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PubMed2005

Correlations between physiological variables and performance in high level cross country off road cyclists.

OBJECTIVES: To examine the relations between maximal and submaximal indices of aerobic fitness and off road cycling performance in a homogeneous group of high level mountain bikers. METHODS: 12 internationally competitive mountain bikers completed the study. Maximum oxygen uptake (Vo(2max)), peak power output (PPO), power output (PO), and oxygen uptake (Vo(2)) at first (VT) and second (RCT) ventilatory thresholds were measured in the laboratory, and correlated with race time during a cross country circuit race. RESULTS: The only physiological indices of aerobic fitness correlated with off road cycling performance were PO and Vo(2) at RCT when normalised to body mass (r = -0.63 and r = -0.66, respectively; p<0.05). VT, Vo(2max), and PPO were not correlated to performance in this homogeneous group of high level mountain bikers. CONCLUSIONS: The results of this study suggest that submaximal indices of aerobic fitness such as PO and Vo(2) at RCT are more important determinants of off road cycling performance than maximal indices such as PPO and Vo(2max). This study confirms the importance of body mass for mountain biking performance. As aerobic fitness explained only 40% of the variance, other physiological and technical factors should be investigated, as they may be important determinants of cross country performance among elite mountain bikers.

Adult↗
PubMed2001

The effects of core and peripheral warming methods on temperature and physiologic variables in injured children.

INTRODUCTION: Injured children are at risk for thermoregulatory compromise, where temperature maintenance mechanisms are overwhelmed by severe injury, environmental exposure, and resuscitation measures. Adequate thermoregulation can be maintained, and heat loss can be prevented, by core (administration of warmed intravenous fluid) and peripheral (application of convective air warming) methods. It is not known which warming method is better to maintain thermoregulation and prevent heat loss in injured children during their trauma resuscitations. The purpose of this feasibility study was to compare the effects of core and peripheral warming measures on body temperature and physiologic changes in a small sample of injured children during their initial emergency department (ED) treatment. METHODS: A prospective, randomized experimental design was used. Eight injured children aged 3 to 14 years (mean = 6.87, SD = 3.44 ) treated in the ED of Children's Hospital of Pittsburgh were enrolled. Physiologic responses (eg, heart rate, blood pressure, respiratory rate, arterial oxygen saturation, core, peripheral temperatures) and level of consciousness were continuously measured and recorded every 5 minutes to detect early thermoregulatory compromise and to determine the child's response to warming. Data were collected throughout the resuscitation period, including transport to CT scan, the inpatient nursing unit, intensive care unit, operating room or discharge to home. Core warming was accomplished with the Hotline Fluid Warmer (Sims Level 1, Inc., Rockland, MA), and peripheral warming was accomplished with the Snuggle Warm Convective Warming System (Sins Level 1, Inc., Rockland, MA). Data were analyzed using descriptive and inferential statistics. RESULTS: There were no statistically significant differences between the two groups on age (t = -0.485, P = 0.645); weight (t = -0.005, P = 0.996); amount of prehospital intravenous (IV) fluid (t = 0314, P = 0.766); temperature on ED arrival (t = 0.287, P = 0.784); total amount of infused IV fluid (t = -0.21, P = 0.8); and length of time from ED admission to hospital admission (t = -0.613, P = 0.56). There were no statistically significant differences between the two groups on RTS (t = -0.516, P = 0.633). When comparing the mean differences in temperature upon hospital admission, no statistically significant differences were found (t = -1.572, P = 0.167). There were no statistically significant differences between the two groups in tympanic [F(15) = 0.71, P = 0.44] and skin [F(15) = 0.06, P = 0.81] temperature measurements over time. CONCLUSION: Core and peripheral warming methods appeared to e effective in preventing heat loss in this stable patient population. A reasonable next step would be to continue this trial in a larger sample of patients who are at greater risk for heat loss and subsequent hypothermia and to use a control group.

Adolescent↗
PubMed2000

Methodological and physiological variability within the ventilatory response to hypoxia in humans.

Measurement of the acute hypoxic ventilatory response (AHVR) requires careful choice of the hypoxic stimulus. If the stimulus is too brief, the response may be incomplete; if the stimulus is too long, hypoxic ventilatory depression may ensue. The purpose of this study was to compare three different techniques for assessing AHVR, using different hypoxic stimuli, and also to examine the between-day variability in AHVR. Ten subjects were studied, each on six different occasions, which were >/=1 wk apart. On each occasion, AHVR was assessed using three different protocols: 1) protocol SW, which uses square waves of hypoxia; 2) protocol IS, which uses incremental steps of hypoxia; and 3) protocol RB, which simulates an isocapnic rebreathing test. Mean values for hypoxic sensitivity were 1.02 +/- 0.48, 1.15 +/- 0.55, and 0.93 +/- 0.60 (SD) l. min(-1). %(-1) for protocols SW, IS, and RB, respectively. These differed significantly (P < 0.01). The coefficients of variation for measurement of AHVR were 20, 23, and 36% for the three protocols, respectively. These were not significantly different. There was a significant physiological variation in AHVR (F (50,100) = 3.9, P < 0. 001), with a coefficient of variation of 26%. We conclude that there was relatively little systematic variation between the three protocols but that AHVR varies physiologically over time.

Adult↗
PubMed1986

[Physiologic variability of erythrocyte concentrations and transport of sodium and potassium].

Sodium concentrations in erythrocytes are lower in women during the luteal phase of the menstrual cycle than in women studied during the follicular phase and in men. Sodium cotransport activity is lower in women during the follicular phase than in men. Women taking oral contraceptives show no monthly variations in erythrocyte sodium concentrations. Subjects with a family history of essential hypertension have higher sodium concentrations in erythrocytes than those with a different family background, partly because of reduction in sodium cotransport activity. Negroes have marked erythrocyte sodium accumulation due to lower activity of the sodium-potassium pump and cotransport system; they also have reduced sodium-lithium counter-transport. There is no difference between negroes with or without haemoglobin S. There are no changes in erythrocyte potassium concentrations in relation to sex, menstrual phase, race, familial essential hypertension, presence of haemoglobin S or use of oral contraceptives. These physiological variations indicate the factors which must be standardized to study sodium concentrations in cells and sodium transmembrane flux.

Adult↗
PubMed2006

Management of physiological variables in neuroanaesthesia: maintaining homeostasis during intracranial surgery.

PURPOSE OF REVIEW: The recent literature on the perioperative maintenance of cerebral homeostasis was reviewed. RECENT FINDINGS: Several studies focused on the regulation of cerebral blood flow in patients without intracranial disease; therefore, further studies in neurosurgical patients are needed. High intracranial pressure and brain swelling can be controlled by the choice of anaesthetic agents, and also by optimal positioning of the patient. The use of positive end-expiratory pressure may impair cerebral blood flow, but the effects of positive end-expiratory pressure seem to depend on the respiratory system compliance. The international multicenter study failed to show any benefit from intraoperative hypothermia in patients with subarachnoid hemorrhage; similarly, the results on corticosteroid therapy in head-injured patients are discouraging. Corticosteroid therapy has prompted studies on the control of blood glucose levels. While tight glycemic control has been recommended, it can have untoward effects manifested as cerebral metabolic stress. SUMMARY: From the clinical point of view, the recent research has added only little to the knowledge on the management of physiological parameters in neurosurgery. More adequately powered studies focusing in specific problems, and having a meaningful aim relative to outcome, are needed also in neuroanaesthesia.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Monitoring physiological variables with membrane probes.

Membrane probes are implantable devices, which can be used to sample from the interstitial fluid of the tissues in which they are implanted. Two types of membrane probes, one based on microdialysis and the other on ultrafiltration, were developed and tested in vitro for the following analytes: sodium, potassium, chloride, glucose and lactate. These membrane probes were then implanted subcutaneously in rats and used to monitor changes in interstitial analytes during the head-down tilt model of microgravity.

Animals↗
PubMedDate not supplied

Concept analysis: an approach to teaching physiologic variables.

Establishment of a knowledge base for nursing practice has been an ongoing goal of nurse professionals for the past decade. Because nurses are especially concerned with management of the body's potential or actual response to illness, the development and use of materials that reflect these body responses seems appropriate. This article is an effort to promote the use of concepts as a basis for nursing practice. A concept analysis approach for didactic instruction, currently being used for organizing and synthesizing pathophysiologic data present in literature, is presented. The process is exemplified by excerpts from the concept "inflammation." Advantages and disadvantages identified by graduate students for the use of concepts and the analysis process as a teaching/learning strategy are included.

Education, Nursing↗
PubMed1996

Computer-assisted learning package for frequency distribution of physiological variables.

There are a variety of ways of picturing a frequency distribution type, viz, the histogram, the frequency polygon, the smoothed curve and the ogive. We have developed a computer package to demonstrate gradual change of a histogram into a curve. For a given set of data on frequency distribution of, say blood pressure levels in specified categories, this package helps the computer to draw bars which gradually rise to the level of the frequencies, and lateron are replaced by the polygon and finally by the frequency curve of the Gaussian type on the computer screen pixel by pixel. This thus demonstrates the meaning and genesis of frequency curves. This package could be very useful in learning the concept of frequency curves particularly the Gaussian form.

Computer Graphics↗
PubMed1999

[Anesthesia in geriatric patients. The determination of physiological variables for cognitive function in geriatric patients after regional or general anesthesia].

OBJECTIVE: The aim of the present study was to show the influence of the parameters of gas exchange (arterial oxygen pressure paO2, arterial oxygen saturation SatO2) and haemodynamics (arterial systolic and mean blood pressure RRs and MAP) on the restitution of cognitive functions in geriatric patients scheduled for elective hip arthroplasty. METHODS: A total of 30 patients (70 years, ASA II) were randomized to be operated either in regional anaesthesia (n = 15) or general anaesthesia (n = 15). PaO2 (by capillary blood gas analysis), RRs and MAP (by oscillometry) were measured 15 and 90 minutes after arrival in the recovery unit (t1 and t2), 24 and 72 hours postoperatively (t3 and t4), and cognitive functions were tested. Intraoperatively, throughout the day and the first night after surgery we measured satO2 by continuous pulse oximetry. We recorded MAP and RRs by oscillometry every 3 minutes during the operation and every 15 minutes for the rest of that day and night. RESULTS: The parameters of gas exchange and haemodynamics did not differ among the groups. PaO2 was significantly reduced in both groups compared to baseline 24 hours postoperatively (t3) and remained low until 72 hours postoperatively (t4). Nearly all cognitive functions were significantly reduced in both groups compared to baseline 15 and 90 minutes after arrival in the recovery unit (t1 and t2), but recovered on the first postoperative day (t3). Both groups kept deficits in verbal memory and reading capacity up to the third postoperative day (t4). There was no correlation between the physiological parameters and the restitution of the tested cognitive functions. CONCLUSION: The restitution of cognitive functions during the first three postoperative days in geriatric patients scheduled for elective hip surgery does not depend on the anaesthetic technique. According to our results regional anaesthesia does not show any advantage for geriatric patients undergoing elective hip arthroplasty.

Aged↗
PubMed2003

Study of active substances involved in skin dysfunction induced by crowding stress. I. Effect of crowding and isolation on some physiological variables, skin function and skin blood perfusion in hairless mice.

The effects of five levels of population density on various organs, the neuroendocrine system, skin function, skin blood perfusion, and blood parameters were studied in the hairless mouse. Skin barrier recovery was evaluated by measuring transepidermal water loss after tape stripping. Blood perfusion was measured by means of a laser Doppler imaging technique. The effect of a parasympathetic nerve stimulator, carpronium chloride, on skin function in the crowded animal model was also examined. A 7 d crowding (10, 15, 20 mice/cage) significantly increased the levels of corticosterone, catecholamines (norepinephrine, epinephrine and dopamine), glucose and serum lactate dehydrogenase activity in circulating blood, induced atrophy of kidney, ovary and thymus and hypertrophy of adrenal glands, and decreased body weight gain in comparison with the control (5 mice/cage). Crowding also increased epidermal thickness and epidermal proliferative activity, and decreased corneocyte size, rate of barrier recovery and skin blood perfusion. Most of these changes became more marked with increasing population density and/or longer exposure to a crowded environment. Isolation (1 mouse/cage) increased the level of norepinephrine and rate of skin blood perfusion, and significantly delayed barrier recovery. Repeated topical applications of carpronium chloride for 7 d improved the changes in skin blood perfusion, barrier recovery, kidney and ovary, and epidermal morphology induced by crowding. The crowded animal model could be useful for quantifying objectively the influence of crowded environment-induced stress on cutaneous function and blood perfusion.

Animals↗
PubMed2004

The validity of physiological variables to assess training intensity in kayak athletes.

It appears that training benefits are compromised if excessive training is performed at intensities that are either too low or too high. This suggests a need for accurate methods to monitor training intensity. It has been suggested that heart rate (HR) or lactate concentration ([La -]) can be used to accurately monitor training intensity. The purpose of the present study therefore, was to examine whether the relationship between HR, [La -] and intensity determined during a kayak graded exercise test (GXT) remained stable during constant-intensity kayak exercise. Sixteen trained kayak paddlers, (22 +/- 4 y, peak V.O (2) = 3.7 +/- 0.9 l x min (-1)) performed a GXT on a wind-braked kayak ergometer. They then performed a 20-min constant-load test on the kayak ergometer at a power output corresponding to their lactate inflection (LI) intensity. Eight subjects also performed a 20-min constant-load test at a power output corresponding to their lactate threshold (LT) intensity. Differences between constant-load and GXT values were determined using one-way ANOVA (p < 0.05). There were no significant differences between values for HR and V.O (2) derived from the GXT and those measured during both constant-load tests. However, while [La -] also provided a valid marker of the LI training intensity (1.8 +/- 0.3 v 2.1 +/- 0.8 mmol x l (-1)), [La -] did not provide a valid marker of the LT training intensity (3.8 +/- 0.7 v 5.1 +/- 1.4 mmol x l (-1)). These results suggest that HR, but not [La -1], is similar during both a GXT and constant-load exercise at the LT intensity.

Adult↗
PubMed1980

The effects of various warming up intensities and durations upon some physiological variables during an exercise corresponding to the WC170.

Empirically, many procedures are used by sportsmen to warm up, such as massage, hot showers, or muscular exercise, although their objective effect on performance is still not evident. The present study investigates different warming up durations and intensities with or without a resting period between warming up and the criterion exercise, both performed on a bicycle ergometer. Heart rate, oxygen consumption, blood lactic acid level, and oxygen debt are measured. When the criterion exercise immediately follows warming up, heart rate, and oxygen consumption generally attain higher values during the criterion exercise but lactic acid level shows no important variation. When introducing a resting period between warming up and the criterion exercise, the heart rate and oxygen consumption values do not differ from those attained without warming up. The results do not conclusively show a positive effect of warming up before exercise.

Adult↗
PubMed1992

Influence of chromium on some physiological variables of Anabaena doliolum: interaction with metabolic inhibitors.

The impact of 2,4-dinitrophenol and chlorophenyl dimethylurea on ATP content, carbon fixation, O2 evolution, nitrogenase activity and Cr uptake of Anabaena doliolum has been studied. 2,4-Dinitrophenol has been found to be more toxic than chlorophenyldimethylurea for all these processes. However, when Cr toxicity to above variables was assessed in their presence the interaction was less than additive. An initial (10-15 min) concentration-dependent rapid Cr uptake, followed by a slow one, indicates a biphasic uptake. A significant inhibition of Cr uptake in the presence of both these metabolic inhibitors suggests the involvement of metabolic processes in Cr uptake.

2,4-Dinitrophenol↗
PubMed1986

[Physiologic variability of plasma catecholamines].

In an earlier publication, we described a modified procedure for the determination of plasma catecholamine levels using high-performance liquid chromatography (HPLC), followed by amperometry. In this paper, we present our results on the variability of normal catecholamine values in plasma for noradrenaline (NA), adrenaline (A) and dopamine (DA). In 122 women and men at rest, the range for NA was 0.15-3.5 nmol/l, for A 0.01-0.8 nmol/l and for DA 0.04-4.5 nmol/l. We also describe the effects of orthostasis, intravenous catheters, food intake, cigarette smoking, age and sex on venous catecholamine levels. The efficiency of the HPLC method allowed us to check, using a large subject group, the results obtained by other authors from studies involving smaller subject groups with more expensive and time-consuming methods.

Adult↗