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Photoplethysmography signal (PPG) provides information about the cardiovascular, respiratory, or nervous system activity. Recent studies proposed methods of apnea identification from PPG using amplitude or baseline modulation, or area under the curve. We hypothesized that analysis of the dicrotic notch could improve the sensitivity and specificity of apnea detection. We applied four methods to detect apnea from PPG records experimentally obtained from 10 volunteers, where each volunteer simulated three apneic pauses. We adopted the Area under the PPG and Pulse wave amplitude parameters, and we proposed the Dicrotic notch area parameter. For the methods, we determined the delay in apnea detection and the sensitivity and specificity of apnea detection. The average delay in detecting an apneic pause from the PPG using the Dicrotic notch area was 6.1 s. Combining the parameters of the Area under the PPG with the Dicrotic notch area increased the specificity of apnea detection from 73.8% to 80.0%, although sensitivity decreased from 91.1% to 85.6%. The newly proposed parameter Dicrotic notch area showed its potential for automatic apnea detection.

The modern trend is to include the novel equipment into the education. The ASL 5000 is a precise simulator of lung mechanics with possible settings of a large amount of intrapulmonary parameters. The ECS simulator can simulate gas diffusion from the lungs to the blood and vice versa, and computes blood pH, partial pressures of blood gases, oxygen saturation etc. This study describes a connection between these two simulators with regard to the optimal use of the properties of both simulators. This connection enables monitoring of lung mechanics and gas diffusion at the same time. The aim of the study is to describe the connection of the systems for the education of the practically oriented students.

A pulse oximeter model linking arterial (SaO2) and peripheral (SpO2) oxygen saturation is the terminal part of a mathematical model of neonatal oxygen transport. Previous studies have confirmed the overestimation of oxygen saturation measured by pulse oximetry in neonates compared to arterial oxygen saturation and the large variability of measured values over time caused by measurement inaccuracies. This work aimed to determine the SpO2 measurement noise that affects the biased SpO2 value at each time point and integrate the noise description with the systematic bias between SaO2 and SpO2. The SaO2–SpO2 bias was based on previously published clinical data from pathological patients younger than 60 days requiring ventilatory support. The statistical properties of the random SpO2 measurement noise were estimated from the SpO2 continuous recordings of 21 pathological and 21 physiological neonates. The result of the work is a comprehensive characterization of the properties of a pulse oximeter model describing the transfer of the input SaO2 value to the output SpO2 value, including the bias and noise typical for the bedside monitoring of neonates. These results will help to improve a computer model of neonatal oxygen transport.

Computer models of neonatal oxygenation could serve as a tool for a comprehensive comparison of closed-loop automated oxygen control systems. The behaviour of such models depends, besides the input data of the inspired fraction of oxygen and the premature infant's breath pattern, on internal parameters of the model. The aim of this study was to perform a sensitivity analysis of a computer model of neonatal oxygen transport to clarify the influence of its internal physiological parameters on the output signal of peripheral oxygen saturation (SpO2). We performed a multi-parameter sensitivity analysis using Monte Carlo simulations for randomly generated values of eight internal parameters. The influence on the model output SpO2 signal was evaluated using five characteristics of the output signal. The relations between the parameters and the output characteristics were displayed using scatter plots and analysed by linear correlation, standardized regression, and partial correlation. The main result of the study is that in our model the oxygen consumption in the tissue and the cardiac output have the greatest influence on the SpO2 drop and minimal SpO2 value during simulated desaturation. The rate of development of desaturation and its duration are most affected by the diffusion resistance of the alveolar-capillary membrane. The results of the sensitivity analysis will help to optimize the performance of the computer model of neonatal oxygen transport.

The pressure reactivity index (PRx) is a parameter for the assessment of cerebrovascular autoregulation, but its calculation is affected by artifacts in the source biosignals—intracranial pressure (ICP) and arterial blood pressure. We sought to describe the most common short-duration artifacts and their effect on the PRx. A retrospective analysis of 935 h of multimodal monitoring data was conducted, and five types of artifacts, characterized by their shape, duration, and amplitude, were identified: rectangular, fast impulse, isoline drift, saw tooth, and constant ICP value. Subsequently, all types of artifacts were mathematically modeled and inserted into undisturbed segments of biosignals. Fast impulse, the most common artifact, did not alter the PRx index significantly when inserted into one or both signals. Artifacts present in one signal exceeded the threshold PRx in less than 5% of samples, except for isoline drift. Compared to that, the shortest rectangular artifact inserted into both signals changed PRx to a value above the set threshold in 55.4% of cases. Our analysis shows that the effect of individual artifacts on the PRx index is variable, depending on their occurrence in one or both signals, duration, and shape. This different effect suggests that potentially not all artifacts need to be removed.

Maintaining a prescribed peripheral oxygen saturation (SpO2) target during routine care of neonates is challenging and inspired fraction of oxygen (FiO2) titration practices differ among caregivers and centers. Algorithms for automatic feedback control of SpO2 are being developed and tested, that would adapt to the changing neonatal organism and better maintain the required SpO2 target range. While clinical data is necessary to validate differences in the titration strategies, a continuous physiological model of oxygenation in neonates would facilitate baseline testing of different approaches, manual or automated. The objective of our study was to enhance a mathematical model of oxygenation of the neonate and to compare the performance of the model with available clinical data. We have implemented the diffusion resistance into the model as well as a variable oxyhemoglobin dissociation relationship and the bias between arterial and peripheral oxygen saturation. Values of model parameters were scaled to fit preterm infant scenarios. The comparison of the clinical data and computer simulations suggest that the model can reliably simulate episodes of oxygen desaturation and describe the relation between ventilation, FiO2and SpO2. It appears that the model may be an effective tool to test manual and automatic FiO2titration strategies.

The advantages of automatic control of the fraction of inspired oxygen in neonates have been documented in recently published clinical trials. Many control algorithms are available, but their comparison is missing in the literature. A mathematical model of neonatal oxygen transport could be a useful tool to compare and enhance both automatic control algorithms and manual control of fraction of inspired oxygen. Besides other components, the model of neonatal oxygen transport must include a module linking arterial (SaO2) and peripheral (SpO2) oxygen saturation. The pulse oximeter module must reflect issues of SpO2 measurement typical for clinical practice, such as overestimation of SpO2 over SaO2 documented by several studies, or inaccurate pulse oximeter readings due to high noise. The aim of this study was to describe both the bias between SaO2 and SpO2 and the noise, characteristic for continuous SpO2 recording, for a computer model of oxygenation of a premature infant. The SpO2-SaO2 bias, derived from available clinical data, describes a typical deviation of the SpO2 measurement as a function of the true SaO2 value in three different SaO2 intervals. The SpO2 measurement noise was considered as a random process that affects biased SpO2values at each time point with statistical properties estimated from SpO2 continuous recordings of 5 stable newborns. The results of the study will help to adjust a computer model of neonatal oxygenation to the real situations observed in the clinical practice.

The synchronized data collection from vital sign monitors has been an ongoing issue. The widely used program S5Collect is a valuable tool especially for research purposes, moreover, in order to customize this program, an added plug-in with trial-specific modification can facilitate the data collection. The main aim of this study was to create a user-friendly plug-in for data capturing in operating rooms during anaesthetic care. The plug-in described was designed in co-operation with anesthesiologists in the LabVIEW software and verified on a fullbody simulator. Results showed that data captured via plug-in correlated well with the data from the simulator. This plug-in is planned to be used for data collection during robotic prostatectomy to analyze hemodynamic and ventilatory changes over the course of this operation, however, it can be easily adjusted for different clinical trials.

We have analyzed dynamic lung impedance recorded by electric impedance tomography in the high-frequency oscillatory ventilation of the laboratory pig. The aim of the study was find out if electrical impedance tomography can be used for an assessing of the tidal volume in high-frequency oscillatory ventilation. The analyzed amplitude of dynamic lung impedance was compared with the tidal volume computed from flow that was measured at the orifice placed before endotracheal tube. We have found out that amplitude of dynamic lung impedance does not correspond with tidal volume within conducted experiment.

There are currently a number of methods by which risks can be assessed, both in the health sector and in other sectors. The aim of this study is to apply a risk analysis to identify possible failures that may occur with individual parts of the lung ventilator used to provide home mechanical ventilation. The FMEA was used for risk assessment, where a team of service technicians was set up to calculate the risk priority number. Furthermore, Pareto analysis was used to determine the most frequent failure components. A total of 22 potential failures were identified. The most common causes of identified failures are clogging of components, exposure to inadequate thermal conditions, and mechanical damage caused by a human factor. Individual corrective actions have been proposed according to the identified causes and assigned evaluation. Turbine, microprocessor, alarm and battery failures account for 80% of all failures. Based on the results of the analysis, it is clear that persons who come into contact with the device must be sufficiently informed about the possible risks and be cautious when using the ventilator.

Non-invasive external ventilation provides breathing support that is more akin to the physiological function of the lungs. Chest cuirass ventilator, which is available in the market, has not in portfolio cuirasses from patients under 1,8 kg, so it is not usable for neonatal patients. This project aims to design a cuirass for extremely immature infants that would provide ventilation support of the respiration using negative external pressure. The cuirass was made by technology of 3D printing.

High-frequency oscillatory ventilation (HFOV), which uses a small tidal volume and a high respiratory rate, is considered a type of protective lung ventilation that can be beneficial for certain patients. A disadvantage of HFOV is its limited monitoring of lung mechanics, which complicates its settings and optimal adjustment. Recent studies have shown that respiratory system reactance (Xrs) could be a promising parameter in the evaluation of respiratory system mechanics in HFOV. The aim of this study was to verify in vitro that a change in respiratory system mechanics during HFOV can be monitored by evaluating Xrs. We built an experimental system consisting of a 3100B high-frequency oscillatory ventilator, a physical model of the respiratory system with constant compliance, and a system for pressure and flow measurements. During the experiment, models of different constant compliance were connected to HFOV, and Xrs was derived from the impedance of the physical model that was calculated from the spectral density of airway opening pressure and spectral cross-power density of gas flow and airway opening pressure. The calculated Xrs changed with the change of compliance of the physical model of the respiratory system. This method enabled monitoring of the trend in the respiratory system compliance during HFOV, and has the potential to optimize the mean pressure setting in HFOV in clinical practice.

We are using life-size mannequins within an education subjects, e.g. “Medical devices” for a demonstration of basic principles of modern clinical devices such as mechanical lung ventilator. Limitation of many simulators is uniformity of its outputs for same input parameters. This paper describes variability of the vital signs of the mannequin when the same scenario was used for different base patients available at human patient simulator.

We have designed a few laboratory exercises within the course "Respiratory therapy" which is taught as an elective course in the studying programme "Biomedical engineer". The aim of the course was to prepare practically oriented education with the use of modern medical devices commonly used in the clinical practice. High fidelity simulators and models were involved into the education to maximally increase an interest of students about the education. The graduates of the course should gain theoretical and practical knowledge from ventilator technique and its use in the clinical practice. A laboratory exercise with a special model of the respiratory system based on the human anatomy was prepared. The developed model has five compartments and each compartment is represented by a demijohn with a proper volume. Each compartment has a unique time constant according to the volume of the demijohn and resistance of the tubes representing airways. A device for synchronous measurement of the pressure in eight places and flow was designed to study pressure and flow distribution in different places of the model. Regional ventilation can be evaluated in the exercise. Another exercise is based on the use of respiratory simulator ASL 5000 (Ingmar Medical, USA). The simulator allows to simulate different values of the respiratory system mechanics. It allows to study the interaction between the ventilator and the simulator. The airway resistance and alveolar compliance can be changed in running scenario and immediate effect can be studied. Also a script that allows studying assistive ventilatory regimens was designed for ASL 5000 simulator. The spontaneous breathing generated by the simulator is combined with a support by connected ventilator. We have also prepared an exercise with a life-size mannequin HPS (CAE Healthcare, USA) supporting intubation and connection of the lung ventilator with the mannequin. Students are supposed to intubate the patient and properly connect the ventilator in the scenario of severe desaturation. It is necessary to watch the values of blood gases and find a settings of the ventilator to provide a proper ventilation and maintain a physiological values of blood gases. A set of practical laboratory exercises with modern medical devices, simulators and models of the respiratory system was designed to ensure maximally practical education within the course “Respiratory therapy".

Main purpose of this paper is to describe a propose and compile a dynamometric measurement system which would measure the isometric force of a handgrip. Although, in the practice, there have already been the mechanic hand dynamometers which could evaluate only a limited amount of information, precisely the maximum strength of a handgrip, our aim is to compile the full electronic hand dynamometer. This work is focused on a design of an appropriate hardware and software for processing and evaluating of the measured data. By the software is able to display the dynamometric graph and also the actual and the maximal strength. It is possible to count maximal gradient of the strength and all these data could be stored in a file. The created dynamometric system might be used in the clinical practice, more accurately on the rehabilitation department where it could replace the current mechanical hand dynamometers or for patients with Parkinson's disease where is possible to evaluate a tremor.

Purpose/Aim : High-frequency oscillatory ventilation (HFOV) is a method of ventilation that theoretically achieves the goals of lung protective ventilation in acute respiratory distress syndrome (ARDS) patients. It is characterized by a rapid delivery of small tidal volumes at high frequencies oscillating around a continuous distending pressure (CDP). Optimization of CDP is not an easy task and it is titrated empirically in the clinical practice. The aim of this study is to investigate whether the level of CDP consistently affects the shape of the partial pressure of oxygen (PaO2) response to stepwise changes in CDP during HFOV of healthy and ARDS-induced pigs.We performed two stepwise maneuvers of CDP in 14 pigs: one before and one after the lung lavage, inducing ARDS. For each CDP step performed, we fitted a segment of PaO2 curve with a one-term power model.PaO2 course follows shapes modeled by root, linear, quadratic, and cubic functions for values of PaO2 ≤ 110 mmHg and PaO2 ≤ 200 mmHg, before and after the lung lavage, respectively. PaO2 course follows a shape modeled exclusively by a root function for values of PaO2110 mmHg and PaO2200 mmHg, before and after the lung lavage, respectively. It is not possible to describe a relationship between the shape of the PaO2 course and the values of CDP.The PaO2 curve may give information about the level of recruitment of alveoli, but cannot be used for optimization of CDP level during HFOV in healthy and ARDS lung model pigs.

The objective was to study the behavior of the subsystems of life-size simulator HPS during spontaneous and assisted ventilation. Demonstration of the assisted ventilation on the mannequin with the use of lung simulator ASL5000 is described. The scenario for a mannequin was designed to simulate an apnea and technical realization of connection of the mannequin and lung simulator is also described. Advantages and disadvantages of assisted lung ventilation are discussed based on the realized experiments.

Mechanical ventilation is used during respiratory failure in many patients. High-frequency oscillatory ventilation is used as a rescue therapy at adult patients. High-frequency ventilation has minimum monitoring and even tidal volume is not routinely measured. Models of the respiratory system can contribute to better understanding about principle of high-frequency oscillatory ventilation. The identification of simple RLC model is described in the study and effect of lung compliance upon tidal volume and alveolar pressure is discussed. It was shown that reduced lung compliance has a minimal effect upon tidal volume whereas it significantly affects an amplitude of alveolar pressure.

The study deals with a design of the scenario of administration of total anesthesia on the life-size simulator. Life-size simulator represents the real human patient and it is being used as a learning tool for medical professionals such as anesthesiologists. Induction of full general anesthesia in life-size simulator is performed by scenario designed in HPS6 software. Scenario reflects real clinical situation and all steps were consulted with anesthesiologists. Weight, age and health status, which may significantly affect the overall administration of anesthesia, were considered when designing a model situation involving a combination of drugs administered to the mannequin, its dose and the settings of the anesthesia machine. The results of the experiment realized with designed scenario, its evaluation and a description of the differences from clinical practice are described.

The study analyses the effect of changes in the mechanical parameters of the respiratory system of the mannequin HPS upon its vital functions during mechanical lung ventilation. The study includes experimental verification of optimal ventilator settings to maintain blood gases at normal physiological values for volume and pressure controlled ventilation. The interaction between mechanical parameters of the respiratory system, vital functions of the simulator and mechanical lung ventilation is demonstrated. Tensions of blood pressures are discussed for a combination of changes in mechanical parameters of the respiratory system.

The aim of the work was to design a metabolic simulator of the human respiratory system consuming oxygen and producing carbon dioxide. The respiratory quotient, tidal volume, mechanical parameters of the system and other parameters should be similar to the physiological values in (healthy) men so that the simulator could be used for simulation of artificial ventilation of real patients. The model consists of a high-volume plastic box assuring the desired lung compliance, a propane-butane burner equipped with a water-based cooling system, oxygen and CO2 analyzers of the "intrapulmonary" gases and a control system. The simulator is an educational device suitable for testing of the influence of the ventilatory parameters upon the intrapulmonary conditions similarly as during artificial lung ventilation of a human patients.

This Study deals with a development of a virtual patient monitor for a mannequin. We have included the virtual patient simulator into the education and we have developed the application of software monitor to increase the interest of the students about the exercises. The application is developed for a PC tablet and the data of vital functions, such as heart rate, saturation of blood by oxygen, partial pressure of oxygen and carbon dioxide in the arterial blood, are transferred from the simulator into the mobile patient monitor. Application is developed in LabVIEW environment and Data Dashboard application from National Instruments is used for displaying the data. Transfer of data between control computer with model and tablet is realized by Shared Variables Engine.

The study deals with design and implementation of a mathematical model of the human respiratory system according to its anatomical structure. The model is designed in order to simulate distribution of important intrapulmonary parameters along the bronchial tree such as pressure amplitude, tidal volume and regional mechanical lung properties. The model is based on the lung morphology and electro-acoustic analogy is used to design the model. The model allows changing the mechanical parameters of the airways and alveolar compliance. conducted simulations suggest that efficiency of artificial lung ventilation is significantly dependent on the mechanical properties of lungs.

The study deals with the modelling of the gas flow during heliox therapy. A special model has been developed to study the effect of the helium upon the gas flow in the airways during the spontaneous breathing. Lower density of helium compared with air decreases the Reynolds number and it allows improving the flow during the spontaneous breathing. In the cases, where the flow becomes turbulent while the patient inspires air the flow is still laminar when the patient inspires heliox. The use of heliox decreases the work of breathing and improves ventilation. It allows in some cases to prevent the intubation of the patients., {"references":["R. Hess, J. B. Fink, S. T. Venkataraman, et. al., \"The History and\nPhysics of Heliox\", Respir. Care, 51(6) (2006), pp. 608-612.","M. Rozanek, K. Roubik, \"Mathematical Model of the Respiratory\nSystem - Comparison of the Total Lung Impedance in the Adult and\nNeonatal Lung\", Proceedings of World Academy of Science,\nEngineering and Technology. Waset.org, 2007, pp. 293-296. ISSN\n1307-6884.","T. R. Myers, \"Use of heliox in children\", Respir. Care, 51(6) (2006), pp.\n619-631.","E. R. Weibel, \"Morphometry of the human lung\", Berlin: Springer-\nVerlag, 1963."]}