Background and objective: Ventilator-induced lung injury (VILI) remains a critical challenge in mechanical ventilation, particularly for patients with impaired pulmonary mechanics. This study introduces a novel adaptive ventilation strategy that dynamically regulates inspiratory pressure and flow to minimize and stabilize mechanical power during inspiration. The central hypothesis is that maintaining a low, constant inspiratory power profile can reduce VILI risk more effectively than traditional ventilation methods. Methods: An optimization framework based on Bellman dynamic programming was developed to compute optimal, time-varying inspiratory pressure and flow profiles under constraints on tidal volume and airway pressure. The algorithm was implemented and validated using a physical lung simulator (SmartLung 2000) coupled with a clinical-grade ventilator (Siemens-Elema Servo 900B). Nine resistance-compliance configurations were tested to simulate healthy and pathological lung conditions. Experimental measurements included flow, pressure, and real-time mechanical power. Results: Compared to conventional volume-controlled ventilation with constant flow, the optimized mode reduced peak inspiratory power by 7.8-30% and mean power by up to 7.3%, without compromising tidal volume delivery. Power profiles were more evenly distributed, minimizing transient mechanical stress on lung tissue. These outcomes were consistent across simulated restrictive and obstructive lung conditions. Conclusion: The proposed strategy offers a new paradigm for real-time, power-aware mechanical ventilation. The integration of dynamic programming-based optimization into ventilator control systems holds promise for enhancing lung protection in critically ill patients. Further work will focus on embedded real-time implementation and in vivo validation.

Background Mechanical ventilation remains a life-saving intervention but carries risks such as barotrauma, volutrauma, ergotrauma, and hemodynamic disturbances. Modern ventilators incorporate adaptive strategies to minimize the work of breathing (WOB), often relying on measurements of respiratory resistance and compliance. However, such measurements are prone to error and often unavailable in real time. This study presents a novel adaptive ventilation concept that dynamically identifies the optimal ventilation frequency minimizing WOB per minute without requiring resistance or compliance measurements.Material and methods Using a validated hybrid respiratory simulator, we conducted simulation experiments across three representative lung conditions: normal mechanics, decreased compliance, and increased resistance. The system conceptually searched for the ventilation frequency minimizing WOB/min while maintaining constant alveolar ventilation, with the optimization process emulated manually in this proof-of-concept study.Results Results confirmed that WOB/min follows a parabolic function of frequency, with optimal frequencies found at 18, 21, and 12 breaths per minute for normal, restrictive, and obstructive patterns, respectively. Importantly, the optimal frequencies aligned with ranges observed in clinical studies of adaptive support ventilation. Furthermore, the system demonstrated natural variability in ventilation rate and tidal volume, which may contribute to alveolar recruitment.Conclusion Our findings validate the concept of energy-based optimization of ventilation independent of online lung mechanics assessment. The proposed method is robust, physiologically grounded, and may become suitable for integration into next-generation intelligent ventilators after full automation of the adaptive algorithm. Future work will focus on full automation of the adaptive algorithm and its evaluation in preclinical and clinical studies targeting WOB and mechanical power minimization.

We aim to develop a non-invasive, bed-side method for supporting personalised ventilation of neonates with congenital diaphragmatic hernia (CDH). Currently, there are no CDH severity measures to do it. As ventilation inhomogeneity (VI) resulting from lung hypoplasia is highly variable in CDH patients, mechanical ventilation is a real challenge and the risk of lung injury is high. We conducted 250 simulations of conventional ventilation of CDH cases using the infant hybrid (numerical-physical) respiratory simulator and a ventilator. Utilising simulation results, we searched for a regression model describing patient ventilation parameters as a function of the respiratory system parameters, ventilator settings and two new CDH severity measures: VI-degree defined as a ratio of time constants ratio of the contralateral and ipsilateral lung (T1/T2) and chest-wall-to-lung compliance ratio (CW/CL). The regression model aimed to find the T1/T2 and CW/CL values for real CDH cases and estimate optimal, matched to VI-degree, peak inspiratory and mean airway pressure (PIP, MAP). The developed regression models (R2 = 0.78 ÷ 0.98; P < 0.001) enabled to find clinically hard-to-measure values of T1/T2 and CW/CL ratios for three patients, respectively: 9 and 6.52 (P1), 3.5 and 4.96 (P2), and 4 and 5.02 (P3). The T1/T2 and CW/CL correlated with defect size (gamma coefficient: 1; P < 0.05), duration of mechanical ventilation and hospitalization (Spearmen’s coefficient: 0.99; P < 0.01). The clinical and estimated PIP and MAP didn’t differ statistically. The T1/T2 and CW/CL indices can help to personalize CDH infants’ ventilation and might be used for prognostication.

Lidocaine, a widely used local anaesthetic, also serves as an adjuvant in pain management. However, its use in children is off-label. This study aimed to determine if intravenous lidocaine alleviates the haemodynamic, metabolic, and hormonal responses to intubation and laparoscopic surgery in children. A single-centre, parallel, double-masked, randomised, placebo-controlled trial. 132 patients, aged 18 months to 18 years, with no contraindications to lidocaine administration and qualified for laparoscopic appendectomy were enrolled. The intervention studied was a lidocaine bolus of 1.5 mg⋅kg− 1 over 5 min given before induction of anaesthesia, followed by intraoperative lidocaine infusion at 1.5 mg⋅kg− 1⋅h− 1 intraoperatively. Patients in the control group were administered a placebo. Mean arterial pressure, glucose, cortisol, lidocaine blood levels, lidocaine-related side effects, and intraoperative opioid requirements were analysed. 132 participants completed the trial. The number of patients who experienced an excessive cardiovascular response to induction of anaesthesia or intubation was 23 (37

Background: Opioids remain the most effective component of systemic analgesia and are considered safe and beneficial when administered at the lowest effective dose. Nevertheless, their potential adverse effects may diminish the quality of the postoperative period or, in some cases, lead to life-threatening complications. This analysis examines whether the mandatory implementation of a standardised protocol offers opioid-sparing potential. Methods: In this single-centre retrospective cohort study, intraoperative opioid consumption during laparoscopic appendectomy was compared between patients anaesthetised according to a standardised protocol (n1 = 132) and those managed at clinicians’ discretion in line with good medical practice (n2 = 212). Length of hospital stay and use of intraoperative non-opioid analgesics were also assessed. Results: The total fentanyl dose administered during anaesthesia was significantly lower in the standardised protocol cohort compared to the cohort without a protocol: 3.13 μg·kg−1 (IQR: 2.98–4.08) vs. 5.19 μg·kg−1 (IQR: 3.89–6.67), p < 0.001. In the protocol cohort, the percentage of patients who received acetaminophen and metamizole was significantly higher—increasing by 57% and 23%, respectively (p < 0.001). No significant inter-cohort difference was observed in terms of length of hospital stay. Conclusions: The use of a mandatory anaesthetic protocol based on a multimodal approach had an opioid-sparing effect in children undergoing laparoscopic appendectomy. This retrospective analysis was approved by the Ethics Committee of the Medical University of Warsaw (identifier: AKBE/118/2025; date of acceptance: 12 May 2025), and the primary trial was registered in the U.S. National Library of Medicine Clinical Trials Registry (registration number: NCT05238506; date of first registration: 14 February 2022).

We assessed the influence of systemic lidocaine administration on ventilatory and circulatory parameters, and the pneumoperitoneum impact on the cardiopulmonary system during a laparoscopic appendectomy in children. A single-center parallel single-masked randomized controlled study was carried out with 58 patients (3–17 years). Intravenous lidocaine bolus of 1.5 mg/kg over 5 min before induction of anesthesia followed by lidocaine infusion at 1.5 mg/kg/h intraoperatively. Respiratory system compliance (C, C/kg), P peak -PEEP and Pulse rate (Pulse), systolic, diastolic and mean blood pressure (NBP s , NBP d , NBP m ), assessed in the Lidocaine and Control group, at the: beginning (P 1 ), minimum lung compliance (P 2 ) and at the end of surgery (P 3 ) were compared. The respiratory/hemodynamic parameters did not differ between the groups at any stage of operation. Blood Pressure and P peak -PEEP were significantly higher at the P 2 compared to P 1 and P 3 stages (P < 0.001, 1 − β ≥ 0.895) that correlated with lung compliance changes: C/kg vs. NBP s and P peak -PEEP (− 0.42, − 0.84; P < 0.001); C vs. Pulse and P peak -PEEP (− 0.48, − 0.46; P < 0.001). Although an increase in intraabdominal pressure up to 12(15) mmHg causes significant changes in hemodynamic/respiratory parameters, there appears to be no risk of fatal reactions in 1E, 2E ASA patients. Systemic lidocaine administration doesn’t alleviate circulatory/respiratory alterations during pneumoperitoneum. No lidocaine related episode of anaphylaxis, systemic toxicity, circulatory disturbances or neurological impairment occurred. ClinicalTrials.gov : 22/03/2019. Trial registration number : NCT03886896.

Congenital Diaphragmatic Hernia (CDH) is a diaphragm defect associated with lung hypoplasia and ventilation inhomogeneity (VI). The affected neonates are usually born with respiratory failure and require mechanical ventilation after birth. However, significant interindividual VI differences make ventilation difficult. So far, there are no clinical methods of VI assessment that could be applied to optimize ventilation at the bedside. A new VI index is a ratio of time constants T1/T2 of gas flows in both lungs. Pressure-controlled ventilation simulations were conducted using an infant hybrid (numerical-physical) respiratory simulator connected to a ventilator. The parameters of the respiratory system model and ventilator settings were based on retrospective clinical data taken from three neonates (2, 2.6, 3.6 kg) treated in the Paediatric Teaching Clinical Hospital of the Medical University of Warsaw. We searched for relationships between respiratory system impedance (Z) and ventilation parameters: work of breathing (WOB), peak inspiratory pressure (PIP), and mean airway pressure (MAP). The study showed the increased VI described by the T1/T2 index value highly correlated with elevated Z, WOB, PIP and MAP (0.8–0.9, the Spearman correlation coefficients were significant at P < 0.001). It indicates that the T1/T2 index may help to improve the ventilation therapy of CDH neonates.

Congenital Diaphragmatic Hernia (CDH) is a serious newborn defect requiring mechanical ventilation. Initial ventilation settings should take into account the severity of lungs inhomogeneity (LI), but it is not assessed in everyday clinical practice. We present a new LI index that can be easily determined at the bedside. It is based on a comparison of resistive-elastic properties of lungs and defined as a ratio of time constants T-1.T-2(-1) of gas flows in both lungs (T-1 = R-1.C-1, T-2 = R-2.C-2). We hypothesised that T-1.T-2(-1) index increase causes a rise of lungs impedance (Z) and requires elevation of peak inspiratory pressure (PIP), mean airway pressure (MAP), and work of breathing (WOB). Infant hybrid (numerical-physical) respiratory simulator and a ventilator were used to simulate conventional ventilation of homogeneous and inhomogeneous lungs, and to measure PIP, MAP and WOB. A high correlation was found between Z, WOB, PIP, MAP and the T-1.T-2(-1) index (r = 0.9, P < 0.001). The increase of T-1.T-2(-1) index from 1 to 20 resulted in significant rise of WOB, PIP and MAP, e.g. at RR = 60 bpm, the WOB (1.05 -> 1.49)J.l(-1)), PIP (15.2 -> 20.5 cmH(2)O) and MAP (6.8 -> 8.4 cmH(2)O), P < 0.005. It seems that T-1.T-2(-1) index could be used for prediction of PIP and MAP required to achieve effective ventilation in CDH infants; it also may affect the choice of ventilation strategy (CMV or HFV) as well as ventilator settings on CMV. We show how the relationships between WOB, PIP, MAP and the T-1.T-2(-1) index could be used in clinical practice in the future. (C) 2021 Nalecz Institute of Biocybernetics and Biomedical Engineering of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Circuit compliance close to lung compliance can create serious problems in effective and safe mechanical ventilation of preterm infants. We considered what ventilation technique is the most beneficial in this case. A hybrid (numerical-physical) simulator of infant respiratory system mechanics, the Bennett Ventilator and NICO apparatus were used to simulate pressure-controlled ventilation (PC) and volume-controlled ventilation with constant flow (VCVCF) and descending flow (VCVDF), under permissive hypercapnia (PHC) (6 ml kg-1) and normocapnia (SV) (8 ml kg-1) conditions. Respiratory rate (RR) was 36 or 48 min-1 and PEEP was 0.3 or 0.6 kPa. Peak inspiratory pressure (PIP), mean airway pressure (MAP), and work of breathing by the ventilator (WOB) were lower (P < 0.01, 1 - β = 0.9) using the PHC strategy compared to the SV strategy. The WOB increased (P < 0.01; 1 - β = 0.9) when the RR increased. The PC, VCVCF, and VCVDF modes did not differ in minute ventilation produced by the ventilator (MVV), but the PC mode delivered the highest minute ventilation to the patient (MVT) (P < 0.01; 1 - β = 0.9) at the same PIP, MAP, and WOB. The most beneficial ventilation technique appeared to be PC ventilation with the PHC strategy, with lower RR (36 min-1). Graphical abstract The effectiveness of an infant ventilation depending on circuit compliance to lung compliance ratio (Cv CL -1) and inspiration time (Ti). VV, VT, tidal volume set on the ventilator and delivered to patient, respectively.

Obstructive lung diseases can be caused by bronchi narrowing or loss of lung tissue elasticity or both. The aim of the work was to develop a new measurement method and an equipment which enables to evaluate the obstruction causes. This Added Compliance and Resistance Method (ACRM) determines the fundamental parameters of the respiratory system mechanics that are the total respiratory system compliance (Crs) and resistance (Rrs). Each case of obstruction can be characterized by the corresponding point location on the Rrs-Crs plane. ACRM was verified by means of experiments performed with the use of our artificial patient developed previously, a commercial spirometer and the developed equipment. ACRM was compared with forced spirometry being the fundamental screening method for diagnosis of obstructive lung diseases and basing on the forced expiratory volume in 1st second (FEV1). Spirometry could not distinguish between pulmogenic and bronchogenic causes of an obstruction. For example, the value of FEV1 did not enable to differentiate moderate, mild and no bronchial obstruction from severe, moderate and mild obstruction, respectively, accompanied with twice increase of Crs. On the other hand, a Crs fall increased FEV1, and thus FEV1 underestimated the bronchial obstruction severity if the severity was determined on the base of its value. In contrast, ACRM could determine the cause of an obstruction case and the higher the severity of the obstruction, the better the differentiation. Concluding, the proposed method should supplement the forced spirometry to determine the patient state more precisely.

Mechanical ventilation of infants with congenital diaphragmatic hernia (CDH) often is a challenge due to different elastic-resistive properties of both lungs. The first step of therapy requires choosing between conventional mechanical ventilation (CMV) and high frequency ventilation (HFV). This study’s aim is to explore why CMV cannot always be applied in infants with ventilation inhomogeneity. The authors hypothesized that lung inhomogeneity is related to higher respiratory system impedance requiring higher respiratory pressure and work of breathing to obtain assumed minute ventilation. Real-time in vitro simulations using hybrid (numerical-physical) model of the respiratory system and a ventilator revealed the risk factors connected with inhomogeneous ventilation of lungs. The pressures and flows registered in the smaller, pinched lung exhibiting decreased compliance can reach dangerously high values and cause lung injury. Such effects were not observed with homogenous lungs as the same minute ventilation has been received at significantly lower pressure delivered to patient airway.

The high resistance of an infant endotracheal tube (ETT) can markedly impair ventilation and gas exchange. Since some manufacturers cover the inner surface of their ETTs with a silicon layer in order to diminish deposition and ease mucous evacuation from airway, via surface roughness decrease, we assessed whether the silicon layer may affect tube resistance, work of breathing and other parameters of ventilation.We compared SUMI (Poland) non-siliconised and siliconised polyvinyl chloride ETTs (2.5, 3.0 and 4.0 mm ID), twenty of each type and size combination. Simulating volume-controlled ventilation with the hybrid (numerical-physical) lung models of a premature infant and a 3-month-old baby peak inspiratory pressure (PIP), peak inspiratory and expiratory flow (PIF, PEF), (patient + ETT) inspiratory and expiratory airway resistance (R-ins, R-exp) and work of breathing by ventilator (WOBvt) were measured. Additionally, images of the both type surfaces were taken using Hitachi TM-1000 electron microscope.When 2.5 and 3.0 mm ID ETTs were examined, laminar flow (Re <2300) across the tube was observed, and there were no clinically significant differences in the ventilation parameters between non-siliconised and siliconised tubes. Whereas, when 4 mm ID ETTs were tested, turbulent flow was observed, and PIP, R-ins, R-exp and WOBvt were significantly lower (5%, 17%, 17%, and 7%, respectively) (P < 0.05), but PIF and PEF were significantly higher (8%, 14%) (P < 0.05). Thus, the silicone inner surface of ETT offers less resistance and WOBvt in presence of turbulent flow. However, artifacts observed on the surface of non-siliconised and siliconised ETTs can potentially impair ventilation. (C) 2017 Nalecz Institute of Biocybemetics and Biomedical Engineering of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.

The influence of preterm birth, bronchopulmonary dysplasia (BPD) and lung inhomogeneity on respiratory system impedance (RSI) was studied. The simulation of spontaneous breathing in full term newborns (FT), very low birth weight (VLBW) and extremely low birth weight (ELBW) preterm infants was carried out using a developed linear RLC respiratory system model. Besides BPD, four types of lung inhomogeneity: (1) one-lung obstruction (OBSTR), (2) one-lung restriction (RESTR), (3) one-lung obstructive-restrictive disturbance (OBSTR-RESTR I), (4) bilateral obstructive-restrictive disturbance (OBSTR-RESTR II), with obstruction of one lung and restriction of the second, were studied. The impact of preterm birth on infant RSI was stronger than the BPD impact. The differences in the real and imaginary parts of RSI, between full term, VLBW and ELBW infants, were much greater than between preterm infants with and without BPD. The shift of resonant frequency between full terms and ELBW amounted to 20 Hz, but between ELBW with and without BPD only 5 Hz. The bilateral obstructive-restrictive lung inhomogeneity (OBSTR-RESTR II) with obstruction of one lung ( R_1=10· R_2) and restriction of the second lung ( C_2=0.1· C_1) , appeared to have the most adverse influence on RSI. In ELBW with OBSTR-RESTR II, both the real and imaginary parts of RSI increased several times compared to healthy ELBW. However, severe one-lung obstruction ( R_1=10· R_2) or one-lung restriction ( C_1=0.1· C_2) in preterm infants prompted significant increases of RSI compared to healthy infants. The 20 ( R_1=1.2· R_2) or lung compliance ( C_1=1.2· R_2) between the left and right lung seemed to be clinically unimportant.

A new hybrid (numerical–physical) simulator of the respiratory system, designed to simulate spontaneous and artificial/assisted ventilation of preterm and full-term infants underwent preliminary evaluation. A numerical, seven-compartmental model of the respiratory system mechanics allows the operator to simulate global and peripheral obstruction and restriction of the lungs. The physical part of the simulator is a piston-based construction of impedance transformer. LabVIEW real-time software coordinates the work of both parts of the simulator and its interaction with a ventilator. Using clinical data, five groups of “artificial infants” were examined: healthy full-term infants, very low-birth-weight preterm infants successfully (VLBW) and unsuccessfully extubated (VLBWun) and extremely low-birth-weight preterm infants without (ELBW) and with bronchopulmonary dysplasia (ELBW_BPD). Pressure-controlled ventilation was simulated to measure peak inspiratory pressure, mean airway pressure, total (patient + endotracheal tube) airway resistance (R), total dynamic compliance of the respiratory system (C), and total work of breathing by the ventilator (WOB). The differences between simulation and clinical parameters were not significant. High correlation coefficients between both types of data were obtained for R, C, and WOB (γ R  = 0.99, P < 0.0005; γ C  = 0.85, P < 0.005; γWOB = 0.96, P < 0.05, respectively). Thus, the simulator accurately reproduces infant respiratory system mechanics.

Respiratory disturbances frequently accompany stuttering. Their influence on lung ventilation can be assessed by measurement of the end-tidal CO2 concentration (EtCO2). The effectiveness of the CO2-based visual feedback method of breath regulation (VF) designed for stuttering therapy was tested in this study. The aim of the study was to answer the question if the VF helps to reduce respiratory disturbances in stuttering and increase speech fluency. 20 stuttering volunteers aged 13-45 years took part in the 3-parts test consisting of: 1. speaking without any techniques improving speech fluency, 2. learning the VF method, 3. VF-assisted speaking. The CO2/time signal and an acoustic signal of an utterance were recorded during the test. Significant increase of FE-the factor of breath ergonomics during speaking (based on both signals), from 47% to 71% (P < 0.01), and significant decrease of % SS-the percent of syllables stuttered, from 14% to 10% (P < 0.01) were received for VF-assisted utterances compared to the utterances without VF assistance. The results indicate that the VF can help to eliminate respiratory disturbances in stuttering and increase speech fluency.

A new CO2-based visual feedback therapy method (VF) for respiratory disturbances in stuttering was preliminarily assessed. Sound and expired CO2 signals were registered in 12 stutterers and 12 fluent speakers while speaking without and with VF to control breathing as well as during rest respiration, before each utterance. In stutterers, the end-tidal CO2 (ETCO2), the area under CO2/a time curve (SCO2), and the average emission of CO2 (ECO2 = SCO2/tbreath_cycle) for the CO2 peaks connected with the phrases containing tonic errors (with reference to rest respiration) were higher than those connected with fluent phrases (p

Background Conventional endotracheal pediatric tubes offer high resistance due to their small diameters and relatively high flow during ventilation. Any increase of the diameter of the tube lumen decreases the airway resistance and subsequently, the work of breathing (WOB). We compared ventilation mechanics using a new, cone-shaped endotracheal tube of our design to the Cole and standard tubes. Methods The study has been divided into three parts: (i) preliminary laboratory tests, (ii) in vitro study with infant lung model, and (iii) clinical study in infants. Flow resistance and WOB were compared, using standard, Cole (in experimental phase only) and cone tubes. Results We proved that inspiratory (Ri) and expiratory (Re) resistance, and WOB, were significantly lower in patients ventilated via a cone tube. Mean Ri decreased by 37%, compared with the baseline values, Re by 35%, and total WOB by 12%. Conclusion The cone tube offers lower resistance to gas flow than the standard, used nowadays in clinical practice. It can be especially beneficial to spontaneously breathing patients reducing WOB and improving gas exchange.

A new control solution for independent, synchronous ventilation of lungs has been developed and a controller to perform it with use of only one respirator and a bilumen intubation tube has been built. The controller enables division of the inspiratory tidal volume between the lungs in desired ratio, and setting of the positive end-expiratory pressure (PEEP) separately for each lung. The model tests have shown that the characteristics of the flow meters used, however not linear, is good enough to achieve clinically accepted accuracy of volume division. The tests have shown that the volume division is independent from the total tidal volume and PEEP. Maximal errors of the tidal volume division was less than 10%. The case study of patient after lung injury has shown significant improvement of the X-ray image and respiratory parameters (blood oxygenation, ventilatory pressures) during the independent ventilation of lungs with the use of the new device. The clinical study of 60 patients has shown that differences between actually realized volume division and the adjusted values are practically negligible.

A design principle, construction and results of preliminary tests of a new hybrid physical-electrical model of lungs mechanics has been presented. The methods leading to development of lungs models of different complexity have been also included. The basic component of the model is a voltage controlled flow source build up with a piston – cylinder system driven by a servomotor. This is used to develop a functional module playing a role of an impedance converter transforming an input electrical impedance Z0 of any electrical network connected to its electrical terminals into a pneumatic impedance Zin. Static and dynamic characteristics of the model connected to different pneumatic signal sources have been presented i.e. for the model connected with the respirator (expiration by the respiratory valve) and for the model with free unobstructed expiration. The very good dynamic features (time constant of the piston flow source less than 1ms) and a small resultant error of impedance conversion (less than 1%) enable the model to be applied in many application especially when new methods of lung ventilation are developed.