Lung-protective Mechanical Ventilation Research Articles

Thoracic Anaesthesia Practices in Turkey: A Survey Study.

In this survey study, we aimed to investigate thoracic anaesthesia practices in Turkey. The survey was sent to the members of the Turkish Society of Anesthesiology and Reanimation by e-mail. Participants were asked to answer 35 questions about their thoracic anaesthesia practice. A total of 148 questionnaires were completed. Most of the participants preferred double-lumen endobronchial tube for one-lung ventilation. 69.6% of auscultation method and 45.9% of fiberoptic bronchoscope method were used to confirm the tube position. The most frequently used additional monitoring method was invasive blood pressure. Generally, intravenous anaesthetic agents were preferred for anaesthesia induction, and a combination of inhalation and intravenous agents was used for anaesthesia maintenance. Most of the participants used intraoperative lung-protective mechanical ventilation strategies. For postoperative analgesia, 75% of participants preferred regional analgesic techniques and 89.9% of them used routine opioid agents. In general, moderate amount of fluid was applied (57.4%), crystalloids were the first choice in fluid therapy, and intraoperative hypotension was generally treated with controlled intravenous fluid and vasoactive agents. The haemoglobin threshold value for blood transfusion was stated as 8 g dL-1 by 35.8% of participants. Our data showed that the anaesthesia management of thoracic surgery in Turkey is generally compatible with the current international guidelines. However, the following conclusion was reached: training on blood transfusion, the use of fiberoptic bronchoscope, regional techniques, and intraoperative additional monitoring would be beneficial, and a national consensus should be reached on the thoracic anaesthesia practice.

Extracorporeal membrane oxygenation circuits in parallel for refractory hypoxemia in patients with COVID-19

ObjectivesRefractory hypoxemia can occur in patients with acute respiratory distress syndrome from COVID-19 despite support with venovenous (VV) extracorporeal membrane oxygenation (ECMO). Parallel ECMO circuits can be used to increase physiologic support. We report our clinical experience using ECMO circuits in parallel for select patients with persistent severe hypoxemia despite the use of a single ECMO circuit. MethodsWe performed a retrospective cohort study of all patients with COVID–19-related acute respiratory distress syndrome who received VV-ECMO with an additional circuit in parallel at Vanderbilt University Medical Center between March 1, 2020, and March 1, 2022. We report demographic characteristics and clinical characteristics including ECMO settings, mechanical ventilator settings, use of adjunctive therapies, and arterial blood gas results after initial cannulation, before and after receipt of a second ECMO circuit in parallel, and before removal of the circuit in parallel, and outcomes. ResultsOf 84 patients with COVID-19 who received VV-ECMO during the study period, 22 patients (26.2%) received a circuit in parallel. The median duration of ECMO was 40.0 days (interquartile range, 31.6-53.1 days), of which 19.0 days (interquartile range, 13.0-33.0 days) were spent with a circuit in parallel. Of the 22 patients who received a circuit in parallel, 16 (72.7%) survived to hospital discharge and 6 (27.3%) died before discharge. ConclusionsIn select patients, the additional use of an ECMO circuit in parallel can increase ECMO blood flow and improve oxygenation while allowing for lung-protective mechanical ventilation and excellent outcomes.

6-Year-Old Male Drowning Complicated by Cardiac Arrest and Ensuing Metabolic and Respiratory Acidosis: Should Presence of Pulses Lead Clinicians to Pursue Prolonged Cardiopulmonary Resuscitation?

BackgroundDrowning is one of the leading causes of death in the pediatric population. Patients arriving to the emergency department (ED) with submersion injuries are often asymptomatic and well-appearing, but can sometimes present critically ill and require prolonged resuscitation. The question of how long to continue resuscitation of a pediatric patient with a submersion injury is a difficult question to answer. Case ReportWe present a case of 6-year-old boy was found by his friends submerged in sea water for 10–15 min. The patient was rescued by lifeguards and evaluated by emergency medical personnel, who found him breathing spontaneously but unresponsive. En route to hospital, the patient became apneic, cardiopulmonary resuscitation (CPR) was started, and the patient was intubated. The patient arrived to the ED in cardiopulmonary arrest, CPR was continued and epinephrine was administered. Return of spontaneous circulation was achieved after 42 min in the ED. Initial laboratory test results showed severe acidosis and chest x-ray study showed diffuse interstitial edema. Ventilator settings were adjusted in accordance with lung protective ventilation strategies and the acidosis began to improve. Over the next several days, the patient was weaned to noninvasive ventilation modalities and eventually made a complete neurologic recovery and continued to be a straight-A student.Why Should an Emergency Physician Be Aware of This?We make the case that, in select drowning patients, duration of CPR longer than 30 min can potentially result in favorable neurologic outcomes. Prolonged CPR should be especially strongly considered in patients with a pulse at any point during evaluation. With the combination of prolonged CPR and judicious use of lung protective mechanical ventilation strategies, we were able to successfully treat the patient in our case.

Prone Positioning and Neuromuscular Blocking Agents as Adjunctive Therapies in Mechanically Ventilated Patients with Acute Respiratory Distress Syndrome.

Neuromuscular blocking agents (NMBAs) and prone position (PP) are two major adjunctive therapies that can improve outcome in moderate-to-severe acute respiratory distress syndrome. NMBA should be used once lung-protective mechanical ventilation has been set, for 48 hours or less and as a continuous intravenous infusion. PP should be used as early as possible for long sessions; in COVID-19 its use has exploded. In nonintubated patients, PP might reduce the rate of intubation but not mortality. The goal of this article is to perform a narrative review on the pathophysiological rationale, the clinical effects, and the clinical use and recommendations of both NMBA and PP.

Effects of Sodium Thiosulfate During Resuscitation From Trauma-and-Hemorrhage in Cystathionine-γ-Lyase Knockout Mice With Diabetes Type 1.

BackgroundSodium thiosulfate (STS) is a recognized drug with antioxidant and H2S releasing properties. We recently showed that STS attenuated organ dysfunction and injury during resuscitation from trauma-and-hemorrhage in CSE-ko mice, confirming its previously described organ-protective and anti-inflammatory properties. The role of H2S in diabetes mellitus type 1 (DMT1) is controversial: genetic DMT1 impairs H2S biosynthesis, which has been referred to contribute to endothelial dysfunction and cardiomyopathy. In contrast, development and severity of hyperglycemia in streptozotocin(STZ)-induced DMT1 was attenuated in CSE-ko mice. Therefore, we tested the hypothesis whether STS would also exert organ-protective effects in CSE-ko mice with STZ-induced DMT1, similar to our findings in animals without underlying co-morbidity.MethodsUnder short-term anesthesia with sevoflurane and analgesia with buprenorphine CSE-ko mice underwent DMT1-induction by single STZ injection (100 μg⋅g–1). Seven days later, animals underwent blast wave-induced blunt chest trauma and surgical instrumentation followed by 1 h of hemorrhagic shock (MAP 35 ± 5 mmHg). Resuscitation comprised re-transfusion of shed blood, lung-protective mechanical ventilation, fluid resuscitation and continuous i.v. norepinephrine together with either i.v. STS (0.45 mg⋅g–1) or vehicle (n = 9 in each group). Lung mechanics, hemodynamics, gas exchange, acid–base status, stable isotope-based metabolism, and visceral organ function were assessed. Blood and organs were collected for analysis of cytokines, chemokines, and immunoblotting.ResultsDiabetes mellitus type 1 was associated with more severe circulatory shock when compared to our previous study using the same experimental design in CSE-ko mice without co-morbidity. STS did not exert any beneficial therapeutic effect. Most of the parameters measured of the inflammatory response nor the tissue expression of marker proteins of the stress response were affected either.ConclusionIn contrast to our previous findings in CSE-ko mice without underlying co-morbidity, STS did not exert any beneficial therapeutic effect in mice with STZ-induced DMT1, possibly due to DMT1-related more severe circulatory shock. This result highlights the translational importance of both integrating standard ICU procedures and investigating underlying co-morbidity in animal models of shock research.

The PANDORA Study: Prevalence and Outcome of Acute Hypoxemic Respiratory Failure in the Pre-COVID-19 Era

OBJECTIVES:To establish the epidemiological characteristics, ventilator management, and outcomes in patients with acute hypoxemic respiratory failure (AHRF), with or without acute respiratory distress syndrome (ARDS), in the era of lung-protective mechanical ventilation (MV).DESIGN:A 6-month prospective, epidemiological, observational study.SETTING:A network of 22 multidisciplinary ICUs in Spain.PATIENTS:Consecutive mechanically ventilated patients with AHRF (defined as Pao2/Fio2 ≤ 300 mm Hg on positive end-expiratory pressure [PEEP] ≥ 5 cm H2O and Fio2 ≥ 0.3) and followed-up until hospital discharge.INTERVENTIONS:None.MEASUREMENTS AND MAIN RESULTS:Primary outcomes were prevalence of AHRF and ICU mortality. Secondary outcomes included prevalence of ARDS, ventilatory management, and use of adjunctive therapies. During the study period, 9,803 patients were admitted: 4,456 (45.5%) received MV, 1,271 (13%) met AHRF criteria (1,241 were included into the study: 333 [26.8%] met Berlin ARDS criteria and 908 [73.2%] did not). At baseline, tidal volume was 6.9 ± 1.1 mL/kg predicted body weight, PEEP 8.4 ± 3.1 cm H2O, Fio2 0.63 ± 0.22, and plateau pressure 21.5 ± 5.4 cm H2O. ARDS patients received higher Fio2 and PEEP than non-ARDS (0.75 ± 0.22 vs 0.59 ± 0.20 cm H2O and 10.3 ± 3.4 vs 7.7 ± 2.6 cm H2O, respectively [p < 0.0001]). Adjunctive therapies were rarely used in non-ARDS patients. Patients without ARDS had higher ventilator-free days than ARDS (12.2 ± 11.6 vs 9.3 ± 9.7 d; p < 0.001). All-cause ICU mortality was similar in AHRF with or without ARDS (34.8% [95% CI, 29.7–40.2] vs 35.5% [95% CI, 32.3–38.7]; p = 0.837).CONCLUSIONS:AHRF without ARDS is a very common syndrome in the ICU with a high mortality that requires specific studies into its epidemiology and ventilatory management. We found that the prevalence of ARDS was much lower than reported in recent observational studies.

Lung-Protective Ventilation Attenuates Mechanical Injury While Hypercapnia Attenuates Biological Injury in a Rat Model of Ventilator-Associated Lung Injury.

Background and Objective: Lung-protective mechanical ventilation is known to attenuate ventilator-associated lung injury (VALI), but often at the expense of hypoventilation and hypercapnia. It remains unclear whether the main mechanism by which VALI is attenuated is a product of limiting mechanical forces to the lung during ventilation, or a direct biological effect of hypercapnia. Methods: Acute lung injury (ALI) was induced in 60 anesthetized rats by the instillation of 1.25 M HCl into the lungs via tracheostomy. Ten rats each were randomly assigned to one of six experimental groups and ventilated for 4 h with: 1) Conventional HighV E Normocapnia (high VT, high minute ventilation, normocapnia), 2) Conventional Normocapnia (high VT, normocapnia), 3) Protective Normocapnia (VT 8 ml/kg, high RR), 4) Conventional iCO 2 Hypercapnia (high VT, low RR, inhaled CO2), 5) Protective iCO 2 Hypercapnia (VT 8 ml/kg, high RR, added CO2), 6) Protective endogenous Hypercapnia (VT 8 ml/kg, low RR). Blood gasses, broncho-alveolar lavage fluid (BALF), and tissue specimens were collected and analyzed for histologic and biologic lung injury assessment. Results: Mild ALI was achieved in all groups characterized by a decreased mean PaO2/FiO2 ratio from 428 to 242 mmHg (p < 0.05), and an increased mean elastance from 2.46 to 4.32 cmH2O/L (p < 0.0001). There were no differences in gas exchange among groups. Wet-to-dry ratios and formation of hyaline membranes were significantly lower in low VT groups compared to conventional tidal volumes. Hypercapnia reduced diffuse alveolar damage and IL-6 levels in the BALF, which was also true when CO2 was added to conventional VT. In low VT groups, hypercapnia did not induce any further protective effect except increasing pulmonary IL-10 in the BALF. No differences in lung injury were observed when hypercapnia was induced by adding CO2 or decreasing minute ventilation, although permissive hypercapnia decreased the pH significantly and decreased liver histologic injury. Conclusion: Our findings suggest that low tidal volume ventilation likely attenuates VALI by limiting mechanical damage to the lung, while hypercapnia attenuates VALI by limiting pro-inflammatory and biochemical mechanisms of injury. When combined, both lung-protective ventilation and hypercapnia have the potential to exert an synergistic effect for the prevention of VALI.

Early Initiation of Physical Therapy While on Extracorporeal Life Support Improves Patients’ Functional Activity on Discharge

PurposeTraditionally, severe acute respiratory distress syndrome (ARDS) patients on veno-venous extracorporeal membrane oxygenation (VV ECMO) receive significant sedation and neuromuscular blockade (NMB) to facilitate lung protective mechanical ventilation. However, we previously showed the feasibility of managing these patients without mechanical ventilation, sedation, or NMB. Reduced levels of sedation allows patients to begin physical and occupational therapy (PT/OT) early on. Here, we investigate the impact of early PT/OT initiation on day of discharge (DOD) functional activity for severe ARDS patients managed on VV ECMO.MethodsThis is a retrospective review of all patients who underwent VV ECMO as management for severe ARDS at a single academic center from February 2018 to June 2021. Data collected included patients’ demographics, co-morbidities, etiology of ARDS, days of ECMO support before PT/OT initiation, and ambulation distance and PT/OT Activity Measure for Post-Acute Care (AMPAC) Six-Clicks score on DOD.Results67 patients were included in this study. Those with >7 days on VV ECMO had decreased ambulation and AMPAC scores compared to those with < 7 days (N=41, 70.5 ± 113.3ft vs N=26, 162.1 ± 154.1ft, p<0.01, 12.3 ± 5.9 vs 16.4 ± 6.8, p=0.01, respectively). PT/OT initiation within 7 days after starting VV ECMO significantly improved ambulation and AMPAC scores compared to those with >7 days of VV ECMO prior to any PT/OT (N=30, 163.5 ± 160.5ft vs N=37, 59.5 ± 93.5ft, p<0.001, 16.6 ± 7.1 vs 11.8 ± 5.2, p<0.01, respectively). In patients with >7 days on VV ECMO, those who began PT/OT within 10 days of starting VV-ECMO had improved ambulation and AMPAC scores compared to those with >10 days of VV ECMO prior to PT/OT (N=9, 151.8 ± 164.8ft vs N=32, 44.2 ± 77.8ft, p<0.01, 16.5 ± 7.7 vs 11.0 ± 54.5, p<0.01, respectively).ConclusionEarly PT/OT initiation in severe ARDS patients managed on VV ECMO is associated with improved patient functional activity on DOD. This may provide benefits such as enhanced recovery, increased ability to complete activities of daily living, and improved cognitive health. Our study further supports the use of VV ECMO in treatment of severe ARDS without mechanical ventilation, sedation or NMB and specifically demonstrates PT/OT should be started early following initiation of VV ECMO to improve patients’ functional outcomes.

369 The impact of asymmetric lung injury on gas and pressures distribution in a mechanical ventilation model with implementation of compartmentalized inspiratory hold

OBJECTIVES/GOALS: Asymmetries in lung pathophysiology can result in a maldistribution of gas between regions of the lungs which may generate dangerous pressures that are not observable by clinicians. Our study aims to demonstrate and quantify this through use of high-fidelity simulators to represent a range of commonly encountered clinical pathologies. METHODS/STUDY POPULATION: A benchtop study was performed with two high-fidelity breathing simulators, each representing one lung. This system allows for real-time monitoring of pressure and lung dynamics in a two-lung asymmetric injury model. One simulator was set to a fixed compliance and a resistance. A second simulator had a range of compliance and resistance values. Data were collected for 15 different test cases across a distribution of asymmetries. Each test case is run for 30 cycles. At the end of each ventilatory cycle, a short expiratory hold is performed, allowing pressure in the lung simulator, tubing, and ventilator circuit to equilibrate between cycles. RESULTS/ANTICIPATED RESULTS: Maldistribution of tidal volume was demonstrated when the compliance ratio between lung models (CL1/CL2) was 0.2 and the resistance ratio (RL1/RL2) was 10 with 23.9% (99% CI: 23.9-24.0%) of the gas volume distributed to lung 1 (103 mL L1 vs 327 mL in L2). Additionally, the injured lung when compared with the normal lung experienced higher peak pressures (12.8 cm H2O vs. 6.9 cm H2O, L1 and L2 respectively) and higher compartmentalized plateau pressures (11.5 cm H2O vs. 6.8 cm H2O, L1 and L2 respectively). DISCUSSION/SIGNIFICANCE: We demonstrate significant maldistribution of volume and pressures between two lungs in an asymmetric injury model. This study suggests significant impact of asymmetry in current lung-protective mechanical ventilation strategies and calls for better understanding of case-specific pathophysiologic changes affecting each of the two lungs.

Optimising respiratory support for early COVID-19 pneumonia: a computational modelling study

BackgroundOptimal respiratory support in early COVID-19 pneumonia is controversial and remains unclear. Using computational modelling, we examined whether lung injury might be exacerbated in early COVID-19 by assessing the impact of conventional oxygen therapy (COT), high-flow nasal oxygen therapy (HFNOT), continuous positive airway pressure (CPAP), and noninvasive ventilation (NIV). MethodsUsing an established multi-compartmental cardiopulmonary simulator, we first modelled COT at a fixed FiO2 (0.6) with elevated respiratory effort for 30 min in 120 spontaneously breathing patients, before initiating HFNOT, CPAP, or NIV. Respiratory effort was then reduced progressively over 30-min intervals. Oxygenation, respiratory effort, and lung stress/strain were quantified. Lung-protective mechanical ventilation was also simulated in the same cohort. ResultsHFNOT, CPAP, and NIV improved oxygenation compared with conventional therapy, but also initially increased total lung stress and strain. Improved oxygenation with CPAP reduced respiratory effort but lung stress/strain remained elevated for CPAP >5 cm H2O. With reduced respiratory effort, HFNOT maintained better oxygenation and reduced total lung stress, with no increase in total lung strain. Compared with 10 cm H2O PEEP, 4 cm H2O PEEP in NIV reduced total lung stress, but high total lung strain persisted even with less respiratory effort. Lung-protective mechanical ventilation improved oxygenation while minimising lung injury. ConclusionsThe failure of noninvasive ventilatory support to reduce respiratory effort may exacerbate pulmonary injury in patients with early COVID-19 pneumonia. HFNOT reduces lung strain and achieves similar oxygenation to CPAP/NIV. Invasive mechanical ventilation may be less injurious than noninvasive support in patients with high respiratory effort.

The Association Between Alveolar Dead Space Fraction and Mortality in Pediatric Acute Respiratory Distress Syndrome: A Prospective Cohort Study.

BackgroundAlveolar dead-space fraction (AVDSF), the volume of alveolar gas that does not participate in gas exchange, has been reported to predict mortality and morbidity in adults with acute respiratory distress syndrome (ARDS). This study aims to characterize AVDSF in patients with pediatric ARDS (PARDS), to determine its association with clinical outcomes and examine the validity of a previously studied cutoff (AVDSF > 0.25).MethodsThis was a prospective cohort study performed in the setting of a lung protective mechanical ventilation protocol. AVDSF was calculated by the equation: AVDSF = [partial pressure of arterial carbon dioxide (PaCO2) – end tidal carbon dioxide (etCO2)]/PaCO2. Receiver operating curve and Youden index were used to identify an AVDSF cutoff associated with mortality, which characterized “high or low AVDSF” groups. Correlation between AVDSF and clinical indices of severity were determined [including daily oxygenation index (OI), admission Pediatric Index of Mortality 2 (PIM 2) and Pediatric Logistic Organ Dysfunction (PELOD) scores]. The primary outcome, mortality in PARDS patients, was compared between the high and low AVDSF groups and analyzed in a multivariable logistic regression adjusting for inotrope use and PIM 2 score. Secondary outcomes included 28-day ventilator-free (VFD) and intensive care unit-free (IFD) days.ResultsSixty-nine PARDS patients with a median (interquartile range) age of 4.5 (0.8, 10.6) years were included in this analysis. Daily AVDSF correlated with daily OI (R2 = 0.10; p < 0.001). Mean AVDSF over the first 7 days of PARDS correlated with PIM 2 (R2 = 0.10; p = 0.010) and PELOD (R2 = 0.12; p = 0.004) scores. The greatest area under the curve identified an AVDSF cutoff of 0.22, which was close to the previously suggested 0.25. The high AVDSF group had higher mortality [7/19 (36.8%) vs. 5/50 (10.0%); p = 0.009] and lower VFD [2 (0, 18) vs. 21 (15, 24); p = 0.007] and IFD [0 (0, 16) vs. 16 (5, 21); p = 0.013]. In the multivariable model, being in the high AVDSF group [adjusted odds ratio 4.67 (95% CI: 1.12, 19.39)] was significantly associated with mortality.ConclusionsHigh AVDSF was independently associated with increased mortality and decreased VFD and IFD. AVDSF may be complementary to oxygenation indices in risk stratifying PARDS and warrant further study.

Sequential lateral positioning as a new lung recruitment maneuver: an exploratory study in early mechanically ventilated Covid-19 ARDS patients

BackgroundA sequential change in body position from supine-to-both lateral positions under constant ventilatory settings could be used as a postural recruitment maneuver in case of acute respiratory distress syndrome (ARDS), provided that sufficient positive end-expiratory pressure (PEEP) prevents derecruitment. This study aims to evaluate the feasibility and physiological effects of a sequential postural recruitment maneuver in early mechanically ventilated COVID-19 ARDS patients.MethodsA cohort of 15 patients receiving lung-protective mechanical ventilation in volume-controlled with PEEP based on recruitability were prospectively enrolled and evaluated in five sequentially applied positions for 30 min each: Supine-baseline; Lateral-1st side; 2nd Supine; Lateral-2nd side; Supine-final. PEEP level was selected using the recruitment-to-inflation ratio (R/I ratio) based on which patients received PEEP 12 cmH2O for R/I ratio ≤ 0.5 or PEEP 15 cmH2O for R/I ratio > 0.5. At the end of each period, we measured respiratory mechanics, arterial blood gases, lung ultrasound aeration, end-expiratory lung impedance (EELI), and regional distribution of ventilation and perfusion using electric impedance tomography (EIT).ResultsComparing supine baseline and final, respiratory compliance (29 ± 9 vs 32 ± 8 mL/cmH2O; p < 0.01) and PaO2/FIO2 ratio (138 ± 36 vs 164 ± 46 mmHg; p < 0.01) increased, while driving pressure (13 ± 2 vs 11 ± 2 cmH2O; p < 0.01) and lung ultrasound consolidation score decreased [5 (4–5) vs 2 (1–4); p < 0.01]. EELI decreased ventrally (218 ± 205 mL; p < 0.01) and increased dorsally (192 ± 475 mL; p = 0.02), while regional compliance increased in both ventral (11.5 ± 0.7 vs 12.9 ± 0.8 mL/cmH2O; p < 0.01) and dorsal regions (17.1 ± 1.8 vs 18.8 ± 1.8 mL/cmH2O; p < 0.01). Dorsal distribution of perfusion increased (64.8 ± 7.3% vs 66.3 ± 7.2%; p = 0.01).ConclusionsWithout increasing airway pressure, a sequential postural recruitment maneuver improves global and regional respiratory mechanics and gas exchange along with a redistribution of EELI from ventral to dorsal lung areas and less consolidation.Trial registration ClinicalTrials.gov, NCT04475068. Registered 17 July 2020, https://clinicaltrials.gov/ct2/show/NCT04475068

Clinical update in critical care of pulmonary medicine 2021

In this review, we outlined the clinical studies in critical care field of pulmonary medicine from November 1, 2020 to September 30, 2021. A Chinese retrospective study for critically ill patients with COVID-19 showed that corticosteroid therapy was associated with a reduced 28-day mortality in patients with the hyperinflammatory phenotype. In hospitalized patients with COVID-19, the use of dexamethasone resulted in lower 28-day mortality among those who were receiving either invasive mechanical ventilation or oxygen alone at randomization, and early sedation with dexmedetomidine exhibited a high probability of reduced 90-day mortality in older patients regardless of operative or non-operative cluster status. High-flow nasal cannula (HFNC) improved the prognosis compared with conventional oxygen therapy in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients with acute compensated hypercapnic respiratory failure. For COVID-19 patients suffering from acute respiratory failure with HFNC therapy, awake prone positioning reduces the incidence of treatment failure and the need for intubation. Compared with pressure-volume curve guiding positive end-expiratory pressure (PEEP) titration for acute respiratory distress syndrome (ARDS) patients, PEEP titration guided with EIT (Electrical impedance tomography) might be associated with improved driving pressure and survival rate. Extracorporeal membrane oxygenation (ECMO) is a life-saving therapy for severe ARDS patients, but the survival among ECMO-assisted patients with COVID-19 is strongly associated with a centre's experience in ECMO during the previous year and early ECMO management. Compared to conventional lung-protective mechanical ventilation (MV), neurally adjusted ventilatory assist (NAVA) decreased duration of MV. These findings also provide evidence for improving the clinical management in critical care of pulmonary medicine.

COVID-19 Pnömonisinde Noninvaziv Mekanik Ventilasyon İlişkili Pnömotoraks ve Subkütan Amfizem

One of the most serious complications of coronavirus disease-2019 (COVID-19) is atypical pneumonia with diffuse bilateral lung involvement. Severe cases present with acute respiratory failure and lung injury and may require ventilatory support. In COVID-19 patients, ventilatory support is provided with oxygen via nasal-cannula or face-mask, high frequency nasal oxygenation (HFNO), non-invasive mechanical ventilation (NIMV) or invasive mechanical ventilation depending on the severity of lung injury. Each ventilation support modality has advantages and disadvantages, and should be tailored according to patient's oxygen demand. This article aims to present NIMV and HFNO related pneumothorax and subcutaneous emphysema developing due to barotrauma in a patient with COVID-19 pneumonia and highlight the issues of lung protective mechanical ventilation with these modalities.

Severe Bronchiolitis as a Cause of ARDS in Early Childhood. Pathophysiology and Strategies to Minimize Lung Injury

Bronchiolitis is one of the most frequent acute diseases of the lower respiratory tract in infants worldwide, and Respiratory Syncytial Virus remains the most common and aggressive viral disease. The course of the disease is usually benign, but its severity may change by evolving into parenchymal disease. In the more severe cases, its clinical and radiological characteristics may be consistent with acute respiratory distress syndrome. Management of these cases includes admission to paediatric intensive care and invasive mechanical ventilation. This paper reviews the definition of paediatric and neonatal acute respiratory distress syndrome, which was primarily designed and validated for adults. The article investigates the pathophysiology of paediatric acute respiratory distress syndrome further, describing how damage to the alveolar-capillary units, surfactant inactivation and inflammation occurs. Mechanisms that contribute to acute lung injury, such as volutrauma, barotrauma, stress and strain, are illustrated in detail, and an overview of the strategies that may help minimize neonatal lung injury and optimize ventilatory support is provided. These strategies include lung-protective mechanical ventilation, surfactant treatment, inhaled nitric oxide, high frequency oscillatory ventilation, recruiting manoeuvres, prone position and neuromuscular blocking agents. The objective is to help clinicians understand the peculiar pathophysiology of severe bronchiolitis and so guide them in preventing or attenuating lung injury during treatment. As such, this paper aims to contribute to defining optimal treatment of severe cases of bronchiolitis.

Current situation in ARDS in the light of recent studies: Classification, epidemiology and pharmacotherapeutics.

In the last 50 years, there have been great research and developments in the definition and pathophysiology of acute respiratory distress syndrome (ARDS), the most progressive form of acute hypoxemic respiratory failure. Although there are various discussions and recommendations, the definition of ARDS is still based on the Berlin 2012 diagnostic criteria. Despite various studies in recent years, there is still no effective pharmacotherapeutic agent for the treatment of ARDS. Lung protective mechanical ventilation (low tidal volume, low plateau pressure, low driving pressure) in all ARDS patients, prone position, neuromuscular blockade (cisatracurium) in moderate-severe ARDS patients, and hydrocortisone therapy in sepsis-associated ARDS patients are treatments that contribute to survival. In this review, current changes in the definition and epidemiology of ARDS, recent pharmacotherapeutic research and mesenchymal stem cell therapies will be discussed in the light of newly introduced ARDS phenotypes.

Pneumomediastinum in COVID-19 Patients with Acute Respiratory Distress Syndrome.

Pneumomediastinum, an uncommon entity, has been on the rise with increasing cases of COVID-Acute respiratory distress syndrome. It has been unclear whether this entity represents an indicator of poor clinical outcome or not. The aims of this study were to find out the incidence of pneumomediastinum in COVID-Acute respiratory distress syndrome patients, describe their clinical characteristics and try to explain its plausible mechanisms.. A descriptive, cross-sectional study was carried out in the ICU of our hospital among 280 patients admitted with COVID-Acute respiratory distress syndrome over a period of 6 months. Demographics along with various clinical, laboratory, and radiological parameters were analyzed. Relevant statistical analyses were done to summarize our findings. The incidence of pneumomediastinum in COVID-ARDS patients was 2.8%. All patients were male, none had pulmonary co-morbidities and six of them (60%) were on invasive mechanical ventilation. All intubated patients were on lung protective mechanical ventilation. The median PEEP, peak airway pressure and plateau pressure were 10 (IQR: 4), 29 (IQR: 8) and 28 (IQR: 4) respectively. The mean CT severity score was 22.7 (SD: 1.64). Five patients died after 6.8 days (SD: 4.8) of diagnosis. The average hospital stay was of 34 days. Pneumomediastinum is a possible complication of COVID-Acute respiratory distress syndrome which could signify the disease severity and vice versa. Furthermore, it could be an indicator of relatively poor prognosis and therefore requires larger studies to establish the association.

Transoesophageal Ultrasound Assessment of Lung Aeration in Patients With Acute Respiratory Distress Syndrome.

Introduction: The effect of positive end-expiratory pressure (PEEP) depends closely on the potential for lung recruitment. Bedside assessment of lung recruitability is crucial for personalized lung-protective mechanical ventilation in acute respiratory distress syndrome (ARDS) patients.Methods: We developed a transoesophageal lung ultrasound (TE-LUS) method in which a quantitative (computer-assisted) grayscale determination served as a guide to PEEP-induced lung recruitment. The method is based on the following hypothesis: when the PEEP increases, inflation of the recruited alveoli leads to significant changes in the air/water ratio. Normally ventilated areas are hypoechoic because the ultrasound waves are weakly reflected while poorly aerated areas or non-aerated areas are hyperechoic. We calculated the TE-LUS re-aeration score (RAS) as the ratio of the mean gray scale level at low PEEP to that value at high PEEP for the lower and upper lobes. A RAS > 1 indicated an increase in ventilated area. We used this new method to detect changes in ventilation in patients with a low (<0.5) vs. high (≥0.5) recruitment-to-inflation (R/I) ratio (i.e., the ratio between the recruited lung compliance and the respiratory system compliance at low PEEP).Results: We included 30 patients with moderate-to-severe ARDS. In patients with a high R/I ratio, the TE-LUS RAS was significantly higher in the lower lobes than in the upper lobes (1.20 [1.12–1.63] vs. 1.05 [0.89–1.38]; p = 0.05). Likewise, the TE-LUS RAS in the lower lobes was significantly higher in the high R/I group than in the low R/I group (1.20 [1.12–1.63] vs. 1.07 [1.00–1.20]; p = 0.04).Conclusion: The increase in PEEP induces a substantial gain in the ventilation detected by TE-LUS of poorly or non-aerated lower lobes (dependent lung regions), especially in patients with a high R/I ratio.

Stochastic Modelling of Respiratory System Elastance for Mechanically Ventilated Respiratory Failure Patients.

While lung protective mechanical ventilation (MV) guidelines have been developed to avoid ventilator-induced lung injury (VILI), a one-size-fits-all approach cannot benefit every individual patient. Hence, there is significant need for the ability to provide patient-specific MV settings to ensure safety, and optimise patient care. Model-based approaches enable patient-specific care by identifying time-varying patient-specific parameters, such as respiratory elastance, Ers, to capture inter- and intra-patient variability. However, patient-specific parameters evolve with time, as a function of disease progression and patient condition, making predicting their future values crucial for recommending patient-specific MV settings. This study employs stochastic modelling to predict future Ers values using retrospective patient data to develop and validate a model indicating future intra-patient variability of Ers. Cross validation results show stochastic modelling can predict future elastance ranges with 92.59 and 68.56% of predicted values within the 5–95% and the 25–75% range, respectively. This range can be used to ensure patients receive adequate minute ventilation should elastance rise and minimise the risk of VILI should elastance fall. The results show the potential for model-based protocols using stochastic model prediction of future Ers values to provide safe and patient-specific MV. These results warrant further investigation to validate its clinical utility.

Pathophysiology of Brain Injury and Neurological Outcome in Acute Respiratory Distress Syndrome: A Scoping Review of Preclinical to Clinical Studies.

Acute respiratory distress syndrome (ARDS) has been associated with secondary acute brain injury (ABI). However, there is sparse literature on the mechanism of lung-mediated brain injury and prevalence of ARDS-associated secondary ABI. We aimed to review and elucidate potential mechanisms of ARDS-mediated ABI from preclinical models and assess the prevalence of ABI and neurological outcome in ARDS with clinical studies. We conducted a systematic search of PubMed and five other databases reporting ABI and ARDS through July 6, 2020 and included studies with ABI and neurological outcome occurring after ARDS. We found 38 studies (10 preclinical studies with 143 animals; 28 clinical studies with 1175 patients) encompassing 9 animal studies (n = 143), 1 in vitro study, 12 studies on neurocognitive outcomes (n = 797), 2 clinical observational studies (n = 126), 1 neuroimaging study (n = 15), and 13 clinical case series/reports (n = 15). Six ARDS animal studies demonstrated evidence of neuroinflammation and neuronal damage within the hippocampus. Five animal studies demonstrated altered cerebral blood flow and increased intracranial pressure with the use of lung-protective mechanical ventilation. High frequency of ARDS-associated secondary ABI or poor neurological outcome was observed ranging 82–86% in clinical observational studies. Of the clinically reported ABIs (median age 49 years, 46% men), the most common injury was hemorrhagic stroke (25%), followed by hypoxic ischemic brain injury (22%), diffuse cerebral edema (11%), and ischemic stroke (8%). Cognitive impairment in patients with ARDS (n = 797) was observed in 87% (range 73–100%) at discharge, 36% (range 32–37%) at 6 months, and 30% (range 25–45%) at 1 year. Mechanisms of ARDS-associated secondary ABI include primary hypoxic ischemic injury from hypoxic respiratory failure, secondary injury, such as lung injury induced neuroinflammation, and increased intracranial pressure from ARDS lung-protective mechanical ventilation strategy. In summary, paucity of clinical data exists on the prevalence of ABI in patients with ARDS. Hemorrhagic stroke and hypoxic ischemic brain injury were commonly observed. Persistent cognitive impairment was highly prevalent in patients with ARDS.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12028-021-01309-x.