The "cost" of silence.

Changes in the organism of control desk operators caused by difficulties faced during productionally relevant speech information processing under conditions of intense occupational noise, represent the psychophysiological "cost" of noise masking. Its presence attests to difficulties in processing before deterioration of the quality of the latter while its quantitative characterisation correlates positively with the degree of the masking effect of noise and with the neuropsychic stress of this particular type of work. For this reason an attempt is made to demonstrate noise masking under laboratory conditions with it approximate quantitative evaluation at two signal/noise ratios- +15 and The statistically significant differences between the values of pulse rate, plethysmography and vocal exertion at the above ratios point to both its presence, and to the necessity to be considered when assessing the occupational burden and standardisation of noise intensity in productions associated with speech signals.

Investigation of noise exposure effect on heart rate variability parameters.

This paper deals with the study of the effect of 135 min exposure to noise with intensity Leq 95 dB(A) in experimental conditions. Three experimental sessions: before, at the onset, and at the end of the noise exposure were conducted. The comparison of heart rate variability (HRV) parameters before and on the onset of the experiment showed tendency for significant decrease of the cardiointervals variability parameters: standard deviation (SD), sum of positive differences between successive cardiointervals (S), total wave energy in the cardiotachogram (S*Ns), mean difference between successive cardiointervals (V). Statistically significant increase of the mean value was found at HRV parameters related to the distribution of the cardiointervals: control adequacy parameter (IARP), equilibrium autonomic parameter (IVE), autonomous balance (IVB), homeostasis parameter (HI). At the end of the third experimental session HRV parameters were almost restored, but they did not achieve the initial values. An elevation of the sympathetic activity under noise exposure effect was found. In this aspect, the heart rate variability parameters were interpreted as a sensitive indicator for the quality of cardiac rhythm and they can be used for assessment of the functional status and the level of preserving of the adaptive reserves of the investigated persons.

Spectral coherence between blood pressure and inter-beat intervals in hypertension.

Continuous registration of blood pressure (BP) was obtained in 31 normotensives and 76 hypertensives (divided into 3 stages of hypertension) by a method where the blood pressure in a human finger was measured non-invasively in a beat-by-beat fully calibrated manner. From this signal, the power density spectra of inter-beat intervals (IBI), systolic blood pressure (SBP) and diastolic blood pressure (DBP) were derived. Total spectral power (TP) and low/high spectral frequency ratios of all spectra were calculated. Cross-correlation analysis between IBI, SBP and DBP spectra showed that the level of amplitude and phase spectral coherence (SC) was strongly dependent of the stage of hypertension. SC was calculated by means of appropriate mathematical algorithms. Multiple step regression analysis pointed out that the observed phenomenon is highly significant for both--the amplitude and the phase SC (p < 0.01).

Tinnitus, heart rate variability, and some biochemical indicators.

Twenty-three tinnitus patients between the ages of 25 and 66 years (mean age, 47.6) were examined completely in the neurootological clinic of the Medical University, Sofia. Heart rate variability measurements were obtained to reveal the relationship between tinnitus and the autonomic equilibrium. Some biochemical indicators (serotonin and the colored sedimentary uric reaction of Kimbarovski [CSURK]) also were followed up. For 19 patients with transitional disturbances in the vertebrobasilar blood circulation, the sympathetic portion of the autonomic nervous system predominates, and heart rate variability is suppressed. The higher suppression of heart rate variability and higher values of the health risk in four occupationally exposed patients are attributable to the higher expressed level of stress connected with the adverse work conditions. Changes in the health risk, CSURK, and serotonin blood values in four tinnitus patients also are discussed.

Relationship between heart rate variability and hypercholesterolaemia.

A statistically significant correlation between chronic (tonic) distress (expressed by long-term depression of heart rate variability-HRV) and the increase of the serum lipid level was found in the experimental group (39 clinically healthy subjects with hypercholesterolaemia; 16 women and 23 men; mean age 42.4 +/- 2.45 years). A statistically significant relationship was found also between the experimental and control group (39 healthy normocholesterolaemic subjects; 18 women and 21 men; mean age 43.7 +/- 2.18 years) when comparing distress indicating HRV-based measurements. Significant predictors of HRV depression were: total cholesterol and low-density lipoprotein cholesterol. The effect of a 3-month special diet served to 17 subjects selected from the experimental group led to a decrease of serum lipids but did not influence substantially HRV parameters. It can be concluded that HRV parameters reflecting stress reaction correlate with atherogenic serum lipids; their separate follow-up (which is quicker, easier and cheaper) can be used for prediction of cardiovascular health risk and probably for disorders in serum lipid metabolism.

Changes in some psychophysiological parameters in speech information processing under masking noise effect.

The aim of the present work was to study the influence of masking broad-band (white), impulse and interrupted noise with intensities LAeq 60 and 90 dB(A) on the execution of some psychophysiological tasks. The following parameters were studied: pulse frequency and variation, breathing frequency and variation, vascular tone etc. The psychological tasks model different parts of the operators' activity and include: conduction of mathematical calculations at datum speed; test related to the information processing; complex optional task supplied by Piorkovski's device. After statistical processing of results by Student-Fischer's t test and monofactor dispersion analysis it was established that the masking noise effect was more strongly expressed in the execution of psychophysiological tasks connected with the main memory. Of all tested physiological parameters the changes in the peripheral circulation, expressed in elevated vascular tone of peripheral blood vessels, were the most significant.

[The hygienic ergonomic protection of speech communication over time]. / Khigieno-ergonomichna zashtita na rechevata komunikatsiia s vremeto.

In the course of the experimental laboratory studies it was found out a significant impairment of the communication following a 2-hour processing of speech signals in conditions of masking noise. In order to diminish the auditory exhaustion in impeded communication the authors created physiologically grounded model of the working and resting regime in accordance to the experimental data, which require the including of two breaks in the first half of the working day, i.e. after a two hour exposition to masking noise. The minimal duration of the break at the end of the second hour (according to the experimental data) must be not less than 10 minutes in order to reach the initial or near to it speech communication. The time of the second break may coincide with the regulated lunch-time. The created working and resting regime was approbated in working conditions at DF "Kremikovtsi". It was found out that following the introduction of the physiological regime of work and rest, the auditory exhaustion decreased which was expressed in lowering of the rate of tone-intensity steps.

[The effect of different masking noises on psychophysiological tasks]. / Prouchvane vliianieto na razlichen maskirasht shum vurkhu niakoi psikhofiziologichni zadachi.

This paper describes experimental investigations aimed at clarifying the influence of wide-range (white), pulsed and interrupted noise with intensities Lequ 60 and 90 dB (A) on some psychophysiologic characteristics of problem solving. Physiologic indicators were recorded: pulse rate and variance, breathing rate and variance, vascular tone, ets. Psychologic problems to be solved modeled various features of operator activities, including: performing mathematical computations at a given rate; a test involving information processing; a compound option problem offered by Piotkovski's apparatus. Statistical data treatment (t-test of Student and Fisher, and monofactorial dispersion analysis) indicated the masking effect of noise to be more marked in dealing with psychophysiologic problems relating to operative memory. From the physiologic parameters tested, most informative proved to be the changes occurring in peripheral circulation, notably, the rise in vascular tone to peripheral vessels.

[The effect of different types of music on the perception of speech information]. / Vliianie na razlichni vidove muzika vurkhu vuzpriemaneto na govorna informatsiia.

Under experimental conditions, the masking effect of three types of music and of "white" masking noise was studied using a special speech-audiometric test (L. Tsaneva 1978, 1993). The signal-to-noise relation was found to be the most significant factor affecting spoken information perception, regardless of the type of music used as masking agent (level of correlation coefficients, jR = 0.89). The types of music used (modern, classical, playback) showed no appreciable differences in masking, remaining at the same time stronger masking factors compared to "white" noise. Conclusions were made as to hygienic-ergonomic aspects to be considered for intensity of musical programs in conforming with pertinent standards.

[Age-related transfer coefficients of the basic indices of cardiac variance]. / Vuzrastovi prevodni koefitsienti na osnovni pokazateli na surdechnata variativnost.

This study was concerned with the relationship of changes in cardiac variance to age. A total of 518 subjects were involved. The following indicators of ACV (analysis of cardiac variance) were investigated: mean--mean value of successive cardiac intervals, SD--standard deviation of mean value of cardiac intervals (R-R), AMo--amplitude of the mode, HI--homeostatic index, Pt--spectral power of R-R related to thermoregulation, Pr--spectral power of R-R related to respiration, IBO--index of centralization. For each one of these ACV indicators, a mathematical expression of its relationship to age was specified. The coefficients obtained from the indicated expressions of the relationship "age-to-ACV indicators" represent transfer coefficients for the particular measured quantities. Their methodological importance lies in the fact that through them it becomes possible to make age corrections of ACV indicator figures for the purpose of comparing individual subjects or groups of subjects. These coefficients help to establish nomograms for the particular age ranges.

[Changes in the status of the adaptation of workers at the television relay station on top of Botev Peak]. / Promeni v sustoianieto na adaptatsiia na raboteshti ot televizionnata retranslatsionna stantsiia na vrukh "Botev".

The state of adaptation of subjects (numbering 17) occupied at Botev Peak TV relay station and thereby exposed to nonionizing radiations--electromagnetic fields (EMF)--was monitored by following changes in analysis of cardiac variance (ACV) indicators. In addition to these, other physiologic indicators studied were systolic and diastolic blood pressure, as well as psychologic indicators, notably, psychosomatic complaints as early manifestations of disturbance in the state of adaptation. Data from the group of subjects studied were compared to those of a control group whose working conditions involved no EMF exposure. This comparison, based on ACV indicators (mean--mean value of successive cardiac intervals, SD--standard deviation of mean value of cardiac intervals (R-R), AMo--amplitude of the mode, SI, ABI, HI--homeostatic index, CP--classification parameter, IC), psychosomatic complaints, systolic and diastolic blood pressure, provided no evidence of reduction of adaptive reserves or deterioration of somatic and mental health state in occupationally exposed workers at Botev Peak TV relay station.

[The correlations between psychological indices and cardiac variance]. / Korelativni zavisimosti mezhdu niakoi psikhologichni pokazateli i surdechnata variativnost.

Correlative links between psychologic and psychologic indicators were studied in subjects occupied either in airline transportation or in the chemical industry. Investigations covered three groups of persons: managers of airline traffic (57 subjects); workers at "Vratsa" Chemical plant (14 subjects); and operators at "Vratsa" Chemical plant (14 subjects). The psychologic parameters measured included indicators of cardiac variance: mean--mean value of successive cardiac intervals, SD--standard deviation of mean value of cardiac intervals (R-R), AMo--amplitude of the mode, HI--homeostatic index, Pt--spectral power of R-R related to thermoregulation, Pp--spectral power of R-R related to respiration, IBO--index of centralization; psychologic parameters included: extrovertiveness, introvertiveness, neuroticism, psychoticism, interpersonality conflicts, self-control, social support, self-confidence, work satisfaction, psychosomatic complaints. There was evidence of significant and highly significant correlative links between indicators of cardiac variance and psychologic indicators. There thus appeared to exist certain relationships between the psychologic and psychologic levels during lengthy stressful occupational exposure.

Clinical meaning of GGT activity in follow-up of patients with alcohol-related liver injury and cholestasis.

The dynamics of GGT was investigated in three groups of patients after removing some primary causes of GGT increase. Group A included 34 patients with alcohol-related liver disease, group B included 16 patients with alcoholic liver injury and cholestasis, caused by concomitant alcoholic pancreatitis and group C included 17 patients with extrahepatic cholestasis, caused by choledocholithiasis. Follow-up assays of GGT were performed on the 7th, 14th and 30th days. Our results showed that the dynamics of GGT was more rapid after removing the cause for cholestasis than in stopping alcohol consumption in patients with chronic liver diseases. On the 14th day more than a 50% decrease in GGT activity was noted in 20% of the patients from groups A and B and in almost all cases from group C. On the 30th day, the reference range of GGT was not attained by any of the patients with liver disease nor in five patients from group C. No significant correlation was found between the severity of liver damage and the extent of GGT increase at the beginning and at the end of the follow-up period.

[Changes in the pulse variability of operators on a 12-hour work shift regimen]. / Promeni v pulsovata variativnost pri operatori na 12-chasov smenen rezhim na rabota.

Studies are carried out on 51 workers from the state works "D. Dimov"--Yambol on the changes of the pulse variability in the course of 12-hour day and night shift work and subjective evaluation of the psychosomatic complaints, in view of assessment the work load and strain. This investigation is performed because the workers have lodged a complaint against the introduction of 12-hour shift regime of work. It is done twice--during the day and during the night shift. No changes giving indication for considerable over pressure of the physiological systems and decrease of the working capacity have been established during the working process. The conclusion is that this type of working activity--12-hour shift schedule endangers neither the health status of the workers, nor the security and reliability of the system "man-machine-environment" therefore its introduction is not in contradiction to the physiologically well-grounded norms for the organization of the working process.

[The assessment of the general functional status and of the psychosomatic complaints of workers at hydroelectric power plants]. / Otsenka na obshtoto funktsionalno sustoianie i psikhosomatchnite oplakvaniia na robotnitsi ot VETs.

Evaluation of the general functional status and psychosomatic complaints of 61 workers from the hydroelectric power stations is made. The following methods are used: 1. Assessment of the general functional state, by means of computer analysis of the cardiac variability, analysing the changes in the values of the following indices: average value of the cardiac intervals (X), their standard deviation (SD), coefficient of variation (CV), amplitude of the mode (AMO), index of stress (IS), index of the vegetative balance (IVB), homeostatic index (HI). The last 3 indices serve for determination of the complex evaluation of chronic fatigue and work adaptation (ChFWA). 2. Evaluation of the psychosomatic complaints, by the use of a questionnaire for the subjective psychosomatic complaints. 3. Studying the systolic and diastolic blood pressure. The average values received in workers from HPS were compared with the average values of the population of the country and with the average values of a similar working activity of a group of operators from the thermal power station HPS. In conclusion it could be noted that concerning ChFWA the received values in workers from HPS are not more unfavourable generalized values from that measured in workers, occupied with similar type of work in other industrial branches of the country. However, they are with more unfavourable data in comparison with the workers from HPS. The subjective evaluation of the operators concerning their psychic and body health status is moderately worse, both in comparison with the values of the index for the country, and in comparison with those of the operators from HPS.

[An assessment of the information value of the indices from analyzing cardiac variability (ACV)in situations related to neuro-emotional stress]. / Otsenka na informativnostta na pokazatelite na analiza na surdechnata variativnost (ASV) pri situatsii, svurzani s nervno-emotsionalno naprezhenie.

A group of 67 students in medicine, sitting for an examination on obstetric and gynaecology, were subject to examinations in the periods: before and immediately after the examination. Taking into consideration the analysis of the heart variability (AHV), the pre-examination period shows more strongly expressed stress component, the main constituent of which is the sense of fear. Between the performance and the changes in the indices of the analysis of the heart variability, reflecting the total functional state, fatigue and distress, no specific differences were discovered. The sexual differences were expressed only in the way that the stress discomfort in women dies out more slowly than in men. A conclusion is made, that the pulse frequency and the indices of the analysis of the heart variability, related to the variability, including the combined index - CI, reflect more clearly the induced by the examination model emotional discomfort, than the indices, obtained from the frequency spectrum of the heart rhythm (Czechoslovakia).

[Changes in the frequency spectrum of the heart rhythm under static muscular effort]. / Promeni v chestotniia spektur na surdechniia ritum pri statichno muskulno usilie.

Certain results are gives which show that the frequency spectrum of the heart rhythm during the fulfillment of static muscle effort to refusal, distinguishes significantly the way in which this test is performed by experienced persons: at complete motivation (physiological refusal) and in incomplete motivation (psychological refusal). The second type of answer is unwanted in practical application of the test in industry, that's why a conclusion is made, that the frequency spectrum of the heart rhythm could serve as criterium of correctness for putting the test into practice.

[A method of determining glucose oxidase-immobilized glucose]. / Metod opredeleniia gliukozy, immobilizovannoi gliukozooksidazoi.

A method for manual measurement of glucose in biologic fluids has been developed, making use of glucose oxidase immobilized on a carbamide derivative of microcrystal cellulose; two variants are suggested: a rapid and a routine one. The method is characterized by a high analytical reliability, its results are in high correlation with the results of measurements by Beckman glucose analyzer (r = 0.92, p less than 0.001). The method is economic (glucose oxidase reagent may be used for more than 300 times), easily available, and is 3 to 6 times more rapid than the method with soluble glucose oxidase. It is particularly convenient for urgent laboratory diagnosis.