Elaboration of neonatal and pediatric mechanical lungs

Pediatric patients or newborns admitted to Neonatal Intensive Care Units (NICU) receive life support care due to various conditions and pathologies. The physiotherapist controls and applies medicinal gases, institutes and monitors invasive and non-invasive mechanical ventilation, as well as performs weaning, among others. Learning ventilatory management must be appropriate for the age and, therefore, consider different lungs for the proper simulations of compliance and resistance. Although the insertion of physical therapists is relatively recent, there are several postgraduate courses and training in this area. The creation of a mechanical lungthat covers, separately, neonatal and pediatric patients will be a fundamental tool for the learning and training of future professionals who will work in the area. To develop two neonatal and pediatric mechanical lungs, as well as to simulate different elastic and resistive behaviors inherent in clinical practice. Experimental study, bench, divided into two stages: creation of mechanical lungs and evaluation of mechanical characteristics. The lungs will be made on a two-story metallic base: on the upper floor, the pediatric lung and the lower floor, the neonatal. In the second stage, the mechanical lung will be connected to a mechanical ventilator, using its own ventilatory parameters used in both types of patients. For the neonatal, respiratory rate of 35rpm, inspiratory time of 0.45 and endotracheal tube of 3.0 mm. The pediatric lung will be ventilated with a volume between 100-120mL, 20-25 compliance and a 4.5mm orotracheal tube. The construction of the neonatal and pediatric mechanical lung will strongly add the teaching of the Neonatal and Pediatric Intensive Physical Therapy specialty in the Undergraduate and Graduate settings, adding value to the teaching and training of professionals.

ASSESSMENT OF RISK FACTORS FOR DEATH OF PATIENTS WITH COVID-19 REQUIRING MECHANICAL LUNG VENTILATION

Relevance: with the increasing incidence of COVID-19, it is clear that early detection of the risk of death in patients on mechanical lung ventilation can help ensure proper treatment planning and optimize health resources.Objectives of our study was to identify predictors of the risk of death in patients with COVID-19 who required mechanical ventilation.Material and methods: research design – retrospective, observational, multicenter. Inclusion criteria: clinical, laboratory, and radiological criteria for severe viral pneumonia. Exclusion criteria: death in the first 12 hours of hospitalization. End points: need for mechanical ventilation and death. One hundred and sixty-eight patients met the inclusion criteria. The number of patients who were given a ventilator was 69 (41,1%), 47 (68,1%) of them died. Risk factors were determined by calculating the odds ratio with a 95% confidence interval. The discriminative ability of factors was evaluated using ROC analysis with the calculation of the area under the curve (AUC ROC).Results: the most significant risk factors for require of mechanical ventilation in patients with COVID-19 were a large extent of changes in the lung parenchyma, more than 5 points of the SOFA scale and blood D-dimers >3000 ng/ml. Deceased patients were more likely to be men and initially had statistically significantly higher points of the SOFA scale, neutrophil-to-lymphocyte ratio, and blood interleukin 6 (IL-6) count >186 ng/ml. However, the discriminative ability of these risk factors was moderate (AUC ROC from 0.69 to 0.76). In deceased patients, there were no changes in the PaO2/FiO2 ratio, blood D-dimer count, and SOFA severity assessment in the first three days of intensive care.Conclusion: Predictors of the development of an unfavorable outcome of the disease with moderate discriminative ability in patients with severe COVID-19 on mechanical ventilation are an increased score on the SOFA scale, an increase of the neutrophil-lymphocyte ratio, high levels of D-dimers and IL-6 in the blood.

Patient-Ventilator Interaction Testing Using the Electro- mechanical Lung Simulator xPULM™during V/A-C and PSV Ventilation Mode

During mechanical ventilation, a disparity between flow, pressure or volume demands of the patient and the assistance delivered by the mechanical ventilator often occurs. Asynchrony effect and ventilator performance are frequently studied from ICU datasets or using commercially available lung simulators and test lungs. This paper introduces an alternative approach of simulating and evaluating patient-ventilator interactions with high fidelity using the electro-mechanical lung simulator xPULM™ under selected conditions. The xPULM™ approximates respiratory activities of a patient during alternating phases of spontaneous breathing and apnoea intervals while connected to a mechanical ventilator. Focusing on different triggering events, volume assist-controlled (V/A-C) and pressure support ventilation (PSV) modes were chosen to test patient-ventilator interactions. In V/A-C mode a double-triggering was detected every third breathing cycle leading to an asynchrony index of 16.67%, being classified as severe. This asynchrony causes a major increase of Peak Inspiratory Pressure PIP = 12.80 ± 1.39 cmH2O and Peak Expiratory Flow PEF = -18.33 ± 1.13 L/min when compared to synchronous phases of the breathing simulation. Additionally, events of premature cycling were observed during PSV mode. In this mode, the peak delivered volume during simulated spontaneous breathing phases almost doubles compared to apnoea phases. The presented approach demonstrates the possibility of simulating and evaluating disparities in fundamental ventilation characteristics caused by double-triggering and premature cycling under V/A-C and PSV ventilation modes. Various dynamic clinical situations can be approximated and could help to identify undesired patient-ventilation interactions in the future. Rapidly manufactured ventilator systems could also be tested using this approach.

Basic principles of neonatal bubble CPAP: effects on CPAP delivery and imposed work of breathing when altering the original design

BackgroundThe original bubble continuous positive airway pressure (bCPAP) design has wide-bore tubing and a low-resistance interface. This creates a stable airway pressure that is reflected by the submersion depth of the expiratory tubing. Several systems with alterations to the original bCPAP design are now available. Most of these are aimed for use in low-income and middle-income countries and have not been compared with the original design.ObjectiveWe identified three major alterations to the original bCPAP design: (1) resistance of nasal interface, (2) volume of dead space and (3) diameter of expiratory tubing. Our aim was to study the effect of these alterations on CPAP delivery and work of breathing in a mechanical lung model. Dead space should always be avoided and was not further tested.MethodsThe effect of nasal interface resistance and expiratory tubing diameter was evaluated with simulated breathing in a mechanical lung model without interface leakage. The main outcome was delivered CPAP and imposed work of breathing.ResultsHigh-resistance interfaces and narrow expiratory tubing increased the work of breathing. Additionally, narrow expiratory tubing resulted in higher CPAP levels than indicated by the submersion depth.ConclusionOur study shows the significant effect on CPAP delivery and imposed work of breathing when using high-resistance interfaces and narrow expiratory tubing in bCPAP systems. New systems should include low-resistance interfaces and wide-bore tubing and be compared with the original bCPAP. Referring to all systems that bubble as bCPAP is misleading and potentially hazardous.

Venous return and pulmonary hemodynamics under the positive end-expiratory pressure mechanical ventilation

In the review we have discussed the mechanisms of the changes of the venous return and pulmonary hemodynamics which take place in clinical cases of the mechanical lung ventilation with positive end-expiratory pressure. In these conditions the elevating of right atrial pressure does not cause the decreasing of the venous return, because the mean circulatory filling pressure also increases. Thus, the gradient for venous return remains relatively constant. In case of the mechanical lung ventilation with positive end-expiratory pressure the decreasing of the venous return is the result of the elevation of the venous resistance as consequence of the direct increasing of the intrathoracic and transdiaphragmatic pressures and activation of the reflectory neurogenic mechanisms. In the conditions, indicated above, the increased alveolar pressure leads to the improvement of the diffused lung capacity for oxygen, which decreases the manifestations of the hypoxic pulmonary vasoconstriction and thus diminishes pulmonary vascular resistance. The character of changes of the last one is determined by the reactions of the two types (alveolar and extraalveolar) intraparenchimal pulmonary vessels. This leads to the changes of the resistive and capacitive functions of the pulmonary vessels. In case of the high levels of the positive end-expiratory pressure (more than 30 cm of water column) the value of alveolar pressure is comparable or even more excessive than pulmonary artery pressure (1216 mm Hg), which can be the reason of the decreasing of the right ventricular contractility and the venous return. The increasing of the capillary filtration coefficient of pulmonary vessels in the conditions of the mechanical lung ventilation with positive end-expiratory pressure can be the result of the activation of the mechanosensitive transient receptor potential vanilloid-4 (TRPV4) channels and the increasing endothelial calcium entry.

Electro-mechanical Lung Simulator Using Polymer and Organic Human Lung Equivalents for Realistic Breathing Simulation

Simulation models in respiratory research are increasingly used for medical product development and testing, especially because in-vivo models are coupled with a high degree of complexity and ethical concerns. This work introduces a respiratory simulation system, which is bridging the gap between the complex, real anatomical environment and the safe, cost-effective simulation methods. The presented electro-mechanical lung simulator, xPULM, combines in-silico, ex-vivo and mechanical respiratory approaches by realistically replicating an actively breathing human lung. The reproducibility of sinusoidal breathing simulations with xPULM was verified for selected breathing frequencies (10–18 bpm) and tidal volumes (400–600 ml) physiologically occurring during human breathing at rest. Human lung anatomy was modelled using latex bags and primed porcine lungs. High reproducibility of flow and pressure characteristics was shown by evaluating breathing cycles (nTotal = 3273) with highest standard deviation |3σ| for both, simplified lung equivalents ($${{\boldsymbol{\mu }}}_{\dot{{\bf{V}}}}$$µV̇ = 23.98 ± 1.04 l/min, μP = −0.78 ± 0.63 hPa) and primed porcine lungs ($${{\boldsymbol{\mu }}}_{\dot{{\bf{V}}}}$$µV̇ = 18.87 ± 2.49 l/min, μP = −21.13 ± 1.47 hPa). The adaptability of the breathing simulation parameters, coupled with the use of porcine lungs salvaged from a slaughterhouse process, represents an advancement towards anatomically and physiologically realistic modelling of human respiration.