Three bedside techniques to quantify dynamic pulmonary hyperinflation in mechanically ventilated patients with chronic obstructive pulmonary disease

Background Dynamic pulmonary hyperinflation may develop in patients with chronic obstructive pulmonary disease (COPD) due to dynamic airway collapse and/or increased airway resistance, increasing the risk of volutrauma and hemodynamic compromise. The reference standard to quantify dynamic pulmonary hyperinflation is the measurement of the volume at end-inspiration (Vei). As this is cumbersome, the aim of this study was to evaluate if methods that are easier to perform at the bedside can accurately reflect Vei. Methods Vei was assessed in COPD patients under controlled protective mechanical ventilation (7 ± mL/kg) on zero end-expiratory pressure, using three techniques in a fixed order: (1) reference standard (Veireference): passive exhalation to atmosphere from end-inspiration in a calibrated glass burette; (2) ventilator maneuver (Veimaneuver): measuring the expired volume during a passive exhalation of 45s using the ventilator flow sensor; (3) formula (Veiformula): (Vt × Pplateau)/(Pplateau − PEEPi), with Vt tidal volume, Pplateau is plateau pressure after an end-inspiratory occlusion, and PEEPi is intrinsic positive end-expiratory pressure after an end-expiratory occlusion. A convenience sample of 17 patients was recruited. Results Veireference was 1030 ± 380 mL and had no significant correlation with Pplateau (r2 = 0.06; P = 0.3710) or PEEPi (r2 = 0.11; P = 0.2156), and was inversely related with Pdrive (calculated as Pplateau −PEEPi) (r2 = 0.49; P = 0.0024). A low bias but rather wide limits of agreement and fairly good correlations were found when comparing Veimaneuver and Veiformula to Veireference. Vei remained stable during the study period (low bias 15 mL with high agreement (95% limits of agreement from − 100 to 130 mL) and high correlation (r2 = 0.98; P < 0.0001) between both measurements of Veireference). Conclusions In patients with COPD, airway pressures are not a valid representation of Vei. The three techniques to quantify Vei show low bias, but wide limits of agreement.

Effect of Dissolution Temperature on Purity of LaNi5 Powder Synthesized with the Combustion-Reduction Method

The LaNi5 intermetallic phase has been extensively investigated because of its excellent properties, such as attractive hydrogen storage, medium plateau pressure, and easy activation. LaNi5 phase is generally produced by a complicated method, which involves several steps, i.e. melting, alloying, casting, softening and making them into powder. This study aimed to develop a new LaNi5 synthesis process by modifying the combustion-reduction method. In this method it is very important to produce La2NiO4, because LaNi5 is formed from the process of reducing this phase. The precursor powders La(NO3)3.6H2O and Ni(NO3)2.6H2O were reacted with distilled water as a solvent medium and mixed using magnetic stirring. The synthesis process was carried out at room temperature, 60 °C, 70 °C, and 80 °C for 10 minutes until the solution became transparent green. The solution was then dried for 2 hours at 100 °C to form a transparent green gel. The gel was calcined at a temperature of 500 °C for 2 hours, producing a black powder. The optimal black powder was then reduced using CO gas at 600 °C for 2 hours. The powder samples were characterized using XRD, FTIR, and SEM-EDX. The analysis revealed that synthesis at room temperature was the most optimal method for the reduction process because it produced the most La2NiO4, at 12.135 wt%.

Clinical Characteristics Between Survivors and Nonsurvivors of COVID-19 Patients Requiring Extracorporeal Membrane Oxygenation (ECMO) Support: A Systematic Review and Meta-Analysis

Background: The use of extracorporeal membrane oxygenation (ECMO) in coronavirus disease 2019 (COVID-19) for refractory respiratory failure, severe cardiac dysfunction, and bridge to lung transplantation has been steadily increasing during the ongoing global pandemic. Objective: Our meta-analysis aims to compare the clinical characteristics between COVID-19 survivors and nonsurvivors requiring ECMO support. Methods: A systematic search of Pubmed, Cochrane, Embase, Scopus, and Web of Science databases was performed between December first, 2019, to June first, 2021. Studies with comparative data of COVID-19 ECMO patients were selected, in which clinical characteristics and complications were assessed. Results: Sixteen cohort studies involving 706 COVID-19 patients requiring ECMO support with pooled mortality rate of 40% were included. Younger age (mean 51 years vs 55 years; P < .001), fewer comorbidities (23% vs 31%; odds ratio [OR] 0.55; P = .02), and less renal replacement therapy (RRT) (21% vs 39%; OR 0.41; P = .007) and vasopressor (76% vs 92%; OR 0.35; P = .008) requirement were demonstrated in COVID-19 survivors requiring ECMO support than nonsurvivors. Survivors also had higher pre-ECMO pH (mean 7.33 vs 7.26; P < .001) than nonsurvivors. No difference was observed in gender, body mass index, duration of mechanical ventilation (MV) before ECMO support initiation, total ECMO support duration, and pre-ECMO parameters of PaO2/FiO2 ratio, tidal volume (mL/kg), positive end-expiratory pressure, and plateau pressure. The rate of bleeding complications was lower in survivors (32% vs 59%; OR 0.36; P = .001) than nonsurvivors, but no difference was observed in thromboembolism and secondary infections. Conclusions: We found advanced age, multiple comorbidities, lower pre-ECMO pH, greater RRT, and vasopressor requirements, and bleeding are predictors of death in COVID-19 patients requiring ECMO support. The duration of MV before ECMO support initiation and total ECMO support duration was similar among survivors and nonsurvivors. Our study results have important clinical implications when considering ECMO support in critically ill COVID-19 patients.

Shock Due to an Obstructed Endotracheal Tube

Endotracheal tube obstruction by a mucus plug causing a ball-valve effect is a rare but significant complication. The inability to pass a suction catheter through the endotracheal tube with high peak and plateau pressure differences are classical features of an endotracheal tube obstruction. A case is described of endotracheal tube obstruction from a mucus plug that compounded severe respiratory acidosis and hypotension in a patient who simultaneously had abdominal compartment syndrome. The mucus plug was not identified until a bronchoscopic assessment of the airway was performed. Due to the absence of classical signs, the delayed identification of the obstructing mucus plug exacerbated diagnostic confusion. It resulted in various treatments being trialed whilst the patient continued to deteriorate from the evasive offending culprit. We suggest that earlier and more routine use of bronchoscopy should be employed in an intensive care unit, especially as a definitive way to rule out endotracheal obstruction.

Design of V-Substituted TiFe-Based Alloy for Target Pressure Range and Easy Activation

Titanium iron (TiFe) alloy is a room-temperature hydrogen-storage material, and it absorbs hydrogen via a two-step process to form TiFeH and then TiFeH2. The effect of V addition in TiFe alloy was recently elucidated. The V substitution for Ti sublattice lowers P2/P1 ratio, where P1 and P2 are the equilibrium plateau pressure for TiFe/TiFeH and TiFeH/TiFeH2, respectively, and thus restricts the two-step hydrogenation within a narrow pressure range. The focus of the present investigation was to optimize the V content such that maximum usable storage capacity can be achieved for the target pressure range: 1 MPa for absorption and 0.1 MPa for desorption. The effect of V substitution at selective Ti or Fe sublattices was closely analyzed, and the alloy composition Ti46Fe47.5V6.5 displayed the best performance with ca. 1.5 wt.% of usable capacity within the target pressure range. At the same time, another issue in TiFe-based alloys, which is a difficulty in activation at room temperature, was solved by Ce addition. It was shown that 3 wt.% Ce dispersion in TiFe alloy imparted to it easy room-temperature (RT) activation properties.

Covid-19 pneumonia: Timing of pneumomediastinum and pneumothorax in 11 patients

Purpose: As the pandemic continues, many complications, previously recognized as rare, are now being reported as more than frequent complications of Covid-19 pneumonia. Of those, pneumomediastinum and pneumothorax are gaining attention. Their mechanism of occurrence/trigger is not fully understood, but the timing at which they occur is unclear.Methods: This is a case series of 11 Covid-19 patients with pneumomediastinum; retrospectively, we shed light on some of the patients’ characteristics, the role of mechanical ventilation, and the timing of pneumomediastinum after initiation of mechanical ventilation.Results: We found that despite following the lung-protective strategy and despite keeping a plateau pressure at an acceptable range, most of our patients had an acute event around the same timing of mechanical ventilation.Conclusions: The similar timing raises questions about other risk factors that remain unknown. Timing and steroids can contribute to the higher incidence of these complications.

Right Ventricular Dysfunction in Ventilated Patients with COVID-19 (COVID-RV)

Purpose COVID-19 is associated with cardiovascular complications, with right ventricular dysfunction (RVD) commonly reported. The combination of acute respiratory distress syndrome (ARDS), injurious invasive ventilation, micro/macro thrombi and the potential for direct myocardial injury create conditions where RVD is likely to occur. No study has prospectively explored the prevalence of RVD, and its association with mortality, in a cohort requiring mechanical ventilation. Methods Prospective, multi-centre, trans-thoracic echocardiographic, cohort study of ventilated patients with COVID-19 in Scottish intensive care units. RVD was defined as the presence of severe RV dilatation and interventricular septal flattening. To explore role of myocardial injury, high sensitivity troponin and N-terminal pro B-type natriuretic peptide (NT-proBNP) were measured in all patients. Results One hundred and twenty-one patients were recruited to COVID-RV, 118 underwent imaging and it was possible to determine the primary outcome in 112. RVD was present in seven (6.2% [95%CI; 2.5%, 12.5%]) patients. Thirty-day mortality was 85.7% in those with RVD, compared to 44.8% in those without (p=0.051). Patients with RVD were more likely to have; pulmonary thromboembolism (p<0.001), higher plateau pressure (p=0.048), lower dynamic compliance (p=0.031), higher NT-proBNP (p<0.006) and more frequent abnormal troponin (p=0.048). Abnormal NT-proBNP (OR 4.77 [1.22, 21.32], p=0.03) and abnormal Troponin (16.54 [4.98, 67.12], p<0.001) independently predicted 30-day mortality. Conclusion COVID-RV demonstrates a prevalence of RVD in ventilated patients with COVID-19 of 6.2% and is associated with a mortality of 85.7%. Association is observed between RVD and each of the aetiological domains of; ARDS, ventilation, micro/macro thrombi and myocardial injury.

Evaluation of Positive End-Expiratory Pressure Strategies in Patients With Coronavirus Disease 2019–Induced Acute Respiratory Distress Syndrome

Background: Different positive end-expiratory pressure (PEEP) strategies are available for subjects with coronavirus disease 2019 (COVID-19)–induced acute respiratory distress syndrome (ARDS) requiring invasive mechanical ventilation. We aimed to evaluate three conventional PEEP strategies on their effects on respiratory mechanics, gas exchanges, and hemodynamics.Methods: This is a prospective, physiologic, multicenter study conducted in China. We recruited 20 intubated subjects with ARDS and confirmed COVID-19. We first set PEEP by the ARDSnet low PEEP–fraction of inspired oxygen (FIO2) table. After a recruitment maneuver, PEEP was set at 15, 10, and 5 cm H2O for 10 min, respectively. Among these three PEEP levels, best-compliance PEEP was the one providing the highest respiratory system compliance; best-oxygenation PEEP was the one providing the highest PaO2 (partial pressure of arterial oxygen)/FIO2.Results: At each PEEP level, we assessed respiratory mechanics, arterial blood gas, and hemodynamics. Among three PEEP levels, plateau pressure, driving pressure, mechanical power, and blood pressure improved with lower PEEP. The ARDSnet low PEEP–FIO2 table and the best-oxygenation strategies provided higher PEEP than the best-compliance strategy (11 ± 6 cm H2O vs. 11 ± 3 cm H2O vs. 6 ± 2 cm H2O, p = 0.001), leading to higher plateau pressure, driving pressure, and mechanical power. The three PEEP strategies were not significantly different in gas exchange. The subgroup analysis showed that three PEEP strategies generated different effects in subjects with moderate or severe ARDS (n = 12) but not in subjects with mild ARDS (n = 8).Conclusions: In our cohort with COVID-19–induced ARDS, the ARDSnet low PEEP/FIO2 table and the best-oxygenation strategies led to higher PEEP and potentially higher risk of ventilator-induced lung injury than the best-compliance strategy.Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT04359251.