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Measuring physiological variables in nursing research.

Physiological indicators of health status are recommended for observational and intervention research with children, adolescents, and families. Sources of measurement error including those relevant to participants, the research protocol, and the specific physiological indicator must be identified and minimized. To this end, information presented is this column is designed to enhance the collection of accurate, reliable, and reproducible data with the ultimate goal of informing and enhancing evidence-based practice.

Bias↗

PubMed2000

Physiological variability in neonatal armadillo quadruplets: within- and between-litter differences.

The role of genetics on neonatal physiological variability was examined in the nine-banded armadillo (Dasypus novemcinctus). Since armadillos give birth to only monozygous quadruplets, the genetic variation within litters is essentially zero. Quadruplets born in captivity were isolated and weighed within 8 h of birth. Oxygen consumption (V.(O2)) was measured in resting neonates by flow-through respirometry, heart rate obtained from an electrocardiogram and ventilation was measured by impedance techniques. Following the measurements, neonates were returned to the mother. Measurements were repeated at 4 and 8 days after birth. Mean heart rate significantly increased from 132 beats min(-1) on the day of birth to 169 beats min(-1) on day 8. Mean ventilation rate significantly decreased from 81 breaths min(-1) on the day of birth to 54 breaths min(-1) on day 8. During this same developmental period, mean mass significantly increased from 100 g to 129 g, and mean mass-specific oxygen consumption significantly decreased from 32.2 ml O(2)kg(-1)min(-1) to 28.6 ml O(2)kg(-1) min(-1). For all variables measured, within-litter variability was always significantly less than between-litter variability, confirming a 'sibling effect' that we attribute to the genetic components determining physiological characters.

Aging↗

PubMed2007

Time course of physiologic variables in response to ventilator-induced lung injury.

BACKGROUND: The time course of the physiological derangements that result from ventilator-induced lung injury has not been adequately described. Similarly, the regional topographies of pleural pressure and tissue edema have not been carefully mapped for this injury process. METHODS: Lung injury was induced in 9 normal pigs by ventilating for 6 hours at a transpulmonary pressure of 35 cm H(2)O, with the animals in the supine position. Eight additional normal pigs received right thoracotomy to place pleural-surface-pressure sensors prior to an identical period and intensity of injurious ventilation. Gas exchange and lung mechanics were tracked in all the animals. Cytokines (tumor necrosis factor alpha, interleukin 6, and interleukin 8) in peripheral blood were assayed at 2 hour intervals, beginning at the onset of mechanical ventilation, from all the animals. RESULTS: After a brief "induction" period, P(aO(2)) and tidal volume declined steadily in the animals that were ventilated to induce lung injury. The rate of decline was greater in the animals that received thoracotomy. The pleural pressure gradient steadily increased from ventral to dorsal. The serum cytokine levels did not evolve with developing injury, but cytokines were elevated at the onset of ventilation. Tissue edema, as assessed by the ratio of wet weight to dry weight, was greater in the thoracotomized animals than in the nonthoracotomized animals, and tissue edema tended to be greater in the caudal lung regions than in the cephalad lung regions. CONCLUSIONS: Following the induction period, the development of ventilator-induced lung injury progressed steadily and then plateaued, as assessed by quantitative physiology variables during 6 hours of ventilation at a transpulmonary pressure of 35 cm H(2)O. Greater injury developed in animals that had a coexisting potential insult (thoracotomy). Injury development was not paralleled by bloodborne inflammatory cytokines.

Animals↗

PubMed2004

Assessment of physiologic variables and subjective comfort under different levels of pressure support ventilation.

STUDY OBJECTIVES: To evaluate the effects of 12 ventilator settings (pressure support ventilation [PSV] plus positive end-expiratory pressure [PEEP], 30 + 0 cm H(2)O; 25 + 5 cm H(2)O; 25 + 0 cm H(2)O; 20 + 5 cm H(2)O; 20 + 0 cm H(2)O; 15 + 5 cm H(2)O; 15 + 0 cm H(2)O; 10 + 5 cm H(2)O; 10 + 0 cm H(2)O; 5 + 5 cm H(2)O; 5 + 0 cm H(2)O; and 0 + 5 cm H(2)O) on physiologic variables; the percentage of ineffective efforts; patient comfort; and whether the diagnosis of COPD may influence results. DESIGN: Prospective, randomized, physiologic study. SETTING: Three weaning centers. PATIENTS: Thirty-six consecutive patients (20 patients with COPD). INTERVENTION: Patients were randomly submitted to the 12 settings. MEASUREMENTS AND RESULTS: Breathing pattern, respiratory drive (p0.1), arterial oxygen saturation (Sato(2)), heart rate, percentage of ineffective efforts per minute, patient comfort measured by means of a visual analogue scale (VAS), and BORG scale were recorded under each setting. Under different levels of assistance, breathing pattern, Sato(2), and p0.1 significantly and linearly changed (p < 0.0001) while VAS and BORG scale presented a significant (p = 0.027) U-shaped trend; high or low assistance caused the most discomfort. Under high levels of assistance, a higher (analysis of variance, p = 0.023) frequency of ineffective effort percentage was observed in the subgroup of 26 patients who presented this phenomenon. Breathing pattern significantly (p = 0.013) changed when compared to PSV alone (PSV plus zero end-expiratory pressure [ZEEP]) at the same total inspiratory pressure assistance (PSV plus PEEP). A huge variability among patients in breathing pattern and comfort was found under the setting rated as the most comfortable by patients. The diagnosis of COPD did not influence the overall results. CONCLUSIONS: The following conclusions are made: (1) physiologic variables followed a linear trend, while comfort followed a U-shaped trend under different levels of PSV (irrespective of COPD diagnosis); (2) high assistance caused an increase in ineffective efforts; (3) only the breathing pattern significantly changed when total assistance was given as PSV plus PEEP when compared to PSV alone (PSV plus ZEEP); and (4) the extreme levels of PSV are not associated with the best comfort.

Aged↗

PubMed1988

An on-line microcomputer program for the monitoring of physiological variables during rest and exercise.

This paper describes a microcomputer system for the on-line display of physiological variables such as: lung ventilation, tidal volume, respiratory frequency, oxygen consumption, heart rate, oxygen pulse, respiratory exchange ratio, grams of fat and carbohydrate metabolised, mean skin temperature, rectal temperature and mean body temperature. The program has been written in Pascal. The modular nature of this language facilitates modification of the program to make it compatible with a variety of hardware and peripherals.

Calibration↗

PubMed1991

The influence of ambient temperature on some commonly measured physiological variables in infants.

Fifty-four infants underwent recording of heart rate, respiratory rate, long term and short term heart rate variability and end tidal carbon dioxide measurements at three different ambient temperatures (20 degrees C, 25-26 degrees C, 30 degrees C) under standardized conditions. The infants' skin and rectal temperature remained normal throughout the study. The ambient temperature of the room where the study was conducted significantly influenced the infants' heart rate, respiratory rate and long and short term heart rate variability but not end tidal carbon dioxide values. The thermal environment in which an infant resides has a significant influence on some physiological variables and should be standardized in future physiological studies.

Body Temperature↗

PubMed1999

Significance of biomechanical and physiological variables during the determination of maximum acceptable weight of lift.

The aim was to identify which biomechanical and physiological variables were associated with the decision to change the weight of lift during the determination of the maximum acceptable weight of lift (MAWL) in a psychophysical study. Fifteen male college students lifted a box of unknown weight at 4.3 lifts/min, and adjusted the weight until their MAWL was reached. Variables such as heart rate, trunk positions, velocities and accelerations were measured during the lifting, as well as estimated spinal loading in terms of moments and spinal forces in three dimensions using an EMG-assisted biomechanical model. Multiple logistic regression techniques identified variables associated with the decision to change the weights up and down prior to a subsequent lift. Results indicated that heart rate, predicted sagittal lift moment and low back disorder (LBD) risk index were associated with decreases in the weight prior to the next lift. Thus, historical measures of LBD risk (e.g. compression, shear force) were not associated with decreases in weight prior to the next lift. Additionally, the magnitudes of the predicted spinal forces and LBD risk were all very high at the MAWL when compared with literature sources of tolerance as well as observational studies on LBD risk. Our findings indicate that the psychophysical methodology may be useful for the decision to lower the weight of loads that may present extreme levels of risk of LBD; however, the psychophysical methodology does not seem to help in the decision to stop changing the weight at a safe load weight.

Adult↗

PubMed1998

Psychologic, situational, and physiologic variables and on-ice performance of youth hockey goalkeepers.

OBJECTIVE: To determine the relationship between psychologic, situational, and physiologic variables and on-ice performance of youth hockey goalkeepers. DESIGN: This study was structured to identify relationships and predictors of goalie performance. MATERIAL AND METHODS: Because athletes playing solo positions in team sports have not been analyzed in depth in terms of precompetition anxiety and because goalkeeper performance is critical to game outcome, we undertook a study of 43 goalies at a hockey camp. These goalies completed psychometric inventories to assess trait and state anxiety, confidence, life stress, and social support. Holter monitors measured heart rate while the goalies rotated through on-ice stations. Goalies were videotaped at the puck-shooting machine station, and performance (percent saves) was calculated. RESULTS: Trait (somatic) anxiety and positive mood state (ability to share) had different but significant relationships with on-ice performance. Heart rates ranged from 88 to 208 beats/min at the on-ice stations. Mean heart rate for older goalies (14 to 18 years of age) was 164 beats/min at the puck-shooting machine and 176 beats/min at other stations such as the slap-shot station. CONCLUSION: Older goalies performed well at a high level of arousal. Better performing goalies were more experienced, had faster heart rates "in the net," and had lower scores on all measures of anxiety.

Adolescent↗

PubMed1993

Progressive brain compression. Changes in vital physiological variables, correlated with brain tissue water content and brain tissue displacement. Experimental MR imaging in dogs.

Continuous recording of vital physiological variables and sequential MR imaging were performed simultaneously during continuous expansion of an epidural rubber balloon over the left hemisphere in anaesthetised dogs. Balloon expansion led to a progressive and slightly nonlinear rise in intracranial CSF pressures and a fall in local perfusion pressures. Changes in systemic arterial pressure, pulse rate, and respiration rate usually appeared at a balloon volume of 4% to 5% of the intracranial volume (reaction volume), together with a marked transtentorial pressure gradient and MR imaging changes consistent with tentorial herniation. Respiratory arrest occurred at a balloon volume of approximately 10% of the intracranial volume (apnoea volume), which was associated with occlusion of the cisterna magna, consistent with some degree of foramen magnum herniation. Increase in tissue water was observed beginning at approximately the reaction volume, presumably due to ischaemic oedema, due to the fall in perfusion pressures.

Animals↗

PubMed1993

The correlation of running ability and physiological variables in thoroughbred racehorses.

The running abilities of 25 Thoroughbred racehorses were measured at distances of 1200, 1600 and 20000 m. Various physiological variables were measured subsequently on the treadmill and correlated with running speed. There was a negative correlation for running speed with the velocity (VLa4) and work rate (WLa4) at which blood lactate reaches a steady-state concentration of 4 mmol/litre and a positive correlation with peak plasma lactate, suggesting that plasma lactate concentrations of faster horses rise more rapidly and to higher levels than do those of slower horses. The correlation between running speeds and heart rates (HR) was stronger for unfit than fit horses, suggesting that cardiovascular effects of training are more beneficial to slower horses. The significant correlation between running speeds and V200 suggests that the HR of faster horses increases more rapidly than in slower horses performing similar exercise. The correlation of running speeds and VO2max suggests that the HR of faster horses increases more rapidly than in slower horses performing similar exercise. The correlation of running speeds and VO2max suggests that faster horses utilise more oxygen during maximal intensity exercise. The correlation of running speeds with minimum pH and minimum HCO3- suggests that faster horses maintain speed at higher hydrogen ion (H+) concentrations. Correlations between running speeds and the measured variables were consistently stronger for the longer distance runs. Because VLa4 and WLa4 were obtained during sub-maximal exercise, these variables were determined to be the best correlates of running performance.

Animals↗

PubMed2006

Physiological variables and performance markers of serving soldiers from two "elite" units of the British Army.

The aim of this study was to compare selected physiological variables and performance markers of soldiers from two "elite" units of the British Army. Ten soldiers from each of the two units were recruited for this study (n = 20). All participants completed three tests while carrying a 20 kg backpack load: (1) a maximal treadmill test using the Bruce protocol; (2) a 2 mile backpack run test specific to Unit A on a consistently flat tarmac road; and (3) a 29 km time-trial over hilly terrain typical of a mountainous area used by Unit B for performance assessment. Heart rate, maximal blood lactate concentration and performance (run time) were assessed during all three tests, with peak oxygen uptake also being measured during the maximal treadmill test. Measurements of anthropometry, isokinetic strength and mental toughness (MT48) were also recorded. There were no significant differences in terms of performance markers between the units (P > 0.05). Performance on the maximal treadmill test correlated with performance on the 2 mile backpack run test (r = -0.57) and 29 km time-trial (r = -0.66). Performance on the 2 mile backpack run test in turn correlated with 29 km time-trial performance (r = -0.77), accounting for 59% of the variance. In conclusion, the maximal treadmill test and the 2 mile backpack run test are useful indicators of performance on the arduous hill march and could be employed in the screening and selection of potential recruits.

Adaptation, Psychological↗

PubMed1992

The contribution of selected anthropometric and physiological variables to 10K performance of wheelchair racers: a preliminary study.

The purpose of this study was to determine the relationship between selected anthropometric and physiological variables and 10K time. Eleven male wheelchair athletes with spinal cord injuries in training for national competition performed continuous progressive exercise tests on a wheelchair ergometer to determine maximal metabolic and cardiorespiratory values. Anthropometric data were also collected. The laboratory data were analyzed for correlation with the best 10K time of each subject during the test period. The subjects averaged 27 min 30 sec for their 10K races, 2.49 L.min-1 for VO2max and 35 percent for maximal gross mechanical efficiency during submaximal exercise. Speed at peak oxygen consumption (r = -0.66), gross mechanical efficiency (r = -0.56), and body density (r = -0.57) was found to be significantly (p less than 0.10) correlated with 10K time. The results show very little correlation between VO2max and 10K time (r = 0.02). Further study is indicated for the relationship between gross mechanical efficiency, speed at maximal oxygen consumption, body density, and 10K time; these variables may be useful in evaluating training programs for improving race performance.

Adult↗

PubMed2005

[Effects of cycled lighting on body weight, physiological variables and behavioral states in low birth weight infants].

PURPOSE: This study was aimed at finding the effects of cycled lighting on body weight, physiological variables and the behavioral state of LBWI (low birth weight infants) in the NICU. METHOD: The subjects were 20 LBWI at 2 NICUs. They were assigned to an experimental or control group which consisted of 10 subjects in each. Cycled light was applied to the experimental group for 10 days. RESULT: It was certified that the application of cycled lighting resulted in increased body weight and O(2) saturation, and decreased heart rate of the LBWI. However, there was no effect in decrease of respiration and stabilization of the behavioral state. CONCLUSION: The application of cycled lighting might be a nursing intervention which would in turn have positive effects on the growth of LBWI.

Circadian Rhythm↗

PubMed1999

The relationship between selected physiological variables of rowers and rowing performance as determined by a 2000 m ergometer test.

The aim of this study was to establish the relationship between selected physiological variables of rowers and rowing performance as determined by a 2000 m time-trial on a Concept II Model B rowing ergometer. The participants were 13 male club standard oarsmen. Their mean (+/- s) age, body mass and height were 19.9+/-0.6 years, 73.1+/-6.6 kg and 180.5+/-4.6 cm respectively. The participants were tested on the rowing ergometer to determine their maximal oxygen uptake (VO2max), rowing economy, predicted velocity at VO2max, velocity and VO2 at the lactate threshold, and their velocity and VO2 at a blood lactate concentration of 4 mmol x l(-1). Percent body fat was estimated using the skinfold method. The velocity for the 2000 m performance test and the predicted velocities at the lactate threshold, at a blood lactate concentration of 4 mmol x l(-1) and at VO2max were 4.7+/-0.2, 3.9+/-0.2, 4.2+/-0.2 and 4.6+/-0.2 m x s(-1) respectively. A repeated-measures analysis of variance showed that the three predicted velocities were all significantly different from each other (P<0.05). The VO2max and lean body mass showed the highest correlation with the velocity for the 2000 m time-trial (r = 0.85). A stepwise multiple regression showed that VO2max was the best single predictor of the velocity for the 2000 m time-trial; a model incorporating VO2max explained 72% of the variability in 2000 m rowing performance. Our results suggest that rowers should devote time to the improvement of VO2max and lean body mass.

Adolescent↗

PubMed2005

Physiologic variability of single-voxel proton MR spectroscopic measurements at 3T.

BACKGROUND AND PURPOSE: Physiologic and scanner variability of proton MR spectroscopy (MRS) measurements can limit the detection of subtle metabolite fluctuations. We assessed the variability of such measurements at 3T and compared two methods to obtain absolute concentrations. METHODS: Variability over 14 days was assessed with short-echo, single-voxel proton MRS in 14 control subjects and in a phantom containing 50 mmol/L N-acetylaspartate (NAA). Spectra were analyzed by using LCModel, scaling factors determined with both the calibration phantom (CP), and water peak intensity (WP) methods. Relative (reflecting the systematic drift) and absolute variability (reflecting the magnitude of scanner variability) was determined. RESULTS: For the phantom, initial (49 +/- 1.7 mmol/L) and second measurements (50 +/- 1.6 mmol/L) showed similar results, with small variability (relative, -0.6 +/- 1.5 mmol/L; absolute, 1.1 +/- 1.1 mmol/L). Control subjects had no systematic difference between the two scans for any measurement. Absolute variabilities in the temporal lobe for total NAA (NAA+NAAG) were 13% (CP) and 11% (WP). The largest variability (29%) was found for glutamate-glutamine (29%) with the CP method, and for myo-inositol with the WP method (28%). Absolute variability was smaller for the frontal lobe measurements (total NAA 7% and overall 6-18% for CP; total NAA 6% and overall 5-19% for WP). No significant difference was observed between the two methods. CONCLUSION: Physiologic variability is the major source of measurement variability and accounts for 12% of the variability in temporal lobe total NAA. Therefore, total NAA variations must clearly exceed this before they can reliably be attributed to an effect of disease.

Adult↗

PubMed1993

Changes in intracranial morphology, regional cerebral water content and vital physiological variables during epidural bleeding. An experimental MR study in dogs.

Epidural bleeding was produced in 8 anaesthetised and heparinised dogs by an artificial system. Changes in vital physiological variables were related to intracranial shifts and tissue water content assessed with MR imaging. Six animals survived while 2 succumbed. In the surviving animals intracranial shifts and compressions remained unchanged from an early stage. The cerebral perfusion pressure was reduced from between 80 and 110 mm Hg to between 40 and 60 mm Hg. Some increase in supratentorial white matter tissue water was observed. In the lethal experiments cerebral perfusion pressure fell to less than 40 mm Hg. Moreover, secondary delayed anatomical changes were seen including hydrocephalus. Increase in cerebral tissue water was more intense and widespread than in the survivors. These findings indicate that the outcome of epidural bleeding is related to cerebral perfusion pressure with secondary deterioration resulting from additional volume loading from increased tissue water and hydrocephalus.

Animals↗

PubMed1990

Rheological modelling of physiological variables during temperature variations at rest.

The evolution with time of cardio-respiratory variables, blood pressure and body temperature has been studied on six males, resting in semi-nude conditions during short (30 min) cold stress exposure (0 degree C) and during passive recovery (60 min) at 20 degrees C. Passive cold exposure does not induce a change in HR but increases VO2, VCO2, Ve and core temperature Tre, whereas peripheral temperature is significantly lowered. The kinetic evolution of the studied variables was investigated using a Kelvin-Voigt rheological model. The results suggest that the human body, and by extension the measured physiological variables of its functioning, does not react as a perfect viscoelastic system. Cold exposure induces a more rapid adaptation for heart rate, blood pressure and skin temperatures than that observed during the rewarming period (20 degrees C), whereas respiratory adjustments show an opposite evolution. During the cooling period of the experiment the adaptative mechanisms, taking effect to preserve core homeothermy and to obtain a higher oxygen supply, increase the energy loss of the body.

Acclimatization↗

PubMed1995

Plasma renin activity in normal healthy volunteers: effect of physiological variables.

Plasma renin activity was determined in hundred normal subjects of either sex (M = 65, F = 35, age range 2-70 yr) using Angiotensin-I test kits. The effect of various physiological variables viz, age, sex, posture and salt intake was determined. The basal values for PRA ranged from 1.19 +/- 0.09 ng/ml/hr for males and 1.02 +/- 0.12 ng/ml/hr for females in erect posture. In contrast high basal supine PRA was noticed in subjects on low salt diet, which showed a significant increase in erect posture. A marked decrease in PRA with advancing age in both the sexes with significantly low values at higher age range was noticed. Captopril produced an insignificant effect on PRA and BP in salt replete supine state, whereas in salt deplete state there was a significant rise in both the parameters.

Adolescent↗