Automatic air volume control system for ventilation of two patients using a single ventilator: a large animal model study.

The COVID-19 pandemic outbreak led to a global ventilator shortage. Hence, various strategies for using a single ventilator to support multiple patients have been considered. A device called Ventil previously validated for independent lung ventilation was used in this study to evaluate its usability for shared ventilation. We performed experiments with a total number of 16 animals. Eight pairs of pigs were ventilated by a ventilator or anesthetic machine and by Ventil for up to 27 h. In one experiment, 200 ml of saline was introduced to one subject's lungs to reduce their compliance. The experiments were analyzed in terms of arterial blood gases and respiratory parameters. In addition to the animal study, we performed a series of laboratory experiments with artificial lungs (ALs). The resistance and compliance of one AL (affected) were altered, while the tidal volume (TV) and peak pressure (Ppeak) in the second (unaffected) AL were analyzed. In addition, to assess the risk of transmission of pathogens between AL respiratory tracts, laboratory tests were performed using phantoms of virus particles. The physiological level of analyzed parameters in ventilated animals was maintained, except for CO2 tension, for which a permissive hypercapnia was indicated. Experiments did not lead to injuries in the animal's lungs except for one subject, as indicated by CT scan analysis. In laboratory experiments, changes in TV and Ppeak in the unaffected AL were less than 11%, except for 2 cases where the TV change was 20%. No cross-contamination was found in simulations of pathogen transmission. We conclude that ventilation using Ventil can be considered safe in patients undergoing deep sedation without spontaneous breathing efforts.

The impact of spontaneous cough on pleural pressure changes during therapeutic thoracentesis.

Cough during therapeutic thoracentesis (TT) is considered an adverse effect. The study was aimed to evaluate the relationship between cough during TT and pleural pressure (Ppl) changes (∆P). Instantaneous Ppl was measured after withdrawal of predetermined volumes of pleural fluid. Fluid withdrawal (FW) and Ppl measurement (PplM) periods were analyzed separately using the two sample Kolmogorov-Smirnov test and the nonparametric skew to assess differences between ∆P distributions in periods with and without cough. The study involved 59 patients, median age 66 years, median withdrawn fluid volume 1800 mL (1330 ÷ 2400 mL). In total, 1265 cough episodes were recorded in 52 patients, in 24% of FW and 19% of PplM periods, respectively. Cough was associated with significant changes in ∆P distribution (p < 0.001), decreasing the left tail of ∆P distribution for FW periods (the skew = - 0.033 vs. - 0.182) and increasing the right tail for PplM periods (the skew = 0.182 vs. 0.088). Although cough was more frequent in 46 patients with normal pleural elastance (p < 0.0001), it was associated with significantly higher ∆P in patients with elevated elastance (median Ppl increase 2.9 vs. 0.2 cmH2O, respectively). Cough during TT is associated with small but beneficial trend in Ppl changes, particularly in patients with elevated pleural elastance, and should not be considered solely as an adverse event.

Impact of therapeutic thoracentesis and pleural pressure changes on breathing pattern, dyspnea, lung function, and arterial blood gases.

INTRODUCTION: Therapeutic thoracentesis is highly effective in providing symptomatic improvement in patients with large volume pleural effusion (PE). However, some physiological effects of pleural fluid (PF) withdrawal are still not fully elucidated. OBJECTIVES: The study aimed to evaluate alterations in the breathing pattern, pulmonary function, and arterial blood gases (ABG) in relation to both withdrawn PF volume and pleural pressure (Ppl) changes in patients undergoing therapeutic thoracentesis. PATIENTS AND METHODS: This prospective, observational, cross­sectional study included 37 patients with large volume PE. Respiratory rate (RR), dyspnea, pulmonary function, and ABG were assessed before the thoracentesis, at the termination of the PF withdrawal and 1, 3, and 24 hours after the procedure. The volume of PF drained, Ppl, and tidal volume (TV) were monitored during the thoracentesis. RESULTS: Thoracentesis resulted in a transient but significant increase in RR directly after the procedure, and a transient decrease, followed by subsequent increase in TV. There was a significant and constant increase in forced vital capacity up to 24 hours after thoracentesis (P = 0.001). Oxygen partial pressure (PaO2) significantly improved directly after PF withdrawal (P = 0.01) and returned to baseline values after 24 hours. Thoracentesis was invariably associated with a significant increase in the amplitude of Ppl (Ppl_ampl) changes during the respiratory cycle (P <0.001). CONCLUSIONS: Therapeutic thoracentesis results in a modest improvement in pulmonary function, tran-sient increase in PaO2 and increase in Ppl_ampl. The improvement in pulmonary function and ABG is closely related to the volume of PF drained and pleural elastance. The increase in Ppl_ampl probably represents a more efficient work of the respiratory muscles.

Independent Lung Ventilation-Experimental Studies on a 3D Printed Respiratory Tract Model.

Independent lung ventilation (ILV) is a life-saving procedure in unilateral pulmonary pathologies. ILV is underused in clinical practice, mostly due to the technically demanding placement of a double lumen endotracheal tube (ETT). Moreover, the determination of ventilation parameters for each lung in vivo is limited. In recent years, the development of 3D printing techniques enabled the production of highly accurate physical models of anatomical structures used for in vitro research, considering the high risk of in vivo studies. The purpose of this study was to assess the influence of double-lumen ETT on the gas transport and mixing in the anatomically accurate 3D-printed model of the bronchial tree, with lung lobes of different compliances, using various ventilation modes. The bronchial tree was obtained from Respiratory Drug Delivery (RDD Online, Richmond, VA, USA), processed and printed by a dual extruder FFF 3D printer. The test system was also composed of left side double-lumen endotracheal tube, Siemens Test Lung 190 and anesthetic breathing bag (as lobes). Pressure and flow measurements were taken at the outlets of the secondary bronchus. The measured resistance increased six times in the presence of double-lumen ETT. Differences between the flow distribution to the less and more compliant lobe were more significant for the airways with double-lumen ETT. The ability to predict the actual flow distribution in model airways is necessary to conduct effective ILV in clinical conditions.

A Compliant Model of the Ventricular Apex to Study Suction in Ventricular Assist Devices.

Ventricular suction is a frequent adverse event in patients with a ventricular assist device (VAD). This study presents a suction module (SM) embedded in a hybrid (hydraulic-computational) cardiovascular simulator suitable for the testing of VADs and related suction events. The SM consists of a compliant latex tube reproducing a simplified ventricular apex. The SM is connected on one side to a hydraulic chamber of the simulator reproducing the left ventricle, and on the other side to a HeartWare HVAD system. The SM is immersed in a hydraulic chamber with a controllable pressure to occlude the compliant tube and activate suction. Two patient profiles were simulated (dilated cardiomyopathy and heart failure with preserved ejection fraction), and the circulating blood volume was reduced stepwise to obtain different preload levels. For each simulated step, the following data were collected: HVAD flow, ventricular pressure and volume, and pressure at the inflow cannula. Data collected for the two profiles and for decreasing preload levels evidenced suction profiles differing in terms of frequency (intermittent vs. every heart beat), amplitude (partial or complete stoppage of the HVAD flow), and shape. Indeed different HVAD flow patterns were observed for the two patient profiles because of the different mechanical properties of the simulated ventricles. Overall, the HVAD flow patterns showed typical indicators of suctions observed in clinics. Results confirmed that the SM can reproduce suction phenomena with VAD under different pathophysiological conditions. As such, the SM can be used in the future to test VADs and control algorithms aimed at preventing suction phenomena.

Pleural Pressure Pulse in Patients with Pleural Effusion: A New Phenomenon Registered during Thoracentesis with Pleural Manometry.

Pleural manometry enables the assessment of physiological abnormalities of lung mechanics associated with pleural effusion. Applying pleural manometry, we found small pleural pressure curve oscillations resembling the pulse tracing line. The aim of our study was to characterize the oscillations of pleural pressure curve (termed here as the pleural pressure pulse, PPP) and to establish their origin and potential significance. This was an observational cross-sectional study in adult patients with pleural effusion who underwent thoracentesis with pleural manometry. The pleural pressure curves recorded prior to and during fluid withdrawal were analyzed. The presence of PPP was assessed in relation to the withdrawn pleural fluid volume, lung expandability, vital and echocardiographic parameters, and pulmonary function testing. A dedicated device was developed to compare the PPP to the pulse rate. Fifty-four patients (32 women) median age 66.5 (IQR 58.5-78.7) years were included. Well visible and poorly visible pressure waves were detected in 48% and 35% of the patients, respectively. The frequency of PPP was fully concordant with the pulse rate and the peaks of the oscillations reflected the period of heart diastole. PPP was more visible in patients with a slower respiratory rate (p = 0.008), a larger amount of pleural effusion, and was associated with a better heart systolic function assessed by echocardiography (p < 0.05). This study describes a PPP, a new pleural phenomenon related to the cyclic changes in the heart chambers volume. Although the importance of PPP remains largely unknown, we hypothesize that it could be related to lung atelectasis or lower lung and visceral pleura compliance.

The use of a virtual patient to follow changes in arterial blood gases associated with therapeutic thoracentesis.

PURPOSES:: Some controversies exist on the effect of therapeutic thoracentesis (TT) on arterial blood oxygen tension. The aim of this study was to evaluate this issue using a previously developed virtual patient. METHODS:: The analysis was based and supported by clinical data collected during 36 TT. Pleural pressure and transcutaneous oxygen and carbon dioxide pressures (PtcO2 and PtcCO2) were measured during pleural fluid withdrawal. Arterial blood oxygen tension and arterial CO2 tension (PaO2 and PaCO2) were analysed in simulations that mimicked TT. Minute ventilation was adjusted to maintain arterial CO2 tension at a constant level unless arterial blood oxygen tension fell below 8 kPa. Specifically, the influence of hypoxic pulmonary vasoconstriction efficiency was tested. RESULTS:: In patients, PtcCO2 remained at an approximately constant level (average amplitude: 0.63 ± 0.29 kPa), while some fluctuations of PtcO2 were observed (amplitude: (1.65 ± 1.18 kPa) were observed. In 42% of patients, TT was associated with decrease in PtcCO2. Simulations showed the following: (a) there were similar PaO2 fluctuations in the virtual patient; (b) the lower the hypoxic pulmonary vasoconstriction efficiency, the more pronounced the PaO2 fall during fluid withdrawal; and (c) the lower the atelectatic lung areas recruitment rate, the slower the PaO2 normalization. The decrease in PaO2 was caused by an increase of pulmonary shunt. CONCLUSION:: Therapeutic thoracentesis may cause both an increase and a decrease in PaO2 during the procedure. Pleural pressure decrease, caused by pleural fluid withdrawal, improves the perfusion of atelectatic lung areas. If the rate of recruitment of these areas is low, a lack of ventilation causes the arterial blood oxygen tension to fall. Effective hypoxic pulmonary vasoconstriction may protect against the pulmonary shunt.

Patterns of pleural pressure amplitude and respiratory rate changes during therapeutic thoracentesis.

BACKGROUND: Although the impact of therapeutic thoracentesis on lung function and blood gases has been evaluated in several studies, some physiological aspects of pleural fluid withdrawal remain unknown. The aim of the study was to assess the changes in pleural pressure amplitude (Pplampl) during the respiratory cycle and respiratory rate (RR) in patients undergoing pleural fluid withdrawal. METHODS: The study included 23 patients with symptomatic pleural effusion. Baseline pleural pressure curves were registered with a digital electronic manometer. Then, the registrations were repeated after the withdrawal of consecutive portions of pleural fluid (200 ml up to 1000 ml and 100 ml above 1000 ml). In all patients the pleural pressure curves were analyzed in five points, at 0, 25%, 50%, 75% and 100% of the relative volume of pleural effusion withdrawn in particular patients. RESULTS: There were 11 and 12 patients with right sided and left sided pleural effusion, respectively (14 M, 9F, median age 68, range 46-85 years). The most common cause of pleural effusion were malignancies (20 pts., 87%). The median total volume of withdrawn pleural fluid was 1800 (IQR 1500-2400) ml. After termination of pleural fluid withdrawal Pplampl increased in 22/23 patients compared to baseline. The median Pplampl increased from 3.4 (2.4-5.9) cmH2O to 10.7 (8.1-15.6) cmH2O (p < 0.0001). Three patterns of Pplampl changes were identified. Although the patterns of RR changes were more diversified, a significant increase between RR at baseline and the last measurement point was found (p = 0.0097). CONCLUSIONS: In conclusion, therapeutic thoracentesis is associated with significant changes in Pplampl during the respiratory cycle. In the vast majority of patients Pplampl increased steadily during pleural fluid withdrawal. There was also an increase in RR. The significance of these changes should be elucidated in further studies. TRIAL REGISTRATION: ClinicalTrial.gov, registration number: NCT02192138 , registration date: July 1st, 2014.

The use of a virtual patient to follow pleural pressure changes associated with therapeutic thoracentesis.

PURPOSE: Influence of therapeutic thoracentesis on the pleural pressure (Pp) has been discussed in many clinical studies, however reasons of Pp changes are not precisely established. The aim of the study was to use a previously elaborated virtual cardiopulmonary patient (VP) in analysis of impact of physiological factors on Pp during the procedure. METHODS: Simulations were performed on VP with default values of parameters for which VP simulated the respiratory system of the average 50-year-old healthy Polish woman according to spirometric examination. Alterations of Pp and the amplitude of Pp changes related to breathing (AP) were analyzed. Model parameters related to chosen factors were deviated from their default values to analyze the degree of their impact on Pp and AP. The analysis was based on and supported by our own clinical data. RESULTS: The Pp and AP alteration intensity appeared to be most sensitive to the compliances of the rib cage and mediastinum, and the nonlinearity of the dependence between the recoil pressure and the lung volume: the lower the compliances and the higher the nonlinearity were, the deeper the Pp fall during the procedure and the bigger the AP increase were observed. CONCLUSIONS: Experiments in silico are very useful in analyzing sophisticated physiological and medical problems. They made it possible to show which factors are particularly responsible for changes in Pp during thoracentesis. In the future, they may be useful in establishing objective conditions under which thoracentesis needs to be stopped.

Photoactive protochlorophyllide-enzyme complexes reconstituted with PORA, PORB and PORC proteins of A. thaliana: fluorescence and catalytic properties.

Photoactive Pchlide-POR-NADPH complexes were reconstituted using protochlorophyllide (Pchlide) and recombinant light-dependent protochlorophyllide oxidoreductase (POR) proteins, His6-PORA, His6-PORB and His6-PORC, from Arabidopsis thaliana. We did not observe any differences in the kinetics of the protochlorophyllide photoreduction at room temperature among the PORA, PORB and PORC proteins. In contrast, the PORC protein showed lower yield of Chlide formation than PORA and PORB when preincubated in the dark for 30 min and then illuminated for a short time. The most significant observation was that reconstituted Pchlide-POR-NADPH complexes showed fluorescence maxima at 77 K similar to those observed for highly aggregated Pchlide-POR-NADPH complexes in prolamellar bodies (PLBs) in vivo. Homology models of PORA, PORB and PORC of Arabidopsis thaliana were developed to compare predicted structures of POR isoforms. There were only slight structural differences, mainly in the organisation of helices and loops, but not in the shape of whole molecules. This is the first comparative analysis of all POR isoforms functioning at different stages of A. thaliana development.

Initial stages of angiosperm greening monitored by low-temperature fluorescence spectra and fluorescence lifetimes.

In Angiosperms, the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide), a penultimate reaction of chlorophyll biosynthesis, is catalyzed by a photoenzyme Pchlide oxidoreductase (POR) and completely inhibited in darkness. This reaction plays also a regulatory role in plant morphogenesis. In the case of dark-grown Angiosperms, Pchlide is accumulated, mainly in the form of complexes with NADPH and POR but also as an unbound pigment. Etioplasts that develop in the place of chloroplasts in the dark contain a highly organized lipid structure termed prolamellar body (PLB), which is the main site of accumulation of the ternary Pchlide:POR:NADPH complexes. An illumination triggers the photoreduction of Pchlide molecules which are bound to the ternary complexes. This is followed by a set of biochemical reactions and structural changes leading to Chl synthesis that can be monitored with fluorescence techniques. This chapter describes the application of low-temperature fluorescence spectroscopy and fluorescence lifetime measurements for monitoring the Pchlide to Chlide conversion in isolated prolamellar bodies. These techniques enable the analysis of heterogeneity of accumulated pigments: Pchlide and Chlide that reflect the different organization of pigment-protein complexes.

Electroporation-induced changes in normal immature rat myoblasts (H9C2).

Application of a high electric field causes an electric shock to the heart. This is utilized in defibrillation to reestablish normal contraction rhythms during dangerous arrhythmias or in cardiac arrest. If shock-induced transmembrane potentials are large enough, they can cause tissue destruction due to irreversible electroporation (EP). Also electrochemotherapy of nearby tissues may have an adverse effect on the heart. Herein, we present experimental data on effects of electroporation in culture of cardiac cells (H9C2). The electric field was applied in short pulses of 25-3250 V/cm, 50 µs each. The viability of cells was tested by MTT assay after 24 hours. For detection of DNA fragmentation, associated with apoptosis, alkaline and neutral comet assays were performed after EP. Additionally phase contrast images of cells obtained directly after EP were analyzed. Although cell images indicated disruption of cell membranes after EP with high intensities, only a few percent of apoptotic cells and no necrotic effects in the cell nucleus could be observed in comet assay tests performed 2 hours post EP. MTT viability test showed that pulse intensities above 375 V/cm are destructive for myocytes viability.