly favoured the longer system response times. When task periods and response time-periods were analysed separately, a shift of electrodermal activity could be observed from task- to response time-periods during the course of trials in the 8s condition. This did not appear in any other condition, which points to psychophysiological excitement that develops when system response times are too long, thus providing support for the concept of optimal system response times.

Adolescent↗

PubMed1998

Demonstration of an early and a late phase of ischemic preconditioning in mice.

It is unknown whether ischemic preconditioning (PC; either early or late) occurs in the mouse. The goal of this study was to answer this question and to develop a reliable and physiologically relevant murine model of both early and late ischemic PC. A total of 201 mice were used. In nonpreconditioned open-chest animals subjected to 30 min of coronary occlusion followed by 24 h of reperfusion, infarct size (tetrazolium staining) averaged 52% of the region at risk. When the 30-min occlusion was performed 10 min after a PC protocol consisting of six cycles of 4-min occlusion and 4-min reperfusion, infarct size was reduced by 75%, indicating an early PC effect. When the 30-min occlusion was performed 24 h after the same PC protocol, infarct size was reduced by 48%, indicating a late PC effect. In mice in which the 30-min occlusion was followed by 4 h of reperfusion, infarct size was similar to that observed after 24 h of reperfusion, indicating that a 4-h reperfusion interval is sufficient to detect the final extent of cell death in this model. Fundamental physiological variables (body temperature, arterial oxygenation, acid-base balance, heart rate, and arterial pressure) were measured and found to be within normal limits. Taken together, these results demonstrate that, in the mouse, a robust infarct-sparing effect occurs during both the early and the late phases of ischemic PC, although the early phase is more powerful. This murine model is physiologically relevant, provides reliable measurements, and should be useful for elucidating the cellular mechanisms of ischemic PC in genetically engineered animals.

Animals↗

PubMed2005

Interpopulational variation in recovery time from chill coma along a geographic gradient: a study in the common woodlouse, Porcellio laevis.

Extreme temperatures restrict the performance of terrestrial arthropods and variations in low temperatures on a latitudinal scale influence physiological variables. Recovery time from chill coma is a measure of cold tolerance and it is a good index of climatic adaptation. We tested differences in recovery time of the common woodlouse (Porcellio laevis) exposed to different thermal conditions. Individuals were sampled from four different populations in Chile, spanning a latitudinal range of approximately 10 degrees . Significant differences were found in recovery time among experimental temperatures and among populations, but no interaction between these factors. The results of recovery time in P. laevis showed a positive increment with annual mean minimum temperature, indicating that there is geographical variation in recovery time. While body mass presented interpopulational variation, this variation was not associated with thermal variables or latitude. Overall, our results agree with previous studies in the sense that recovery time from chill coma decreases towards high latitudes, and it is independent of taxa, continent and hemisphere.

Adaptation, Physiological↗

PubMed1984

Monitoring system gas concentrations.

With proper measurement of inhaled and exhaled gas concentrations as well as end-tidal concentrations, patient concentrations of oxygen, carbon dioxide, and the volatile anesthetic agents may be inferred; additional information for vigilance monitoring, control of depth of anesthesia, and calculation of physiologic variables can be obtained. From this information, the anesthesiologist will be able to administer improved patient care through more immediate and complete knowledge and control of both equipment and patient function.

Anesthetics↗

PubMed2005

High-resolution computed tomography in idiopathic pulmonary fibrosis: diagnosis and prognosis.

RATIONALE: High-resolution computed tomography (HRCT) is an integral aspect of the evaluation of patients with suspected idiopathic pulmonary fibrosis (IPF). However, few studies have evaluated its use in a large cohort. OBJECTIVES: To describe HRCT features in patients with mild to moderate IPF, compare diagnostic evaluations by a radiology core (three thoracic radiologists) with those by study-site radiologists, correlate baseline clinical and physiologic variables with HRCT findings, and evaluate their association with mortality. METHODS: We assessed HRCT scans from patients with IPF (n = 315) enrolled in a randomized controlled study evaluating IFN-gamma1b. MEASUREMENTS AND MAIN RESULTS: There was concordance between study-site and core radiologists regarding the diagnosis of IPF in 86% of cases. Diffusing capacity of carbon monoxide (DLCO) was the physiologic characteristic most highly correlated with HRCT findings. Multivariate analysis identified three independent predictors of mortality: a higher extent of fibrosis score increased the risk of death (p < 0.0001), whereas a higher percent-predicted DLCO (p = 0.004) and treatment assignment to IFN-gamma1b rather than placebo (p = 0.04) reduced the risk of death. CONCLUSIONS: A study-site diagnosis of IPF on HRCT was regularly confirmed by core radiologists. Extent of reticulation and honeycombing on HRCT is an important independent predictor of mortality in patients with IPF.

Female↗

PubMed1999

The importance of physical fitness in the performance of adequate cardiopulmonary resuscitation.

The aim of the present investigation was to evaluate the influence of the physical fitness of a cardiopulmonary resuscitation (CPR) provider on the performance of and physiologic response to CPR. To this end, comparisons were made of sedentary and physically active subjects in terms of CPR performance and physiologic variables. Two study groups were established: group P (n=14), composed of sedentary, professional CPR rescuers (mean [+/-SD]; age, 34+/-6 years; VO2max, 32.5+/-5.5 mL/kg/min), and group Ex (n=14), composed of physically active, nonexperienced subjects (age, 34+/-6 years; VO2max, 44.5+/-8.5 mL/kg/min). Each subject was required to perform an 18-min CPR session, which involved manual external cardiac compressions (ECCs) on an electronic teaching mannequin following accepted standard CPR guidelines. Subjects' gas exchange parameters and heart rates (HRs) were monitored throughout the trial. Variables indicating the adequacy of the ECCs (ECC depth and the percentage of incorrect compressions and hand placements) also were determined. Overall CPR performance was similar in both groups. The indicators of ECC adequacy fell within accepted limits (ie, an ECC depth between 38 and 51 mm). However, fatigue prevented four subjects from group P from completing the trial. In contrast, the physiologic responses to CPR differed between groups. The indicators of the intensity of effort during the trial, such as HR or percentage of maximum oxygen uptake (VO2max) were higher in group P subjects than group Ex subjects, respectively (HRs at the end of the trial, 139+/-22 vs 115+/-17 beats/min, p < 0.01; percentage of VO2max after 12 min of CPR, 46.7+/-9.7% vs 37.2+/-10.4%, p < 0.05). These results suggest that a certain level of physical fitness may be beneficial to CPR providers to ensure the adequacy of chest compressions performed during relatively long periods of cardiac arrest.

Adult↗

PubMed1998

Daily torpor and energetics in a tropical mammal, the northern blossom-bat Macroglossus minimus (Megachiroptera).

Little is known about torpor in the tropics or torpor in megachiropteran species. We investigated thermoregulation, energetics and patterns of torpor in the northern blossom-bat Macroglossus minimus (16 g) to test whether physiological variables may explain why its range is limited to tropical regions. Normothermic bats showed a large variation in body temperature (Tb) (33 to 37 degrees C) over a wide range of ambient temperatures (Tas) and a relatively low basal metabolic rate (1.29 ml O2 g-1 h-1). Bats entered torpor frequently in the laboratory at Tas between 14 and 25 degrees C. Entry into torpor always occurred when lights were switched on in the morning, independent of Ta. MRs during torpor were reduced to about 20-40% of normothermic bats and Tbs were regulated at a minimum of 23.1 +/- 1.4 degrees C. The duration of torpor bouts increased with decreasing Ta in non-thermoregulating bats, but generally terminated after 8 h in thermoregulating torpid bats. Both the mean minimum Tb and MR of torpid M. minimus were higher than that predicted for a 16-g daily heterotherm and the Tb was also about 5 degrees C higher than that of the common blossom-bat Syconycteris australis, which has a more subtropical distribution. These observations suggest that variables associated with torpor are affected by Ta and that the restriction to tropical areas in M. minimus to some extent may be due to their ability to enter only very shallow daily torpor.

Adaptation, Physiological↗

PubMed2005

Unusual ECG findings mimicking complete heart block in an unrecognised calcium antagonist overdose.

We present a case of severe cardiovascular instability which required intensive care management after a myocardial infarction had been diagnosed incorrectly. Unusual ECG findings were diagnostic of calcium antagonist toxicity as the cause of the cardiovascular collapse. A discussion of the potential pitfalls in the management of patients intoxicated with these agents is undertaken. Of particular interest is the prolonged period of supportive therapy required prior to the return of an unsupported circulation. The physiological variables encountered with this type of poisoning were confirmed by the use of a PiCCO device.

Angina Pectoris↗

PubMed2005

A physiologically-based early warning score for ward patients: the association between score and outcome.

We analysed the physiological values and early warning score obtained from 1047 ward patients assessed by an intensive care outreach service. Patients were either referred directly from the wards (n = 245, 23.4%) or were routine critical care follow-ups. Decisions were made to admit 135 patients (12.9%) to a critical care area and limit treatment in another 78 (7.4%). An increasing number of physiological abnormalities was associated with higher hospital mortality (p < 0.0001) ranging from 4.0% with no abnormalities to 51.9% with five or more. An increasing early warning score was associated with more intervention (p < 0.0001) and higher hospital mortality (p < 0.0001). For patients with scores above one (n = 660), decisions to admit to a critical care area or limit treatment were taken in 200 (30.3%). Scores of all physiological variables except temperature contributed to the need for intervention and all variables except temperature and heart rate were associated with hospital mortality.

Adult↗

PubMed1994

Cardiorespiratory behavior during sleep in full-term and preterm neonates at comparable postconceptional term ages.

Cardiorespiratory behavior during sleep has been investigated by comparing visually analyzed minutes of EEG sleep with the digitized values of these two physiologic variables for each corresponding minute. Continuous 3-h nighttime sleep studies on 37 full-term and preterm neonates at comparable postconceptional term ages were acquired under controlled conditions, using a 24-channel computerized monitoring system and an automated event-marker program. Five thousand, two hundred ninety-four minutes were assigned an EEG state by traditional criteria. Eighteen preterm infants were compared with 19 full-term infants with respect to six cardiac and six respiratory measures: two nonspectral calculations (i.e. average per minute and variance of the means) and four spectral calculations of the cardiorespiratory signal (i.e. bandwidth, spectral edge, mean frequency, and ratio of harmonics). The relative capabilities of these measures to predict a sleep state change were investigated using discriminant analysis. A stepwise selection algorithm in discriminant analysis was used to identify the order of significance for the remaining variables. Eight cardiorespiratory measures were then submitted to multivariate analysis of variance to assess sleep state or preterm-full-term differences: mean frequency, bandwidth, average per minute, and ratio of harmonics for cardiac signals; and spectral edge, mean frequency, logarithm of variance, and ratio of harmonics for respiratory signals. Differences among the sleep states and between neonatal groups were highly significant (p < 0.0001). Interaction between sleep state and neonatal group was also significant (p < 0.034). Two variables differentiated preterm from full-term respiratory behavior: ratio (p < or = 0.001) and mean frequency (p < or = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular Physiological Phenomena↗

PubMed2005

Central sleep apnea in stable methadone maintenance treatment patients.

STUDY OBJECTIVES: Methadone, a long-acting mu-opioid agonist, is an effective treatment for heroin addiction. Our previous data show that 6 of 10 methadone maintenance treatment (MMT) patients had central sleep apnea (CSA). This study aims to confirm these results and to investigate the pathogenesis of the CSA. METHODS: Twenty-five male and 25 female MMT patients and 20 age-, sex-, and body mass index (BMI)-matched normal subjects were tested with polysomnography, blood toxicology, and ventilatory responses to hypoxia and hypercapnia. Resting cardiorespiratory tests were performed in the MMT group RESULTS: MMT patients and normal subjects were 35 +/- 9 years old (mean +/- SD), and BMI values were 27 +/- 6 kg/m2 and 27 +/- 5 kg/m2, respectively. Thirty percent of MMT patients had a central apnea index (CAI) > 5, and 20% had a CAI > 10. All normal subjects had a CAI < 1, and no difference was found in obstructive apnea-hypopnea index between the two groups. Methadone blood concentration was the only significant variable (t = 2.33, p = 0.025) associated with CAI and explains 12% of the variance. Awake Pa(CO2), antidepressant use, reduced ventilatory response to hypercapnia, and widened awake alveolar-arterial oxygen pressure gradient together explain a further 17% of the CAI variance. CONCLUSIONS: Thirty percent of stable MMT patients have CSA, a minority of which can be explained by blood methadone concentration. Other physiologic variables may also play a role in the pathogenesis of CSA in MMT patients, and further research is indicated in this area.

Adult↗

PubMed2006

Continuous muscle tissue oxygenation in critically injured patients: a prospective observational study.

BACKGROUND: Despite normalization of vital signs, critically injured patients may remain in a state of occult underresuscitation that sets the stage for sepsis, organ failure, and death. A continuous, sensitive, and accurate measure of resuscitation after injury remains elusive. METHODS: In this pilot study, we evaluated the ability of two continuous measures of peripheral tissue oxygenation in their ability to detect hypoperfusion: the Licox polarographic tissue oxygen monitor (PmO2) and the InSpectra near-infrared spectrometer (StO2). We hypothesized that deltoid muscle tissue oxygenation measurements could detect patients in "occult shock" who are at increased risk for post-injury complications. The study was designed to (1) define values for PmO2 and StO2 in patients who by all standard measures appeared to be clinically resuscitated; (2) evaluate the relationship between PmO2, StO2 and other physiologic variables including mean arterial pressure (MAP), lactate and base deficit (BD); and (3) examine the relationship between early low tissue oxygen values and the subsequent development of infections and organ dysfunction. Licox probes were inserted into the deltoid muscle of critically injured patients after initial surgical and radiologic interventions, and transcutaneous StO2 monitors were applied over the same muscle bed. PmO2, StO2, and standard physiologic data were collected continuously using a multimodal bioinformatics system. RESULTS: Twenty-eight critically injured patients were enrolled in this study at admission to the intensive care unit (ICU). For patients who appeared to be well resuscitated (defined as MAP > or = 70 mm Hg, heart rate [HR] < or = 110 bpm, BD > or = -2, and partial pressure of arterial oxygen (PaO2) = 80 and 150 mm Hg), the mean PmO2 was 34 +/- 11 mm Hg and StO2 was 63 +/- 27%. There was a strong relationship between PmO2 and BD (p < 0.001) but no significant relationship between StO2 and BD. The relationship between PmO2 and StO2 was weak but statistically significant. Early low values of both PmO2 and StO2 identified patients at risk for infectious complications or multiple organ failure (MOF). In patients who were well resuscitated by standard continuous parameters (HR and MAP), low PmO2 during the first 24 hours after admission (PmO2 < or = 25 for at least 2 hours) was strongly associated with the development of infectious complications (Odds Ratio = 16.5, 95% CI 1.49 to 183, p = 0.02). CONCLUSIONS: PmO2 is a responsive, reliable and continuous monitor of changes in base deficit. Initial low values for either PmO2 or StO2 were associated with post-injury complications. PmO2 monitoring may be useful in identifying patients in the state of occult underresuscitation who remain at risk for developing infection and MOF.

Adolescent↗

PubMed1998

Randomised controlled trial of eutectic mixture of local anaesthetics cream for venepuncture in healthy preterm infants.

AIM: To assess the safety and efficacy of EMLA cream (eutectic mixture of local anaesthetics) used to induce surface anaesthesia for venepuncture in healthy preterm infants. METHODS: Nineteen infants, median gestational age 31 weeks (range 26-33 weeks) were assessed in a randomised, double blind, placebo controlled, cross-over trial. Changes in physiological variables (heart rate, blood pressure, oxygen saturation) and behavioural responses (neonatal facial coding system score, crying time) before and after venepuncture with EMLA cream were compared with those obtained with a placebo cream to assess efficacy. Toxicity was assessed by comparing methaemoglobin concentrations at 1 hour and 8 hours after application. RESULTS: There was no significant difference in efficacy between EMLA and placebo creams in physiological and behavioural responses. There was no significant difference in methaemoglobin concentrations one hour after the cream had been applied. At eight hours, however, concentrations were significantly higher after EMLA than placebo (p = 0.016). There was no evidence of clinical toxicity. CONCLUSION: This study does not support the routine use of EMLA for venepuncture in healthy preterm infants.

Anesthesia, Local↗

PubMed2002

[Prediction of the length of stay in Intensive Care Units using artificial neural networks].

BACKGROUND: The prediction of the length of stay at the moment of hospital admission is of utmost importance. Many studies have used lineal models to predict this variable, but there are inherent limitations to these models. The use of non lineal models has been scarce. AIM: To develop a non lineal model to predict length of stay in intensive care units. MATERIAL AND METHODS: Retrospective analysis of 294 patients admitted to two intensive care units in Santiago, Chile. The severity of the disease motivating the admission was nominally quantified. This and other physiological variables were included in the model. The length of stay was modeled using Artificial Neural Networks. RESULTS: The model yielded an error of 8.7% (3.6 +/- 0.4 days, CI 95%) and a correlation coefficient of 0.9 (p < 0.001) for the prediction of length of stay. Using net sensitivity analysis, the model determined that gastrointestinal diseases, infections and respiratory problems were the main causes of prolongation of intensive care unit stay. CONCLUSIONS: Intensive care units should have, in the future, computer systems that gather vital information to predict length of stay.

Female↗