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PubMed1996

A videodensitometric study of transmural heterogeneity of cyclic echo amplitude variation in human myocardium.

The aims of this study were: (1) to assess whether variations in cyclic echo amplitude might be detected across the human myocardium by videodensitometric analysis of images obtained with epicardial echocardiography; and (2) to explore the possible relation between cyclic gray level variation and left ventricular (LV) hypertrophy and function. Experimental studies show that transmural differences in contractile performance across the normal myocardium are paralleled by differences in the cyclic (diastolic-to-systolic) variation of myocardial echo amplitude. Thirty-three patients (aged 60 +/- 11 years) undergoing cardiac surgery were studied by intraoperative epicardial echocardiography. LV mass index as normal (<110 g/m2 in women, <131 g/m2 in men) in 10 patients and increased in 22. Two-dimensional echocardiographic images were obtained with a 5 MHz transducer and digitized off-line. Videodensitometric analysis was performed at end-diastole and end-systole with regions of interest across the septal and posterior wall. The cyclic variation was more pronounced in the left than in the right septal subendocardium (31% +/- 14% vs 16% +/- 14% <0.01) and higher in the subendocardial than in the subepicardial layer of the posterior wall (30% +/- 21% vs 23 +/- 18%, p <0.01). Cyclic variation of the left septal subendocardium was higher in 11 patients with nonhypertrophic ventricles than in 22 with hypertrophic left ventricles (42% +/- 15% vs 27% +/- 12%; p <0.01). The percent cyclic variation of the left septal subendocardium appeared to be much more tightly related to percent systolic thickening in patients with eccentric LV hypertrophy (r=0.80 p <0.01) than in patients with concentric LV hypertrophy (r=0.27, p=0.9) or normal LV mass (r=0.43, p=0.2). A cyclic gray level variation can be consistently detected in different human myocardial regions and layers. It is more obvious in the subendocardial than in the subepicardial layer, and in nonhypertrophic than hypertrophic ventricles. The cyclic subendocardial variation is tightly related to regional systolic thickening in patients with eccentric LV hypertrophy.

Aged↗

PubMed2003

Evaluation of optineurin sequence variations in 1,048 patients with open-angle glaucoma.

PURPOSE: To investigate the association of sequence variations in the optineurin (OPTN) gene in patients with open-angle glaucoma. DESIGN: Prospective case control study. METHODS: The OPTN gene was screened for sequence variations using a combination of single-strand conformational polymorphism analysis and automated DNA sequencing. A total of 1,299 subjects (1048 glaucoma patients and 251 controls) were screened for variations in the four portions of the gene that had been previously associated with glaucoma. A subset of these subjects (376 patients and 176 controls) was screened for variations in the entire coding sequence. Twenty-four percent of the patients and 35% of the controls were Japanese, whereas the remainder were predominantly Caucasian. Allele frequencies were compared with the Fisher exact test. RESULTS: The OPTN sequence variations were not significantly associated with any form of high-tension open-angle glaucoma. One proband with familial normal-tension glaucoma was found to harbor the previously reported Glu50Lys variation. Another previously reported change, Met98Lys, was associated with normal-tension glaucoma in Japanese but not in Caucasian patients. CONCLUSIONS: This study provides some additional evidence for the association of the Glu50Lys OPTN sequence variation with familial normal tension glaucoma. However, because familial normal-tension glaucoma is so rare, this change seems to be responsible for less than 0.1% of all open-angle glaucoma. The Arg545Gln variation is likely to be a nondisease-causing polymorphism. The Met98Lys change may be associated with a fraction of normal-tension glaucoma in patients of Japanese ethnicity.

Base Sequence↗

PubMed2001

Seasonal and biological variation of urinary epinephrine, norepinephrine, and cortisol in healthy women.

BACKGROUND: There is a significant circadian and seasonal periodicity in various endocrine functions. The present study describes the within-day and seasonal fluctuation for urinary catecholamines and cortisol and estimates the within- (CV(i)) and between-subject (CV(g)) coefficients of variation for healthy women undertaking their routine work. In addition, index of individuality (I(i)) and power calculations were derived. METHODS: Eleven healthy females undertaking their routine life-style at work participated in the study. Each subject collected six samples during 24 h 15 days over a year, giving a total number of 990 samples. Using a random effect analysis of variance, we estimated CV(g) and total within-subject variation (CV(ti)), i.e. combined within-subject and analytical variation, from logarithmically transformed data. Analytical variation was subtracted from CV(ti) to give CV(i). CV(i) was estimated from samples collected monthly during 1 year (CV(iy)), weekly during 1 month (CV(im)), and six to eight times/day (CV(id)). RESULTS: A seasonal variation was demonstrated for excretion of epinephrine, norepinephrine, and cortisol standardized with creatinine. Concentrations of urinary epinephrine were higher during June and July compared to the rest of the year, whereas concentrations of urinary cortisol were higher during December and January compared to the rest of the year. Excretion of norepinephrine was lower during working hours and higher during hours off work for June and July compared to the rest of the year. There was a high within- and between-subject variation, which could not be explained by menstrual cycle, behavioral, emotional, or cognitive stress reactions. CONCLUSIONS: Despite high biological variation a reasonably low sample size, e.g. 10-50 individuals, is adequate for practical applicability, i.e. studying differences above 150%. The present study recommends to include the sampling time in the statistical evaluation of data and to be aware of the changes in diurnal variations over seasons. When single measurements are to be evaluated, reference intervals are recommended.

Adult↗

PubMed1999

Monthly intra-individual variation in lipids over a 1-year period in 22 normal subjects.

OBJECTIVES: Previous reports on biological variation in lipids differ widely in the time interval between sampling, the number of samples analyzed per patient and the total study period. The present investigation was carried out to determine monthly intra-individual variation in lipids over 1 year and to establish whether there was a consistent change in lipid values over the summer months. The importance of taking this variation into consideration during the assessment of risk of coronary heart disease (CHD) was also examined. DESIGN AND METHODS: Cholesterol, triglycerides, HDL, apo A1, and apo B were measured at monthly intervals for 12 months in 22 healthy, free-living volunteers (11 females, 11 males) by standardized methods. RESULTS: When compared to analytical variation, biological variation was the dominant component of the intra-individual changes observed during the 1-year study period. As expected, triglycerides showed the greatest biological variation; the ratio of biological/analytical variation was 33.1. Much smaller ratios were observed for the other lipids measured in this study with values ranging from 4.2 to 6.8. Different subjects attained their maximum and minimum values in virtually every month of the year. There were significant reductions in cholesterol, HDL, LDL, and apo A1 in the summer months while triglycerides showed a non-significant increase and apo B a non-significant decrease during this period. CONCLUSIONS: All the analytes showed considerable intra-individual variation. It is, therefore, important to measure lipids sequentially over several weeks to arrive at an average value for risk stratification for CHD.

Adult↗

PubMed1997

The day-to-day variation in insulin sensitivity in non-insulin-dependent diabetes mellitus patients assessed by the hyperinsulinemic-euglycemic clamp method.

The objective was to study the day-to-day variation in insulin sensitivity in non-insulin-dependent diabetes mellitus (NIDDM) and to analyze within- and between-person variances in the glucose infusion rate during steady state (M value). Ten NIDDM patients attending the outpatient clinic at Aarhus Amtssygehus were studied three times under standardized conditions. Each time, a 120-minute hyperinsulinemic-euglycemic clamp was performed. Similar M values were found on the 3 study days, with difference between M values on the 3 days of (mean +/- SD) 0.3 +/- 1.8 mg glucose/kg lean body mass (LBM)/min. The total coefficient of variation (CV) for M values was 57% after the first clamp, 55% after the second, and 53% after the third. Ninety percent of the total day-to-day variation in M values could be ascribed to between-person variation and 10% to within-person variation. Within-person components of variance included all sources of variation other than between-person variation. The within-person CV for M values was 11.9% +/- 7.2% after two clamp studies and 12.1% +/- 7.3% after three (P < .55). In conclusion, under standardized conditions, a valid estimate of insulin sensitivity assessed by the hyperinsulinemic-euglycemic clamp in NIDDM patients is obtained after a single measurement. Because of large between-person variation, paired data should be used when comparing insulin sensitivity in NIDDM patients.

Blood Glucose↗

PubMedDate not supplied

Genetic variation and inferences about perceived taste intensity in mice and men.

The study of genetic variation in taste produces parallels between mice and men. In mice, genetic variation across strains has been documented with psychophysical and anatomical measures as well as with recordings from whole nerves. In humans, the variation has been documented with psychophysical and anatomical measures. Whole-nerve recordings from animals and psychophysical ratings of perceived intensities from human subjects have a similar logical limitation: absolute comparisons across individuals require a standard stimulus that can be assumed equally intense to all. Comparisons across whole-nerve recordings are aided by single-fiber recordings. Comparisons across psychophysical ratings of perceived intensity have been aided by recent advances in methodology; these advances now reveal that the magnitude of genetic variation in human subjects is larger than previously suspected. In females, hormones further contribute to variation in taste. There is evidence that the ability to taste (particularly bitter) cycles with hormones in women of child-bearing age, rises to a maximum early in pregnancy and declines after menopause. Taste affects food preferences, which in turn affect dietary behavior and thus disease risks. Valid assessment of taste variation now permits measurement of the impact of taste variation on health. Advances in psychophysical methodology were essential to understanding genetic variation in taste. In turn, the association of perceived taste intensities with tongue anatomy now provides a new tool for psychophysics. The ability of a psychophysical scale to provide across-subject comparisons can be assessed through its ability to show the fungiform papillae density-taste association.

Animals↗

PubMed1997

Accuracy of gamma-variate fits to concentration-time curves from dynamic susceptibility-contrast enhanced MRI: influence of time resolution, maximal signal drop and signal-to-noise.

Concentration-time curves derived from dynamic susceptibility-contrast enhanced magnetic resonance imaging are widely used to calculate cerebrovascular parameters. To exclude effects of recirculation, a non-linear regression method is used to fit a gamma-variate function to the concentration-time course. In previous studies the errors arising from the fitting procedure have not been quantified. In a computer simulation we investigate the uncertainties of parameters calculated from the fitted gamma-variate function, exploring the dependencies on signal-to-noise (SNR), time resolution (delta t), and maximal signal drop (MSD). Our study was performed to give a framework on how to design MR-sequences and choose contrast media and their application in order to yield concentration-time curves which allow a reliable performance of the gamma-variate fitting procedure. We recorded 396 concentration-time curves from regions of interest of 40 patients. The gamma-variate fitting procedure was applied to these curves resulting in 396 parameter sets. Ideal concentration-time curves as gamma-variate functions were generated from these sets with a given delta t, MSD, and SNR. Recirculation effect was simulated. Then the gamma-variate fitting was performed again. From ideal and simulated gamma-variate function the area and the normalized first moment were calculated. The uncertainties of the values calculated from the simulated curve relating to the values of the original one were determined. Increase of SNR decreases the involved errors. With SNR values of 100 and more there is only minor influence of delta t and MSD and the fitted curve approximates the original data very well. Smaller values of SNR lead to a stronger influence of delta t and MSD and a higher number of fitting failures. With increasing delta t the uncertainties also increase. Intermediate values of MSD (30% to 70%) yield the smallest errors while increasing or decreasing MSD yields an increase of uncertainty. To achieve low uncertainties in the calculation of cerebrovascular parameters from gamma-variate fits, delta t of the imaging sequence and MSD must be considered. This is more important the lower SNR is. The shown dependencies should be taken into account when choosing MR sequence parameters and application of contrast media.

Artifacts↗

PubMed2001

Circadian and longitudinal variation of serum C-telopeptide, osteocalcin, and skeletal alkaline phosphatase in C3H/HeJ mice.

Inbred strains of mice are increasingly being used as an animal model to investigate skeletal disorders relevant to humans. In the bone field, one of the most convenient endpoints for evaluating genetic, physiological, or pharmaceutical perturbations is the use of biochemical markers. To apply biochemical markers in an effective manner, it is of key importance to establish the biological variation and appropriate sampling time. In this study, we evaluate two components: (i) circadian changes, and (ii) longitudinal variation for three serum markers, osteocalcin, C-telopeptide, and skeletal alkaline phosphatase (sALP), using 6-week-old C3H/HeJ (C3H) mice. To study circadian rhythms, the mice were randomly divided into eight groups of 15 mice each. Blood was collected at 3 h intervals, starting at 9:00 A.M. and continuing until 6:00 A.M. the next day. To determine whether circadian rhythm is intrinsically regulated or influenced by restricted food intake, it was also studied after a 12 h fasting period. Serum osteocalcin and C-telopeptide levels were measured by enzyme-linked immunoassay (ELISA) and skeletal alkaline phosphatase by a kinetic assay. The results demonstrated significant circadian variations in osteocalcin and C-telopeptide levels with a peak value between 0900 and 1200 h during daytime and a nadir between 15:00 and 18:00 h. The peak levels of C-telopeptide and osteocalcin were 26%-66% higher as compared with 24 h mean values. The pattern of the circadian variation of C-telopeptide and osteocalcin was similar in female and male animals and was not significantly affected by restricted food intake. The sALP levels were only marginally affected by the circadian rhythm. Longitudinal variations, expressed as coefficient of variation (CV), for osteocalcin, C-telopeptide, and sALP concentrations were 17%, 14%, and 16%, respectively. In addition, the longitudinal variations were not significantly influenced by the time of blood collection in sALP and osteocalcin levels, whereas C-telopeptide levels showed significantly higher within-subject day-to-day variation in morning samples, as compared with blood samples collected in the afternoon. The results highlight the importance of: (i) the timing of sample collection for appropriate interpretation of the bone marker data; and (ii) using the appropriate number of samples based on the variance obtained herein.

Alkaline Phosphatase↗

PubMed2004

Detection of human immunodeficiency virus type 1 envelope peptide- stimulated T-helper cell responses and variations in the corresponding regions of viral isolates among vertically infected children.

Although human immunodeficiency virus type 1 (HIV-1) specific CD4 T-helper cells are vital in mediating antiviral defence, little is known concerning the influence of HIV-1 antigenic variation on CD4 T-cell responses. In this study, the amino acid sequences of 5 synthetic HIV-1 envelope peptides used for in vitro stimulation (T2, P18 MN, P18 IIIB, T1 and TH4.1) were compared to the corresponding amino acid sequences of the gp 160 region of viruses isolated from HIV-1 infected children to determine whether variation in the envelope region of HIV-1 was associated with the ability to detect Env-specific T-helper cell responses. Although the T2 region appeared to offer some evidence as to the role antigenic variation may have played in class II-restricted CD4 T-cell responses between those children who showed a detectable Env-stimulated T-helper cell response and those who did not, the other regions studied showed no evidence of being more conserved among those children who showed detectable responses. The combined amino acid variation across the specific peptide regions studied was not associated with peripheral levels of HIV-1, nor did the degree of amino acid variation dictate the clinical category into which the children had been classified, although there was a tendency towards HIV-1 isolates from the younger children showing a greater degree of amino acid variation than isolates from the older children. These results suggest that HIV-1 specific CD4 responses may be somewhat tolerant of viral variation, although further studies are required to fully elucidate the effect of antigenic variation on immune recognition.

Amino Acid Sequence↗

PubMed1995

Modes of vocal variation in Sykes's monkey (Cercopithecus albogularis) squeals.

Acoustic and laryngographic measurements of Sykes's monkey (Cercopithecus albogularis) squeals showed that acoustic variation between exemplars was principally due to 4 underlying modes of modification: (Class I) variation in the transfer function produced by articulation, (Class II) variation in F0 produced by inflection, (Class III) variation in turbulence, and (Class IV) variation in the pattern of vibration of laryngeal tissue with large or small surface areas (polyphonic variation). These findings suggest that some modes of variation (Class I, II, and III calls) were due to phonatory and articulatory acts resembling, at a very general level, sound production mechanics used in speech. Acoustic variation in the polyphonic group (Class IV calls) is not evident in speech and was attributed to the possibility of independent and simultaneous vibrations of the vocal lip and the principal component of the vocal folds.

Animal Communication↗

PubMed1994

Short-term variation in the elastic properties of a muscular artery in humans.

1. Information on the interaction between mechanical strain and the elastic properties of large arteries could give insight to the origin of haemodynamic vascular injury, possibly resulting in formation of atherosclerotic plaques. Intra-individual variation in the elastic properties of muscular arteries measured using non-invasive techniques has been observed. This variation could be due to changes in blood pressure, since the elastic properties of muscular arteries are strongly non-linear. 2. The objective of the present study was to evaluate variability in the elastic properties of a muscular artery over a time period of up to 1 h. Furthermore, the relation between changes in elastic properties and alterations in blood pressure was studied. With a non-invasive high-resolution ultrasound technique, the diameter and distension of the femoral artery were assessed by repeated measurements in 10 healthy subjects (mean age 27 +/- 2.9 years) under resting conditions over 40-60 min. Intra-arterial blood pressure of the contralateral common femoral artery and heart rate were recorded simultaneously. From the distension and pulse pressure, the distension/pressure ratio was calculated, a measure of the compliance. For each parameter the variation coefficient was computed. 3. In all subjects a considerable variation was found in distension (mean variation coefficient 14.8%) but not in pulse pressure (mean variation coefficient 3.7%). The expected positive correlation between pulse pressure and distension was absent in eight subjects. As a consequence, large intra-individual variation was found in the distension/pressure ratio (mean variation coefficient 15.3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed2000

Circadian variation in serum free and total insulin-like growth factor (IGF)-I and IGF-II in untreated and treated acromegaly and growth hormone deficiency.

OBJECTIVE: It is generally accepted that there is no clinically significant circadian variation in total insulin-like growth factor (IGF)-I or total IGF-II in healthy subjects. In contrast there is a significant nocturnal decrease in free IGF-I in healthy subjects, corresponding to the nocturnal increase in IGF binding protein-1. In this study we have investigated the circadian variation in circulating free IGF-I and IGF-II in patients with acromegaly and patients with adult onset growth hormone deficiency. PATIENTS: Seven acromegalic patients were studied with and without treatment with a slow-release formulation of octreotide. Seven GH-deficient patients were studied without GH replacement. In addition 5 of the GH-deficient patients were studied during GH replacement. DESIGN: Serum samples were obtained every hour for 24 h. Free IGF-I and IGF-II were measured every 2nd hour. Total IGF-I and IGF-II were measured every 2nd hour (acromegalic patients) or every 4th hour (GH deficient patients). IGF binding protein (IGFBP)-1 was measured every 2nd hour (acromegalic patients) or every hour (GH deficient patients). RESULTS: In the untreated acromegalic patients there was a significant nocturnal decrease in free IGF-I, but not free IGF-II, before treatment. During treatment there was a significant nocturnal decrease in both free IGF-I and free IGF-II. Peak values of free IGF-I were 112% and 75% above trough (treatment and withdrawal, respectively). In the GH-deficient patients there were no significant circadian variations in free IGF-I or free IGF-II in either of the two occasions. In contrast, there was a significant circadian variation of total IGF-I after adjustment for changes in plasma volume in both treated and untreated acromegaly and GH deficiency in all cases with a peak between 0300 h and 0400 h. The nocturnal increase in total IGF-I ranged from 20% to 35%. CONCLUSIONS: A significant circadian variation in free IGF-I and IGF-II was demonstrated in acromegalic patients. In contrast no significant circadian variation in free IGF-I and IGF-II was found in GH-deficient patients. Part of the variations may be due to poorly understood variations in IGF-I release. It is not clear whether and to what extent the observed circadian changes in free and total IGF-I are involved in circadian changes in IGF-I bioactivity.

Acromegaly↗

PubMed1996

The day-to-day variation (test-retest reliability) of residual urine measurement.

OBJECTIVE: To determine the variation in repeated measurements of post-void residual urine volume (PVR), determined by transabdominal ultrasonography (TAUS), within an individual over time (test-retest reliability). PATIENTS AND METHODS: Forty men with symptomatic benign prostatic hyperplasia and awaiting transurethral resection of the prostate were studied over 3 months. Each underwent TAUS to determine both pre- and post-micturition residual volumes on six occasions within the study period. RESULTS: Although one-third of the patients had approximately constant residual volumes (variation in range < 120 mL), two-thirds had wide intra-individual variations over time (variation in range 150-670 mL). The values were log transformed to give a normal distribution and subjected to analysis of variance; there was a wide variation between and also within individuals. The larger the mean PVR, the larger was the overall variation in time. For those with a mean PVR of < 100 mL, the variation was less marked and these patients showed a more consistent test-retest repeatability. CONCLUSIONS: Although the PVR determined by TAUS may be useful to indicate aspects of bladder dysfunction or outlet obstruction, the wide variation in repeated measurements in the same individual limits its use for any clinical purpose that requires repeated assessment, e.g. in monitoring the response to treatment. There is poor test-retest reliability and PVRs cannot be determined reliably from a single measurement.

Aged↗

PubMed1991

[Diurnal variations of symptoms of depression].

New symptom-statistical, chronobiological and experimental investigations concerning diurnal variation in endogenous depression (melancholia) are reported and interpreted referring to psychopathological, biological and phenomenological aspects. According to recent studies, the so-called typical diurnal variation of mood (with morning low) is not as frequent, as it was assumed before, and even intraindividually unstable. Although more frequent than other daily rhythmus, the so called typical diurnal variation should not be used for diagnostic purposes, because it is quite frequent in different depressive states as well. During their healthy intervals endogenous depressive patients show not rarely an analogous diurnal variation of mood; this was also found in healthy subjects. Therefore the so called typical variation in mood is not specific, and it is questionable whether it is a marker of endogenous depression at all. Concerning circadian rhythm biological functions were examined more often than the depressive symptomatology itself (especially temperature, heart rate, cortisol and other neuroendocrine parameters). Unexpectedly there were only slight variations of the circadian diurnal curves in melancholic patients compared to healthy subjects. The circadian rhythm in endogenous depression does not seem to be very different from the physiological diurnal course. Comparing the biological circadian curves in endogenous depression to the curves of the depression symptomatology, the similarities outline the differences. Sleep research didn't show any results, supporting the suggestion of a specific rhythm variation either. Therefore the opinion, that the circadian rhythm is altered basically in melancholia, cannot be maintained, neither psychopathologically nor biologically. Experiments of time estimation in the course of the day could'nt explain the diurnal variation in mood either.

Circadian Rhythm↗

PubMed1999

Geographic variations in utilization rates in Veterans Affairs hospitals and clinics.

BACKGROUND: In the United States, geographic variation in hospital use is common. It is uncertain whether there are similar geographic variations in the health care system of the Department of Veterans Affairs (VA), which differs from the private sector because it predominantly serves men with annual incomes below $20,000, has a central system of administration, and uses salaried physicians. Thus, it might be less likely to have geographic variations. METHODS: We used VA data bases to obtain information on patients treated for eight diseases (chronic obstructive pulmonary disease, pneumonia, congestive heart failure, angina, diabetes, chronic renal failure, bipolar disorder, and major depression). We analyzed their use of hospital and outpatient services by assessing the risk-adjusted numbers of hospital days (the average number of days a patient spent in the hospital per 12 months of follow-up, regardless of the number of hospital stays), hospital-discharge rates, and clinic-visit rates from 1991 through 1995 for the entire system and within the 22 geographically based health care networks. RESULTS: We found substantial geographic variation in hospital use for all eight cohorts of patients and all the years studied. Variations in the numbers of hospital days per person-year among the networks were greatest among patients with chronic obstructive pulmonary disease (ranging from a factor of 2.7 to a factor of 3.1) during a given year and smallest among patients with angina (ranging from a factor of 1.5 to a factor of 2.1). Levels of hospital use were highest in the Northeast and lowest in the West. The variation in the rates of clinic visits for principal medical care among the networks ranged from a factor of approximately 1.6 to a factor of 4.0; variations in the rates were greatest among patients with chronic renal failure and smallest among patients with chronic obstructive pulmonary disease. There was no clear geographic pattern in the rates of outpatient-clinic use. CONCLUSIONS: There are significant geographic variations in the use of hospital and outpatient services in the VA health care system. Because VA physicians are unable to increase their income by changing their patterns of practice, our findings suggest that their practice styles are similar to those of other physicians in their geographic regions.

Chronic Disease↗

PubMed1996

The annual variation in activity and funding for acute public hospitals in NSW, 1988-89 to 1992-93.

Casemix-based funding was introduced into the Victorian health system without an assessment of the annual variation in inpatient activity. Before undertaking such a funding reform, it would be appropriate to determine the level of annual variation in inpatient activity for individual hospitals that could be attributable to chance or random variation. If the annual random variation is not accounted for, then casemix-based funding may actually lead to inefficiencies. For this study, hospital inpatient activity and funding data for 120 acute public hospitals from New South Wales for the years 1988-89 to 1992-93 were used to estimate the standard deviation of the annual random variation in activity and gross operating payment. Through linear regression, estimates of the standard deviation of random variation about the underlying trend were obtained for each hospital. The results showed that, depending on the size of the hospital, total diagnosis related group cost weights have a standard deviation in the range of 2 to 16 per cent of total activity, whilst gross operating payment has an equivalent standard deviation that ranges from 1 to 10 per cent annually. The magnitude of the variation would suggest that funding of hospitals should either be based on average activity over several years or based on bands of activity in order to reduce the potential random variation in funding levels.

Bed Occupancy↗

PubMed1998

Rhythmical variations of haemoglobin oxygenation in cutaneous capillaries.

The consequences of rhythmical arteriolar vasomotion for nutrition and the tissue oxygen supply to human skin are largely unknown. In the study presented here, the periodic variations of haemoglobin oxygenation in the small cutaneous vessels have been evaluated with a new reflection spectrophotometer. For the assessment of spatial variations, we examined 24 different sites in 20 healthy volunteers. For quantification of the relatively long duration of periodic variations, a Digital Fourier Transformation with a specially programmed filter was used. In 265 out of 480 spectra (55.2%), periodic variations of the haemoglobin oxygenation were found. The average of the main frequency of waves was 7.0 +/- 2.5 cycles per minute. The occurrence of variations of haemoglobin oxygenation depended on the measuring site. In the gluteal region, variations were observed in 17 out of 20 subjects, on the palms in 16 out of 20, at the foot plantar in 18 out of 20 in comparison to the cheek (8/20), the lip (5/20) and the eyelid (6/20). On the head we observed significantly more variations per minute than in the lower extremities. Because these variations, with duration of up to 30 s, have a relatively slow dynamic compared with heart rate and breathing frequency, consequences for the cutaneous diffusion and metabolism of other substrates are very likely.

Adult↗

PubMed2002

Perceptual integration of timing and intensity variations in the perception of musical accents.

The author investigated the detection of timing and intensity variations in tone sequences within the framework of perceptual independence or integration. The participants listened to sequences of tones that contained variations in timing, intensity, or both. Each participant tried to detect variations in the dimension that was declared relevant, which was either timing or intensity. The irrelevant dimension was held constant, or varied in a manner uncorrelated with the relevant dimension, or varied in a correlated manner. When the variations in the 2 dimensions were correlated, the correlation could be either positive (i.e., timing and intensity created accents in the same sequences) or negative (i.e., timing and intensity created accents in different sequences). Uncorrelated variation in the irrelevant dimension interfered with the detection of variations in the relevant dimension. In the case of a positive correlation between the 2 dimensions, the detection of variations was better than it was with the absence of variation in the irrelevant dimension only for participants who attended to timing. In the case of a negative correlation, the effect was the opposite. The results showed that timing and intensity accents were not processed by completely independent channels. Rather, information from the 2 dimensions combined at a late stage of processing.

Auditory Perception↗