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To calculate the load capacity of gear stages within complex drivetrains under varying external loads, multi-body-systems (MBS) are used to simulate the vibrational behaviour of integral systems. In order to model a flexible hypoid gear stage, methods like the modal reduction of FEM-models were already introduced. However, the modelling of such systems is complex, challenging and sensitive to its discretisation. The co-simulation within a multi-body-system simulation offers the possibility to outsource the calculation of the tooth contact and therefore the reaction forces under consideration of friction. This leads to a simplification and an improvement of the modelling of gear stages in multi-body-systems.The further developed co-simulation module offers a compromise between computational speeds and exact solutions. To improve the quality of the results and reduce the calculation time the load distribution calculation is investigated specifically. The article describes a method to reduce fluctuations of computed reaction forces and moments during gear movement. The aim is to keep the level of fluctuations of a high contact zone discretisation with a significant smaller contact point count.

Approaches toward lung-protective ventilation have increasingly been investigated in recent years. Despite evidence being found in adults undergoing surgery, data in younger children are still scarce and controversial. From a physiological perspective, however, the continuously changing characteristics of the respiratory system from birth through adolescence require an approach based on the analysis of each individual patient. The modern anesthesia workstation provides such information, with the technical strengths and weaknesses being discussed in a review preceding the present work (see Part I). The present summary aims to provide ideas on how to translate the information displayed on the anesthesia workstation to patient-oriented clinical ventilation settings.

The population of children with chronic respiratory failure requiring long-term mechanical ventilation in the home has grown worldwide. The optimal choice from an increasing number of home ventilators commercialized for children is often challenging for the attending physicians. The aim of the present study was to compare the trigger performance of five pediatric bilevel home ventilators and one intensive care unit ventilator depending on circuit type and system leak.The trigger performances of the ventilators were compared in combination with all compatible circuits using a physical model of the lung with increasing system leak. The flow generator simulated the patient's breathing effort with flow rates of 2.7-6.4 L/min at a frequency of 30 breaths/min. All ventilators were set to deliver 16 cmHTrigger thresholds varied from 1.5 to 8 L/min, the pressure rise time to 90% of the maximum from 140 to 385 ms and the trigger work from 0.5 to 6.6 mbar · s. All devices had very short trigger delays below 40 ms. The leak compensation depended on the circuit type. The internal diameter of the circuit had no relevant impact on the trigger performance or the leak compensation.We observed considerable differences in the triggering performance of the evaluated home ventilators depending on leak size and type of circuit. Therefore, an optimal combination of device and circuit should consider the patient's age and condition and the probability of system leak.

More and more simulation tools are being used in the development of gears in order to save development time and costs while improving the gears. BECAL is a comprehensive software tool for the tooth contact analysis (TCA) of bevel, hypoid, beveloid and spur gears. The gear geometry is provided by a manufacturing simulation or a geometry import. To determine the exact contact conditions in the TCA, the discrete flank points are converted into a continuous and differentiable surface representation. At present, it is an approximation by means of Bézier tensor product surfaces. With this surface representation, significant deviations to the target points can occur depending on the tooth geometry. In particular tip, root and end relief, strongly curved tooth root geometries or discontinuous topological measurement data due to e.g. micro-pitting can only be considered insufficiently.Hence, a new method for surface approximation with non-uniform rational b‑spline surfaces (NURBS) is presented. Its application can significantly improve the surface representation compared to the target geometry, leading to more realistic results regarding contact stress, tooth root stress and transmission error. To illustrate the advantages, NURBS-based surfaces are compared with the Bézier tensor product surfaces. Finally, the potential of the new approach regarding the prediction of lifetime and acoustics is demonstrated by application to different gear geometries.

Objective. The worldwide rising quantity of surgeries and the corresponding need of mechanical ventilation means a rising number of patients are at risk of suffering from post-operative pulmonary complications. To prevent this risk, individual mechanics of the lung should be considered when setting the parameters of mechanical ventilation. Intratidal compliance analysis based on transpulmonal pressure would provide an estimate for individual lung mechanics. The downside of such measure, however, is its invasiveness. Accurate measurement requires recording of the esophageal pressure as surrogate for the actual pleural pressure. Measuring pressure at the airway opening is considerably easier, but the resulting mechanics of the respiratory system may not represent the actual lung mechanics in a straightforward fashion. Approach. In order to evaluate if the mechanics of the lungs are represented by analysis of the mechanics of the respiratory system we determined intratidal dynamic compliance-volume profiles of both in 23 lung-healthy mechanically ventilated patients undergoing elective surgery. We also compared the accuracy of the compliance profiles resulting from analysis of the total breath with those resulting from the analysis of inspiration data only. Main results. When the whole breath was analyzed 54.3%, and with only inspiration data 69.6%, of compliance profiles of the respiratory system matched those of the lung. With both approaches profiles of the lung and the respiratory system matched or deviated by only one neighboring step (75% whole breath, 91.3% inspiration only), and never contradicted each other. Significance. Compliance profiles calculated from volume and pressure data of the respiratory system are an adequate surrogate for the compliance profiles of the lungs of lung-healthy patients. Therefore, invasive assessment of esophageal pressure for achievement of intrapleural pressure is unnecessary. The compliance profiles based on only inspiratory data appear more sensitive for indicating intratidal derecruitment than those based on data of the whole breath.

BACKGROUND: According to a population-based study, approximately 6.8% of children and adolescents in Germany suffer from acute or chronic constipation. It can be of organic or functional origin and may be associated with comorbid disturbances, particularly fecal incontinence. METHODS: We selectively searched the PubMed and Google Scholar databases for articles with the keywords “constipation,” “children and adolescents,” and “incontinence“. Recommendations are based on the AWMF guideline on constipation and fecal incontinence and on international guidelines and reviews. RESULTS: More than 90% of cases of chronic constipation are of functional origin. Organic causes vary with age and call for targeted differential diagnosis. Invasive tests are only rarely necessary. Functional constipation may be associated with fecal and urinary incontinence, and the relative risk of urinary tract infections is 2.2 to 6.5. There may be associated psychological symptoms and mental disorders in 30–50% of cases. The cornerstone of treatment is patient and parent education, along with laxative medication and toilet training. Instructional programs have been found effective in otherwise refractory cases. CONCLUSION: The treatment of constipation in childhood should begin as soon as the differential diagnostic evaluation is completed. The education of parents, follow-up at close intervals, and drug treatment and behavioral therapy that are adapted to the symptoms can improve quality of life.

What is the central question of the study? Does respiratory support ensure blood gas homeostasis and the relevance of experimental outcomes? What is the main finding and its importance? Spontaneous breathing during surgical intervention under anaesthesia results in impaired gas exchange and loss of diaphragm muscle strength in rats. Subsequent short-term mechanical ventilation restored blood gas homeostasis and diaphragm muscle strength. Blood gas homeostasis interferes substantially with experimental conditions and may alter study results. Monitoring and maintenance of blood gas balance is required to ensure quality and relevance of physiological animal experiments.In pre-clinical small animal studies with surgical interventions under general anaesthesia, animals are often left to breathe spontaneously. However, anaesthesia may impair respiratory functions and result in disturbed blood gas homeostasis. In turn, the disturbed blood gas homeostasis can affect physiological functions and thus unintentionally impact the experimental results. We hypothesized that short-term mechanical ventilation restores blood gas balance and physiological functions despite anaesthesia and surgical interventions. Therefore, we investigated variables of blood gas analyses and diaphragm muscle strength in rats anaesthetized with ketamine/medetomidine after tracheotomy and catheterization of the carotid artery under spontaneous breathing and after 20 min of mechanical ventilation following the same surgical intervention. Spontaneous breathing during general anaesthesia and surgical intervention resulted in unphysiological blood oxygen partial pressure (65 mmHg) and carbon dioxide partial pressure (55 mmHg). After subsequent short-term mechanical ventilation, blood gas partial pressures were restored to their physiological ranges. Additionally, diaphragm muscle strength of animals breathing spontaneously was lower compared to animals that received subsequent mechanical ventilation (P = 0.0063). We conclude that spontaneous breathing of rats under ketamine/medetomidine anaesthesia is not sufficient to maintain a physiological blood gas balance. Disturbed blood gas balance is related to reduced diaphragm muscle strength. Mechanical ventilation for only 20 min restores blood gas homeostasis and muscle strength. Therefore, monitoring and maintenance of blood gas balance should be conducted to ensure quality and relevance of small animal experiments.

Mechanical ventilation is associated with the risk of ventilator induced lung injury. For reducing lung injury in mechanically ventilated patients, the application of small tidal volumes and positive end-expiratory pressures has become clinical standard. Recently, an approach based on linear airway pressure decline and decelerated expiratory flow during expiration implied lung protective capacities. We assumed that ventilation with a smoothed, i.e. sinusoidal airway pressure profile may further improve ventilation efficiency and lung protection. We compared the effects of mechanical ventilation with sinusoidal airway pressure profile (SINE) regarding gas exchange, respiratory system compliance and histology to conventional volume and pressure controlled ventilation (VCV and PCV) and to VCV with flow-controlled expiration (FLEX) in two rat models of lung injury, tween induced surfactant depletion and high tidal volume mechanical ventilation. In both lung injury models ventilation with SINE showed more efficient CO2 elimination and blood oxygenation, improved respiratory system compliance and resulted in lower alveolar wall thickness, compared to VCV, PCV and FLEX. Optimization of the airway pressure profile may provide a novel means of lung protective mechanical ventilation.

For investigating the effects of mechanical ventilation on the respiratory system, experiments in small mammal models are used. However, conventional ventilators for small animals are usually limited to a specific ventilation mode, and in particular to passive expiration. Here, we present a computer-controlled research ventilator for small animals which provides conventional mechanical ventilation as well as new type ventilation profiles. Typical profiles of conventional mechanical ventilation, as well as flow-controlled expiration and sinusoidal ventilation profiles can be generated with our new ventilator. Flow control during expiration reduced the expiratory peak flow rate by 73% and increased the mean airway pressure by up to 1 mbar compared with conventional ventilation without increasing peak pressure and end-expiratory pressure. Our new ventilator for small animals allows for the application of various ventilation profiles. We could analyse the effects of applying conventional ventilation profiles, pressure-controlled ventilation and volume-controlled ventilation, as well as the novel flow-controlled ventilation profile. This new approach enables studying the mechanical properties of the respiratory system with an increased freedom for choosing independent ventilation parameters.

Supplemental Digital Content is available in the text., Objectives: Lung-protective ventilation for acute respiratory distress syndrome aims for providing sufficient oxygenation and carbon dioxide clearance, while limiting the harmful effects of mechanical ventilation. “Flow-controlled ventilation”, providing a constant expiratory flow, has been suggested as a new lung-protective ventilation strategy. The aim of this study was to test whether flow-controlled ventilation attenuates lung injury in an animal model of acute respiratory distress syndrome. Design: Preclinical, randomized controlled animal study. Setting: Animal research facility. Subjects: Nineteen German landrace hybrid pigs. Intervention: Flow-controlled ventilation (intervention group) or volume-controlled ventilation (control group) with identical tidal volume (7 mL/kg) and positive end-expiratory pressure (9 cm H2O) after inducing acute respiratory distress syndrome with oleic acid. Measurements and Main Results: Pao2 and Paco2, minute volume, tracheal pressure, lung aeration measured via CT, alveolar wall thickness, cell infiltration, and surfactant protein A concentration in bronchoalveolar lavage fluid. Five pigs were excluded leaving n equals to 7 for each group. Compared with control, flow-controlled ventilation elevated Pao2 (154 ± 21 vs 105 ± 9 torr; 20.5 ± 2.8 vs 14.0 ± 1.2 kPa; p = 0.035) and achieved comparable Paco2 (57 ± 3 vs 54 ± 1 torr; 7.6 ± 0.4 vs 7.1 ± 0.1 kPa; p = 0.37) with a lower minute volume (6.4 ± 0.5 vs 8.7 ± 0.4 L/min; p < 0.001). Inspiratory plateau pressure was comparable in both groups (31 ± 2 vs 34 ± 2 cm H2O; p = 0.16). Flow-controlled ventilation increased normally aerated (24% ± 4% vs 10% ± 2%; p = 0.004) and decreased nonaerated lung volume (23% ± 6% vs 38% ± 5%; p = 0.033) in the dependent lung region. Alveolar walls were thinner (5.5 ± 0.1 vs 7.8 ± 0.2 µm; p < 0.0001), cell infiltration was lower (20 ± 2 vs 32 ± 2 n/field; p < 0.0001), and normalized surfactant protein A concentration was higher with flow-controlled ventilation (1.1 ± 0.04 vs 1.0 ± 0.03; p = 0.039). Conclusions: Flow-controlled ventilation enhances lung aeration in the dependent lung region and consequently improves gas exchange and attenuates lung injury. Control of the expiratory flow may provide a novel option for lung-protective ventilation.

Objective. Electrical impedance tomography is a valuable tool for monitoring global and regional lung mechanics. To evaluate the recorded data, an accurate estimate of the lung area is crucial. Approach. We present two novel methods for estimating the lung area using functional tidal images or active contouring methods. A convolutional neural network was trained to determine, whether or not the heart region was visible within tidal images. In addition, the effects of lung area mirroring were investigated. The performance of the methods and the effects of mirroring were evaluated via a score based on the impedance magnitudes and their standard deviations in functional tidal images. Main results. Our analyses showed that the method based on functional tidal images provided the best estimate of the lung area. Mirroring of the lung area had an impact on the accuracy of area estimation for both methods. The achieved accuracy of the neural network’s classification was 94%. For images without a visible heart area, the subtraction of a heart template proved to be a pragmatic approach with good results. Significance. In summary, we developed a routine for estimation of the lung area combined with estimation of the heart area in electrical impedance tomography images.

Background Pursed-lips breathing (PLB) is a technique to attenuate small airway collapse by regulating the expiratory flow. During mandatory ventilation, flow-controlled expiration (FLEX), which mimics the expiratory flow course of PLB utilizing a digital system for measurement and control, was shown to exert lung protective effects. However, PLB requires a patient’s participation and coordinated muscular effort and FLEX requires a complex technical setup. Here, we present an adjustable flow regulator to mimic PLB and FLEX, respectively, without the need of a patient’s participation, or a complex technical device. Methods Our study consisted of two parts: First, in a lung model which was ventilated with standard settings (tidal volume 500 ml, respiratory rate 12 min−1, positive end-expiratory pressure (PEEP) 5 cmH2O), the possible reduction of the maximal expiratory flow by utilizing the flow regulator was assessed. Second, with spontaneously breathing healthy volunteers, the short-term effects of medium and strong expiratory flow reduction on airway pressure, the change of end-expiratory lung volume (EELV), and breathing discomfort was investigated. Results In the lung model experiments, expiratory flow could be reduced from − 899 ± 9 ml·s−1 down to − 328 ± 25 ml·s−1. Thereby, inspiratory variables and PEEP were unaffected. In the volunteers, the maximal expiratory flow of − 574 ± 131 ml·s−1 under baseline conditions was reduced to − 395 ± 71 ml·s−1 for medium flow regulation and to − 266 ± 58 ml·s−1 for strong flow regulation, respectively (p 2O to 2.9 ± 0.4 cmH2O with medium flow regulation and to 5.4 ± 2.4 cmH2O with strong flow regulation, respectively (p Conclusions The flow regulator represents an adjustable device for application of a self-regulated expiratory resistive load, representing an alternative for PLB and FLEX. Future applications in spontaneously breathing patients and patients with mandatory ventilation alike may reveal potential benefits. Trial registration: DRKS00015296, registered on 20th August, 2018; URL: https://www.drks.de/drks_web/setLocale_EN.do.

Personalized antibiotherapy ensures that the antibiotic concentration remains in the optimal therapeutic window to maximize efficacy, minimize side effects, and avoid the emergence of drug resistance due to insufficient dosing. However, such individualized schemes need frequent sampling to tailor the blood antibiotic concentrations. To optimally integrate therapeutic drug monitoring (TDM) into the clinical workflow, antibiotic levels can either be measured in blood using point-of-care testing (POCT), or can rely on noninvasive sampling. Here, a versatile biosensor with an antibody-free assay for on-site TDM is presented. The platform is evaluated with an animal study, where antibiotic concentrations are quantified in different matrices including whole blood, plasma, urine, saliva, and exhaled breath condensate (EBC). The clearance and the temporal evaluation of antibiotic levels in EBC and plasma are demonstrated. Influence of matrix effects on measured drug concentrations is determined by comparing the plasma levels with those in noninvasive samples. The system's potential for blood-based POCT is further illustrated by tracking ss-lactam concentrations in untreated blood samples. Finally, multiplexing capabilities are explored successfully for multianalyte/sample analysis. By enabling a rapid, low-cost, sample-independent, and multiplexed on-site TDM, this system can shift the paradigm of "one-size-fits-all" strategy., Advanced Materials, 34 (2), ISSN:0935-9648, ISSN:1521-4095

Gear lapping is a highly productive method of hard finishing hypoid gears for appliances with high demands regarding transmission noise. The absence of a solid tool, however, makes the prediction of the resulting topology difficult. Thus, the design of a lapping program resulting in a desirable topology is a matter of personal experience and empirical efforts. In this paper, a simulation of the local surface wear produced by lapping bevel and hypoid gears is extended to incorporate the influence of the abrasive particles on the local distribution of flank pressure and wear depth. High-resolution experimental investigations of lapped tooth flanks are used to validate the accuracy of the current simulation method and deduce possible improvements. Finally, two methods to integrate the simulation in a production-driven gear design process are proposed.

To calculate the load capacity of gear stages within complex drivetrains under varying external loads, multi-body-systems (MBS) are used to simulate the vibrational behaviour of integral systems. Available solutions are either slow, when using FEM-co-simulation, or are too simplified and produce questionable results. The proposed co-simulation method offers a compromise between computation speed and exact solutions. To speed up the calculation, the tooth stiffnesses are precomputed with a boundary element method (BEM). The fundamental computation of the penetrations of the meshing gears is based on the true flank geometry. The non-linear stiffness of the contact is computed efficiently during the co-simulation. As this calculation is based on precise penetrations, curvatures and other local influences the accuracy can be improved in comparison to faster methods. While flank modifications and pitch deviations can be accounted for, the examination of flank pressures and tooth root stresses is possible.

Flow-controlled ventilation (FCV) is a new mechanical ventilation mode that maintains constant flow during inspiration and expiration with standard tidal volumes via cuffed narrow-bore endotracheal tubes. Originating in manually operated 'expiratory ventilation assistance', FCV extends this technique by automatic control of airway flow, monitoring of intratracheal pressure and control of peak inspiratory pressure and end-expiratory pressure. FCV has not yet been described in a clinical study.The aim of this study was to provide an initial assessment of FCV in mechanically ventilated patients undergoing ear, nose and throat surgery and evaluate its potential for future use.An observational study.Two German academic medical centres from 24 November 2017 to 09 January 2018.Consecutive patients (≥ 18 years) scheduled for elective ear, nose and throat surgery. Exclusion criteria were planned laser surgery, intended fibreoptic awake intubation, emergency procedures, increased risk of aspiration, American Society of Anesthesiologists (ASA) physical status more than III and chronic obstructive pulmonary disease classified as GOLD stage more than II.Peri-operative use of FCV provided by a new type of ventilator (Evone) via a narrow-bore endotracheal tube (Tritube).Minute volume, respiratory rate, intratidal tracheal pressure amplitude (Δp) and end-tidal CO2 (PetCO2) were recorded every 5 min. All adverse events were noted. Data are presented as median [IQR].Sixteen patients provided 15 evaluable data sets. A minute volume of 5.0 [4.4 to 6.4] l min and a respiratory rate of 9 [8 to 11] min generated a PetCO2 of 4.9 [4.8 to 5.0] kPa. Δp was 10 [9 to 12] cmH2O. Five adverse events were recorded: a tube obstruction due to airway secretions and four tube dislocations (two attributed to coughing, two not study-related).FCV achieves adequate PetCO2 levels with minute volume and Δp in the normal range. Tritube's high flow resistance may increase the likelihood of tube dislocations if the patient coughs. Although further evaluation is necessary, FCV provides a new option for short-term mechanical ventilation. The successful operation of FCV with narrow-bore tubes contributes to the armamentarium for airway management.DRKS00013312.

To investigate renal pelvic pressures during percutaneous nephrolithotomy (PCNL) in the standard, mini, and ultramini PCNL systems.We studied an ultramini PCNL system (UMP, outer shaft diameter 13F), a mini PCNL system (MPCNL, shaft 18F, nephroscope 12F), and a standard PCNL system (SPCNL, shaft 27F, nephroscope 24F). Pressure profiles were first investigated in an open model setup, subsequently in a closed model, and finally in an ex vivo porcine kidney. Measurements were determined with the nephroscope in an advanced and pulled-back position for all models.In the advanced position, maximum pressures of 41.61 ± 0.20 mmHg (UMP), 15.61 ± 0.15 mmHg (MPCNL), and 15.46 ± 0.14 mmHg (SPCNL) were measured in the closed model. In the pulled-back position, maximum pressures were 16.04 ± 0.22 mmHg (UMP), 17.02 ± 0.11 mmHg (MPCNL), and 20.50 ± 0.11 mmHg (SPCNL). In the ex vivo porcine kidney model, maximum pressures were 13.81 ± 6.04 mmHg (UMP), 5.64 ± 0.21 (MPCNL), and 9.21 ± 0.52 (SPCNL) with the nephroscope pushed to end position. After retracting the nephroscope from the outer shaft, pressures in all systems did not exceed 10 mmHg.The maximum pressures achieved with the three PCNL systems in all three models were kept below the 30 mmHg critical threshold value. High pressures were only determined for the UMP system with the nephroscope pushed to its end position. This was attributed to the conical shape of the nephroscope, which occupies the space between the nephroscope and outer shaft, resulting in outflow obstruction.

Antimicrobial resistance is increasing with an alarming rate for which the prime suspect is the “one size-fits-all” dosage strategies of antibiotics. Personalized antibiotherapy framework appears as a viable option to counteract inadequate dosage, as it offers the application of the optimal dosage regimen for each individual. Such individualized scheme, however, needs frequent sampling to tailor the blood antibiotic concentration to respond unique pharmacokinetic/pharmacodynamic (PK/PD) of the patient. Herein, there are two alternative paths for feasible therapeutic drug monitoring (TDM); transforming our understanding to utilize blood based sampling within the scope of point-of-care (POC), or focusing on non-invasive samples. Here, we present a versatile biosensor along with an antibody-free assay that can be utilized in both paths for on-site TDM. The developed platform is evaluated in a large animal study (pigs exposed with overdose, normal dose, and underdose of ß lactams), in which antibiotic concentrations are quantified in matrices including whole blood, plasma, urine, saliva, and exhaled breath condensate (EBC). Herein, the detection and the clearance of drug concentrations in EBC is demonstrated for the first time. Influence of the secretion mechanisms on measured drug concentrations is then quantified by comparing the plasma concentrations with those in EBC, saliva and urine. The potential of the developed platform for blood-based POC application is further illustrated by tracking ß lactam concentrations in untreated blood samples. Finally, multiplexing capabilities are explored successfully for multianalyte/sample analysis. Enabling a rapid, low-cost, sample-independent, and multiplexed on-site TDM, this system could pave the way for the personalized drug therapies and thus, shift the paradigm of “one size-fits-all” strategies.

Objective.Flow-controlled expiration (FLEX) has been shown to attenuate ventilator-induced lung injury in animal models. It has also shown to homogenize compartmental pressure distribution in a physical model of the inhomogeneous respiratory system having independent compartments. We hypothesized that the homogenizing effects of FLEX are also effective in this regard when the independence of compartments is suspended by simulated chest wall compliance.Approach.A four compartment physical model of the respiratory system having chest wall compliance (137 ml/cmH2O) was developed. Two of the four compartments had high compliance (18 ml/cmH2O) and two had low compliance (10 ml/cmH2O). These compartments were each combined with either high (6.8 cmH2O·s/l) or low resistance (3.5 cmH2O·s/l). The model was ventilated in the volume-controlled ventilation mode with either passive expiration or with FLEX. The maximal pressure differences (ΔPmax) and the maximal differences of mean pressure (ΔPmean) between the compartments during expiration were determined.Main results.With passive expiration ΔPmaxreached up to 3.4 ± 0.03 cmH2O but only 0.9 ± 0.01 cmH2O with FLEX (p

Objective. Passivity of the diaphragm during prolonged mechanical ventilation can lead to ventilation-induced diaphragmatic dysfunction reasoned by a reduction of diaphragmatic muscle strength. Electrical stimulation may be utilised to modulate diaphragm muscle strength. Therefore we intended to investigate diaphragmatic muscle strength based on stimulation with electric impulses. Approach. Diaphragms of Wistar rats were excised, embedded in various incubation solutions and placed in a diaphragm force measurement device. Pressure amplitudes generated by the diaphragm in dependency of the embedding solution, stimulation frequency and time (360 min) were determined. Furthermore, the diaphragms were histologically evaluated. Main results. The ex vivo diaphragms evoked no pressure if embedded in incubation solutions with high potassium concentrations and up to >20 cmH2O if embedded in incubation solutions with extracellular potassium concentrations. Although vitality was well maintained after 360 min (78%) cultivation, the diaphragm’s force dropped by 90.8% after 240 min. The decline in the diaphragm’s force progressed faster if stimulation was performed every 20 min compared to every 120 min. The size of Type I muscle fibres was largest in diaphragms stimulated every 120 min. The fibre size of Type 2b/x muscle cells was lower in diaphragms after electrical stimulation compared to non-stimulated diaphragms. Significance. The force that the diaphragm can develop in ex vivo conditions depends on the incubation solution and the conditions of activation. Activity-related changes in the diaphragm’s muscular force are accompanied by specific changes in muscle fibre size.

The use of robots in combination with artificial intelligence (AI) is a trend with the promises to relieve humans from difficult-, time consuming- or dangerous work. Intelligent robots aim to solve tasks more efficiently, safer or partly more stable. Independent of the domain-specific challenge, the configuration of both (a) the robot and (b) the AI currently requires expert knowledge in robot implementation, security and safety regulations, legal and ethical assessments and expertise in AI. In order to enable a co-creation of domain-specific solutions for robots with AI, we performed a laboratory survey – consisting of stakeholder interaction, literature research, proof-of-concept experiments using OMiLAB and prototypes using a Robot Laboratory – to elicit requirements for an assistant system that (i) simplifies and abstracts robot interaction, (ii) enables the co-creative assessment and approval of the robot configuration using AI, and (iii) ensures a reliable execution. A model-based approach has been elaborated in the national funded project complAI that demonstrates the key components of such an assistance system. The main concepts paving the way for a shift from research and innovation into real-world applications are discussed as an outlook.

BACKGROUND The success of ventilation with a laryngeal mask depends crucially on the seal between the mask and the periglottic tissue. Increasing the laryngeal mask's cuff volume is known to reduce oral air leakage but may lead to gastric insufflation. OBJECTIVE We hypothesised that a lower cuff pressure would result in less gastric insufflation. We sought to compare gastric insufflation with laryngeal mask cuff pressures of 20 cmH2O (CP20) and 60 cmH2O (CP60) during increasing peak airway pressures in a randomised controlled double-blind cross-over study. We also evaluated the incidence of gastric insufflation at the recommended peak airway pressure of 20 cmH2O or less and during both intermittent positive airway pressure and continuous positive airway pressure. METHODS After obtaining ethics approval and written informed consent, 184 patients ventilated via laryngeal mask received a stepwise increase in peak airway pressure from 15 to 30 cmH2O with CP20 and CP60 in turn. Gastric insufflation was determined via real-time ultrasound and measurement of the cross-sectional area of the gastric antrum. The primary endpoint was the incidence of gastric insufflation at the different laryngeal mask cuff pressures. RESULTS Data from 164 patients were analysed. Gastric insufflation occurred less frequently at CP20 compared with CP60 (P

BACKGROUND Inhomogeneous lung ventilation and pulmonary air leaks are common adverse effects of mechanical ventilation in preterm infants suffering from respiratory distress syndrome. We hypothesized that shortening of inspiratory times can improve the homogeneity of lung aeration. We assumed that ultrashort inspiratory times lead to a full build-up of pressure in regions with low compliance while maintaining incomplete filling of regions with high compliance. METHODS We connected a two-compartment model of the lung with different compliances of the two compartments to a neonatal ventilator. Pressures and flow rates were measured separately for each compartment at inspiratory times ranging from 0.1 to 0.8 s and various combinations of tidal volumes. RESULTS An inspiratory time of 0.8 s resulted in near total pressure equalization between the airway pressure and the two compartments, as 97% of the maximum applied peak pressure was reached in the low compliance compartment and 95% in the high compliance compartment. The distribution of the tidal volume was proportional to the compartment compliance. Ultrashort inspiratory times lowered the peak pressure and tidal volume in the high compliance compartment but maintained higher pressure and volume in the low compliance compartment. An inspiratory time of 0.2 s resulted in a peak pressure of 80% of peak airway pressure in the low compliance compartment and in 61% of peak airway pressure in the high compliance compartment (p

A potential shortage of intensive care ventilators has led to the idea to ventilate more than one patient with a single ventilator. Besides other problems, this is associated with the lack of knowledge concerning distribution of tidal volume and the patients’ individual respiratory system mechanics.In this study we used two simple hand-manufactured adaptors to connect physical models of two adult respiratory systems to one ventilator. The artificial lungs were ventilated in the pressure-controlled mode and we investigated if disconnecting one lung from the ventilation circuit for several breaths would allow to determine reliably the other lung’s tidal volume and compliance.Compliances and volumes were measured both with the ventilator and external sensors corresponded well. However, tidal volumes measured via the ventilator were smaller compared to the tidal volumes measured via the external sensors with an absolute error of 5.3 ± 2.5%. The tidal volumes of the individual artificial lungs were distributed in proportion to the compliances and did not differ relevantly when both artificial lungs were connected to when one was disconnected.We conclude that in case of emergency, ventilation of two patients with one ventilator requires two simple hand-crafted tubes as adaptors and available standard breathing circuit components. In such a setting, respiratory system mechanics and tidal volume of each individual patient can be reliably measured during short term clamping of the tracheal tube of the respective other patient.

BACKGROUND The lungs of pediatric patients are subjected to tidal derecruitment during mechanical ventilation and in contrast to adult patients this unfavorable condition cannot be resolved with small c increases. This raises the question if higher end-expiratory pressure increases or recruitment maneuvers may resolve tidal derecruitment in pediatric patients. AIMS We hypothesized that higher PEEP resolves tidal derecruitment in pediatric patients and that recruitment maneuvers between the pressure changes support the improvement of respiratory system mechanics. METHODS The effects of end-expiratory pressure changes from 3 to 7 cmH2 O and vice versa without and with intermediate recruitment maneuvers on respiratory system mechanics and regional ventilation were investigated in 57 mechanically ventilated pediatric patients. The intratidal respiratory system compliance was determined from volume and pressure data before and after PEEP changes and categorized to indicate tidal derecruitment. RESULTS Tidal derecruitment occurred comparably frequently at PEEP 3 cmH2 O without (13 out of 14 cases) and with recruitment maneuver (14 out of 14 cases) and at PEEP 7 cmH2 O without (13 out of 14 cases) and with recruitment maneuver (13 out of 15 cases). CONCLUSIONS We conclude that contrary to our hypothesis, PEEP up to 7 cmH2 O is not sufficient to resolve tidal derecruitment and that recruitment maneuvers may be dispensable in mechanically ventilated pediatric patients.

Background In obese patients, high closing capacity and low functional residual capacity increase the risk for expiratory alveolar collapse. Constant expiratory flow, as provided by the new flow-controlled ventilation (FCV) mode, was shown to improve lung recruitment. We hypothesized that lung aeration and respiratory mechanics improve in obese patients during FCV. Methods We compared FCV and volume-controlled (VCV) ventilation in 23 obese patients in a randomized crossover setting. Starting with baseline measurements, ventilation settings were kept identical except for the ventilation mode related differences (VCV: inspiration to expiration ratio 1:2 with passive expiration, FCV: inspiration to expiration ratio 1:1 with active, linearized expiration). Primary endpoint of the study was the change of end-expiratory lung volume compared to baseline ventilation. Secondary endpoints were the change of mean lung volume, respiratory mechanics and hemodynamic variables. Results The loss of end-expiratory lung volume and mean lung volume compared to baseline was lower during FCV compared to VCV (end-expiratory lung volume: FCV, − 126 ± 207 ml; VCV, − 316 ± 254 ml; p

BACKGROUND Breathing circuits connect the ventilator to the patients' respiratory system. Breathing tubes, connectors, and sensors contribute to artificial airway resistance to a varying extent. We hypothesized that the flow-dependent resistance is higher in pediatric breathing systems and their components compared to respective types for adults. AIMS We aimed to characterize the resistance of representative breathing systems and their components used in pediatric patients (including devices for adults) by their nonlinear pressure-flow relationship. METHODS We used a physical model to measure the flow-dependent pressure gradient (∆P) across breathing tubes, breathing tube extensions, 90°- and Y-connectors, flow- and carbon dioxide sensors, water traps and reusable, disposable and coaxial breathing systems for pediatric and for adult patients. ∆P was analyzed for usual flow ranges and statistically compared at a representative flow rate of 300 mL∙s-1 (∆P300 ). RESULTS ∆P across pediatric devices always exceeded ∆P across the corresponding devices for adult patients (all P < .001 [no 95% CI includes 0]). ∆P300 across breathing system components for adults was always below 0.2 cmH2 O but reached up to 4.6 cmH2 O in a flow sensor for pediatric patients. ∆P300 was considerably higher across the reusable compared to the disposable pediatric breathing systems (1.9 vs 0.3 cmH2 O, P < .001, [95% CI -1.59 to -1.56]). CONCLUSION The resistances of pediatric breathing systems and their components result in pressure gradients exceeding those for adults several fold. Considering the resistance of individual components is crucial for composing a breathing system matching the patient's needs. Compensation of the additional resistance should be considered if a large composed resistance is unavoidable.

Background The anaesthesia ventilator represents the key equipment for intraoperative respiratory care. Improper operation of this device may threaten a patient's health. A self-explanatory interface facilitates handling and decreases the risk of operating errors. This study systematically evaluates the usability of user interfaces in four modern anaesthesia ventilators. Methods Twenty naive operators were asked to execute 20 tasks on each of four different anaesthesia ventilators (Avance CS2™, GE Healthcare; Flow-i™, Maquet; and Perseus™ and Primus™, Drager) in a randomized order. The success of task execution, frequency of requests for assistance, and processing times were recorded. During the tasks, the operators' visual focus was measured via eye-tracking. Additionally, subjective assessments of usability were evaluated by a standardized questionnaire. For comparison, six experienced operators undertook the same protocol. Results The overall rate of falsely executed tasks was low. Naive operators requested assistance least when using the Perseus (26). Pooled processing times were shortest for the Perseus (222 s), followed by the Primus (223 s), the Avance (238 s), and the Flow-i (353 s). Task-specific processing times differed considerably between the devices. Eye-tracking analyses revealed associated interface issues that impeded the operators' performance. Operators rated usability best for the Perseus [mean ( sd ): 67 (17) arbitrary units] and worst for the Flow-i [50 (16) arbitrary units]. Results from experienced operators support these findings by trend. Conclusions The usability of modern anaesthesia ventilators differs considerably. Interface issues of specific tasks impair the operator's efficiency. Eliminating the specific usability issues might improve the operator's performance and, as a consequence, the patient's safety.