A Damaged-Informed Lung Ventilator Model for Ventilator Waveforms

Motivated by a desire to understand pulmonary physiology, scientists have developed physiological lung models of varying complexity. However, pathophysiology and interactions between human lungs and ventilators, e.g., ventilator-induced lung injury (VILI), present challenges for modeling efforts. This is because the real-world pressure and volume signals may be too complex for simple models to capture, and while complex models tend not to be estimable with clinical data, limiting clinical utility. To address this gap, in this manuscript we developed a new damaged-informed lung ventilator (DILV) model. This approach relies on mathematizing ventilator pressure and volume waveforms, including lung physiology, mechanical ventilation, and their interaction. The model begins with nominal waveforms and adds limited, clinically relevant, hypothesis-driven features to the waveform corresponding to pulmonary pathophysiology, patient-ventilator interaction, and ventilator settings. The DILV model parameters uniquely and reliably recapitulate these features while having enough flexibility to reproduce commonly observed variability in clinical (human) and laboratory (mouse) waveform data. We evaluate the proof-in-principle capabilities of our modeling approach by estimating 399 breaths collected for differently damaged lungs for tightly controlled measurements in mice and uncontrolled human intensive care unit data in the absence and presence of ventilator dyssynchrony. The cumulative value of mean squares error for the DILV model is, on average, ≈12 times less than the single compartment lung model for all the waveforms considered. Moreover, changes in the estimated parameters correctly correlate with known measures of lung physiology, including lung compliance as a baseline evaluation. Our long-term goal is to use the DILV model for clinical monitoring and research studies by providing high fidelity estimates of lung state and sources of VILI with an end goal of improving management of VILI and acute respiratory distress syndrome.

OPTIMIZATION OF LUNG VENTILATOR MAINTENANCE PROCESSES DUE TO THE COVID-19 PANDEMIC: A CASE STUDY IN BRAZIL

The COVID-19 pandemic was an event of enormous proportions that drastically changed the planet. With it, hospital respiratory support equipment has become crucial in maintaining life in the most severely ill patients. This has led to increased demand for this equipment worldwide. This work presents a case study regarding the maintenance of pulmonary ventilators of a company located in Belo Horizonte, MG, aiming to present recommendations for the optimization of its internal processes. The case study took place through visits to the company and access granted to its Internal Standards Operating Procedures related to the services provided by technicians and engineers. Through the analysis of Tickets and Service Orders (SO), the results obtained comprised the following chapters (quoted in quotation marks): The “Diagnosis of Maintenance Processes”, identified through flowcharts that approximately 30% of the problems claimed by customers are solved with instructions for use. The "Improvement Demand Assessment" identified in 2020 a significant increase in SO's of equipment with approved budget (from 12% to 35%), mostly related to public network customers who obtained federal funds to approve the budgets. Thus, in “Process Optimization Recommendations” an action plan was drawn up and it was concluded that is crucial, the implementation of six improvement actions by the company, in order to correct errors and ensure a significant increase in the efficiency of the process maintenance of pulmonary ventilators, to maximize operational, financial results and, above all, patient safety.

Developing Algorithms and Programs for an Artificial Lung Ventilator

Описаны алгоритмы и программы для аппарата искусственной вентиляции легких, которые обеспечивают различные режимы работы аппарата. Работа является актуальной в условиях пандемии COVID-19 в связи с возросшим спросом на данные устройства.Цель исследования – разработка программного комплекса для микроконтроллера STM32L151ZDTx-LQFP144, используемого на переносном аппарате ИВЛ Axion A-IVL-E-03 и обеспечивающего работу в различных режимах вентиляции, графическое отображение динамики дыхания на дисплее и подачу оператору голосовых подсказок и световых сигналов во время работы. Разработанные алгоритмы также предназначены для управления периферийными устройствами и контроля правильности их работы, разрешения аварийных ситуаций с помощью дисплея, голосовых подсказок и световой индикации. Кроме того, в качестве инструмента, который позволяет врачу понять важное взаимодействие между входными параметрами пациента (частота, давление в дыхательных путях и степень вдоха) и клинически важными параметрами (дыхательный объем, средний объем минутной вентиляции), предложены математические модели вентиляции легких с контролируемым давлением. Реализация данных математических моделей показала их применимость для симуляции данных сложных процессов. Разработан удобный и интуитивно понятный графический пользовательский интерфейс.В статье также приводится сравнение существующих аналогов с предложенными разработками.

Accuracy of Computed Equations for Predicting the Resting Energy Requirements in Patients with Generalized Secondary Peritonitis

Nutritional support is central to prompt treatment of patients with generalized secondary peritonitis (GSP).These patients desperately need a simple and affordable solution to evaluate their daily energy need.Objective: to determine accuracy of estimating the Resting Energy Expenditure (REE) in GSP patients.Materials and methods. Study design: a prospective, single center study. The inclusion criteria: diagnosed GSP and stay at the Intensive Care Unit (ICU). Three treatment arms were formed. The first arm included all patients (n=61), the second arm included patients capable to breath spontaneously and adequately (n=29), and the third arm included patients on artificial ventilation (n=32). Reference values of REE were calculated by Indirect Calorimetry (IC) method using Engstrom Carestation Lung Ventilator and Metabolic (General Electric,USA). Six equations were used to predict REE values: Ideal Body Weight multiplied by 25 (IBWX25); Actual Body Weight multiplied by 25 (ABWX25); J. A. Harris, F. Benedict (HB); HB with corrective ratio 1.25 (HBX1.25); C. Ireton-Jones, 1992 (IJ); PennState, 2003 equation, in modification (PS). SPSS Software Package was used for statistical analysis of the results. The zero hypothesis was rejected at P<0.05.Results. In patients with GSP, the REE value determined by means of Indirect Calorimetry method was equal to 25.78±1.37 kcal/kg/day. If compared with Indirect Calorimetry results, predictive accuracy of calculation equations in the second and third arm, respectively, were as follows: IBWX25: 30 and 0%, HB: 36.7 and 9.9%, HBX1.25: 49.9 and 45.5%, IJ: 51.8 and 53.2%, ABWX25: 63.4 and 60.6%, PS (as determined in patients on mechanical ventilation only): 42.4%.Conclusion. Indirect Calorimetry method is the only accurate way of REE evaluation in GSP patients. ABWX25 and IJ showed the highest predictive accuracy. IBWX25 and HB had the lowest predictive accuracy.

Sites of respiratory rhythmogenesis during development in the tadpole

During ontogeny, amphibian larvae experience a dramatic alteration in the motor act of breathing as the premetamorphic gill breather develops into the postmetamorphic lung ventilator. We tested the hypothesis that the site of lung rhythmogenesis relocates during metamorphosis by recording fictive lung ventilation before and after transecting the in vitro brain stem of pre- and postmetamorphic Rana catesbeiana into four segments. In premetamorphic tadpoles, the two caudalmost brain stem segments combined proved to be the minimum brain stem configuration necessary and sufficient for lung burst generation. In the postmetamorphic counterpart, this function was supplied by the combination of the two rostralmost brain stem segments. In the postmetamorphic brain stem, a 500-μm segment lying just rostral to cranial nerve IX conveys rhythmogenic capability to neighboring rostral or caudal segments. We conclude that lung rhythmogenic capability translocates rostrally during development as the tadpole shifts from gill to lung ventilation.