Swept-sines provide a tool for fast and high-resolution measurement of evoked otoacoustic emissions. During the measurement, a response to swept-sine(s) is recorded by a probe placed in the ear canal. Otoacoustic emissions can then be extracted by various techniques, e.g., Fourier analysis, the heterodyne method, and the least-square-fitting (LSF) technique. This paper employs a technique originally proposed with exponential swept-sines, which allows for direct emission extraction from the measured intermodulation impulse response. It is shown here that the technique can be used to extract distortion-product otoacoustic emissions (DPOAEs) evoked with two simultaneous swept-sines. For proper extraction of the DPOAE phase, the technique employs previously proposed adjusted formulas for exponential swept-sines generating so-called synchronized swept-sines (SSSs). Here, the SSS technique is verified using responses derived from a numerical solution of a cochlear model and responses measured in human subjects. Although computationally much less demanding, the technique yields comparable results to those obtained by the LSF technique, which has been shown in the literature to be the most noise-robust among the emission extraction methods.

• MeSH
• Fourierova analýza MeSH
• kochlea * fyziologie   MeSH
• lidé MeSH
• otoakustické emise spontánní * fyziologie   MeSH
• zvukovod fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Microfabricated electroacoustic transducers with perforated moving plates used as microphones or acoustic sources have appeared in the literature in recent years. However, optimization of the parameters of such transducers for use in the audio frequency range requires high-precision theoretical modeling. The main objective of the paper is to provide such an analytical model of a miniature transducer with a moving electrode in the form of a perforated plate (rigid elastically supported or elastic clamped at all boundaries) loaded by an air gap surrounded by a small cavity. The formulation for the acoustic pressure field inside the air gap enables expression of the coupling of this field to the displacement field of the moving plate and to the incident acoustic pressure through the holes in the plate. The damping effects of the thermal and viscous boundary layers originating inside the air gap, the cavity, and the holes in the moving plate are also taken into account. The analytical results, namely, the acoustic pressure sensitivity of the transducer used as a microphone, are presented and compared to the numerical (FEM) results.

• Publikační typ
• časopisecké články MeSH

Rapid development of computer technologies leads to the intensive automation of many different processes traditionally performed by human experts. One of the spheres characterized by the introduction of new high intelligence technologies substituting analysis performed by humans is sleep scoring. This refers to the classification task and can be solved - next to other classification methods - by use of artificial neural networks (ANN). ANNs are parallel adaptive systems suitable for solving of non-linear problems. Using ANN for automatic sleep scoring is especially promising because of new ANN learning algorithms allowing faster classification without decreasing the performance. Both appropriate preparation of training data as well as selection of the ANN model make it possible to perform effective and correct recognizing of relevant sleep stages. Such an approach is highly topical, taking into consideration the fact that there is no automatic scorer utilizing ANN technology available at present.

• MeSH
• elektroencefalografie metody   MeSH
• lidé MeSH
• neuronové sítě (počítačové) MeSH
• polysomnografie metody   MeSH
• spánek fyziologie   MeSH
• stadia spánku fyziologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

The aim of this study was a comparison of risk stratification for death in patients after myocardial infarction (MI) and of risk stratification for malignant arrhythmias in patients with implantable cardioverter-defibrillator (ICD). The individual risk factors and more complex approaches were used, which take into account that a borderline between a risky and non-risky value of each predictor is not clear-cut (fuzzification of a critical value) and that individual risk factors have different weight (area under receiver operating curve – AUC or Sommers´ D – Dxy). The risk factors were baroreflex sensitivity, ejection fraction and the number of ventricular premature complexes/hour on Holter monitoring. Those factors were evaluated separately and they were involved into logit model and fuzzy models (Fuzzy, Fuzzy- AUC, and Fuzzy-Dxy). Two groups of patients were examined: a) 308 patients 7-21 days after MI (23 patients died within period of 24 month); b) 53 patients with left ventricular dysfunction examined before implantation of ICD (7 patients with malignant arrhythmia and electric discharge within 11 month after implantation). Our results obtained in MI patients demonstrated that the application of logit and fuzzy models was superior over the risk stratification based on algorithm where the decision making is dependent on one parameter. In patients with implanted defibrillator only logit method yielded statistically significant result, but its reliability was doubtful because all other tests were statistically insignificant. We recommend evaluating the data not only by tests based on logit model but also by tests based on fuzzy models.

• MeSH
• algoritmy MeSH
• baroreflex MeSH
• časové faktory MeSH
• defibrilátory implantabilní MeSH
• elektrická defibrilace přístrojové vybavení   MeSH
• elektrokardiografie ambulantní MeSH
• financování organizované MeSH
• fuzzy logika MeSH
• hodnocení rizik MeSH
• infarkt myokardu mortalita   patofyziologie   MeSH
• komorové extrasystoly patofyziologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• logistické modely MeSH
• prognóza MeSH
• reprodukovatelnost výsledků MeSH
• rizikové faktory MeSH
• ROC křivka MeSH
• senioři MeSH
• srdeční arytmie patofyziologie   prevence a kontrola   MeSH
• tepový objem MeSH
• ukazatele zdravotního stavu MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• senioři MeSH
• Publikační typ
• srovnávací studie MeSH

In our previous studies, a decreased blood pressure was reported in children treated by anthracycline (AC). The aim of this study was to assess the long-term effects of AC anticancer therapy in 45 subjects aged 13-22 years by repeated 24-hour Holter monitoring of blood pressure. Sixty four aged-matched subjects served as controls. The differences between mean values of systolic (SBP) and diastolic blood pressure (DBP) in each hour of both groups were evaluated by Mann-Whitney test. Also the parameters of the least-squares fit of the sinusoidal curve in each subject were estimated (M – mesor, midline-estimating, a mean value of sinusoidal curve corresponds to 24-hours mean pressure; A – amplitude, double amplitude corresponds to nightday difference; Acr – acrophase is a time of maximal value of a sinusoidal curve). SBP and DBP was significantly lower only during night hours in anthracycline patients 19-22 years old. Also M was lower in this age subgroup of patients comparing to age matched controls (SBP: 112±6 mm Hg versus 117±7 mm Hg, p<0.05; DBP: 67±3 mm Hg versus 69±6 mm Hg, p<0.05), A was not different, Acr in patients was shifted one hour earlier (SBP: 2.4 p.m. versus 3.6 p.m., p<0.05; DBP: 2.1 p.m. versus 3.3 p.m., p<0.01). This corresponds to the shift of the morning blood-pressure increase seen on 24-hours blood pressure profiles. M correlated with age in controls (SBP: r=0.374, p<0.01; regression coefficient b=1.34 mm Hg/1 year; DBP: r=0.365, p<0.01; b=0.95 mm Hg/1 year), but not in patients (SBP: r=0.182, DBP: r=0.064). A and Acr were age-independent in all subjects. It is concluded that blood pressure in 19-22 years old AC patients is lower during night hours, the age-dependent increase of blood pressure seen in healthy controls between 13 and 22 years of age does not occur in patients. This finding is consistent with the long-lasting impairment of the sympathetic nervous system caused by anthracyclines.

• MeSH
• antibiotika antitumorózní škodlivé účinky   MeSH
• antracykliny škodlivé účinky   MeSH
• cirkadiánní rytmus MeSH
• elektrokardiografie ambulantní MeSH
• financování organizované MeSH
• krevní tlak účinky léků   MeSH
• lidé MeSH
• metoda nejmenších čtverců MeSH
• mladiství MeSH
• mladý dospělý MeSH
• přežívající MeSH
• studie případů a kontrol MeSH
• sympatický nervový systém účinky léků   MeSH
• věkové faktory MeSH
• výsledek terapie MeSH
• Check Tag
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH

Non-invasive methods of determination of baroreflex sensitivity (BRS, ms/mmHg) are based on beat-to-beat systolic blood pressure and inter-beat interval recording. Sequential methods and spectral methods at spontaneous breathing include transient superposition of breathing and 0.1 Hz rhythms. Previously, a cross-spectral method of analysis was used, at constant breathing rate using a metronome set at 0.33 Hz, enabling separate determination of BRS at 0.1 Hz (BRS0.1Hz) and respiratory rhythms (BRS0.33Hz). The aim of the present study was to evaluate the role of breathing in the spectral method of BRS determination with respect to age and hypertension. Such information would be important in evaluation of BRS at pathological conditions associated with extremely low BRS levels. Blood pressure was recorded by Finapres (5 minutes, controlled breathing at 0.33 Hz) in 118 healthy young subjects (YS: mean age 21.0±1.3 years), 26 hypertensive patients (HT: mean age 48.6±10.3 years) with 26 age-matched controls (CHT: mean age 46.3±8.6 years). A comparison of BRS0.1Hz and BRS0.33Hz was made. Statistically significant correlations were found between BRS0.1Hz and BRS0.33Hz in all groups: YS: r=0.52, p<0.01, HT: r=0.47, p<0.05, and CHT: r=0.70, p<0.01. The regression equations indicated the existence of a breathing-dependent component unrelated to BRS (YS: BRS0.33Hz=2.63+1.14*BRS0.1Hz; HT: BRS0.33Hz=3.19+0.91*BRS0.1Hz; and CHT: BRS0.33Hz=1.88+ +1.01*BRS0.1Hz; differences between the slopes and the slope of identity line were insignificant). The ratios of BRS0.1Hz to BRS0.33Hz were significantly lower than 1 (p<0.01) in all groups (YS: 0.876±0.419, HT: 0.628±0.278, and CHT: 0.782±0.260). Thus, BRS evaluated at the breathing rate overestimates the real baroreflex sensitivity. This is more pronounced at low values of BRS, which is more important in patients with pathologic low BRS. For diagnostic purposes we recommend the evaluation of BRS at the frequency of 0.1 Hz using metronome-controlled breathing at a frequency that is substantially higher than 0.1 Hz and is not a multiple of 0.1 Hz to eliminate respiratory baroreflexnon- related influence and resonance effect on heart rate fluctuations.

• MeSH
• baroreflex MeSH
• časové faktory MeSH
• dospělí MeSH
• financování organizované MeSH
• hypertenze patofyziologie   MeSH
• krevní tlak MeSH
• lidé středního věku MeSH
• lidé MeSH
• mechanika dýchání MeSH
• měření krevního tlaku metody   MeSH
• mladý dospělý MeSH
• modely kardiovaskulární MeSH
• prediktivní hodnota testů MeSH
• srdeční frekvence MeSH
• věkové faktory MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• mladý dospělý MeSH
• Publikační typ
• srovnávací studie MeSH

We studied the relationship between blood pressure (BP), body mass index (BMI, kg/m(2)) and baroreflex sensitivity (BRS, ms/mmHg) in adolescents. We examined 34 subjects aged 16.2+/-2.4 years who had repeatedly high causal BP (H) and 52 controls (C) aged 16.4+/-2.2 years. Forty-four C and 22 H were of normal weight (BMI between 19-23.9), and 8 C and 12 H were overweight (BMI between 24-30). Systolic BP was recorded beat-to-beat for 5 min (Finapres, controlled breathing 0.33 Hz). BRS was determined by the cross-spectral method. The predicting power of BMI and BRS for hypertension was evaluated by sensitivity, specificity, and receiver operating curve (ROC - plot of sensitivity versus specificity). H compared with C had lower BRS (p<0.01) and higher BMI (p<0.05). Multiple logistic regression analysis (p<0.001) revealed that a decreased BRS (p<0.05) and an increased BMI (p<0.01) were independently associated with an increased risk of hypertension. No correlation between BMI and BRS was found either in H or in C. Following optimal critical values by ROC, the sensitivity, specificity and area under ROC were determined for: BMI - 22.2 kg/m(2), 61.8 %, 69.2 %, 66.0 %; BRS - 7.1 ms/mmHg, 67.7 %, 69.2 %, 70.0 %; BMI and BRS - 0.439 a.u., 73.5 %, 82.7 %, and 77.3 %. Decreased BRS and overweight were found to be independent risk factors for hypertension.

• MeSH
• baroreflex MeSH
• dítě MeSH
• dospělí MeSH
• financování organizované MeSH
• hodnocení rizik MeSH
• hypertenze etiologie   patofyziologie   MeSH
• index tělesné hmotnosti MeSH
• krevní tlak MeSH
• lidé MeSH
• logistické modely MeSH
• mladiství MeSH
• nadváha komplikace   patofyziologie   MeSH
• prediktivní hodnota testů MeSH
• rizikové faktory MeSH
• ROC křivka MeSH
• senzitivita a specificita MeSH
• studie případů a kontrol MeSH
• systola MeSH
• věkové faktory MeSH
• Check Tag
• dítě MeSH
• dospělí MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH

Výuku formou E-learningu pro bakalářský obor Zdravotnická technika na 1.LF UK jsme začali připravovat pro 1. ročník v předmětech z biofyziky a informatiky. V 1. ročníku se potýkáme s velmi rozdílnou úrovní znalostí přijatých studentů, a proto jsme se zaměřili v informatice na přípravu úvodního kursu a v biofyzice na sestavení katalogu metod a přístrojů.

The article describes development of e-learning supports for the study programme „Medical Engineering“ offered by Charles University 1st Faculty of Medicine (Prague). E-learning methodology has been introduced into the 1st year courses in Biophysics and Informatics where we are facing problems with different student skill levels. Therefore, we created the introductory course in Informatics, and a catalog of basic methods and devices in Biophysics. The course comprises the key terminology in the field of informatics, units, coding, basic classification of the computers, basic hardware and the peripheral devices, basic software and operation systems. The catalog contains the methods and devices used in medical biophysics sorted alphabetically. Each reference contains basic description of the method or device. The methods students will encounter in practice are described more precisely. Some of them are accompanied with videorecordings that helps students prepare for practicals.

• MeSH
• biofyzika výchova   MeSH
• lékařská informatika výchova   MeSH
• počítačem řízená výuka * metody   využití   MeSH
• pomocný zdravotnický personál * výchova   MeSH
• programovaná výuka jako téma využití   MeSH
• studium vysokoškolské metody   trendy   MeSH
• využití lékařské informatiky MeSH
• Geografické názvy
• Česká republika MeSH

• MeSH
• baroreflex fyziologie   MeSH
• elektrofyziologické techniky kardiologické metody   využití   MeSH
• extrasystoly diagnóza   etiologie   patofyziologie   MeSH
• financování organizované MeSH
• funkce levé komory srdeční fyziologie   MeSH
• fuzzy logika MeSH
• infarkt myokardu diagnóza   mortalita   MeSH
• lidé MeSH
• náhlá srdeční smrt etiologie   patologie   prevence a kontrola   MeSH
• rizikové faktory MeSH
• srdeční frekvence fyziologie   MeSH
• statistika jako téma metody   MeSH
• Check Tag
• lidé MeSH