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PubMed1994

Ventilatory threshold and work efficiency during exercise on cycle and paddling ergometers in young female kayakists.

The aim of this study was to assess the effects of increasing specific (paddling ergometer) and non-specific (cycle ergometer) exercise on parameters relating to the ventilatory threshold (Th(vent)) and work efficiency in 11 young female flat-water kayakists. When these trained subjects were tested using non-specific workloads, their oxygen uptake (VO2) values at Th(vent), as a percentage of VO2max (%VO2max), were close to those of untrained subjects [74.2 (5.6) % VO2max, mean (SD)]. However, when we tested the same subjects using specific exercise, we recorded values typical of highly trained athletes [84.8 (4.7) % VO2max). For the non-specific exercise on the cycle ergometer, we recorded work efficiency values close to those of untrained subjects [22.3 (2.5) %]; however, for the specific exercise on the paddling ergometer, we recorded much lower values [13.4 (3.0) %] both at the level of Th(vent). The work efficiency at two warm-up submaximal exercise loads on the paddling ergometer was non-significantly lower than values at Th(vent) [12.3 (2.8) % and 12.9 (2.9) % respectively]. Significant correlations were found between maximal-performance VO2 (ml.kg-1.min-1) and performance at Th(vent) during paddling and race performance (0.623, 0.630 and 0.648 respectively, all P < 0.05). Because the results of both specific and non-specific submaximal exercise tests are different, we suggest caution in the interpretation of physiological variables that may be sensitive to training status. The evaluation of Th(vent) and work efficiency as supplementary parameters during laboratory studies enables the determination of the effectiveness of the training process and the specific adaptation of the subjects.

Adaptation, Physiological↗

PubMed1998

Psychological and physiological parameters of masticatory muscle pain.

The objective of this research was to identify the psychological and physiological variables that differentiate persons reporting masticatory muscle pain (MMP) from normal controls (NC). This study examined the characteristics of 35 MMP patients in comparison to 35 age-, sex-, and weight-matched NCs. All subjects completed a series of standardized questionnaires prior to undergoing a laboratory evaluation consisting of a psychosocial stressor and pressure pain stimulation at multiple body sites. During the evaluation, subjects' emotional and physiological responses (heart rate, blood pressure, respiration, skin temperature, and muscle activity) were monitored. Results indicated that persons with MMP reported greater fatigue, disturbed sleep, depression, anxiety, menstrual symptoms, and less self-deception (P's < 0.05) than matched controls. At rest, MMPs had lower end tidal carbon dioxide levels (P < 0.04) and lower diastolic blood pressures than the NCs (P < 0.02). During laboratory challenge, both groups responded to the standard stressor with significant physiological activity and emotional responding consistent with an acute stress response (P < 0.01), but there were no differences between the MMPs and NCs. Muscle pain patients reported lower pressure pain thresholds than did NCs at the right/left masseter and right temporalis sites (P's < 0.05); there were no differences in pressure pain thresholds between MMPs and NCs for the left temporalis (P < 0.07) and right/left middle finger sites (P's > 0.93). These results are discussed in terms of the psychological and physiological processes that may account for the development of muscle pain in the masticatory system.

Adult↗

PubMed2000

Physiological responses to cycling for 60 minutes at maximal lactate steady state.

Changes in physiological variables during a 60-min continuous test at maximal lactate steady state (MLSS) were studied using highly conditioned cyclists (1 female and 9 males, aged 28.3 +/- 8.1 years). To determine power at MLSS, we tested at 8-min increments and interpolated the power corresponding to a blood lactate value of 4 mmol/L. During the subsequent 60-min exercise at MLSS, we observed a sequential increase of physiological parameters, in contrast to stable blood lactate. Heart rate drifted upward from beginning to end of exercise. This became statistically significant after 30 min. From 10-60 min of exercise, a change of +12.6 +/- 3.2 bpm was noted. Significant drift was seen after 30 min for the respiratory exchange ratio, after 40 min for the rate of perceived exertion using the Borg scale, and after 50 min for % VO(2)max/kg and minute ventilation. This slow component of VO(2)max may be the result of higher recruitment of type II fibers.

Adult↗

PubMedDate not supplied

Relaxation training as a nursing intervention versus pro re nata medication.

To determine the effect of relaxation training on the frequency of intake of pro re nata medication for relief of tension and to compare the difference between live and taped instructions of this training 60 patients on PRN minor tranquilizers and sedatives in one nursing unit were studied. Subjects were randomly assigned to three groups: group A, control; group B, live instruction; group C, taped instruction. Dependent variables monitored were: 1) frequency of intake of PRN medication; 2) pre- and postinstruction change in blood pressure, pulse, and respiration; 3) change in the Taylor Manifest Anxiety Scale; and 4) change on the Minnesota Multiphasic Personality Inventory score. Although no significant difference was found between method of relaxation training, there was evidence that group B surpassed group C in terms of benefit of the treatment. Physiologic variables as well as MMPI scales K, I, and VII yielded better results for group B. Not all variables demonstrated significant differences. Groups B and C were more similar at the conclusion of the study than had been anticipated-perhaps because subjects responded favorably to inclusion in the study regardless of method of training.

Analysis of Variance↗

PubMed2002

Propofol infusion is associated with a higher rapid shallow breathing index in patients preparing to wean from mechanical ventilation.

OBJECTIVE: To determine whether propofol affects spontaneous breathing patterns in critically ill patients recovering from respiratory failure during initial attempts at liberation from mechanical ventilation. DESIGN: Observational cohort study. PATIENTS: Ten critically ill patients in the medical intensive care unit of a 300-bed community teaching hospital. MEASUREMENTS: Demographic and physiologic variables, including respiratory frequency and minute volume, were recorded while patients breathed on continuous positive airway pressure (of 5 cm H(2)O) during and 20-30 min after cessation of propofol infusion. The ratio of respiratory frequency to tidal volume (rapid shallow breathing index or RSBI) was computed for both sets of measurements and values measured during and after propofol infusion were compared. RESULTS: The mean (+/- SEM) age was 54.0 +/- 5.2 years and the mean (+/- SEM) APACHE II (Acute Physiology and Chronic Health Evaluation) score was 18.4 +/- 2.0. During propofol infusion, patients breathed with a significantly lower tidal volume (0.245 vs 0.342 L, p = 0.006), higher RSBI (155.6 vs 114.8 breaths/min/L, p = 0.004), and tended to breathe more rapidly (34.3 vs 31.7 breaths/min, p = 0.18) than at 20-30 min after stopping propofol infusion. Three of 10 patients had RSBIs that were unfavorable (> 105 breaths/min/L) for weaning while on propofol but that became favorable (< 105 breaths/min/L) 20-30 min following cessation of propofol. The weight-adjusted dose of propofol was not correlated with the changes in any of the variables. CONCLUSIONS: Propofol causes changes in breathing pattern that could lead a caregiver to erroneously conclude that a patient is not ready to begin spontaneous breathing trials. Since this effect has also been noted following benzodiazepine infusion, the clinician should consider the patient's "sedation history" when using RSBI to guide weaning decisions.

APACHE↗

PubMed2006

Applied physiology of tennis performance.

Competitive tennis play requires a combination of the major physiological variables; however, the specifics of these variables have yet to be determined appropriately. General strength and flexibility training have been suggested as being beneficial for performance and injury prevention, yet specific guidelines are lacking. This paper provides a review of specific studies that relate to competitive tennis, and highlights the need for tennis-specific training as opposed to generalised physical training. It identifies specific studies that support the premise that tennis has physiological requirements which need to be understood when designing training and research programmes.

Adolescent↗

PubMed2006

The detrimental effects of allostasis: allostatic load as a measure of cumulative stress.

Since its inception in the 1980s, through further developments during the 1990s, and continuing today, the paradigm of allostatic load (AL) has becomed an important paradigm for predicting senescence and mortality. AL is a cumulative measure of the effects of multiple stressors and the process of responding to stressors on the soma. AL measurements of individuals is being tested on various samples and species and being reported across a variety of medical and social science journals. From the ISI Web of Science, all articles published between January 2000 and June 2005 with AL in any default category were obtained and transferred to Endnote. These articles, categorized as theory/review or data-driven, human or animal, and variability in risk factors used to estimate AL, are reviewed here. Only two of 90 reports were published in anthropological journals, likely, at least partly, because research on AL has focused more on western, industrialized populations where data are more easily obtained. From 2000-2005, 12 of 42 data-driven reports focused on elderly humans. Studies of animal models also are common (0 in 2000, but 4 in 2004 covering 21 species). During the last year, multiple additional potential physiological variables have been tested as measures of AL (10 to 20 in any one article). In the past half decade, AL also has been introduced to a wide range of disciplines, including psychology, anthropology, gerontology, veterinary medicine, and medical specialties, as a viable research theme. AL appears to provide a useful method for determining cumulative somatic stress such as that seen with senescence and frailty at older ages.

Adaptation, Physiological↗

PubMed2002

Circadian patterns of breathing.

In the rat, a mostly nocturnal animal, activity, body temperature and metabolic rate increase during the dark hours of the day. Since all these variables are known to influence breathing, it is expected that also pulmonary ventilation (VE) will present a circadian pattern. In rats chronically instrumented for measurements of body temperature and activity by telemetry, carbon dioxide production and oxygen consumption (V(O(2))) were measured continuously for several days by an open-circuit method, while VE was monitored by a modification of the barometric technique. Tidal volume, frequency, and VE increased in the dark (D) compared to the light (L) hours, with minor L-D differences in VE/V(O(2)). L-D differences in activity were not responsible for the circadian pattern of VE. Both in hypoxia and in hypercapnia the degree of hyperventilation (percent increase in VE/V(O(2))) was essentially independent of the time of the day, despite the fact that in hypoxia, differently from hypercapnia, the amplitude of the circadian pattern of all variables decreased, activity being the least affected, and body temperature the most. These effects of hypoxia, which occurred before and after sino-aortic denervation and did not compromise the period of the biological clock, may be mediated by the hypothalamic thermoregulatory centers. The data of these experiments and of others reviewed in this article indicate that (1) breathing and its control mechanisms accompany the daily oscillations of numerous physiological variables, and (2) the advantages of a biological clock do not compromise the adequacy of the hyperventilatory responses to chemical challenges.

Animals↗

PubMed1989

Different 1.2 MAC combinations of nitrous oxide-enflurane cause unique cerebral and spinal cord metabolic responses in the rat.

The effect of three different 1.2 MAC combinations of nitrous oxide (N2O) and enflurane upon glucose metabolism in the central nervous system was evaluated in male rats (n = 30). Anesthesia was induced with enflurane and N2O prior to tracheal intubation and mechanical ventilation. Physiologic variables (temperature, blood pressure, pH, PaO2, PaCO2, serum glucose, and hematocrit) were maintained within normal limits. Each rat was randomly assigned one of the following 1.2 MAC anesthetic regimens: 1) control--0% N2O/2.76% enflurane, 2) treatment 1--30% N2O/2.26% enflurane, or 3) treatment II--60% N2O/2.12% enflurane. Following anesthetic equilibration, an autoradiographic evaluation of local cerebral and spinal cord glucose utilization was performed. There were no differences in the physiologic data. As enflurane was partially replaced by an equivalent MAC fraction of N2O (0-30%), a heterogeneous activation of cerebral metabolism was observed in selected sensory input structures, and in components of the limbic system. The values tended to return to control when N2O was increased to 60% (and the enflurane was appropriately reduced). At all spinal cord levels, a homogeneous increase in metabolism was observed in both white and grey matter when enflurane was replaced by the 0-30% N2O change, with a return to control when the N2O was further increased from 30-60%. Thus, in rats, increasing the N2O concentration (while concurrently decreasing enflurane) produced a biphasic metabolic response. Metabolism was activated when N2O was increased from 0-30%, with a relative depression in metabolism when N2O was further increased from 30-60%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2006

Inflammatory, coagulatory and circulatory responses to logarithmic increases in the endotoxin dose in the anaesthetised pig.

Although porcine intravenous endotoxin shock models are widely employed in experimental sepsis, endotoxin dose-effect studies are scarce. Our primary aim was to establish the dose response to increasing endotoxin doses in inflammatory, coagulatory and haemodynamic effect variables, as well as to determine the optimal time point for assessment in a pig model. A secondary aim was to study pathophysiological covariations between the different responses. Twenty anaesthetised piglets received endotoxin intravenously in doses of 0.063 (n = 3), 0.25 (n = 3), 1.0 (n = 3), 4.0 (n = 3), 8 (n = 3) and 16 microg/kg/h (n = 2). In addition, non-endotoxin piglets constituted a control group (n = 3). Physiological variables were registered and blood samples analysed for TNF-alpha, IL-6, leukocyte, platelet and haemoglobin concentrations hourly for 6 h. Increases in the endotoxin dose induced significant log-log cytokine responses as well as log-linear leukocyte and platelet responses. Significant log-linear responses were observed for circulatory parameters, plasma leakage, hypoperfusion and pulmonary compliance. Significant covariations in the responses were noted. In conclusion, there were log-log or log-linear responses to endotoxin suggesting a greater effect of a given dose at lower pre-existing endotoxin concentrations and lower doses of < or = 1 microg/kg/h may be of advantage in experiments designed to study potential anti-endotoxin effects of experimental drugs or measures.

Anesthesia↗

PubMed2004

Sleep-promoting functions of the hypothalamic median preoptic nucleus: inhibition of arousal systems.

Recent work supports the hypotheses developed by von Economo and Nauta and elaborated by Sallanon et al. that the POA contains a sleep-promoting output that opposes wake-promoting neuronal groups in the PH. The POA gives rise to descending pathways that terminate within wake-promoting populations in pLH, PH and midbrain. Current evidence suggests that this output originates in POA sleep-active GABAergic neurons. This output also seems to convey the signals of homeostatic drive. Disynaptic projections from the SCN to both MnPN and VLPO were recently identified. These may regulate the circadian control of sleep propensity. The hypothesis that the descending projections from POA sleep-active neurons to sites of arousal-related neurons originates in GABAergic neurons must be confirmed. Also to be further clarified is the anatomical distribution of putative sleep-active GABAergic neurons within the POA. Segregated groups have been found in the MnPN and VLPO, but unit recording studies of sleep-active neurons, lesion studies and local neurochemical application studies all indicate that sleep-active neurons may be found diffusely in the POA and adjacent areas. The MnPN has been shown previously to be involved in water balance and blood pressure regulation and to be responsive to hyperthermia. Our studies suggest that this nucleus also contains sleep-active, putative sleep-promoting neurons. However, interactions between sleep control and physiological variables must be considered. In particular, the details of neuronal basis of the coupling of warm-sensitive neurons in MnPN to the POA hypnogenic output has not been explored. It is also worth noting that both the VLPO and MnPN lie close to the ventricular and subarachnoid surface and are punctuated by radial arterioles. The possibility that the sleep-regulatory functions of these sites is coupled to physiological signals conveyed through epithelial cells has been suggested for the actions of PGD2 but has yet to be explored in detail for other putative hypnogens.

Action Potentials↗

PubMed1977

Is nicotine important to tobacco smoking?

Tobacco smoking is generally regarded as a form of nicotine dependence, but the evidence for this is slender. Two experiments are described here which examine the hypothesis that habitual smokers need nicotine and that they regulate their intakes of this drug. A laboratory test for smoking was devised which permitted the continuous monitoring of puffing as well as of selected physiologic variables; the procedure was also designed to reduce the influence of smoking habits and rituals. In the first experiment, inhaled amounts of tobacco smoke reduced subsequent ad libitum smoking in a dose-related way. In the second experiment comparable doses of nicotine were given intravenously to the same subjects, but they failed to affect ongoing smoking. However, both the inhaled and intravenous doses of the drug produced very similar physiologic effects. These experiments do not, therefore, support the nicotine-dependence hypothesis; thus the ways, if any, in which this drug sustains the tobacco-smoking habit merit further examination.

Adult↗

PubMed1983

Variability in the human drug response.

Variations in response to drugs may be pharmacodynamic, implying inter-individual differences in the response of receptors in equal concentrations of drug, or pharmacokinetic, implying that individuals receiving the same dose of drug will have different concentrations of drug in their body fluids. Either type of variation can be inherited or acquired. Variations in receptor sensitivity do occur but few instances, inherited or acquired, have well documented clinical relevance. If the dose response relationship for the drug in question is not steep, or if the therapeutic index is low, drug concentration in the region of the receptor will not be critical and causes of kinetic variation are unlikely to be clinically significant. However, it is the many causes of kinetic variation which are best described. These include effects due to drug formulation and changes in the absorption, distribution, metabolism and excretion of drugs. If a consideration of dynamics suggests that drug concentration will determine therapeutic efficacy, analysis and prediction of variability due to these factors is desirable. Prediction requires an accurate description of the system but commonly used pharmacokinetic models may fail when prediction is a goal. The variables, volume of distribution (Vd) and rate constant of elimination (Ke) are hybrid in that they arise from the interaction of patient and drug characteristics. Important events including macromolecular binding and altered blood flow may not be represented. More data is required to determine the clinical significance of pharmacodynamic variation but better analytical tools are required to deal with kinetic variation when this is important. Specifically, pharmacokinetic models should represent physiological variables and levels of unbound drug in body fluids should receive greater emphasis.

Biological Availability↗

PubMed2005

Performance and cardiovascular measures in normal adults with extreme MSLT scores and subjective sleepiness levels.

STUDY OBJECTIVES: The purpose of this study was to determine the relationship of subjective and objective sleepiness across several nights. Extreme groups were chosen based upon both Multiple Sleep Latency Test (MSLT) findings and report of characteristic subjective sleepiness, and groups were compared across sleep, demographic, performance, and physiologic variables. DESIGN AND SETTING: Subjects spent 3 baseline nights and the following days in the laboratory. Standard polysomnographic recordings were made on each night. On each day, subjects had an MSLT, performance testing, and metabolic and heart rate observation periods. PARTICIPANTS: Participants were 50 adult normal sleepers. INTERVENTIONS: None. MEASUREMENT AND RESULTS: Those subjects with sleep latencies on the MSLT of more than 10 minutes following the adaptation night (Alert) were compared with 2 groups of subjects with sleep latencies on the MSLT of less than 7 minutes following the adaptation night. Subjects with MSLT < 7 were divided into those who reported subjective sleepiness during the day (subjective sleepiness > 1 SD above the mean for the entire group-Sleepy-Sleepy) and those who did not report subjective sleepiness (subjective sleepiness < 1 SD above the mean for the entire group--Sleepy-Alert). The Alert group maintained longer sleep latencies than the other groups and had improved performance on vigilance compared to the Sleepy-Sleepy group on all days and on some days compared to the Sleepy-Alert group. Vigilance was improved in the Sleepy-Alert group compared with the Sleepy-Sleepy group on all days. The Alert group had higher heart rate and increased low/high spectral heart rate power compared to both sleepy groups, and the Sleepy-Alert group had higher heart rate and increased low/high spectral heart rate power compared to the Sleepy-Sleepy group at some points. CONCLUSIONS: It was concluded that normal adults with short MSLT latencies differ from those with longer latencies on both cardiac and performance variables. Also, those individuals with short latencies can be divided into subgroups claiming subjective sleepiness or denying sleepiness. Those denying sleepiness have improved vigilance performance and greater heart rate and low/high spectral heart rate power compared to those with subjective sleepiness. Both the MSLT group differences and the subjective group differences imply that ability to maintain wakefulness and performance in sedentary situations may be related to innate ability to maintain physiologic arousal.

Adolescent↗

PubMedDate not supplied

Phenytoin-induced hyperglycaemia may confound rat cerebroprotection models.

1. The anticonvulsant phenytoin (PHT) has been used with variable success in animal models of cerebral ischaemia. Although PHT has been reported to alter glucose regulation in man, this potential effect has been largely ignored in animals. Because hyperglycaemia strongly influences the outcome of cerebral ischaemia, we sought to systematically delineate the effects of PHT on serum glucose in several rat strains. 2. We studied the PHT dose-response curve for serum PHT and glucose concentrations and several physiological variables. Phenytoin induces a significant, concentration-dependent hyperglycaemia, even in the ranges commonly used for humans and in animal models. 3. Hypothermia of several degrees was observed during PHT administration, but no hypotension or bradycardia was found. 4. Both hyperglycaemia and hypothermia must be considered when PHT is studied as a neuroprotective agent in animal models.

Animals↗

PubMed2005

American ginseng supplementation attenuates creatine kinase level induced by submaximal exercise in human beings.

AIM: To investigate whether American ginseng (AG, Panax quinquefolium) supplementation was able to improve endurance exercise performance. METHODS: Thirteen physically active male college students were divided into two groups (AG or placebo) and received supplementation for 4 wk, before the exhaustive running exercise. Treadmill speed was increased to a pace equivalent to 80% VO2max of the subject. A 4-wk washout period followed before the subjects crossed over and received the alternate supplement for the next 4 wk. They then completed a second exhaustive running exercise. The physiological variables that were examined included time to exhaustion and oxygen pulse. Moreover, the plasma creatine kinase (CK) and lactate were measured prior to the exercise, at 15 and 30 min during exercise, immediately after exercise, and 20, 40, 60, and 120 min after exercise. RESULTS: The major finding of this investigation was that the production plasma CK during the exercise significantly decreased for group AG than for group P. Secondary physiological finding was that 80% VO2max running was not improved over a 4-wk AG supplementation regimen. CONCLUSION: Supplementation with AG for 4 wk prior to an exhaustive aerobic treadmill running reduced the leakage of CK during exercise, but did not enhance aerobic work capacity. The reduction of plasma CK may be due to the fact that AG is effective for the decrease of skeletal muscle cell membrane damage, induced by exercise during the high-intensity treadmill run.

Adult↗

PubMed1991

Techniques for measuring arterial pressure in the postoperative cardiac surgery patient.

Blood pressure measurement and management of the cardiac surgical patient do not appear to be simple processes. The critical care nurse needs to understand thoroughly the many technical and physiologic variables pertaining to the equipment used (i.e., cuff size, stethoscope placement, automated device cycling patterns, and monitoring system accuracy and reliability); the patient (i.e., cardiac output, PVR, hypothermia, and placement site and length of the intra-arterial catheter); and the relationship of indirect to direct measurement. The choice of therapy, i.e., volume or drug therapy (vasodilator or vasopressor), should be based on a thorough understanding of the technical and physiologic factors influencing the readings and their relationship to indirect and direct measurement of the blood pressure. Once the nurse understands the correlation of the indirect and direct blood pressure readings, choosing the pressure reading that one "likes" will no longer be an issue.

Blood Pressure Monitors↗

PubMed1990

Effect of four heavy metals on the biology of Nostoc muscorum.

This study presents the effects of Cr, Pb, Ni and Ag on growth, pigments, protein, DNA, RNA, heterocyst frequency, uptake of NH4+ and NO3-, loss of electrolytes (Na+ and K+), nitrate reductase and glutamine synthetase activities of Nostoc muscorum. The statistical tests revealed a direct positive correlation between the metal concentration and inhibition of different processes. Ni was found to be more toxic against growth, pigments and heterocyst differentiation compared to the other metals. Inhibition of pigment showed the following trend: chlorophyll greater than phycocyanin greater than carotenoid. No generalized trend for inhibition of macromolecules was observed. The loss of K+ and Na+ as affected by Cr, Ni and Pb was similar but more pronounced for K+ than Na+. The inhibition of physiological variables depicted the following trend: Na+ loss greater than K+ loss greater than glutamine synthetase greater than NH4+ uptake greater than growth greater than NO3- uptake greater than nitrate reductase greater than heterocyst frequency. This study therefore suggests that loss of electrolytes can be used as a first signal of metal toxicity in cyanobacteria. However, further study is needed to confirm whether the abnormality induced by nickel (branch formation) is a physiological or genetic phenomenon.

Ammonia↗