Effects of different classroom temperatures on cardiac autonomic control and cognitive performances in undergraduate students.

OBJECTIVE: Indoor microclimate may affect students' wellbeing, cardiac autonomic control and cognitive performance with potential impact on learning capabilities. To assess the effects of classroom temperature variations on the autonomic profile and students' cognitive capabilities. APPROACH: Twenty students attending Humanitas University School, (14M, age 21 ± 3 years) underwent a single-lead ECG continuous recording by a portable device during a 2 h lecture when classroom temperature was set 'neutral' (20 °C-22 °C, Day 1) and when classroom temperature was set to 24 °C-26 °C (Day 2). ECGs were sent by telemetry to a server for off-line analysis. Spectral analysis of RR variability provided indices of cardiac sympathetic (LFnu), vagal (HF, HFnu) and cardiac sympatho-vagal modulation (LF/HF). Symbolic analysis of RR variability provided the percentage of sequences of three heart periods with no significant change in RR interval (0V%) and with two significant variations (2V%) reflecting cardiac sympathetic and vagal modulation, respectively. Students' cognitive performance (memory, verbal comprehension and reasoning) was assessed at the end of each lecture using the Cambridge Brain Sciences cognitive evaluation tool. MAIN RESULTS: Classroom temperature and CO2 were assessed every 5 min. Classroom temperatures were 22.4 °C ± 0.1 °C (Day 1) and 26.2 °C ± 0.1 °C (Day 2). Student's thermal comfort was lower during Day 2 compared to Day 1. HR, LF/HF and 0V% were greater during Day 2 (79.5 ± 12.1 bpm, 6.9 ± 7.1 and 32.8% ± 10.3%) than during Day 1 (72.6 ± 10.8 bpm, 3.4 ± 3.7, 21.4% ± 9.2%). Conversely, 2V% was lower during Day 2 (23.1% ± 8.1%) than during Day 1 (32.3% ± 11.4%). Short-term memory, verbal ability and the overall cognitive C-score scores were lower during Day 2 (10.3 ± 0.3; 8.1 ± 1.2 and 10.9 ± 2.0) compared to Day 1 (11.7 ± 2.1; 10.7 ± 1.7 and 12.6 ± 1.8). SIGNIFICANCE: During Day 2, a shift of the cardiac autonomic control towards a sympathetic predominance was observed compared to Day 1, in the presence of greater thermal discomfort. Furthermore, during Day 2 reduced cognitive performances were found.

Short-term complexity indexes of heart period and systolic arterial pressure variabilities provide complementary information.

It is unclear whether the complexity of the variability of the systolic arterial pressure (SAP) provides complementary information to that of the heart period (HP). The complexity of HP and SAP variabilities was assessed from short beat-to-beat recordings (i.e., 256 cardiac beats). The evaluation was made during a pharmacological protocol that induced vagal blockade with atropine or a sympathetic blockade (beta-adrenergic blockade with propranolol or central sympathetic blockade with clonidine) alone or in combination, during a graded head-up tilt, and in patients with Parkinson's disease (PD) without orthostatic hypotension undergoing orthostatic challenge. Complexity was quantified according to the mean square prediction error (MSPE) derived from univariate autoregressive (AR) and multivariate AR (MAR) models. We found that: 1) MSPE(MAR) did not provide additional information to that of MSPE(AR); 2) SAP variability was less complex than that of HP; 3) because HP complexity was reduced by either vagal blockade or vagal withdrawal induced by head-up tilt and was unaffected by beta-adrenergic blockade, HP was under vagal control; 4) because SAP complexity was increased by central sympathetic blockade and was unmodified by either vagal blockade or vagal withdrawal induced by head-up tilt, SAP was under sympathetic control; 5) SAP complexity was increased in patients with PD; and 6) during orthostatic challenge, the complexity of both HP and SAP variabilities in patients with PD remained high, thus indicating both vagal and sympathetic impairments. Complexity indexes derived from short HP and SAP beat-to-beat series provide complementary information and are helpful in detecting early autonomic dysfunction in patients with PD well before circulatory symptoms become noticeable.

[Syncope and work: role of the occupational physician and global risk stratification]. / Sincope e rischio lavorativo: ruolo del medico del lavoro e stratificazione globale del rischio.

Safety risk for subjects suffering from syncope while working has not been as yet addressed by occupational medicine. The present study was aimed at evaluating a new developed methodology for job tasks risk stratification in patients with syncope. During a work-shop on syncope and occupational risk, 149 occupational physicians (OP) with about 10 years of clinical experience were asked to fulfil a Visual Analogue Scale (VAS) concerning the doctor's estimated potential damage (D) to the worker and the probability of a damage to occur (P) should syncope take place during the job task. Five job tasks characterized by different risk for safety (1, driving; 2, toxic products handling; 3, job performed closed to hot surfaces o free flames; 4, surgical activity; 5, office job) were identified. OP correctly stratified the risk associated to the different job tasks in patients with syncope. Unexpectedly, task #3 was given a risk similar to that obtained in drivers. This might be of paramount clinical and social importance when patients with syncope have to return to their job tasks.

[Syncope and occupational risk survey: the role of continuing education and multidisciplinary approach]. / Indagine conoscitiva sulla percezione del problema sincope in relazione al rischio lavorativo nella pratica clinica: ruolo della formazione e dell'approccio multidisciplinare.

Syncope is a common disorder characterized most of the times by a positive clinical outcome. However, it may turn to a life threatening event even for working colleagues and third party when occurring during an high risk job. We have recently found that, out of 670 patients admitted to the Emergency Department (ED) for syncope, about 50% were potential workers, being their age between 18 and 65 years. Also, we found that in this group of patients syncope recurrence was as high as 11% at 6 months. It is unknown how physicians address the problem of the occupational risk in patients suffering from syncope and how occupational aspects are taken into account in the clinical judgment before work readmission. One hundred eighty five doctors (149 occupational physicians, OP), participating in a work-shop on syncope, were asked to fulfill a questionnaire about their clinical experience and their attention to the occupational aspects in patients after syncope. Despite long lasting clinical experience, 41% of OP did not scrutinize syncope as a relevant symptom in their daily activity. 65% of the other specialists were used to address the occupational risk aspects in their syncope patients. A multidisciplinary approach involving continuing education on safety at work might reduce work accidents due to syncope relapse and promote a safe and suitable re-employment of patients with syncope. scrutinize syncope as a relevant symptom in their daily activity. 65% of the other specialists were used to address the occupational risk aspects in their syncope patients. A multidisciplinary approach involving continuing education on safety at work might reduce work accidents due to syncope relapse and promote a safe and suitable re-employment of patients with syncope.

[Syncope and work. STePS study (Short Term Prognosis of Syncope)]. / La sincope in età lavorativa. Studio multicentrico prospettico STePS.

BACKGROUND: Recurrent syncope is a common medical problem responsible for 3-5% of emergency department (ED) accesses and 1-6% of hospital admissions. If syncope occurs in a subject working in a critical safety task, the consequences of this event might be very dangerous for the worker, colleagues, others or for the environment. Therefore, syncope management is a major problem for occupational medicine, converning the general safety at work. AIMS: To evaluate the syncope events in a group of potential workers aged 18 to 65 years; to evaluate the symptoms preceding syncope and the presence of associated illnesses and recurrent events. POPULATION AND RESULTS: This study is part of the prospective study STePS (Short Term Prognosis of Syncope), and included 305 consecutive patients (aged 18-65 years, female 56%) who had syncope as a main symptom and presented at ED of four general hospitals in the Milan area, Italy, between the 23rd of January and 30th of June 2004. The 24% of subjects were hospitalized. In 21% the syncope occurs suddenly without any preceding symptom. The 67% of subjects didn't have any important illness at the time. 50% of subjects had recurrent syncope. In four subjects another syncope occurred in a 10 day follow-up. CONCLUSIONS: occupational medicine should consider syncope scrupulously. Proper diagnostic management is important to permit a correct evaluation of work safety issues.

[Urinary hexafluoroisopropanol in the assessment of occupational exposure to sevoflurane: methodologic features and critical points]. / L'esafluoroisopropanolo urinario nella valutazione dell'esposizione professionale a sevofluorano: aspetti metodologici e punti critici.

The increasing use of sevoflurane as anaesthetic leads to the need for finding a biological index to evaluate the occupational exposure in surgical activity. Several studies indicate that Hexafluoroisopropanol (HFIP) is a specific sevoflurane metabolite quickly glucuronidated and excreted as HFIP-glucuronide in the urine (HFIPu). Therefore the HFIP removal kinetics in occupational exposure and the correlation between sevoflurane exposure and HFIPu are poorly understood. We studied no. 86 operating room workers of Novara Hospital to evaluate the correlation between the sevoflurane individual exposure (SE) and the HFIPu at the end of the shift expressed in microgram/L (A-HFIPu) and in microgram/g creat. (C-HFIPu). Therefore, in the same group of subjects we evaluated the HFIPu in the urine sampled at 8.00 a.m. before the work. The correlation coefficient was R2 = 0.782 (p < 0.0001) for SE/A-HFIPu and R2 = 0.862 (p < 0.0001) for SE/C-HFIPu; HFIPu normalized for urinary creatinine (C-HFIPu) is an index more suitable than the A-HFIPu. Furthermore we concluded for the usefulness of pre-shift HFIPu.

Modifications of cardiac autonomic profile associated with a shift schedule of work.

BACKGROUND: Shift work is associated with an increased rate of cardiovascular diseases and accidents. Discordance between circadian rhythms of stress-related biological variables and the work-sleep schedule might explain the reduced efficiency of work. It is not clear whether a shift schedule of work may induce similar discordance in the 24-hour oscillatory pattern of the cardiac autonomic control in respect to the work-sleep periods. METHODS AND RESULTS: Twenty-two healthy male blue-collar shift workers underwent 24-hour ECG recordings during each of the 3 different shifts (first, 6 AM to 2 PM; second, 2 to 10 PM; third, 10 PM to 6 AM). Spectral analysis of heart rate variability over 24 hours provided the normalized markers of cardiac sympathetic (LF(nu)) and vagal (HF(nu)) modulation of the sinoatrial node activity and of the sympathovagal balance (LF/HF). LF(nu) and LF/HF exhibited 24-hour oscillations with different times of maximum and minimum in accordance with the working and sleeping periods, respectively. Lower values of LF(nu) and LF/HF suggestive of a reduced cardiac sympathetic modulation were present when the job task was performed at night compared with the values observed when the work was performed during morning and evening. CONCLUSIONS: Continuous weekly changes of time of maximum and minimum in the cardiac sympathetic and vagal autonomic control may play a role in the excessive rate of cardiovascular diseases in shift workers. The reduced values of the indexes of cardiac sympathetic modulation during night work might be related to the presence of sleepiness or diminished alertness, which in turn could facilitate errors and accidents.

Cardiac autonomic patterns preceding occasional vasovagal reactions in healthy humans.

BACKGROUND: The wide range of clinical presentation of orthostatic vasovagal syncope suggests different underlying changes in the cardiac autonomic modulation. METHODS AND RESULTS: To evaluate the beat-by-beat modifications in the neural control of heart period preceding a syncopal event, we studied RR interval variability in 22 healthy subjects who experienced fainting for the first time during a 90 degrees head-up tilt and in 22 control subjects by means of time-variant power spectral analysis. Sympathetic and vagal modulations to the sinoatrial node were assessed by the normalized power of the low-frequency (LF, approximately 0.1-Hz) and high-frequency (HF, approximately 0.25-Hz) oscillatory components of RR variability. When the patients were supine, no differences were observed in the hemodynamic and spectral parameters of the 2 groups. During the tilt procedure, RR, LFNU, and HFNU (NU=normalized units) values were relatively stable in control subjects. During early tilt (T1), subjects with syncope had reduced RR intervals compared with control subjects. In 13 subjects with syncope, RR decreased while LFNU and LF/HF increased in the last minute of tilt before syncope (T2). Conversely, in the remaining 9 fainters, LFNU and LF/HF decreased from T1 to T2 and HFNU increased slightly. CONCLUSIONS: Two different patterns may be recognized in the cardiac autonomic changes preceding an occasional vasovagal event, namely, one characterized by a progressive increase of the marker of cardiac sympathetic modulation up to the onset of syncope, the other by a sympathetic inhibition with an impending vagal predominance. The recognition of different pathophysiological mechanisms in fainters may have important therapeutic implications.

Cobalt myocardiopathy. A critical review of literature.

Cobalt is regarded as being responsible for a form of myocardiopathy whose pathogenesis and clinical description must still find a specific place in the range of congestive myocardiopathies. In spite of this, epidemiological studies are not sufficient to prove the role of cobalt in inducing myocardiopathy in hard metal workers. This critical review intends to evaluate if hard metal exposure may induce toxic effects on the heart. In this context, the literature considered ranges from pioneer reports on 'beer drinkers' to the more recent papers concerning cases of patients occupationally exposed; subjects who, after a surgical operation died of fulminant heart failure and, lastly, hard metal workers who were examined for their cardiac function. Various pathogenetic mechanisms related to possible cardiac effects in hard metal workers have been analyzed. The most likely should be the inhibition of cellular respiration due to inhibition of the mitochondrial dehydrogenase.

Uncommon evolution of fibrosing alveolitis in a hard metal grinder exposed to cobalt dusts.

This study reports a case of fibrosing alveolitis with uncommon evolution in a 27-year-old male non-smoker, working as a hard metal grinder for 10 years. Personal and occupational history, routine clinical and laboratory check-up, chest X-rays, lung function tests, fiberoptic bronchoscopy with bronchoalveolar lavage and open lung biopsy returned a diagnosis of hard metal lung fibrosis. The patient felt greatly improved after removal from the workplace, without any therapy. At present, he is complaining of only mild exertional dyspnea and shows an attenuation of his ventilatory defect. The radiological picture has clearly improved and the cellular pattern of bronchoalveolar lavage was normal.

Effects of different compounds of metals and of their mixtures on the growth and survival of Thiobacillus ferrooxidans.

The iron oxidation by Thiobacillus ferrooxidans was studied in the presence of different concentrations of metals as sulphates, chlorides, nitrates, and in some other compounds. The bacteriological oxidation of ferro-ions develops in all solutions in nearly the same way, with the only difference that, as the ion concentration increases, the beginning of measurable oxidation is postponed, i.e., with ion concentration increasing, the lag-phase expands. When salts are mixed in different proportions, the toxic concentration of such a mixture corresponds, in a defined way, to the total of salts, i.e., of their ions.

Bacterial leaching of waste uranium materials.

The effect of ferrobacteria and thiobacteria on the leaching of waste uranium materials from which 70-80% of uranium was previously leached by classical chemical hydrometallurgical procedure has been investigated. The bacteria used are found in the ore and the mine water of Zletovska River locality, Yugoslavia. Parameters of biological leaching were examined in the laboratory. Leaching conditions were changed with the aim of increasing the amount of uranium leached. The effect of pyrite added to the waste materials before the beginning of leaching has also been examined. Uranium leaching is directly proportional to the composition and number of ferrobacteria and thiobacteria, and increased by almost twice the value obtained from the same starting materials without using bacteria. Increased sulphuric acid concentrations stimulate considerably the rate of leaching. Uranium leaching is increased up to 20% while sulphuric acid consumption is simultaneously decreased by the addition of pyrite. Uranium concentrations in starting waste materials used for leaching were extremely low (0.0278 and 0.372% U) but about 60% recovery of uranium was obtained, with relatively low consumption of sulphuric acid.

Effect of mineral acids on iron bacteria.

The oxidative ability of Thiobacillus ferroxidans in the presence of different concentrations of H2SO4, HC1, HNO3, and their mixtures was investigated. Bacteriological oxidation of FeSO4 is expressed as a function of time and acid concentration. For each acid and for their mixtures lethal concentrations for T. ferroxidans were found experimentally. On the basis of the lethal concentration for each acid separately the lethal concentrations of their mixtures were computed and it was found that they are in good agreement with the experimental data.