269 research outputs found
A mock circulation loop to test extracorporeal CO2 elimination setups
Background: Extracorporeal carbon dioxide removal (ECCO2R) is a promising yet
limited researched therapy for hypercapnic respiratory failure in acute respiratory
distress syndrome and exacerbated chronic obstructive pulmonary disease. Herein,
we describe a new mock circuit that enables experimental ECCO2R research without
animal models. In a second step, we use this model to investigate three experimental
scenarios of ECCO2R: (I) the influence of hemoglobin concentration on CO2 removal. (II)
a potentially portable ECCO2R that uses air instead of oxygen, (III) a low-flow ECCO2R
that achieves effective CO2 clearance by recirculation and acidification of the limited
blood volume of a small dual lumen cannula (such as a dialysis catheter).
Results: With the presented ECCO2R mock, CO2 removal rates comparable to previous
studies were obtained. The mock works with either fresh porcine blood or diluted
expired human packed red blood cells. However, fresh porcine blood was preferred
because of better handling and availability. In the second step of this work, hemoglobin
concentration was identified as an important factor for CO2 removal. In the second
scenario, an air-driven ECCO2R setup showed only a slightly lower CO2 wash-out than the
same setup with pure oxygen as sweep gas. In the last scenario, the low-flow ECCO2R,
the blood flow at the test membrane lung was successfully raised with a recirculation
channel without the need to increase cannula flow. Low recirculation ratios resulted in
increased efficiency, while high recirculation ratios caused slightly reduced CO2 removal
rates. Acidification of the CO2 depleted blood in the recirculation channel caused an
increase in CO2 removal rate.
Conclusions: We demonstrate a simple and cost effective, yet powerful, âin-vitroâ
ECCO2R model that can be used as an alternative to animal experiments for many
research scenarios. Moreover, in our approach parameters such as hemoglobin level can
be modified more easily than in animal models
New Materials and Structures for Transistors based on Spin, Charge and Wavefunction Phase Control
Exposure of patients to di(2-ethylhexy)phthalate (DEHP) and its metabolite MEHP during extracorporeal membrane oxygenation (ECMO) therapy
The plasticizer di(2-ethylhexyl)phthalate (DEHP) is often used for PVC medical devices, that are also largely used for intensive care medical treatments, like extracorporeal membrane oxygenation (ECMO) therapy. Due to the toxicological potential of DEHP, the inner exposure of patients with this plasticizer is a strong matter of concern as many studies have shown a high leaching potential of DEHP into blood. In this study, the inner DEHP exposure of patients undergoing ECMO treatment was investigated. The determined DEHP blood levels of ECMO patients and the patients of the control group ranged from 31.5 to 1009 ÎŒg/L (median 156.0 ÎŒg/L) and from 19.4 to 75.3 ÎŒg/L (median 36.4 ÎŒg/L), respectively. MEHP blood levels were determined to range from < LOD to 475 ÎŒg/L (median 15.9 ÎŒg/L) in ECMO patients and from < LOD to 9.9 ÎŒg/L (median 3.7 ÎŒg/L) in the control group patients, respectively. Increased DEHP exposure was associated with the number of cannulas and membranes of the ECMO setting, whereas residual diuresis decreased the exposure. Due to the suspected toxicological potential of DEHP, its use in medical devices should be further investigated, in particular for ICU patients with long-term exposure to PVC, like in ECMO therapy
Comparison of Serial and Parallel Connections of Membrane Lungs against Refractory Hypoxemia in a Mock Circuit
Extracorporeal membrane oxygenation (ECMO) is an important rescue therapy method
for the treatment of severe hypoxic lung injury. In some cases, oxygen saturation and oxygen partial
pressure in the arterial blood are low despite ECMO therapy. There are case reports in which patients
with such instances of refractory hypoxemia received a second membrane lung, either in series or in
parallel, to overcome the hypoxemia. It remains unclear whether the parallel or serial connection
is more effective. Therefore, we used an improved version of our full-flow ECMO mock circuit to
test this. The measurements were performed under conditions in which the membrane lungs were
unable to completely oxygenate the blood. As a result, only the photometric pre- and post-oxygenator
saturations, blood flow and hemoglobin concentration were required for the calculation of oxygen
transfer rates. The results showed that for a pre-oxygenator saturation of 45% and a total blood flow of
10 L/min, the serial connection of two identical 5 L rated oxygenators is 17% more effective in terms
of oxygen transfer than the parallel connection. Although the idea of using a second membrane lung
if refractory hypoxia occurs is intriguing from a physiological point of view, due to the invasiveness
of the solution, further investigations are needed before this should be used in a wider clinical setting
Respiratory Physiology of COVID-19 and Influenza Associated Acute Respiratory Distress Syndrome
There is ongoing debate whether lung physiology of COVID-19-associated
acute respiratory distress syndrome (ARDS) differs from ARDS of other origin. Objective: The aim
of this study was to analyze and compare how critically ill patients with COVID-19 and Influenza
A or B were ventilated in our tertiary care center with or without extracorporeal membrane oxygenation (ECMO). We ask if acute lung failure due to COVID-19 requires different intensive care
management compared to conventional ARDS. Methods: 25 patients with COVID-19-associated
ARDS were matched to a cohort of 25 Influenza patients treated in our center from 2011 to 2021.
Subgroup analysis addressed whether patients on ECMO received different mechanical ventilation
than patients without extracorporeal support. Results: Compared to Influenza-associated ARDS,
COVID-19 patients had higher ventilatory system compliance (40.7 mL/mbar [31.8â46.7 mL/mbar]
vs. 31.4 mL/mbar [13.7â42.8 mL/mbar], p = 0.198), higher ventilatory ratio (1.57 [1.31â1.84] vs. 0.91
[0.44â1.38], p = 0.006) and higher minute ventilation at the time of intubation (mean minute ventilation 10.7 L/min [7.2â12.2 L/min] for COVID-19 vs. 6.0 L/min [2.5â10.1 L/min] for Influenza,
p = 0.013). There were no measurable differences in P/F ratio, positive end-expiratory pressure
(PEEP) and driving pressures (âP). Respiratory system compliance deteriorated considerably in
COVID-19 patients on ECMO during 2 weeks of mechanical ventilation (Crs, mean decrease over
2 weeks â23.87 mL/mbar ± 32.94 mL/mbar, p = 0.037) but not in ventilated Influenza patients on
ECMO and less so in ventilated COVID-19 patients without ECMO. For COVID-19 patients, low
driving pressures on ECMO were strongly correlated to a decline in compliance after 2 weeks
(Pearsonâs R 0.80, p = 0.058). Overall mortality was insignificantly lower for COVID-19 patients
compared to Influenza patients (40% vs. 48%, p = 0.31). Outcome was insignificantly worse for
patients requiring veno-venous ECMO in both groups (50% mortality for COVID-19 on ECMO
vs. 27% without ECMO, p = 0.30/56% vs. 34% mortality for Influenza A/B with and without
ECMO, p = 0.31). Conclusion: The pathophysiology of early COVID-19-associated ARDS differs
from Influenza-associated acute lung failure by sustained respiratory mechanics during the early
phase of ventilation. We question whether intubated COVID-19 patients on ECMO benefit from
extremely low driving pressures, as this appears to accelerate derecruitment and consecutive loss of
ventilatory system compliance
Comparison of Circular and Parallel-Plated Membrane Lungs for Extracorporeal Carbon Dioxide Elimination
Extracorporeal carbon dioxide removal (ECCO2R) is an important technique to treat critical lung diseases such as exacerbated chronic obstructive pulmonary disease (COPD) and mild or
moderate acute respiratory distress syndrome (ARDS). This study applies our previously presented
ECCO2R mock circuit to compare the CO2 removal capacity of circular versus parallel-plated membrane lungs at different sweep gas flow rates (0.5, 2, 4, 6 L/min) and blood flow rates (0.3 L/min,
0.9 L/min). For both designs, two low-flow polypropylene membrane lungs (Medos Hilte 1000,
Quadrox-i Neonatal) and two mid-flow polymethylpentene membrane lungs (Novalung Minilung,
Quadrox-iD Pediatric) were compared. While the parallel-plated Quadrox-iD Pediatric achieved the
overall highest CO2 removal rates under medium and high sweep gas flow rates, the two circular
membrane lungs performed relatively better at the lowest gas flow rate of 0.5 L/min. The low-flow
Hilite 1000, although overall better than the Quadrox i-Neonatal, had the most significant advantage
at a gas flow of 0.5 L/min. Moreover, the circular Minilung, despite being significantly less efficient
than the Quadrox-iD Pediatric at medium and high sweep gas flow rates, did not show a significantly
worse CO2 removal rate at a gas flow of 0.5 L/min but rather a slight advantage. We suggest that
circular membrane lungs have an advantage at low sweep gas flow rates due to reduced shunting as
a result of their fiber orientation. Efficiency for such low gas flow scenarios might be relevant for
possible future portable ECCO2R devices
A Novel Mock Circuit to Test Full-Flow Extracorporeal Membrane Oxygenation
Extracorporeal membrane oxygenation (ECMO) has become an important therapeutic
approach in the COVID-19 pandemic. The development and research in this field strongly relies on
animal models; however, efforts are being made to find alternatives. In this work, we present a new
mock circuit for ECMO that allows measurements of the oxygen transfer rate of a membrane lung at
full ECMO blood flow. The mock utilizes a large reservoir of heparinized porcine blood to measure the
oxygen transfer rate of the membrane lung in a single passage. The oxygen transfer rate is calculated
from blood flow, hemoglobin value, venous saturation, and post-membrane arterial oxygen pressure.
Before the next measuring sequence, the blood is regenerated to a venous condition with a sweep
gas of nitrogen and carbon dioxide. The presented mock was applied to investigate the effect of a
recirculation loop on the oxygen transfer rate of an ECMO setup. The recirculation loop caused a
significant increase in post-membrane arterial oxygen pressure (paO2
). The effect was strongest for
the highest recirculation flow. This was attributed to a smaller boundary layer on gas fibers due to
the increased blood velocity. However, the increase in paO2 did not translate to significant increases
in the oxygen transfer rate because of the minor significance of physically dissolved oxygen for gas
transfer. In conclusion, our results regarding a new ECMO mock setup demonstrate that recirculation
loops can improve ECMO performance, but not enough to be clinically relevant
Acute Respiratory Distress Syndrome due to Mycoplasma pneumoniae Misinterpreted as SARS-CoV-2 Infection
Background. In 2020, a novel coronavirus caused a global pandemic with a clinical picture termed COVID-19, accounting for numerous cases of ARDS. However, there are still other infectious causes of ARDS that should be considered, especially as the majority of these pathogens are specifically treatable. Case Presentation. We present the case of a 36-year-old gentleman who was admitted to the hospital with flu-like symptoms, after completing a half-marathon one week before admission. As infection with SARS-CoV-2 was suspected based on radiologic imaging, the hypoxemic patient was immediately transferred to the ICU, where he developed ARDS. Empiric antimicrobial chemotherapy was initiated, the patient deteriorated further, therapy was changed, and the patient was transferred to a tertiary care ARDS center. As cold agglutinins were present, the hypothesis of an infection with SARS-CoV-2 was then questioned. Bronchoscopic sampling revealed Mycoplasma (M.) pneumoniae. When antimicrobial chemotherapy was adjusted, the patient recovered quickly. Conclusion. Usually, M. pneumoniae causes mild disease. When antimicrobial chemotherapy was adjusted, the patient recovered quickly. The case underlines the importance to adhere to established treatment guidelines, scrutinize treatment modalities, and not to forget other potential causes of severe pneumonia or ARDS
Antibiotic therapeutic drug monitoring in intensive care patients treated with different modalities of extracorporeal membrane oxygenation (ECMO) and renal replacement therapy: a prospective, observational single-center study
Background: Efective antimicrobial treatment is key to reduce mortality associated with bacterial sepsis in patients
on intensive care units (ICUs). Dose adjustments are often necessary to account for pathophysiological changes or
renal replacement therapy. Extracorporeal membrane oxygenation (ECMO) is increasingly being used for the treatment of respiratory and/or cardiac failure. However, it remains unclear whether dose adjustments are necessary to
avoid subtherapeutic drug levels in septic patients on ECMO support. Here, we aimed to evaluate and comparatively
assess serum concentrations of continuously applied antibiotics in intensive care patients being treated with and
without ECMO.
Methods: Between October 2018 and December 2019, we prospectively enrolled patients on a pneumological
ICU in southwest Germany who received antibiotic treatment with piperacillin/tazobactam, ceftazidime, meropenem, or linezolid. All antibiotics were applied using continuous infusion, and therapeutic drug monitoring of serum
concentrations (expressed as mg/L) was carried out using high-performance liquid chromatography. Target concentrations were defned as fourfold above the minimal inhibitory concentration (MIC) of susceptible bacterial isolates,
according to EUCAST breakpoints
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