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Results for “physiologic variables”

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PubMed2000

Effects of gradient and load carried on human haemodynamic responses during treadmill walking.

This study examined the effects of different loads carried and gradients, on haemodynamic and cardiovascular responses during 45 min of treadmill walking. A group of 20 male endurance-trained athletes [mean maximal oxygen uptake 61.4 (SD 4) ml x kg(-1) x min(-1)] volunteered for this study. The subjects took part in three separate trials. The first involved a backpack weighing 25 kg, the second a 35 kg backpack, and the third trial, unladen, while walking on a treadmill at a speed of 5 km x h(-1). The subjects began walking on the treadmill with the randomized load at 0% gradient. After 15 min, the gradient was increased by 5% every 15 min for a total of 45 min. The order of the loads carried was randomized among subjects. No significant differences were noted for all the variables measured attributable to loads between 25 kg and 35 kg. However, significant (P<0.05) differences were seen for all variables each time the gradient was increased. Cardiac output increased from 11.4 (SD 0.6) 1 x min(-1) at 0% to 13.6 (SD 0.8) l x min(-1) at 5% and to 17.6 (SD 1.3) l x min(-1) at 10% carrying the 35 kg load. Similarly, lactic acid concentrations in the blood increased from 2.8 (SD 0.2) to 3.1 (SD 0.6) and to 5.3 (SD 1.3) mmol x l(-1), respectively. Similar changes were observed for all variables while carrying the 25 kg load. In addition, steady states in oxygen uptake and other physiological variables were obtained throughout the course of the tests. These data suggest that during isodynamic exercise, one of the main factors determining metabolic and haemodynamic responses will be the change in gradient and to a lesser extent, the mass of the load carried.

Adolescent↗

PubMed1997

Comparison of collateral vascular responses in the donor and recipient coronary artery during transient coronary occlusion assessed by intracoronary blood flow velocity analysis in patients.

OBJECTIVES: This study was designed to evaluate the hemodynamic variables of the collateral circulation during acute coronary occlusion. BACKGROUND: There is limited information on the physiology of the collateral circulation in coronary artery disease. METHODS: Angiography of the contralateral donor artery was performed before and during balloon coronary occlusion in 57 patients with one-vessel disease. Recruitable collateral flow was assessed during coronary occlusion by blood flow analysis of the contralateral donor artery (n = 19) or the ipsilateral recipient artery (n = 15), or both (n = 23), using a Doppler catheter or guide wire. Ischemia was evaluated by the ST segment shift (> or = 0.1 mV) on a 12-lead electrocardiogram at 1 min of coronary occlusion. RESULTS: The presence (n = 39), compared with the absence (n = 18), of recruitable collateral vessels was associated with an increase of blood flow velocity in the donor artery (20 +/- 19% vs. 4.8 +/- 5.9% [mean +/- SD], p = 0.003) and the recipient artery (velocity integral 7.2 +/- 5.5 vs. 2.8 +/- 2.2 cm, p = 0.02) related to a reduced relative collateral vascular resistance (9.2 +/- 10 vs. 20 +/- 11, p = 0.003). Collateral flow in the donor artery yielded a similar predictive value for recruitability of collateral vessels as collateral flow determined in the recipient artery or the coronary wedge/aortic pressure ratio (areas under the receiver operating characteristics curves 0.76 +/- 0.07, 0.78 +/- 0.08, 0.77 +/- 0.07, respectively, p = NS). Collateral flow in the recipient artery was a better predictor for ischemia than collateral flow in the donor artery or angiographic grading of collateral vessels (areas 0.90 +/- 0.05, 0.64 +/- 0.10, 0.73 +/- 0.07, respectively, p < 0.05). CONCLUSIONS: Coronary blood flow velocity analysis of the donor and recipient coronary arteries can characterize the dynamics of the collateral circulation during acute coronary occlusion. The protective effect of recruitable collateral vessels relates to an increase of flow in the donor and recipient coronary arteries due to a reduced collateral vascular resistance. This study underscores the importance of physiologic variables for the evaluation of the function of recruitable collateral vessels.

Adult↗

PubMed1993

Perceived exertion. Antecedents and applications.

The field of perceived exertion has largely concerned itself with the problem of identifying the primary antecedents to this psychophysiological phenomenon. A vast literature has evolved addressing this problem, but it is fraught with contradictions. At this stage a comprehensive theory of perceived exertion does not exist. It is generally accepted that perception of exertion is dominated by physiological determinants. Physiological sensory cues have been separated into 2 categories: local factors (sensations from the working muscles and joints), and central factors (sensations from the cardiopulmonary system). Major reviews in this area generally agree that local factors dominate perception of exertion. Recent work in perceived exertion has placed an emphasis on examining the contributing psychological factors. Research into the psychological factors affecting perceived exertion has been highly fragmented with no apparent theoretical framework as a base. At the same time it is clear that an integration of psychological and physiological variables is required to obtain theoretically meaningful knowledge of this multidimensional construct. The assumed dominance of physiological factors has been challenged by the contention that in field situations, in which a variety of social psychological influences operate, psychological determinants of perceived exertion may be vastly more influential than previously estimated. Identification of the primary determinants of perceived exertion and knowledge of how these factors are integrated is vital for a concrete theory of perceived exertion to evolve.

Exercise Therapy↗

PubMed1981

Relationship between arterial and peak expired carbon dioxide pressure during anesthesia and factors influencing the difference.

To determine how closely peak expired PCO2 measured by mass spectrometry reflects arterial PCO2 during anesthesia and what variables contribute to a difference between the two measurements, peak expired CO2, arterial PCO2, and other physiologic variables were measured simultaneously. There was a significant correlation between peak expired and arterial PCO2 (p less than 0.001). The difference between temperature-corrected arterial and peak expired PCO2 was related to the presence or absence of lung disease, age, A.S.A. class, and systolic blood pressure. No significant relationship was seen between the temperature-corrected difference and duration of anesthesia, diastolic pressure, expired O2 concentration, or anesthetic agent. Mean temperature-corrected arterial PCO2 exceeded mean peak expired PCO2 by 1.7 torr in all patients, 0.8 torr in patients without lung disease, and 3.3 torr in patients with lung disease. In patients in whom more than one arterial sample was obtained, initial differences correlated significantly with subsequent differences (p less than 0.001).

Anesthesia, Endotracheal↗

PubMed2000

Hematological and pulmonary responses to high altitude in Quechuas: a multivariate approach.

This study investigates the relationships among hematological variables, pulmonary function, and age in a sample of high-altitude natives. The following anthropometric and physiological variables were examined in 77 adult Quechua males from the Peruvian Central Andes (Huancavelica, 3,680 m): height, weight, sitting height, chest diameters, chest and abdominal circumferences, forced vital capacity (FVC), forced expiratory volume at 1 sec (FEV1), peak expiratory flow (PEF), hemoglobin concentration (Hb), red blood cells (RBC), hematocrit (Htc), diastolic and systolic blood pressure, body temperature, pulmonary rate, and pulse rate. The means of these variables for the Huancavelica sample fall within the range of variability previously observed in Andean populations. Principal components analysis and canonical correlation analysis suggest that in this native Andean population: 1) aging decreases lung function but does not affect hematological features, and 2) there is a negative age-independent correlation between lung function (FVC, FEV1, PEF) and hematological traits (Hb, RBC, Htc).

Adaptation, Physiological↗

PubMed2005

Psychosocial factors and respiratory and cardiovascular parameters during psychophysiological stress profiling in working men and women.

The relationship between psychosocial factors and psychophysiological reactions to a situation including stressors and relaxation in a working population was examined. A sample of 115 working men and women aged 26-65 was used. Each participant was examined at baseline, during deep breathing, experimentally induced stress and relaxation. Heart rate, exhalation carbon dioxide, oxygen saturation and blood pressure were monitored. Significant variations across experimental conditions were observed for all physiological variables. There was a pronounced lowering of blood pressure during deep breathing. Women showed significantly more pronounced physiological variation than men. Participants with low education reacted with significantly more systolic blood pressure elevation during the stressful conditions than others. The implication of the results for therapeutic and preventive exercises with deep breathing are discussed.

Adult↗

PubMed1994

Biological uniqueness and the definition of normality. Part 1--The concept of 'intrinsic' homeostasis.

The patterns of biochemical and physiological variables values are subject-specific and quite stable over time. Thus, within the limits imposed by physiological requirements, the composition of the 'milieu intérieur' varies between individuals. It follows that having all values of blood constituents within the norm (defined statistically from populations of healthy subjects) might not be sufficient to identify biological normality, and a revised definition of biological normality should take into account inter-individual differences. Our concept of 'intrinsic' homeostasis means that the differences between subjects' concentrations of blood constituents express subject-specific constraints in the organization of their physiology, and that these differences might play a greater role than usually recognized. We list the consequences for medical research of the existence of biological uniqueness and propose to give more importance to the study of biological 'fingerprints' and 'intrinsic' homeostasis in physiology and clinical medicine.

Homeostasis↗

PubMed2001

Direct biologically based biosensing of dynamic physiological function.

Dynamic regulation of biological systems requires real-time assessment of relevant physiological needs. Biosensors, which transduce biological actions or reactions into signals amenable to processing, are well suited for such monitoring. Typically, in vivo biosensors approximate physiological function via the measurement of surrogate signals. The alternative approach presented here would be to use biologically based biosensors for the direct measurement of physiological activity via functional integration of relevant governing inputs. We show that an implanted excitable-tissue biosensor (excitable cardiac tissue) can be used as a real-time, integrated bioprocessor to analyze the complex inputs regulating a dynamic physiological variable (heart rate). This approach offers the potential for long-term biologically tuned quantification of endogenous physiological function.

Animals↗

PubMed2005

Finger extensor variability in TMS parameters among chronic stroke patients.

BACKGROUND: This study determined the reliability of topographic motor cortical maps and MEP characteristics in the extensor digitorum communis (EDC) evoked by single-pulse TMS among patients with chronic stroke. METHODS: Each of ten patients was studied on three occasions. Measures included location of the EDC hotspot and center of gravity (COG), threshold of activation and average amplitude of the hotspot, number of active sites, map volume, and recruitment curve (RC) slope. RESULTS: Consistent intrahemispheric measurements were obtained for the three TMS mapping sessions for all measured variables. No statistically significant difference was observed between hemispheres for the number of active sites, COG distance or the RC slope. The magnitude and range of COG movement between sessions were similar to those reported previously with this muscle in able-bodied individuals. The average COG movement over three sessions in both hemispheres was 0.90 cm. The average COG movement in the affected hemisphere was 1.13 (+/- 0.08) cm, and 0.68 (+/- 0.04) cm) for the less affected hemisphere. However, significant interhemispheric variability was seen for the average MEP amplitude, normalized map volume, and resting motor threshold. CONCLUSION: The physiologic variability in some TMS measurements of EDC suggest that interpretation of TMS mapping data derived from hemiparetic patients in the chronic stage following stroke should be undertaken cautiously. Irrespective of the muscle, potential causes of variability should be resolved to accurately assess the impact of pharmacological or physical interventions on cortical organization as measured by TMS among patients with stroke.

Journal Article↗

PubMed1997

Comparing the subjective, psychomotor and physiological effects of intravenous nalbuphine and morphine in healthy volunteers.

The purposes of this study were to characterize the subjective, psychomotor and physiological effects of nalbuphine in healthy non-drug abusing volunteers and to compare and contrast the effects of equianalgesic doses of nalbuphine and morphine. Subjects (12 males, 4 females) without histories of opiate dependence were injected in an upper extremity vein with 0, 2.5, 5.0 or 10 mg/70 kg nalbuphine, or with 10 mg/70 kg morphine, using a randomized, double-blind, crossover design. The 10-mg doses of nalbuphine and morphine are considered equianalgesic and are doses commonly given for relief of postoperative pain. Subjective effects of nalbuphine included increased scores on the Pentobarbital-Chlorpromazine-Alcohol Group scale and the Lysergic Acid Diethylamide scale of the Addiction Research Center Inventory; increased adjective checklist ratings of "nodding," "numb" and "sweating"; increased visual analog scale ratings of "coasting or spaced out," "high" and "sleepy" and increased "feel drug effect" and drug-liking ratings. Ten milligrams of nalbuphine had subjective effects similar, and similar in magnitude, to those of 10 mg of morphine. Nalbuphine produced exophoria and impairment on the Digit Symbol Substitution Test in a dose-related fashion. Ten milligrams of morphine produced exophoria but did not affect performance on the Digit Symbol Substitution Test. Both nalbuphine and morphine induced miosis and decreases in respiration rate. The results of the present study demonstrate that 2.5 to 10 mg nalbuphine had orderly, dose-related effects on subjective, psychomotor and physiological variables. The results also indicate that 10 mg of nalbuphine produces a profile of subjective, psychomotor and physiological effects similar to that of an equianalgesic dose of morphine (10 mg). The similarity in profiles between drugs at this dose is consistent with both infrahuman studies, which suggests that nalbuphine is a mu agonist, and studies with nondependent opioid abusers, in which relatively low doses of nalbuphine (such as 10 mg) produce morphine-like effects.

Adult↗

PubMed1987

Applications of nonlinear dynamics to clinical cardiology.

(1) Nonlinear mechanisms may apply both to the understanding of SA-AV node interactions and to bifurcations leading to certain types of AV block. (2) The fractal His-Purkinje system serves as the structural substrate for the generation of the broadband, inverse power-law spectrum of the stable ventricular depolarization (QRS) waveform. (3) Fractal anatomy is also seen in multiple other systems: pulmonary, hepatobiliary, renal, etc. Fractal morphogenesis may reflect a type of critical phenomenon that results in the generation of these irregular, but self-similar structures. (4) Self-similar (fractal) scaling may underlie the 1/f-like spectra seen in multiple systems (e.g., interbeat interval variability, daily neutrophil fluctuations). This fractal scaling may provide a mechanism for the "constrained randomness" that appears to underlie physiological variability and adaptability. (5) Behavior consistent with subharmonic bifurcations is seen in cardiac electrophysiology (e.g., sick sinus syndrome) and hemodynamic perturbations (e.g., swinging heart phenomenon in pericardial tamponade). (6) Ventricular tachyarrhythmias associated with sudden cardiac death (e.g., torsades de pointes, ventricular fibrillation) appear to reflect relatively periodic, not chaotic (turbulent) processes resulting from disruption of the physiologic fractal depolarization sequence. (7) Spectral analysis of Holter monitor data may help in the detection of patients at high risk for sudden death.

Cardiovascular Diseases↗

PubMed1991

Human performance capability in psychomotor tasks at variable difficulty levels and physiological reactions under noise and heat conditions.

The effects of noise and heat on the efficiency of human performance of psychomotor tasks at variable difficulty levels were investigated. Twenty four young, healthy volunteers with normal hearing, randomly divided into 4 equal sized groups, were tested in a climatic chamber under 4 combinations of two environmental conditions made up of noise and heat, each at two levels: 70 dB (A) (quiet), 100 dB (A) (noise): 28 degrees C (comfortable), 35 degrees C (heat). A statistically balanced procedure was followed. Three physiological variables were also recorded: Heart rate, blood pressure and body temperature. A 2 x 2 analysis of variance showed rise in the physiological variables by noise and heat respectively as well as by their interactions. Performances of the psychomotor tasks were affected differently by noise and heat depending on the difficulty levels of the tasks. The interaction of noise and heat entailed superior performance of the tasks of memory and search, two hand coordination and reaction time, at moderate difficulty levels, but no distinct interaction effect was observed on the performance of tweezer dexterity.

Adult↗

PubMed1982

Cardiovascular variability and introversion/extroversion, neuroticism and psychoticism.

Forty-eight subjects were measured during a 10 min rest period for pulse wave velocity (PWV) and heart rate (HR) level and variability, using a Cyborg BL 907 instrument. These subjects were also evaluated by means of the Eysenck Personality Questionnaire for I-E, N, P and L. These data were factor analyzed. Five factors were identified which were accounted for 80.6% of the variance. These factors were: 'cardiovascular lability', 'heart rate time trends', 'cardiovascular balance', 'sex effects' and 'self reports'. The EPQ measurements separated from the physiological measurements in the factor analysis and none were found to be significantly loaded on any physiological variables. On the other hand, significant physiological correlations were found with N. This study adds a possible blood pressure and heart rate descripter to N.

Blood Pressure↗

PubMed2005

Physiological and biomechanical responses while running with and without a stroller.

AIM: This study examined the effects of pushing a jogging stroller on biomechanical and physiological variables. The hypothesis was that running with a stroller for 30 minutes would shorten stride length and increase physiological indices of exercise. METHODS EXPERIMENTAL DESIGN: this was a repeated measures design. SETTING: participants were recruited from road races in the Dallas/Fort Worth, TX area. Graded exercise tests were performed in a laboratory setting, field tests were performed on a 400 m all-weather outdoor track. PARTICIPANTS: 5 males and 5 females were assessed. INTERVENTIONS: participants performed a graded exercise test and 2 field tests. The 1st field test involved running at 75% VO2max for 30 minutes without a stroller and the 2nd involved running at the same speed with the stroller. MEASURES: VO2, stride length, heart rate, lactate, ventilation, and RPE were evaluated. RESULTS: No differences for VO2 or stride length were evident. Heart rate (p=0.0001), lactate concentration (p=0.025), ventilation (p=0.009), and RPE (p=0.002) increased from 10 to 30 minutes while running with the stroller. Heart rate (p=0.002), lactate concentration (p=0.0001), ventilation (p=0.006), and RPE (p=0.001) were significantly higher while running with the stroller after 30 minutes compared to running without it. CONCLUSION: These results indicate that pushing a stroller affects some indices of exercise intensity while running. Gait does not change. These data do not support an association between stroller use during running and an increase risk of orthopedic injury. Further studies should examine these variables at lower intensities that are run by most recreational joggers.

Adult↗

PubMed1989

Roles of neurotransmitter receptors in behavior: recovery of function following decreases in muscarinic receptor density induced by cholinesterase inhibition.

Cholinergic neurotransmitter levels were elevated in rat brain by reducing its inactivating enzyme, acetylcholinesterase (AChE), with an anti-AChE agent. Elevated levels result in decreases in cholinergic (muscarinic) receptors. Withdrawal of agent after 10 days of chronic treatment began a gradual return of neurochemical variables toward normal states, yet not fully achieving them within the following 29 days of the experiment. All behavioral and physiological variables measured showed significant effects at the start of the treatment period, developing tolerance at different rates as treatments continued. They also recovered differentially during withdrawal. Results are consistent with a theoretical model in which thresholds for normal functioning of different behavioral and physiological processes are associated with different receptor densities.

Acetylcholine↗

PubMed1987

Psychophysiologic assessment of posttraumatic stress disorder imagery in Vietnam combat veterans.

This study utilized psychophysiologic techniques to assess emotional arousal during imagery of psychologically traumatic experiences. All subjects were medication-free Vietnam combat veterans, classified on the basis of DSM-III-R criteria into groups with posttraumatic stress disorder (PTSD, n = 18) and no mental disorder (control, n = 15), which did not differ in extent of combat or in the judged severity of the traumatic experiences reported. "Scripts" describing each subject's combat experiences as well as other experiences were read to them in the laboratory, and they were instructed to imagine the events the scripts portrayed, while heart rate, skin conductance, and frontalis electromyogram were recorded. The PTSD subjects' physiologic responses to their combat scripts were markedly higher than the controls'. The combined physiologic variables identified PTSD subjects with a specificity of 100% and a sensitivity of 61%. The results demonstrate exaggerated physiologic arousal during recollection of traumatic experiences in PTSD.

Adult↗

PubMed1986

Cardiac and ventilatory arousal responses and their habituation in goldfish: effects of the intensity of the eliciting stimulus.

Recordings were made of cardiac and ventilatory responses of goldfish to the onset of 10 sec illumination presented at 2 min intervals. These responses were measured by increases in cardiac interbeat interval, ventilatory interbreath interval and by reductions in ventilatory amplitude. Four groups of fish were subjected to intensities of 52, 78, 90 and 160 lux. Habituation of responses was considered to have occurred when its magnitude fell within the limits of normal variation of the physiological variable. It was found that the more intense the stimulus the greater was the magnitude of the initial physiological response and correlated with this the number of stimulus presentations required for habituation. The relationship between stimulus intensity, initial response magnitude and resistance to habituation was consistent for cardiac responses. The results are discussed with respect to current knowledge of arousal and its habituation.

Animals↗

PubMed1993

Clinical studies in Alzheimer patients with positron emission tomography.

Brain imaging techniques will in the future play an important role in the assessment of patients with neurogenerative disorders such as Alzheimer's disease (AD). An early diagnosis of AD is today hampered by lack of reliable diagnostic markers. Positron emission tomography (PET) permits the quantification and three-dimensional imaging of physiological variables. This provides the clinician with a non-invasive imaging technique which allows in vivo quantification of physiological processes in AD underlying dysfunction of cognition. PET studies regarding changes in cerebral blood flow and metabolism are rather consistent at least in moderate/advanced cases of AD. How early in the progress of the disease deficits in these parameters can be observed is still an open question. Longitudinal studies will here be important and especially in individuals with a family history of AD. Since deficits in cholinergic neurotransmission have been measured in autopsy AD brains attempts have also been made to visualized cholinergic activity in vivo. Nicotinic and muscarinic receptors have been visualized in normal and AD brains. A reduced uptake and binding of [11C]nicotine in the temporal and frontal cortices have been measured in AD patients by PET. Few treatment studies in AD have been evaluated by PET. Long-term treatment with the cholinesterase inhibitor tacrine increase the uptake of [11C]nicotine. Significant reduction in uptake between the two enantiomers (S)(-) and (R)(+)-[11C]nicotine has been observed compatible with a restoration of nicotinic receptors. Tacrine also significantly increased the glucose metabolism. PET studies indicate that long-term tacrine treatment in AD patients with mild dementia improves functional activities in brain. When an AD patient with moderate dementia was treated with nerve growth factor (NGF) PET studies revealed increase in cortical blood flow and nicotinic receptors. PET studies will in the future play an important role in the evaluation of new therapeutic drug strategies in AD.

Aged↗