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PubMed2006

Autonomic response and Fos expression in the NTS following intermittent vagal stimulation: importance of pulse frequency.

Chronic intermittent stimulation of the vagus nerve (VNS) is an approved adjunctive therapy of refractory epilepsy. Nevertheless, the circuits triggered by VNS under the variable conditions used in patients are not well understood. We analyzed the effect of increasing pulse frequency on physiological variables (intragastric pressure, cardiac and respiratory frequencies) and neuronal activation in the solitary tract nucleus (NTS), the entry level of peripheral vagal afferents, in the rat. For this purpose, we compared the subnuclear distribution of Fos-like immunoreactivity within the NTS following VNS at frequencies selected for their low (1 Hz) or high (10 Hz) therapeutic efficacy. In addition, NADPH diaphorase histochemistry was conducted in double-labeling experiments to check whether activated neurons may express nitric oxide (NO). We demonstrated that increasing pulse frequency had a major influence on the cardiorespiratory response to VNS and on the amount of activated neurons within NTS subdivisions engaged in cardiorespiratory control. These data, in line with clinical observations, suggested that within the range of therapeutic frequency, VNS may favor the regulation by vagal inputs of cortical activities within limbic areas involved in both epileptogenesis and cardiorespiratory afferent control. Furthermore, we did not find any evidence that anticonvulsant VNS might trigger NOergic neurons in the NTS.

Animals↗

PubMed1987

The effect of methodology and tracer identity on a non-invasive index of liver blood flow.

There are a number of clinical conditions in which quantification of the relative flow in the arterial and portal vessels supplying the liver may be of diagnostic use. The hepatic perfusion index has been proposed as a non-invasive indicator of relative blood flows. The technique involves analysis of first-pass time-activity curves over the liver and kidney with the calculations of an index which is derived from the slopes of the hepatic curve before and after the renal peak. In previously published studies, the methodology adopted has been variable, both in the analysis and in tracer identity. This study examines the effect of both physical and physiological variables on the index. The results indicate that in addition to relative arterial and portal flows, the index is dependent on bolus quality, the length of time over which the slopes are averaged, transit times through the liver and splenic and mesenteric circulations, and the degree of tracer extraction. Furthermore, the data suggest that values in the currently considered abnormal range may be poor indicators of relative arterial and portal venous flows.

Humans↗

PubMed1991

Rate-responsive cardiac pacemakers.

Pacemaker technology continues to advance in the direction of restoring a normal hemodynamic response under varying physiologic conditions. Rate-responsive pacemakers meet this challenge by adjusting the pacing rate in response to a sensed physiologic variable other than sinus node activity. In an effort to design the ideal rate-responsive system, various physiologic cues have been tested. To translate shifts in the sensed physiologic indicator into an appropriate pacing rate, specialized sensor systems also have been developed and include mechanical, chemical, thermal, and electrical sensors. Although each sensor system offers advantages and disadvantages, continued research and clinical experience will determine the future of this exciting new form of cardiac pacing.

Cardiac Output↗

PubMed1987

Case study of psychophysiological diary: infradian rhythms.

A 4-year case study was made of a 42-year-old white woman as seen through the psychophysiological diary. There was an awakening diary and a bedtime diary composed of 125 variables. The data are divided into two series: series I containing a manic episode, and series II as a control. Spectral analysis shows infradian rhythms in hypoglycemia and fear (11 days) and time to fall asleep (5 days). Depressed feelings showed a circatrigintan (28-day) rhythm, which was not correlated with menses. Mania had an annual rhythm (spring) but no circatrigintan or less rhythm. The following correlations have a P value less than or equal to 0.01: mania was directly correlated with number of sleeping pills, time to really wake up, need for rest, moodiness, and helplessness, and indirectly with expectations, pressure at work, sense of time, and emotional state. Interestingly, awakening pulse is directly correlated with awakening temperature, number of sleeping pills, bedtime pulse, tiredness at bedtime, hypoglycemia, and fear. Bedtime pulse is directly correlated with awakening pulse and awakening temperature. Both pulse and temperature at bedtime are directly correlated with negative variables such as tiredness, moodiness, helplessness, and depression, and inversely correlated with positive variables such as happiness, loving, performance at work, and thinking efficiency. This study demonstrates a significant correlation between physiological variables.

Adult↗

PubMed2005

Extracorporeal sensing techniques.

Many physiologic variables have been measured in the extracorporeal circulation by experimental systems but only a few systems have reached technical maturity for everyday application. Variables relating to cardiovascular function, which today can be measured in the extracorporeal system, are pressure, temperature, and measures of blood composition such as hematocrit, hemoglobin, and total protein concentration. While the measurement of blood composition and temperature is well established, and while the use of extracorporeal pressure information awaits further analysis for robust application, recent interest focused on continuous measurement of plasma sodium concentration which is believed to be of major importance for optimal blood treatment. However, problems with a simple, reliable, and continuous measurement of plasma sodium for everyday use have not yet been resolved. As can be seen from the growing interest in isothermic or isonatremic treatment modes which turns away from constant and profiled treatment modes without feedback control, the treatment goal is now to provide stable conditions within the patient so as to minimize interference with intrinsic physiological control mechanisms. This, however, requires valid and reliable measurement of the specific patient variables of interest.

Blood Physiological Phenomena↗

PubMed1999

Spatial response properties of contralateral inhibited lobula plate tangential cells in the fly visual system.

This study describes the spatial response properties of a particular group of motion-sensitive and directionally selective neurons located in the lobula plate of the fly visual system. Their preferred motion direction is front-to-back (depolarization), and their null direction is back-to-front (hyperpolarization). They receive inhibitory input from the contralateral eye during pattern motion from back to front (regressive). In this study, we call these neurons regressive contralateral inhibited lobula plate tangential cells (rCI-LPTCs). Three physiologic groups of rCI-neurons (rCI-I, rCI-IIa, and rCI-IIb) can be distinguished on the basis of their ipsilateral pattern size dependence and their inhibitory contralateral input. rCI-I neurons depolarize during the motion of small ipsilateral patterns from front to back, but they become hyperpolarized by large ipsilateral patterns moving in the same direction. rCI-IIa and rCI-IIb neurons receive bidirectional inhibitory input from the contralateral eye. rCI-IIa neurons respond best to small ipsilateral pattern sizes, but unlike rCI-I neurons, their net response to large patterns is positive. rCI-IIb neurons respond best to large ipsilateral patterns. The anatomical and physiologic variability of the rCI-neurons suggests that more than three types of rCI-neurons exist. The suggested physiologic groups might be preliminary. We recorded one neuron that could mediate the bidirectional inhibitory input that rCI-IIa and rCI-IIb neurons receive from the contralateral eye. In the case of the rCI-IIa neurons at least one further contralateral inhibitory element has to be assumed. The tuning of rCI-IIa neurons to small ipsilateral pattern sizes is likely to be based on an on-center/off-surround organization of their synaptic input.

Animals↗

PubMed1995

Serotonergic modulation of anticholinergic effects on cognition and behavior in elderly humans.

Cholinergic neurotransmission is thought to be modulated by serotonin as documented in animal and human studies. We examined the effects of the muscarinic antagonist scopolamine (0.4 mg IV) given alone or together with the serotonin mixed agonist/antagonist m-chlorophenylpiperazine (m-CPP, 0.08 mg/kg IV), and the selective 5-HT3 receptor antagonist ondansetron (0.15 mg/kg IV). Ten normal elderly volunteers each received five separate pharmacologic challenges (placebo, ondansetron, scopolamine, scopolamine+ondansetron, and scopolamine+m-CPP). Cognitive, behavioral, and physiologic variables were analyzed using repeated measures analysis of variance. The acute effects of scopolamine in certain cognitive, behavioral, and physiological measures were significantly exaggerated by the addition of m-CPP. Scopolamine's cognitive effects were unaffected by ondansetron at the dose tested, nor did ondansetron given alone affect basal cognitive performance. This pilot study suggests that the serotonin mixed agonist/antagonist m-CPP may influence cholinergic neurotransmission. The changes associated with the combination of scopolamine and m-CPP do not appear to be secondary to simple pharmacokinetic alterations and suggest a complex interaction between the cholinergic and serotonergic systems centrally.

Aged↗

PubMed1981

Design of the mammalian respiratory system. VIII Capillaries in skeletal muscles.

The relationship between capillary density and mitochondrial volume density in skeletal muscle tissue is investigated on 25 African mammals ranging in body mass from 0.4 to 251 kg. As a general trend higher capillary densities, NA (c,f) are found in muscles with higher volume densities of mitochondria, Vv(mt,f). The individual data however show considerable scatter. Part of this scatter can be explained by the fact that NA (c,f) alone is not a sufficient parameter to account for functional properties of the vascular supply. The regional variability of the capillary network from arterial to venous end also contributes to the data spread. A number of physiological variables of the vascular compartment may also influence the relationship of capillary counts to the mitochondrial densities of muscle fibers. This relationship therefore cannot be expected to be a simple one.

Africa↗

PubMed1996

Circadian adjustment of men and women to night work.

OBJECTIVES: The aims of the present study were to define the adjustment of sleep-wakefulness and other circadian rhythms during consecutive night shifts and to study the effect of gender on the adjustment to night work. METHODS: Twenty experienced shift workers, 9 men and 11 women, were studied under controlled laboratory conditions. After a night of habituation, the subjects worked one day shift and three night shifts. Rectal temperature was measured continuously during the study. Salivary melatonin and cortisol were assessed at 2-h intervals, and subjective sleepiness was checked every hour during the work shifts. Sleep was registered by the static-charge sensitive bed (SCSB) method after the workshifts. RESULTS: Subjective sleepiness varied both between the work shifts and between the men and women. The subjects felt most alert during the day shift and were the sleepiest during the first night shift. Sleepiness decreased during the consecutive night shifts but did not reach the level of the day shift during the three nights. The sleepiness of the women decreased more than that of the men, the difference being significant during the second and third night shifts (P < 0.05). The circadian rhythm of body temperature, salivary cortisol, and time in bed changed significantly (P < 0.05) between the workshifts, but no differences were found between the men and women in the circadian adjustment of the physiological variables to night work. CONCLUSIONS: The men felt sleepier than the women during the consecutive night shifts, although no physiological differences were found between the genders. However, since normal social and domestic factors were excluded, the findings cannot be considered as evidence of women's better adaptation to night work in everyday life.

Adaptation, Physiological↗

PubMed1998

Cardiovascular chronobiology: implications for critical care nursing.

Critical care clinicians must consider known expected circadian rhythms when interpreting fluctuations in patients' hemodynamic values. As noted in the case study, knowledge of circadian rhythmicity in cardiovascular variables may help clinicians anticipate hemodynamic changes and develop and evaluate chronobiologically sensitive interventions, including prescriptions for activity, modification of the timing of medications, and provision of protective interventions for patients with disrupted rhythms. Felver provides excellent guidelines for the systematic review of possible causes for overt changes in circadian patterns. This review highlights the need to evaluate (1) the effect of disease progression on temporal patterns, (2) the patient's underlying endogenous rhythms, (3) the zeitgebers that may entrain the patient's biological rhythms (e.g., light, social cues, and sleep-wake cycles), and (4) how the zeitgebers change in a critical care environment. The body of literature on the rhythmic fluctuation of cardiovascular variables in healthy, young subjects is extensive. During the past 10 years, research on the chronobiologic fluctuations of numerous physiological variables (cardiovascular, pulmonary, hematologic, and endocrine) in critical illness has increased. As information on the fluctuations in critically ill patients increases, critical care clinicians will be challenged to develop and evaluate a chronobiologically sensitive plan of care for these patients.

Humans↗

PubMed1995

Replication and extended analysis of behavior state, environmental events, and related variables among individuals with profound disabilities.

Knowledge from previous studies pertaining to state behavior of individuals with profound and multiple disabilities and its relation to other environmental and physiological variables was replicated and extended. Behavior state and environmental data were collected over a 5-hour period for most of 66 students with profound disabilities from 21 educational settings. Results showed general consistency in state patterns and profile groupings with previous investigations, a strong relation between different state profiles and measures of development, and consistency of state patterns across CA levels. Transitional probabilities and z scores were used to confirm changes in state behavior of half of the subjects following primarily adult interactions. Results were discussed in relation to theoretical implications and intervention recommendations.

Activities of Daily Living↗

PubMed1975

Correlation of psychophysiologic variables with vocational rehabilitation outcome in patients with chronic obstructive pulmonary disease.

Despite the magnitude of the public health problem presented by respiratory diseases, there have been few studies concerned with vocational rehabilitation (VR) potential of patients with chronic obstructive pulmonary disease (COPD). Certain physiologic variables which show a high degree of relationship to VR success are identified. The three independent variables which most highly correlate with the VR potential of patients with COPD are the percentages predicted for the first-second forced expiratory volume (FEV(1.0)), forced expiratory flow between 25 and 75 percent of the forced vital capacity (FEF(25-75 percent)), and maximum voluntary ventilation (MVV). The mean "cutting" percentages for inclusion in VR programs were 50, 27, and 40, respectively. The emotional variables studied do not differentiate potential VR success or failure as clearly as the physiologic factors. The criteria set forth not only can be used by rehabilitation workers but could serve as a basis for future demonstration studies.

Adult↗

PubMed1989

Oxygen delivery in patients with adult respiratory distress syndrome who undergo surgery. Correlation with multiple-system organ failure.

Identification of the physiologic determinants of survival in patients with adult respiratory distress syndrome (ARDS) has been largely unsuccessful. We evaluated multiple physiologic variables over the first three reversible phases of ARDS. A stepwise multivariant linear regression analysis was used to identify correctable physiologic correlates with survival. Our goal was improved survival. We found that the oxygen delivery and alveolar-arterial oxygen gradient on the third day after the diagnosis of ARDS were the two most important correctable correlates. Both eventually effected the development of multiple-system organ failure and survival. These data provide clinical evidence that optimization of both the oxygen delivery and alveolar-arterial oxygen gradient after the onset of ARDS may allow resolution of ARDS, prevent additional organ dysfunction, and improve survival.

Adult↗

PubMed1988

A systems theoretic approach to the study of CNS function.

This paper presents a paradigm for using a general systems theoretic approach to study central nervous system function. Neuronal systems are conceptualized as consisting of different populations of neurons, each of which may be treated as a unit with its own dynamic properties. These dynamic properties of each population are determined by fundamental characteristics of its constituent neurons. Different populations interact with each other through the network structure in which they are embedded. We are modeling the linear and nonlinear properties of these systems using a theoretical framework based on two complementary approaches. First, a functional power series is used to characterize the input/output properties of the system. Second, a state-variable approach is used to characterize the internal structure and function of the system and to identify specific relationships among physiological variables. We have extensively investigated the functional power series approach to study the cat somatosensory system and the rabbit hippocampal formation. Both of these systems exhibit nonlinear properties in their response to electrical stimulation, and these nonlinear properties are characterized by the high-order kernels of the functional power series. State-variable models are being formulated to map these input/output properties onto internal models of the systems.

Animals↗

PubMed2001

Remifentanil versus meperidine for monitored anesthesia care: a comparison study in older patients undergoing ambulatory colonoscopy.

UNLABELLED: Colonoscopy is one of the most frequently performed outpatient procedures in the United States. This study was designed to test the hypothesis that a remifentanil infusion would be superior to boluses of meperidine in older patients undergoing ambulatory colonoscopy. One hundred ASA physical status I-IV patients undergoing colonoscopy were randomized in this double-blinded study to receive either remifentanil infusions (n = 49) or titrated boluses of meperidine (n = 51). Patient tolerance was assessed using physiologic variables and side effects associated with opioid analgesia. Verbal pain/anxiety and patient/operator satisfaction were also assessed. As a group, the physiologic characteristics demonstrated no significant differences in the response to the colonoscopy procedure. Although the patient and operator satisfaction surveys were similar between groups, the incidences of tachycardia, hypotension, and nausea were less and the adjusted verbal pain and anxiety scores were more in the Remifentanil group compared with the Meperidine group. This study demonstrates that remifentanil and meperidine were equally well tolerated in older patients undergoing ambulatory colonoscopy when administered by an anesthesia provider. The differences in the pharmakinetics of remifentanil and meperidine most likely account for the differences noted between the two treatment groups. IMPLICATIONS: Remifentanil infusions and meperidine boluses are equally well tolerated in older patients undergoing ambulatory colonoscopy when administered by an anesthesia provider.

Adjuvants, Anesthesia↗

PubMed2002

Physiological measurements and upper and lower respiratory tract evaluation in French Standardbred Trotters during a standardised exercise test on the treadmill.

There are a variety of reasons for poor performance in racehorses. Exercise intolerance has often been associated with subclinical respiratory abnormalities, and diagnostic aids are therefore used to enhance clinical detection. Physiological variables can also be measured in order to evaluate the metabolic reponse to exercise. This study evaluated the relationship between physiological measurements and upper airway videoendoscopy during a standardised treadmill exercise test and bronchoalveolar lavage (BAL) cytology in control horses (good racing performance, n = 14) and poor performers (n = 27). The poor performers were divided into 2 groups: Group 1 = both upper and lower respiratory airway abnormal findings (n = 10); Group 2 = lower respiratory airway abnormal findings (n = 17). Horses in Group 2 were divided into 3 categories: Group 2A = exercise-induced pulmonary haemorrhage (EIPH ; n = 5); Group 2B = small airway inflammation (SAI +/- EIPH; n = 7) and Group 2C = other (n = 5). During exercise, the poor performers had significantly lower arterial PaO2 and higher HR and blood lactate concentrations compared to controls. Total nucleated cell count of BAL fluid collected from poor racing performers was significantly higher than in controls; also, epithelial cells and haemosiderophage percentage collected from poor racing performers were significantly higher than in controls. Eight horses with dorsal displacement of the soft palate also had cytological evidence of lower respiratory airway disease. The results of this study suggest that there is a significantly different metabolic response (HR, blood lactate, PaO2) to exercise in poor compared to good performers. As both upper and/or lower respiratory problems can be associated with poor racing performance, a detailed examination of the upper and lower respiratory tracts at rest, during and after exercise is advised.

Animals↗

PubMed1994

Predicting orthostatic intolerance: physics or physiology?

To adequately assess the viability of any particular causal theory of orthostatic intolerance, physical and physiological parameters thought to be associated with orthostasis must be evaluated simultaneously within the same individual. Time, cost, and complexity of instrumentation generally limit studies of orthostatic intolerance to a single independent effect for any given sample of subjects. We, therefore, measured 6 key physical and physiological variables associated with various theories of orthostatic intolerance in 14 males to test the hypothesis that physical factors rather than physiological reflex mechanisms were dominant in contributing to orthostatic tolerance. Measurements included height, plasma volume (expressed as percent of total weight), variation in R-R interval, leg compliance, and carotid-cardiac (high pressure), and cardiopulmonary (low pressure) baroreflex sensitivity. Subjects' orthostatic intolerance was quantified by time to syncope during progressive supine lower body decompression. Correlations, regression coefficients, and indices of replicability were calculated using 500 to 1,000 bootstrap resamplings of the original 14 observations. Although all six measurements correlated with time to syncope when evaluated individually, only height (negative), percent plasma volume weight (positive), and, to a lesser extent, carotid-cardiac baroreflex sensitivity yielded consistent (reproducible) results when all measures were tested simultaneously. These results suggest that while orthostatic intolerance may be dependent upon a variety of physiological reflexes, physical factors such as height and plasma volume tend to dominate the prediction of time to syncope during lower body negative pressure (LBNP). Physiological reflexes, which act to maintain adequate profusion to the brain during normal terrestrial posture in humans, may be overwhelmed by the additional orthostatic challenge imposed by progressive lower body decompression.

Adult↗

PubMed2004

[Garbage in-garbage out: influence of preanalytical variables on hematological analysis].

Preanalytical factors have a significant impact on the quality of hematological analyses and must not be disregarded during clinical interpretation of laboratory data. Besides unchangeable physiological variables such as age, sex, race, patient preparation, an expert phlebotomy, rapid transport to the laboratory as well as many other variable factors play a crucial role in obtaining correct laboratory results. More advanced tests (erythrocyte enzymes, evaluation of hemoglobinopathies, molecular biology, flowcytometric characterization of leucocytes etc.) performed by specialized centers require special preanalytical measures. The centers should be consulted about the preanalytical conditions before blood sampling is performed or--if possible--the patient should be sent to these centers for phlebotomy.

Analysis of Variance↗