Alveolar-arterial Oxygen Gradient Research Articles

Intraoperative effects of an alveolar recruitment manoeuvre in patients undergoing laparoscopic colon surgery

IntroductionPulmonary atelectasis is common in patients undergoing laparoscopic abdominal surgery under general anaesthesia, which increases the risk of perioperative respiratory complications. Alveolar recruitment manoeuvres (ARM) are used to open up the lung parenchyma with atelectasis, although the duration of their benefit has not been clearly established. The aim of this study was to determine the effectiveness of an ARM in laparoscopic colon surgery, the duration of response over time, and its haemodynamic impact. MethodsTwenty-five patients undergoing laparoscopic colon surgery were included. After anaesthetic induction and initiation of surgery with pneumoperitoneum, an ARM was performed, and then optimal PEEP determined. Respiratory mechanics and gas exchange variables, and haemodynamic parameters, were analysed before the manoeuvre and periodically over the following 90 min. ResultsThree patients were excluded for surgical reasons. The alveolar arterial oxygen gradient went from 94.3 (62.3−117.8) mmHg before to 60.7 (29.6−91.0) mmHg after the manoeuvre (P < .05). This difference was maintained during the 90 min of the study. Dynamic compliance of the respiratory system went from 31.3 ml/cmH2O (26.1–39.2) before the manoeuvre to 46.1 ml/cmH2O (37.5−53.5) after the manoeuvre (P < .05). This difference was maintained for 60 min. No significant changes were identified in any of the haemodynamic variables studied. ConclusionIn patients undergoing laparoscopic colon surgery, performing an intraoperative ARM improves the mechanics of the respiratory system and oxygenation, without associated haemodynamic compromise. The benefit of these manoeuvres lasts for at least one hour.

A BAYESIAN MACHINE LEARNING APPROACH FOR ESTIMATING HETEROGENEOUS SURVIVOR CAUSAL EFFECTS: APPLICATIONS TO A CRITICAL CARE TRIAL.

Assessing heterogeneity in the effects of treatments has become increasingly popular in the field of causal inference and carries important implications for clinical decision-making. While extensive literature exists for studying treatment effect heterogeneity when outcomes are fully observed, there has been limited development in tools for estimating heterogeneous causal effects when patient-centered outcomes are truncated by a terminal event, such as death. Due to mortality occurring during study follow-up, the outcomes of interest are unobservable, undefined, or not fully observed for many participants in which case principal stratification is an appealing framework to draw valid causal conclusions. Motivated by the Acute Respiratory Distress Syndrome Network (ARDSNetwork) ARDS respiratory management (ARMA) trial, we developed a flexible Bayesian machine learning approach to estimate the average causal effect and heterogeneous causal effects among the always-survivors stratum when clinical outcomes are subject to truncation. We adopted Bayesian additive regression trees (BART) to flexibly specify separate mean models for the potential outcomes and latent stratum membership. In the analysis of the ARMA trial, we found that the low tidal volume treatment had an overall benefit for participants sustaining acute lung injuries on the outcome of time to returning home but substantial heterogeneity in treatment effects among the always-survivors, driven most strongly by biologic sex and the alveolar-arterial oxygen gradient at baseline (a physiologic measure of lung function and degree of hypoxemia). These findings illustrate how the proposed methodology could guide the prognostic enrichment of future trials in the field.

Alveolar-Arterial Oxygen Gradient Ratio (Gaao2) As A Predictor of Early Mechanical Ventilation In A Patient with Suspected Sars Cov-2 Infection in the Adult Continuous Admission Area of The "Dr. Gaudencio González Garza” Of The La Raza National Medical Center.

Background: Viruses and mainly COVID and the pneumonia it causes are among the pathologies that cause the greatest damage to the alveolus-capillary membrane of the lungs in patients with this disease. Objectives: To relate the alveolar arterial oxygen gradient (GAaO2) and the start of early mechanical ventilation in patients with SARS COV - 2 virus infection in the continuous admission area. Methodology: Descriptive, retrospective, observational, cross-sectional, with 165 clinical records of patients admitted to the emergency area in a period from April 2020 to 2021. Kolmogorov – Smirnov test, Mann-Whitney U and Pearson correlation coefficient were performed. with p&gt;0.05, ROC curve for sensitivity and specificity with Youden index and multivariable regression analysis for correlation. Results: A cut-off point of GAaO2 = 210.25 was obtained with sensitivity of 95% and specificity of 94%, with 2 times more risk of starting mechanical ventilation and correlation of 89%. Conclusion: It was observed that the cut-off point was related to greater risk and correlation of initiation of mechanical ventilation. This is a reliable value to decide the start of invasive ventilation.

Efficacy of repeated pronations in patients affected by COVID-19-related acute respiratory distress syndrome: think it twice!

Prone position is widely used to ameliorate gas exchange in severe COVID-19-related ARDS (CARDS), through its beneficial effects on shunt and dead space. However, the effectiveness of repeated pronation has never been explored in this category of patients. We then retrospectively analyzed the changes of the alveolar-arterial oxygen gradient (A-aO2grad), as shunt index, and the ratio EtCO2/paCO2 ratio, as dead space index, during repeated pronation cycles in 7 patients with CARDS admitted to our Intensive Care Unit. The A-aO2grad decreased significantly more during the first pronation than the second (-43.6% vs -12.2% - p0.008) and, similarly, the improvement was maintained only after the first supination (-26.2% vs +9% - p0.04). The EtCO2/paCO2 ratio showed similar behavior but did not achieve statistical significance. Considering our findings, with the inherent limitations of the study, since pronation entails risks for the patient, as well as requiring a lot of effort from the nursing staff, further caution appears to be necessary in indicating pronation.

Alveolar–arterial oxygen gradient nonlinearly impacts the 28‐day mortality of patients with sepsis: Secondary data mining based on the MIMIC‐IV database

Lung is often implicated in sepsis, resulting in acute respiratory distress syndrome (ARDS). The alveolar-arterial oxygen gradient [D(A-a)O2 ] reflects lung diffusing capacity, which is usually compromised in ARDS. But whether D(A-a)O2 impacts the prognosis of patients with sepsis remains to be explored. Our study aims to investigate the association between D(A-a)O2 and 28-day mortality in patients with sepsis using a large sample, multicenter Medical Information Mart for Intensive Care (MIMIC)-IV database. We extracted a data of 35 010 patients with sepsis from the retrospective cohort MIMIC-IV database, by which the independent effects of D(A-a)O2 on 28-day death risk was investigated, with D(A-a)O2 as being the exposure variable and 28-day fatality being the outcome variable. Binary logistic regression and a two-piecewise linear model were employed to explore the relationship between D(A-a)O2 and the 28-day death risk after confounding factors were optimized including demographic indicators, Charlson comorbidity index (CCI), Sequential Organ Failure Assessment (SOFA) score, drug administration, and vital signs. A total of 18 933 patients were finally included in our analysis. The patients' average age was 66.67 ± 16.01 years, and the mortality at 28 days was 19.23% (3640/18933). Multivariate analysis demonstrated that each 10-mmHg rise of D(A-a)O2 was linked with a 3% increase in the probability of death at 28 days either in the unadjusted model or in adjustment for demographic variables (Odds ratio [OR]: 1.03, 95% CI: 1.02 to 1.03). But, each 10 mmHg increase in D(A-a)O2 was associated with a 3% increase of death (OR: 1.03, 95% CI: 1.023 to 1.033) in the case of adjustment for all covariants. Through smoothed curve fitting and generalized summation models, we found that non-linear relationship existed between D(A-a)O2 and the death at 28-day, which demonstrated that D(A-a)O2 had no any impacts on the prognosis of patients with sepsis when D(A-a)O2 was less than or equal to 300 mmHg, but once D(A-a)O2 exceeded 300 mmHg, however, every 10 mmHg elevation of D(A-a)O2 is accompanied by a 5% increase of the 28-day death (OR: 1.05; 95% CI:1.04 to 1.05, p < 0.0001). Our findings suggests that D(A-a)O2 is a valuable indicator for the management of sepsis patient, and it is recommended that D(A-a)O2 be maintained less than 300 mmHg as far as possible during sepsis process.

Aerosolized Pulmonary Delivery of mRNA Constructs Attenuates Severity of Escherichia coli Pneumonia in the Rat.

Acute respiratory distress syndrome (ARDS), a rapid onset inflammatory lung disease with no effective specific therapy, typically has pathogenic etiology termed pneumonia. In previous studies nuclear factor-κB (NF-κB) inhibitor α super-repressor (IκBα-SR) and extracellular superoxide dismutase 3 (SOD3) reduced pneumonia severity when prophylactically delivered by viral vector. In this study, mRNA coding for green fluorescent protein, IκBα-SR, or SOD3 was complexed with cationic lipid, passed through a vibrating mesh nebulizer, and delivered to cell culture or directly to rats undergoing Escherichia coli pneumonia. Injury level was then assessed at 48 h. In vitro, expression was observed as early as 4 h in lung epithelial cells. IκBα-SR and wild-type IκBα mRNAs attenuated inflammatory markers, while SOD3 mRNA induced protective and antioxidant effects. In rat E. coli pneumonia, IκBα-SR mRNA reduced arterial carbon dioxide (pCO2) and reduced lung wet/dry ratio. SOD3 mRNA improved static lung compliance and alveolar-arterial oxygen gradient (AaDO2) and decreased bronchoalveolar lavage (BAL) bacteria load. White cell infiltration and inflammatory cytokine concentrations in BAL and serum were reduced by both mRNA treatments compared to scrambled mRNA controls. These findings indicate nebulized mRNA therapeutics are a promising approach to ARDS therapy, with rapid expression of protein and observable amelioration of pneumonia symptoms.

Changes in Arterial-Alveoli Oxygen Gradient During and after Cardiac Surgery in Patients with Congenital Heart Disease

ABSTRACT Objective: Disturbance in gas exchange leads to increased ventilation needs, time to stay in the ICU and death. Arterial-alveoli oxygen gradient (A-a) has been studied in adults but has not been considered in children under one year of age who have congenital heart disease and had undergone heart surgery. We decided to examine (A-a) in these patients. Materials and Methods: This study is a retrospective study. Patients were divided into two groups based on mortality. Arterial blood gas information was extracted the post-anesthesia, post-bypass, and 4 hours to 16 hours after surgery. The values (A-a) were calculated using a standard formula. Data were analyzed by SPSS software. P &lt; 0.05 was considered statistically significant. Results: 14 boys and 9 girls were examined. Among these patients, four girls and three boys died. Arterial-alveolar oxygen gradient changes are similar in the living and the dead (P = 0.508). The mean arterial-alveolar oxygen gradients did not show a significant difference between the alive persons and the dead (P = 0.337). Arterial-alveolar oxygen gradient changes during the time, and this change was statistically significant (P = 0.000). Arterial-alveolar oxygen gradient in cardiac surgery in children under one year of age declines up to 16 hours after surgery. The duration of hospitalization (P = 0.290 (or intubation in the ICU (P = 0.792) does not affect the alveolar-arterial oxygen gradient. Conclusion: Arterial-alveolar changes in oxygen in heart surgery in children under one year of age were significant during the time and generally decreased 16 hours after the surgery. There was no statistically significant relationship between the length of hospital stay or intubation in the ICU with the arterial alveolar oxygen gradient.

Inhaled Sargramostim (Recombinant Human Granulocyte-Macrophage Colony-Stimulating Factor) for COVID-19-Associated Acute Hypoxemia: Results of the Phase 2, Randomized, Open-Label Trial (iLeukPulm).

Granulocyte-macrophage colony-stimulating factor (GM-CSF), a protein produced in the lung, is essential for pulmonary host defense and alveolar integrity. Prior studies suggest potential benefits in several pulmonary conditions, including acute respiratory distress syndrome and viral infections. This trial evaluated the effect of the addition of inhaled sargramostim (yeast-derived, glycosylated recombinant human GM-CSF) to standard of care (SOC) on oxygenation and clinical outcomes in patients with COVID-19-associated acute hypoxemia. A randomized, controlled, open-label trial of hospitalized adults with COVID-19-associated hypoxemia (oxygen saturation <93% on ≥2 L/min oxygen supplementation and/or PaO2/FiO2 <350) randomized 2:1 to inhaled sargramostim (125 mcg twice daily for 5 days) plus SOC versus SOC alone. Institutional SOC before and during the study was not limited. Primary outcomes were change in the alveolar-arterial oxygen gradient (P(A-a)O2) by day 6 and the percentage of patients intubated within 14 days. Safety evaluations included treatment-emergent adverse events. Efficacy analyses were based on the modified intent-to-treat population, the subset of the intent-to-treat population that received ≥1 dose of any study treatment (sargramostim and/or SOC). An analysis of covariance approach was used to analyze changes in oxygenation measures. The intubation rate was analyzed using the chi-squared test. All analyses are considered descriptive. The study was institutional review board approved. In total, 122 patients were treated (sargramostim, n = 78; SOC, n = 44). The sargramostim arm experienced greater improvement in P(A-a)O2 by day 6 compared to SOC alone (least squares [LS] mean change from baseline [SE]: -102.3 [19.4] versus -30.5 [26.9] mmHg; LS mean difference: -71.7 [SE 33.2, 95% CI -137.7 to -5.8]; P = .033; n = 96). By day 14, 11.5% (9/78) of sargramostim and 15.9% (7/44) of SOC arms required intubation (P = .49). The 28-day mortality was 11.5% (9/78) and 13.6% (6/44) in the sargramostim and SOC arms, respectively (hazard ratio 0.85; P = .76). Treatment-emergent adverse events occurred in 67.9% (53/78) and 70.5% (31/44) on the sargramostim and SOC arms, respectively. The addition of inhaled sargramostim to SOC improved P(A-a)O2, a measure of oxygenation, by day 6 in hospitalized patients with COVID-19-associated acute hypoxemia and was well tolerated. Inhaled sargramostim is delivered directly to the lung, minimizing systemic effects, and is simple to administer making it a feasible treatment option in patients in settings where other therapy routes may be difficult. Although proportionally lower rates of intubation and mortality were observed in sargramostim-treated patients, this study was insufficiently powered to demonstrate significant changes in these outcomes. However, the significant improvement in gas exchange with sargramostim shows this inhalational treatment enhances pulmonary efficiency in this severe respiratory illness. These data provide strong support for further evaluation of sargramostim in high-risk patients with COVID-19.

Obstructive sleep apnoea and sleep disorders in pregnancy.

This review provides a summary for obstetricians, midwives, other health professionals and women contemplating pregnancy about the interactions between pregnancy and breathing during sleep. This review will first examine the normal physiological changes of pregnancy and their relationship to sleep-disordered breathing (SDB), and it will then summarise the current knowledge of SDB in pregnancy. Many changes in the respiratory system during pregnancy, particularly during the third trimester, can alter respiratory function during sleep, increasing the incidence and severity of SDB. These changes include increased ventilatory drive and metabolic rate, reduced functional residual capacity and residual volume, increased alveolar-arterial oxygen gradients and changes in the upper airway. The clinical importance of these changes during pregnancy is demonstrated by the increased incidence of snoring and obstructive sleep apnoea hypopnoea syndrome. As SDB is associated with obesity, the increasing incidence of obesity pre-pregnancy will likely increase SDB during pregnancy over the next decade. If a physician is asked to review a pregnant patient, they should always consider the possibility of SDB.

Negative-pressure-assisted ventilation lowers driving pressure and mechanical power in an ARDS model.

Increased lung heterogeneity from regional alveolar collapse drives ventilator-induced lung injury in patients with acute respiratory distress syndrome (ARDS). New methods of preventing this injury require study. Our study objective was to determine whether the combination of temporary transvenous diaphragm neurostimulation (TTDN) with standard-of-care volume-control mode ventilation changes lung mechanics, reducing ventilator-induced lung injury risk in a preclinical ARDS model. Moderate ARDS was induced using oleic acid administered into the pulmonary artery in pigs, which were ventilated for 12 h postinjury using volume-control mode at 8 mL/kg, positive end-expiratory pressure (PEEP) 5 cmH2O, with respiratory rate and [Formula: see text] set to achieve normal arterial blood gases. Two groups received TTDN, either every second breath [mechanical ventilation (MV) + TTDN50%, n = 6] or every breath (MV + TTDN100%, n = 6). A third group received volume-control ventilation only (MV, n = 6). At study-end, [Formula: see text]/[Formula: see text] was highest and alveolar-arterial oxygen (A-a) gradient was lowest for MV + TTDN100% (P < 0.05). MV + TTDN100% had the smallest end-expiratory lung volume loss and lowest extravascular lung water at study-end (P < 0.05). Static lung compliance was highest and transpulmonary driving pressure was lowest at baseline, postinjury, and study-end in MV + TTDN100% (P < 0.05). The total exposure to transpulmonary driving pressure, mechanical power, and mechanical work was the lowest in MV + TTDN100% (P < 0.05). Lung injury score and total inflammatory cytokine concentration in lung tissue were the lowest in MV + TTDN100% (P < 0.05). Volume-control ventilation plus transvenous diaphragm neurostimulation on every breath improved [Formula: see text]/[Formula: see text], A-a gradient, and alveolar homogeneity, as well as reduced driving pressure, mechanical power, and mechanical work, and resulted in lower lung injury scores and tissue cytokine concentrations in a preclinical ARDS model.NEW & NOTEWORTHY Combining temporary transvenous diaphragm neurostimulation with volume-control ventilation on every breath, called negative-pressure-assisted ventilation, improved gas exchange and alveolar homogeneity in a preclinical model of moderate ARDS. Transpulmonary driving pressure, mechanical power, and mechanical work reductions were observed and resulted in lower lung injury scores and tissue cytokine concentrations in the every-breath-neurostimulation group compared with volume-control ventilation only. Negative-pressure-assisted ventilation is an exciting new potential tool to reduce ventilator-induced lung injury in patients with ARDS.

Alveolar-arterial Oxygen Gradient in COVID-19 Pneumonia Initiated on Noninvasive Ventilation: Looking into the Mortality-prediction Ability.

How to cite this article: Karim HMR, Esquinas AM. Alveolar-arterial Oxygen Gradient in COVID-19 Pneumonia Initiated on Noninvasive Ventilation: Looking into the Mortality-prediction Ability. Indian J Crit Care Med 2022;26(10):1152.

Índices de oxigenación como marcadores evolutivos de lesión pulmonar aguda por SARS-CoV-2

Background: acute lung injury (APL) is a heterogeneous syndrome manifested by acute respiratory failure; SARS-CoV-2 is an emerging virus capable of causing APL. The oxigenation index (OI) are the numerical expression that reflect the capillary alveolus gas exchange, highlighting the alveolar-arterial oxygen gradient (G (Aa) O2), the arterial pressure of oxygen / inspired oxygen fraction (PaO2 / FiO2) and the respiratory index (IR). Objective: to identify the clinical evolution of APL through OI. Material and methods: retrospective, longitudinal, descriptive, analytical study. Patients with a diagnosis of a suspected or confirmed case of SARS-CoV-2 or COVID-19 pneumonia were classified according to the supplemental oxygen device used at the time of admission to the ICU. Group 1: No invasive respiratory support. Group 2: With invasive respiratory support. The OIs were calculated at admission, at 24 hours and at 96 hours and the outcome of the patients was observed. Results: 175 patients were recruited, for group 1 the GA-aO2 at 96hrs had AUC 0.965 (95% CI 0.914-1.000) p = 0.000 and for group 2 the PaO2 / FiO2 at 96hrs with AUC of 0.836 (CI 95% 0.766-0.905) and the IR with AUC of 0.832 (95% CI 0.761-0.902) p = 0.000. Conclusion: OIs are markers of the progression of APL by SARS-CoV-2, improving their diagnostic performance over time.

Mixed venous oxygen tension is a crucial prognostic factor in pulmonary hypertension: a retrospective cohort study

BackgroundThe prognostic value of mixed venous oxygen tension (PvO2) at pulmonary hypertension diagnosis treated with selective pulmonary vasodilators remains unclear. This study sought to investigate the association of PvO2 with long-term prognosis in pulmonary arterial hypertension (PAH) and medically treated chronic thromboembolic pulmonary hypertension (CTEPH) and to identify the distinct mechanisms influencing tissue hypoxia in patients with CTEPH or PAH.MethodsWe retrospectively analyzed data from 138 (age: 50.2 ± 16.6 years, 81.9% women) and 268 (age: 57.4 ± 13.1 years, 72.8% women) patients with PAH and CTEPH, respectively, diagnosed at our institution from 1983 to 2018. We analyzed the survival rates of patients with/without tissue hypoxia (PvO2 < 35 mmHg) and identified their prognostic factors based on the pulmonary hypertension risk stratification guidelines.ResultsSurvival was significantly poorer in patients with tissue hypoxia than in those without it for PAH (P = 0.001) and CTEPH (P = 0.017) treated with selective pulmonary vasodilators. In patients with PAH, PvO2 more strongly correlated with prognosis than other hemodynamic prognostic factors regardless of selective pulmonary vasodilators usage. PvO2 was the only significant prognostic factor in patients with CTEPH treated with pulmonary hypertension medication. Patients with CTEPH experiencing tissue hypoxia exhibited significantly poorer survival than those in the intervention group (P < 0.001). PvO2 more strongly correlated with the cardiac index (CI) than the alveolar-arterial oxygen gradient (A-aDO2) in PAH; whereas in CTEPH, PvO2 was more strongly correlated with A-aDO2 than with CI.ConclusionsPvO2 may represent a crucial prognostic factor for pulmonary hypertension. The prognostic impact of tissue hypoxia affects different aspects of PAH and CTEPH, thereby reflecting their distinct pathogenesis.

Alveolar-Arterial Gradient Is an Early Marker to Predict Severe Pneumonia in COVID-19 Patients.

Background: One of the main challenges in the management of COVID-19 patients is to early assess and stratify them according to their risk of developing severe pneumonia. The alveolar–arterial oxygen gradient (D(A-a)O2) is defined as the difference between the alveolar and arteriolar concentration of oxygen, an accurate index of the ventilatory function. The aim of this study is to evaluate D(A-a)O2 as a marker for predicting severe pneumonia in COVID-19 patients, in comparison to the PaO2/FiO2. Methods: This retrospective, multicentric cohort study included COVID-19 patients admitted to two Italian hospitals between April and July 2020. Clinical and laboratory data were retrospectively collected at the time of hospital admission and during hospitalization. The presence of severe COVID-19 pneumonia was evaluated, as defined by the Infectious Diseases Society of America (IDSA) criteria for community-acquired pneumonia (CAP). Patients were divided in severe and non-severe groups. Results: Overall, 53 COVID-19 patients were included in the study: male were 30/53 (57%), and 10/53 (19%) had severe pneumonia. Patients with severe pneumonia reported dyspnea more often than non-severe patients (90% vs. 39.5%; p = 0.031). A history of chronic obstructive pulmonary disease (COPD) was recalled by 5/10 (50%) patients with severe pneumonia, and only in 6/43 (1.4%) of non-severe cases (p = 0.023). A ROC curve, for D(A-a)O2 >60 mmHg in detecting severe pneumonia, showed an area under the curve (AUC) of 0.877 (95% CI: 0.675–1), while the AUC of PaO2/FiO2 < 263 mmHg resulted 0.802 (95% CI: 0.544–1). D(A-a)O2 in comparison to PaO2/FiO2 had a higher sensibility (77.8% vs. 66.7%), positive predictive value (75% vs. 71.4%), negative predictive value (94% vs. 91%), and similar specificity (94.4% vs. 95.5%). Conclusions: Our study suggests that the D(A-a)O2 is more appropriate than PaO2/FiO2 to identify COVID-19 patients at risk of developing severe pneumonia early.

Thromboembolic disorder in a dog after cesarean surgery

A 3-year female dog (intact primiparous) overweight Labrador Retriever was presented as an emergency (fever, lethargy, and anorexia)patient. Four days earlier, this dog had a dystocia (secondary uterine inertia with stillborn fetus) that was relieved via cesareansurgery. Disseminated intravascular coagulation panel indicated marked increases in D-dimers, increases in partial prothrombintime, and decreases in antithrombin III activity. Abdominal ultrasonography revealed a severely mottled spleen with multifocalinfarction. Arterial blood gas analysis indicated increases in alveolar-arterial oxygen gradient. Pulmonary thromboembolism wassuspected. Based on the history (peripartum obesity and cesarean delivery) and clinical manifestation, it was hypothesized that thepregnancy-related hypercoagulable state and postpartum period led to the development of venous thromboembolism. To authors’knowledge, this is the first case report of a suspected thromboembolic disorder in a postcesarean dog.

Alveolar Arterial Gradient and Respiratory Index in Predicting the Outcome of COVID-19 Patients; a Retrospective Cross-Sectional Study

Introduction:Alveolar arterial (A-a) oxygen gradient and respiratory index can be of immense help for the critical care physician in clinical decision making. This study aimed to evaluate the potential application of A-a oxygen gradient and respiratory index in predicting the survival of COVID-19 patients in intensive care unit (ICU).Method:This is a retrospective cross-sectional study involving 215 adult patients with COVID-19 disease, admitted to the ICU between 1st April 2020 and 30 June 2021. Details regarding demographic variables, comorbidities, laboratory and arterial blood gas (ABG) findings were recorded. Alveolar-arterial gradient and respiratory index were calculated and tested as predictors of survival. Result:The mean age of the patients was 51.92 years (65.6 % male). Hypertension was the most common comorbidity and oxygen via non-rebreathing mask was the most common modality used at the time of ICU admission. Mortality was 28.37% and average length of stay was 12.84 days. Patients who died were older (p=0.02), mostly male (p=0.017), had at least one comorbidity (p<0.001), and higher heart rate and respiratory rate (<0.001 and p=0.03, respectively), lower pH on arterial blood gas (ABG) (p=0.002), higher FiO2 requirement (p<0.001), and increased A-a oxygen gradient on admission compared to survivors. According to receiver operating characteristic (ROC) curve analysis, A-a oxygen gradient and respiratory index were not sensitive or specific in predicting mortality in the studied patient subset. Conclusion:A-a oxygen gradient and respiratory index calculated at time of admission to ICU in patients with COVID-19 were poor predictors of survival.

Critical roles of interleukin-33/suppression of tumorigenicity 2 (IL-33/ST2) in pulmonary disorders.

Critical roles of interleukin-33/suppression of tumorigenicity 2 (IL-33/ST2) in pulmonary disorders.

Effect of two different levels of positive end-expiratory pressure (PEEP) on oxygenation and ventilation during pneumoperitoneum for laparoscopic surgery in children: A randomized controlled study.

Positive end-expiratory pressure (PEEP) is used to attenuate the changes in respiratory parameters because of pneumoperitoneum during laparoscopic (LAP) surgery. As the ideal level of PEEP during LAP in children is not known, this study compared the effect of 5- and 10-cm H2O of PEEP on oxygenation, ventilator, and hemodynamic parameters during pediatric LAP. After obtaining approval from the Institute Ethics Committee and written informed parental consent, 30 American Society of Anesthesiologists (ASA) I and II children aged 2-10 years, undergoing LAP were randomized to receive PEEP of 5- or 10-cm H2O during pneumoperitoneum. Baseline hemodynamic and ventilatory parameters, PaO2, and PaCO2 were measured 2 min after tracheal intubation, 2 min and 1 h after pneumoperitoneum, and after deflation of pneumoperitoneum. Oxygenation index, dynamic compliance, and alveolar-arterial oxygen gradient (D (A-a) O2) were calculated at the above-mentioned time points. Data were analyzed using Student's t-test and repeated measures ANOVA with Bonferroni correction. The oxygenation index and D(A-a)O2 decreased in PEEP 5 Group and increased in PEEP 10 Group after pneumoperitoneum, the difference between the two groups being statistically significant (P = 0.001). The dynamic compliance decreased in PEEP 5 Group and increased or remained the same in PEEP 10 Group after pneumoperitoneum, the difference between the two groups being significant (P = 0.001). There were no significant changes in the hemodynamic parameters in the two groups. Use of 10-cm H2O PEEP during pneumoperitoneum in children improves ventilation and oxygenation, without significant hemodynamic changes.

Impact of hepatopulmonary syndrome in liver transplantation candidates and the role of angiogenesis.

Hepatopulmonary syndrome affects 10-30% of patients with cirrhosis and portal hypertension. We evaluated the serum angiogenic profile of hepatopulmonary syndrome and assessed the clinical impact of hepatopulmonary syndrome in patients evaluated for liver transplantation. The Pulmonary Vascular Complications of Liver Disease 2 study was a multicentre, prospective cohort study of adults undergoing their first liver transplantation evaluation. Hepatopulmonary syndrome was defined as an alveolar-arterial oxygen gradient ≥15 mmHg (≥20 mmHg if age >64 years), positive contrast-enhanced transthoracic echocardiography and absence of lung disease. We included 85 patients with hepatopulmonary syndrome and 146 patients without hepatopulmonary syndrome. Patients with hepatopulmonary syndrome had more complications of portal hypertension and slightly higher Model for End-Stage Liver Disease-Na score compared to those without hepatopulmonary syndrome (median (interquartile range) 15 (12-19) versus 14 (10-17), p=0.006). Hepatopulmonary syndrome patients had significantly lower 6-min walk distance and worse functional class. Hepatopulmonary syndrome patients had higher circulating angiopoietin 2, Tie2, tenascin C, tyrosine protein kinase Kit (c-Kit), vascular cell adhesion molecule 1 and von Willebrand factor levels, and lower E-selectin levels. Patients with hepatopulmonary syndrome had an increased risk of death (hazard ratio 1.80, 95% CI 1.03-3.16, p=0.04), which persisted despite adjustment for covariates (hazard ratio 1.79, 95% CI 1.02-3.15, p=0.04). This association did not vary based on levels of oxygenation, reflecting the severity of hepatopulmonary syndrome. Hepatopulmonary syndrome was associated with a profile of abnormal systemic angiogenesis, worse exercise and functional capacity, and an overall increased risk of death.

198 Intrapulmonary shunt assessment in pulmonary arterial hypertension

Abstract Aims Pulmonary arterial hypertension (PAH) is a rare, progressive disease with a poor prognosis. It is characterized by the presence of mean pulmonary arterial pressure (mPAP) ≥25 mmHg along with a pulmonary arterial wedge pressure (PAWP) ≤15 mmHg and pulmonary vascular resistance (PVR) &amp;gt;3 Wood units at right heart catheterization, in the absence of other causes of pre-capillary PH such as PH due to lung diseases, chronic thromboembolic PH, or other rare diseases. Hypoxaemia is a frequent finding in patients with PAH and could be related to ventilation–perfusion mismatch, reduced diffusing capacity, decreased cardiac output, or the opening of intrapulmonary (IP) or intracardiac shunt. Purpose of the present study is to detect IP shunts in PAH patients and its determinants. Methods and results We retrospectively enrolled 29 PAH patients, collecting clinical parameters, haemodynamic and blood gas analysis at baseline and after specific therapies at follow-up. Shunt fraction was calculated by the formula (Cc—Ca)/(Cc—Cv) during oxygen supplementation (FiO2 100%). Intracardiac defects were excluded by echo contrast examination. As expected, after treatments our results showed a significant decrease of PAPm (−7.2 ± 11.6 mmHg) and a significant decrease of PVR (−2.1 ± 3.9 WU). However, it was reported a statistically significant decrease in Hb value (−1.2 ± 1.7 g/dl), in SpO2 (−2.1 ± 3.8%) and in the alveolar–arterial oxygen gradient (a-ADO2) (+54.5 ± 113.1 mmHg). 6MWT and NYHA decreased at follow-up but not statistically significance was detected. IP shunt increase was detected at follow-up after specific treatments (delta Shunt +6.9 ± 6.5%). At multivariate analysis delta PVR remains the only independent determinants of delta Shunts with a significative increment of shunts when PVR are reduced by more than three WU. Conclusions Specific PAH treatments determine a decrease of PVR, but a reverse correlation with IP shunt was noticed. Increase of IP shunt could be not a favourable clinical feature. In fact high IP shunt fraction could determine hypoxaemia and the need of a chronic oxygen supply therapy. Although a not statistically significant decrease of 6MWT and NYHA was found, it is reasonable that a long-standing hypoxaemia could reduce the aerobic function capacity. Ours results unfortunately were deeply influenced by the loss of a great part of elective patients during the pandemic, with the most part of data coming from patients needing hospitalization. This could explain why the delta shunt fraction is higher than expected.