Plateau Pressure Research Articles

Elevated Driving Pressure and Elastance Does Not Increase In-Hospital Mortality Among Obese and Severely Obese Patients With Ventilator Dependent Respiratory Failure.

To determine if driving pressure (DP) and total respiratory system elastance (Ers) differ among normal/overweight (body mass index [BMI] < 30 kg/m2), obese, and severely obese ventilator-dependent respiratory failure (VDRF) patients and if there any associations with clinical outcomes. Retrospective observational cohort study during 2016-2018 at two tertiary care academic medical centers using electronic health record data from the first 2 full days of mechanical ventilation. The cohort was stratified by BMI classes to measure median DP, time-weighted mean tidal volume, plateau pressure, and Ers for each BMI class. Mechanically ventilated patients in medical and surgical ICUs. Primary outcome and effect measures included relative risk of in-hospital mortality, ventilator-free days, ICU length of stay, and hospital length of stay with multivariable adjustment. The cohort included 3,204 patients with 976 (30.4%) and 382 (11.9%) obese and severely obese patients, respectively. Severe obesity was associated with a DP greater than or equal to 15 cm H2O (relative risk [RR], 1.51 [95% CI, 1.26-1.82]) and Ers greater than or equal to 2 cm H2O/(mL/kg) (RR, 1.31 [95% CI, 1.14-1.49]). Despite elevated DP and Ers, there were no differences in in-hospital mortality, ventilator-free days, or ICU length of stay among all three groups. Despite higher DP and ERS among obese and severely obese VDRF patients, there were no differences in in-hospital mortality or duration of mechanical ventilation, suggesting that DP has less prognostic value in obese and severely obese VDRF patients.

Ultra-lung-protective ventilation and biotrauma in severe ARDS patients on veno-venous extracorporeal membrane oxygenation: a randomized controlled study

BackgroundUltra-lung-protective ventilation may be useful during veno-venous extracorporeal membrane oxygenation (vv-ECMO) for severe acute respiratory distress syndrome (ARDS) to minimize ventilator-induced lung injury and to facilitate lung recovery. The objective was to compare pulmonary and systemic biotrauma evaluated by numerous biomarkers of inflammation, epithelial, endothelial injuries, and lung repair according to two ventilator strategies on vv-ECMO.MethodsThis is a prospective randomized controlled study. Patients were randomized to receive during 48 h either ultra-lung-protective ventilation combining very low tidal volume (1–2 mL/kg of predicted body weight), low respiratory rate (5–10 cycles per minute), positive expiratory transpulmonary pressure, and 16 h of prone position or lung-protective-ventilation which followed the ECMO arm of the EOLIA trial (control group).ResultsThe primary outcome was the alveolar concentrations of interleukin-1-beta, interleukin-6, interleukin-8, surfactant protein D, and blood concentrations of serum advanced glycation end products and angiopoietin-2 48 h after randomization. Enrollment was stopped for futility after the inclusion of 39 patients. Tidal volume, respiratory rate, minute ventilation, plateau pressure, and mechanical power were significantly lower in the ultra-lung-protective group. None of the concentrations of the pre-specified biomarkers differed between the two groups 48 h after randomization. However, a trend to higher 60-day mortality was observed in the ultra-lung-protective group compared to the control group (45 vs 17%, p = 0.06).ConclusionsDespite a significant reduction in the mechanical power, ultra-lung-protective ventilation during 48 h did not reduce biotrauma in patients with vv-ECMO-supported ARDS. The impact of this ventilation strategy on clinical outcomes warrants further investigation.Trial registration Clinical trial registered with www.clinicaltrials.gov (NCT03918603). Registered 17 April 2019.

Weaning in Asthmatics: A Finely Supervised Action

Respiratory failure from severe asthma is a potentially reversible, life-threatening condition. Since asthma involves bronchospasm and mucous plugging, it causes increased pressure difference between peak and plateau pressure. The increased pressure difference between the two can be due to ventilatory strategy of asthma itself which involves increased inspiratory flow rate and square flow pattern to increase expiratory time. It is important that clinicians managing such patients understand the use of mechanical ventilation since wrong interpretation may lead to inappropriate decision making during weaning.

Strategies to Prevent Ventilator.associated Lung Injury in Critically Ill Patients

Life-saving mechanical ventilation (MV) induces or exacerbates a range of pulmonary pathologies, collectively known as ventilator-induced lung injury if there is evidence of direct causation (i.e., in the research laboratory). However, in clinical practice, the term ventilator-associated lung injury (VALI) is more appropriate. While several factors are involved, the main drivers of the pathogenesis are regional overdistention and clinical atelectasis. This understanding has led to search for strategies to attenuate VALI and improve survival. The current approaches focus on reduction of lung stress and strain by limitation of alveolar–plateau pressure and tidal volume. Recent data suggest that control of driving pressure (plateau pressure–positive end-expiratory pressure) and mechanical power applied during ventilation may also be beneficial. More exciting are the various new techniques for MV (e.g., airway pressure release ventilation and neurally adjusted ventilatory assist), emerging alternative modalities for gas exchange (e.g., extracorporeal membrane oxygenation), and novel biological therapies (e.g., anti-inflammatory stem cells) that promise to revolutionize the management of respiratory failure and relegate VALI to the ash heap of history. However, there are currently insufficient data to recommend their use in routine clinical practice.

Prone Ventilation in ARDS

ARDS is a clinical syndrome characterised by severe refractory hypoxaemia associated with significant mortality and morbidity. Low tidal volume ventilation and restricting plateau pressure has got maximum survival benefit. Various others measures to tackle refractory hypoxaemia in patients with ARDS have been studied. Prone ventilation is one such rescue therapy which has shown promising results. This article is intended to discuss the benefits of prone ventilation and to clarify some of the common queries one has in practising prone ventilation.

A Plasma Pressure Plateau in the Night Sector of the Earth’s Magnetosphere and Its Stability

A Plasma Pressure Plateau in the Night Sector of the Earth’s Magnetosphere and Its Stability

Lung mechanics during video-assisted abdominal surgery in Trendelenburg position: a cross-sectional propensity-matched comparison between classic laparoscopy and robotic-assisted surgery

BackgroundVideo-assisted surgery has become an increasingly used surgical technique in patients undergoing major thoracic and abdominal surgery and is associated with significant perioperative respiratory and cardiovascular changes. The aim of this study was to investigate the effect of intraoperative pneumoperitoneum during video-assisted surgery on respiratory physiology in patients undergoing robotic-assisted surgery compared to patients undergoing classic laparoscopy in Trendelenburg position.MethodsTwenty-five patients undergoing robotic-assisted surgery (RAS) were compared with twenty patients undergoing classic laparoscopy (LAS). Intraoperative ventilatory parameters (lung compliance and plateau airway pressure) were recorded at five specific timepoints: after induction of anesthesia, after carbon dioxide (CO2) insufflation, one-hour, and two-hours into surgery and at the end of surgery. At the same time, arterial and end-tidal CO2 values were noted and arterial to end-tidal CO2 gradient was calculated.ResultsWe observed a statistically significant difference in plateau pressure between RAS and LAS at one-hour (26.2 ± 4.5 cmH2O vs. 20.2 ± 3.5 cmH2O, p = 0.05) and two-hour intervals (25.2 ± 5.7 cmH2O vs. 17.9 ± 3.1 cmH2O, p = 0.01) during surgery and at the end of surgery (19.9 ± 5.0 cmH2O vs. 17.0 ± 2.7 cmH2O, p = 0.02). Significant changes in lung compliance were also observed between groups at one-hour (28.2 ± 8.5 mL/cmH2O vs. 40.5 ± 13.9 mL/cmH2O, p = 0.01) and two-hour intervals (26.2 ± 7.8 mL/cmH2O vs. 54.6 ± 16.9 mL/cmH2O, p = 0.01) and at the end of surgery (36.3 ± 9.9 mL/cmH2O vs. 58.2 ± 21.3 mL/cmH2O, p = 0.01). At the end of surgery, plateau pressures remained higher than preoperative values in both groups, but lung compliance remained significantly lower than preoperative values only in patients undergoing RAS with a mean 24% change compared to 1.7% change in the LAS group (p = 0.01). We also noted a more significant arterial to end-tidal CO2 gradient in the RAS group compared to LAS group at one-hour (12.9 ± 4.5 mmHg vs. 7.4 ± 4.4 mmHg, p = 0.02) and two-hours interval (15.2 ± 4.5 mmHg vs. 7.7 ± 4.9 mmHg, p = 0.02), as well as at the end of surgery (11.0 ± 6.6 mmHg vs. 7.0 ± 4.6 mmHg, p = 0.03).ConclusionVideo-assisted surgery is associated with significant changes in lung mechanics after induction of pneumoperitoneum. The observed changes are more severe and longer-lasting in patients undergoing robotic-assisted surgery compared to classic laparoscopy.

Effect of positive end-expiratory pressure on pulmonary compliance and pulmonary complications in patients undergoing robot-assisted laparoscopic radical prostatectomy: a randomized control trial

BackgroundTo observe the effects of different positive end-expiratory pressure (PEEP) ventilation strategies on pulmonary compliance and complications in patients undergoing robotic-assisted laparoscopic prostate surgery.MethodsA total of 120 patients with the American Society of Anesthesiologists Physical Status Class I or II who underwent elective robotic-assisted laparoscopic prostatectomy were enrolled. We randomized the patients divided into divided into three groups of 40 patients each: PEEP0, PEEP5, or PEEP10. Master Anesthetist used volume control ventilation intraoperatively with an intraoperative deep muscle relaxation strategy. Respiratory mechanics indexes were recorded at six time-points: 10 mimuts after anaesthesia induction, immediately after pneumoperitoneum establishment, 30 min, 60 min, 90 min, and at the end of pneumoperitoneum. Arterial blood gas analysis and oxygenation index calculation were performed 10 mimuts after anaesthesia induction, 60 mimuts after pneumoperitoneum, and after tracheal extubation. Postoperative pulmonary complications were also recorded.ResultsAfter pneumoperitoneum, peak inspiratory pressure (Ppeak), plateau pressure (Pplat), mean pressure (Pmean), driving pressure (ΔP), and airway resistance (Raw) increased significantly, and pulmonary compliance (Crs) decreased, persisting during pneumoperitoneum in all groups. Between immediately after pneumoperitoneum establishment, 30 min, 60 min, and 90 min, pulmonary compliance in the 10cmH2OPEEP group was higher than in the 5cmH2OPEEP (P < 0.05) and 0cmH2OPEEP groups(P < 0.05). The driving pressure (ΔP) immediately after pneumoperitoneum establishment, at 30 min, 60 min, and 90 min in the 10cmH2OPEEP group was lower than in the 5cmH2OPEEP (P < 0.05) and 0cmH2OPEEP groups (P < 0.05). Sixty min after pneumoperitoneum and tracheal extubation, the PaCO2 did not differ significantly among the three groups (P > 0.05). The oxygenation index (PaO2/FiO2) was higher in the PEEP5 group than in the PEEP0 and PEEP10 groups 60 min after pneumoperitoneum and after tracheal extubation, with a statistically significant difference (P < 0.05). In postoperative pulmonary complications, the incidence of atelectasis was higher in the PEEP0 group than in the PEEP5 and PEEP10 groups, with a statistically significant difference (p < 0.05).ConclusionThe use of PEEP at 5cmH2O during RARP increases lung compliance, improves intraoperative oxygenation index and reduces postoperative atelectasis.Trial registrationThis study was registered in the China Clinical Trials Registry on May 30, 2020 (Registration No. ChiCTR2000033380).

Mechanical Ventilation in ARDS With an Automatic Resuscitator.

The Oxylator is an automatic resuscitator, powered only by an oxygen cylinder with no electricity required, that could be used in acute respiratory failure in situations in which standard mechanical ventilation is not available or feasible. We aimed to assess the feasibility and safety of mechanical ventilation by using this automatic resuscitator in an animal model of ARDS. A randomized experimental study in a porcine ARDS model with 12 pigs randomized to the Oxylator group or the control group (6 per group) and ventilated for 4 h. In the Oxylator group, peak pressure was set at 20 cm H2O and PEEP was set at the lowest observed breathing frequency during a decremental PEEP titration. The control pigs were ventilated with a conventional ventilator by using protective settings and PEEP at the crossing point of collapse and overdistention, as indicated by electrical impedance tomography. Our end points were feasibility and safety as well as respiratory mechanics, gas exchange, and hemodynamics. After lung injury, the mean ± SD respiratory system compliance and PaO2 /FIO2 were 13 ± 2 mL/cm H2O and 61 ± 17 mm Hg, respectively. The mean ± SD total PEEP was 10 ± 2 cm H2O and 13 ± 2 cm H2O in the control and Oxylator groups, respectively (P = .046). The mean plateau pressure was kept to < 30 cm H2O in both groups. In the Oxylator group, the tidal volume was transiently > 8 mL/kg but was 6 ± 0.4 mL/kg at 4 h, whereas the breathing frequency increased from 38 ± 4 to 48 ± 3 breaths/min (P < .001). There was no difference in driving pressure, compliance, PaO2 /FIO2 , and pulmonary shunt between the groups. The mean ± SD PaCO2 was higher in the Oxylator group after 4 h, 74 ± 9 mm Hg versus 58 ± 6 mm Hg (P < .001). There were no differences in hemodynamics between the groups, including blood pressure and cardiac output. Short-term mechanical ventilation by using an automatic resuscitator and a fixed pressure setting in an ARDS animal model was feasible and safe.

Abstract 12769: Association of Lung Protective Ventilation and Outcomes in Patients With Cardiogenic Shock on ECLS

Background: In Acute Respiratory Distress Syndrome, lung protective ventilation (LPV) improves patient outcomes by minimizing the risk of ventilator-associated lung injury. For patients with cardiogenic shock (CS) requiring VA-ECLS, the extracorporeal heart-lung circuit provides a unique opportunity to provide LPV. At present, there are limited data regarding optimal ventilator strategies for patients in CS on VA-ECLS. We hypothesized that CS patients on VA-ECLS who require ventilator support will have better outcomes with LPV. Methods: We queried Extracorporeal Life Support Organization (ELSO) registry for hospital admissions between 2009 and 2019 for CS patients on VA-ECLS and mechanical ventilation. Patients with multiple ECLS runs, congenital heart disease, pre-ECLS cardiac arrest, and durable mechanical circulatory support were excluded. We defined LPV as peak inspiratory pressure (PIP24)&lt;30 cm H 2 O at 24 hours on ECLS. ELSO registry does not report tidal volume, hence, PIP24 was used as surrogate for plateau pressure. PIP24 and driving pressure (PIP24 minus PEEP24) at 24 hours (DP24) were also studied as continuous variables. Our primary outcome was survival to discharge. Multivariable analysis adjusted for baseline SAVE score, age, race, BMI, etiology of CS, intubation hours prior to ECMO and history of chronic lung disease. Results: A total of 2,226 CS patients on VA-ECLS were included of which 1904 received LPV. LPV patients had a significantly lower BMI (median 28.28 vs 31.14, p&lt;0.001), and were less sick, as assessed by their baseline SAVE score (-1.79 vs -2.79, p=0.002). The primary outcome of survival to discharge was significantly greater in LPV cohort (47.4% vs 32.6%, p&lt;0.001). Median PIP24 (22 vs 24, p&lt;0.001) as well as DP24 (14.5 vs 16, p&lt;0.001) were significantly lower in those surviving to discharge. Adjusted OR for primary outcome with LPV was 1.69 (p=0.0023). Adjusted OR for primary outcome with incremental rise in PIP24 (0.78, p=0.0003) and DP24 (0.75, p&lt;0.0001) were also statistically significant. Conclusions: In VA-ECLS patients requiring mechanical ventilation, LPV and lower PIP and DP at 24 hours is associated with improved survival to discharge.

Impacts of Ce dopants on the hydrogen storage performance of Ti-Cr-V alloys

Vanadium-based alloys are considered to be one of the most promising hydrogen storage materials due to their high hydrogen storage capacity under ambient conditions. However, their complex activation at high temperature and poor stability pose serious challenges for large-scale applications. In this work, a series of TiCr3V16Cex (x = 0, 0.1, 0.2, 0.4, 1) hydrogen storage alloys were developed with different Ce contents using arc melting. The hydrogen storage and desorption performance, activation mechanism, and hydrogen absorption mechanism of the prepared alloys were investigated. Physical characterization confirms that the alloy is body-centered cubic (BCC) with Ce dopants, which exist in the form of oxides. The pressure-composition-temperature (PCT) test showed that the hydrogen storage plateau pressure of the Ce-doped alloy is increased compared to the Ce-free counterparts, while the hydrogen storage capacity decreased slightly with increasing Ce content. In addition, the influence of Ce doping on the alloy kinetics and thermodynamics is also discussed. The results showed that the TiCr3V16Cex (x = 0.2, 0.4, 1) alloys could absorb and release hydrogen at room temperature without activation. As an optimum, the TiCr3V16Ce0.2 alloy shows a hydrogen absorption rate of up to 3.69 wt%, and an effective hydrogen desorption capacity of 2.29 wt% at 25 °C. After hydrogen absorption and desorption cycles, the alloy almost maintains its original capacity. The Ce-doped BCC alloy developed in this work provides a new route to achieve high hydrogen storage performance under mild conditions.

Effects of Zr doping on activation capability and hydrogen storage performances of TiFe-based alloy

Activation difficulty is the key problem limiting the application of TiFe-based hydrogen storage alloys. The addition of transition group elements helps to improve the activation properties of TiFe-based hydrogen storage alloy. In our previous work, the Ti1.08Y0.02Fe0.8Mn0.2 alloy exhibits extremely high hydrogen storage capacity (1.84 wt%) at room temperature with excellent kinetic properties, but it still needs an incubation period of about 1500s. In this study, the composition of Ti1.08Y0.02Fe0.8Mn0.2Zrx (x = 0, 0.02, 0.04, 0.06, 0.08) alloys was prepared by electromagnetic induction melting. The quantitative analysis of elements by energy dispersive spectrometer shows that in the second phase region containing Zr, the content of Ti element is significantly higher than that of Fe. Meanwhile, the first-principle calculation on Zr-doped TiFe system indicates that Zr is more attractive to substitute Ti than Fe. Therefore, the doping of Zr partially replaces the Ti. The solubility of Zr in TiFe is limited, when x ≤ 0.04, the alloy consists of pure TiFe phase. When x > 0.4, the excess Zr forms precipitates, which reduces the reversible hydrogen absorption and desorption capacity of the TiFe alloy. The addition of Zr significantly shortens the activation time and reduces the plateau pressure of TiFe alloys. The Ti1.08Y0.02Fe0.8Mn0.2Zr0.04 alloy can be directly activated without the incubation period and its absolute values of enthalpy change (ΔH) and entropy change (ΔS) are minima (ΔH for 23.2 kJ/mol and ΔS for 83.1 J/mol/K).

Pre-clinical validation of a turbine-based ventilator for invasive ventilation-The ACUTE-19 ventilator.

The Severe Acute Respiratory Syndrome (SARS)-Coronavirus 2 (CoV-2) pandemic pressure on healthcare systems can exhaust ventilator resources, especially where resources are restricted. Our objective was a rapid preclinical evaluation of a newly developed turbine-based ventilator, named the ACUTE-19, for invasive ventilation. Validation consisted of (a) testing tidal volume (V_T) delivery in 11 simulated models, with various resistances and compliances; (b) comparison with a commercial ventilator (VIVO-50) adapting the United Kingdom Medicines and Healthcare products Regulatory Agency-recommendations for rapidly manufactured ventilators; and (c) in vivo testing in a sheep before and after inducing acute respiratory distress syndrome (ARDS) by saline lavage. Differences in V_T in the simulated models were marginally different (largest difference 33ml [95%-confidence interval (CI) 31-36]; P&lt;.001ml). Plateau pressure (P_plat) was not different (-0.3cmH₂O [95%-CI -0.9 to 0.3]; P=.409), and positive end-expiratory pressure (PEEP) was marginally different (0.3 cmH₂O [95%-CI 0.2 to 0.3]; P&lt;.001) between the ACUTE-19 and the commercial ventilator. Bland-Altman analyses showed good agreement (mean bias, -0.29, [limits of agreement, 0.82 to -1.42], and mean bias 0.56 [limits of agreement, 1.94 to -0.81], at a P_plat of 15 and 30cmH₂O, respectively). The ACUTE-19 achieved optimal oxygenation and ventilation before and after ARDS induction. The ACUTE-19 performed accurately in simulated and animal models yielding a comparable performance with a VIVO-50 commercial device. The acute 19 can provide the basis for the development of a future affordable commercial ventilator.

Biological impact of restrictive and liberal fluid strategies at low and high PEEP levels on lung and distal organs in experimental acute respiratory distress syndrome.

Background: Fluid regimens in acute respiratory distress syndrome (ARDS) are conflicting. The amount of fluid and positive end-expiratory pressure (PEEP) level may interact leading to ventilator-induced lung injury (VILI). We therefore evaluated restrictive and liberal fluid strategies associated with low and high PEEP levels with regard to lung and kidney damage, as well as cardiorespiratory function in endotoxin-induced ARDS. Methods: Thirty male Wistar rats received an intratracheal instillation of Escherichia coli lipopolysaccharide. After 24h, the animals were anesthetized, protectively ventilated (VT = 6ml/kg), and randomized to restrictive (5ml/kg/h) or liberal (40ml/kg/h) fluid strategies (Ringer lactate). Both groups were then ventilated with PEEP = 3 cmH2O (PEEP3) and PEEP = 9 cmH2O (PEEP9) for 1h (n = 6/group). Echocardiography, arterial blood gases, and lung mechanics were evaluated throughout the experiments. Histologic analyses were done on the lungs, and molecular biology was assessed in lungs and kidneys using six non-ventilated animals with no fluid therapy. Results: In lungs, the liberal group showed increased transpulmonary plateau pressure compared with the restrictive group (liberal, 23.5 ± 2.9 cmH2O; restrictive, 18.8 ± 2.3cmH2O, p = 0.046) under PEEP = 9 cmH2O. Gene expression associated with inflammation (interleukin [IL]-6) was higher in the liberal-PEEP9 group than the liberal-PEEP3 group (p = 0.006) and restrictive-PEEP9 (p = 0.012), Regardless of the fluid strategy, lung mechanical power and the heterogeneity index were higher, whereas birefringence for claudin-4 and zonula-ocludens-1 gene expression were lower in the PEEP9 groups. Perivascular edema was higher in liberal groups, regardless of PEEP levels. Markers related to damage to epithelial cells [club cell secreted protein (CC16)] and the extracellular matrix (syndecan) were higher in the liberal-PEEP9 group than the liberal-PEEP3 group (p = 0.010 and p = 0.024, respectively). In kidneys, the expression of IL-6 and neutrophil gelatinase-associated lipocalin was higher in PEEP9 groups, regardless of the fluid strategy. For the liberal strategy, PEEP = 9 cmH2O compared with PEEP = 3 cmH2O reduced the right ventricle systolic volume (37%) and inferior vena cava collapsibility index (45%). Conclusion: The combination of a liberal fluid strategy and high PEEP led to more lung damage. The application of high PEEP, regardless of the fluid strategy, may also be deleterious to kidneys.

Annealing temperature-dependent phase structure and electrochemical hydrogen storage properties of AB4-type La1.5Y1.5Ni12-xMnx (x = 0, 1.0) superlattice alloys

AB4-type La1.5Y1.5Ni12-xMnx (x = 0, 1.0) alloys with the rhombohedral structure were prepared by optimizing the annealing temperature. As the annealing temperature rises, the hexagonal Pr5Co19-type phase transforms into the rhombohedral AB4-type phase, and the 3R-AB4-type single-phase La1.5Y1.5Ni12 and La1.5Y1.5Ni11Mn1.0 alloys could be obtained at 1120 °C and 1088 °C, respectively. The partial Mn substitution for Ni increases the subunit volume but reduces the subunit volume mismatch of the AB4-type superlattice structure, thus lowering the hydrogen absorption/desorption plateau pressure and improving the electrochemical properties. Compared with annealed multi-phase alloys or single-phase A5B19-type alloy, the AB4-type single-phase alloy exhibits better overall electrochemical performance with a maximum discharge capacity of 345.6 mAh/g, a rate performance HRD600 of 84.03%, and a capacity retention S200 of 70.12%. The La1.5Y1.5Ni11Mn1.0 alloy with the rhombohedral structure demonstrates potential as a new anode for nickel-metal hydride batteries.

A Comprehensive Review of the Management of Acute Respiratory Distress Syndrome.

Acute respiratory distress syndrome (ARDS) is an inflammatory process in the lungs that induces non-hydrostatic protein-rich pulmonary edema.ARDS occurs in roughly halfof coronavirus disease 2019 (COVID-19) pneumonia patients, with most of them requiring intensive care. Oxygen saturation, partial pressure of the oxygen, and the fraction of the inspired oxygen are health indicators that may indicate a severe illnessnecessitating further investigation.As treatments have evolved, a typical pattern of ARDS has likewise evolved. In cases where mechanical ventilation is required, the use of low tidal volumes (<6 ml/kg ideal body weight) and airway pressures (plateau pressure <30 cmH2O) was recommended. For patients with moderate/severe ARDS (partial pressure to fractional inspired oxygenratio <20), prone positioning was recommended for at least 16 hours per day. By contrast, high-frequency oscillation was not recommended. The use of inhaled vasodilators was recommended in patients with persistent hypoxemia despite invasive ventilation and prone position until extracorporeal membrane oxygenation (ECMO). The use of a conservative fluid management strategy was suggested for all patients. Mechanical ventilation with high positive end-expiratory pressure (PEEP) was suggestedfor patients with ARDS with a ratio of arterial oxygen partial pressure to fractional inspired oxygen (PF) ratios. ECMO was suggested as an adjunct to protective mechanical ventilation for patients with severe ARDS. In the absence of adequate evidence, research recommendations were made for corticosteroids and extracorporeal carbon dioxide removal. While decades of research have been conducted, treatment options for underlying pathologies remain limited, and mechanical ventilation, which removes carbon dioxide from the body, remains essential to achieving better clinical outcomes. This review aims to identify the best ARDStreatments that are currently available.

Respiratory Mechanics and Gas Exchange in Acute Respiratory Distress Syndrome Associated with COVID-19

Aim. To compare respiratory mechanics and gas exchange in patients with acute respiratory distress syndrome (ARDS) with and without COVID-19.Material and methods. We examined 96 patients, who were divided into two groups. The main group included 48 patients with COVID-19-associated ARDS. The control group included 48 patients with ARDS not associated with COVID-19. Most characteristic patients were selected for the following baseline parameters: age, sex, SAPS II score, disease severity, plateau pressure (Pplateau), oxygenation index (PaO₂/FiO₂), and arterial-alveolar oxygen gradient (A-aO₂). Respiratory mechanics and gas exchange parameters assessed immediately after ARDS diagnosis and on days 1, 3 and 7 of treatment included arterial oxygen (PaO₂) and carbon dioxide (PaCO₂) pressure, tidal volume (Vt), respiratory rate (RR), respiratory minute volume (RMV), positive end expiratory pressure (PEEP), and Pplateau.Results. Patients in the main group had higher Vt (9.7 vs. 5.1 ml/kg, P&lt;0.001), RR (38 vs. 30 min-1, P&lt;0.001), and RMV (27.7 vs. 10.5 l/min, P&lt;0.001). Control group patients showed hypercapnia (PaCO₂ 43 vs. 38 mmHg, P&lt;0.001), lower respiratory compliance (30 vs. 48 ml/cm H₂O, P&lt;0.001) and ventilation ratio (VR) (1.5 vs. 2.0, P&lt;0.01). Lower PEEP values were required for patients in the main group. However, despite the higher rate of tracheal intubation in the control group (50% vs 16.7%) in the initial period of intensive care, the proportion of patients receiving invasive lung ventilation was significantly higher in the main group (33.3% vs.14.6%) by day 7.Conclusion. The initial phase (the first 7 days) of ARDS associated with COVID-19 is characterized by higher values of Vt, RR and RMV, as well as lung compliance vs «typical» ARDS with almost identical PaO₂/FiO₂ values.

Mix optimization of hybrid steel and polypropylene fiber-reinforced concrete for anti-thermal spalling

Concrete tends to spall explosively under fire due to the combined effect of thermal stress and pore pressure build-up. For an anti-spalling strategy in the concrete mix design, one can add steel fibers to improve the material strength and fine-polypropylene (PP) fibers to mitigate the pore pressure build-up. However, the addition of steel fibers causes noticeable increments in the spalling risk, while the addition of PP fibers causes slight decrements in the material strength capacity. Hence, the mix optimization of hybrid fiber reinforced concrete (HFRC) is studied in this research focusing on the individual and synergistic effects of steel and PP fibers on the mechanical degradations and pore pressure peaks at elevated temperatures. An apparent plateau in the pore pressure rises at 165 °C (PP melting point) is frequently observed in HFRC, which is the combined opposite effects of the two different fiber types. The increase of PP fiber length, rather than the dosage, is recommended to mitigate the pore pressure build-up, because of the better retention of residual strength and improvement in pore connection thanks to the observed fiber adhering effect (FAE) on aggregates. Based on a comprehensive experimental investigation, the cementitious mix with 1% of steel and 0.2% of 19-mm-length PP fiber in volume is recommended to obtain a high strength capacity and low pore pressure at elevated temperature. Finally, a new mathematical formula for prediction of the maximum pore pressure variation when steel, PP, or both fibers are employed in the concrete mix is here proposed for guiding the anti-spalling mix design of fiber-reinforced cementitious material.

Ventilatory Parameters in Obstetric Patients With COVID-19 and Impact of Delivery: A Multicenter Prospective Cohort Study

BackgroundCurrent evidence on obstetric patients requiring advanced ventilatory support and impact of delivery on ventilatory parameters is retrospective, scarce and controversial.Research QuestionWhat are the ventilatory parameters for COVID-19 obstetric patients and how does delivery impact them? And what are the risk factors for invasive mechanical ventilation (IMV) and for maternal/fetal/neonatal mortality?Study Design and MethodsProspective, multicenter, cohort study including pregnant/postpartum patients with COVID-19 requiring advanced ventilatory support in ICU.Results91 patients were admitted to 21 ICUs at 29.2±4.9 weeks-63(69%) antepartum. Maximal ventilatory support: IMV (69;76%), high flow nasal cannula (20;22%) and non-invasive mechanical ventilation (2;2%). SOFA24 was the only risk factor for IMV (OR 1.97[1.29-2.99]p0.001). Respiratory parameters at IMV onset for pregnant patients were: plateau pressure (PP) 24.3±4.5, driving pressure (DP) 12.5±3.3, static compliance (SC) 31[26-40] and PaO2/FiO2 142[110-176]. Respiratory parameters before (<2h) and after delivery (≤2h and 24h), respectively: PP (25.6±6.6, 24±6.7 and 24.6±5.2; p0.59); DP (13.6±4.2, 12.9±3.9 and 13±4.4; p0.69); SC (28[22.5-39], 30[24.5-44] and 30[24.5-44]; p0.058) and PaO2/FiO2 (134[100-230], 168[136-185] and 192[132-232.5], p0.022). Reasons for induced delivery: maternal (43/71; 60.5%), maternal and fetal (21/71; 29.5%) and fetal (7/71; 9.9%). Fourteen patients (22.2%) continued pregnancy after ICU discharge. Risk factors for maternal mortality: BMI (OR 1.10[1.006-1.204];p0.037) and comorbidities (OR 4.15[1.212- 14.20];p0.023). Risk factors for fetal/neonatal mortality: gestational age at delivery (OR 0.67[0.52-0.86]p0.002) and SOFA24 (OR 1.53[1.13-2.08]p0.006).InterpretationContrary to expectations, pregnant patient lung mechanics were similar to the general COVID-19 ICU population. Delivery was mainly induced for maternal reasons but did not change ventilatory parameters other than PaO2/FiO2. SOFA24 was the only risk factor for IMV. Maternal mortality was independently associated with BMI and comorbidities. Risk factors for fetal/neonatal mortality were SOFA24 and gestational age at delivery.

P-091 IMPROVEMENT OF RESPIRATORY PHYSIOLOGY AFTER POSTERIOR COMPONENT SEPARATION TAR: A PILOT STUDY

Abstract Aim Patients with incisional hernia with a width greater than 9 centimeters, submitted to Posterior Component Separation Trasversus Abdominis Release, by Department of Emergency and Transplantation Surgery in Varese Hospital, were analyzed to define the modifications in respiratory physiology after surgery. Material and Methods Patients that underwent Posterior Component Separation were prospectively analyzed by evaluating: volume of laparocele, volume of abdominal cavity and their ratio. Furthermore Pulmonary Peak pressures and Pulmonary Plateau pressures were measured in three different times: at the induction of the anaesthesia, when the mesh was placed and at the closure of the anterior muscular layer. All patients were submitted to a pre-operative simple spirometry, and re-examinated three months after the surgical procedure with the same procedure to check if modifications in their respiratory function were present. Results Primary results of the study will be shown to define how this surgical procedure impacts on the respiratory function of the patients. The expectation is that an improvement of the respiratory physiology happens independently from a pulmonary pressure elevation which is determinated by the re-allocation of the herniated viscera in the abdomen when the anterior muscular fascia is closed. Conclusions the aim of this study is to show how, the reconstitution of a functional abdominal wall with an efficient respiratory accessory musculature guaranteed by the laparocele correction with Posterior Component Separation, ensures an improvement of respiratory physiology visible with spirometry, independently from the development of a superior intrathoracic pressure.