P/FP ratio: incorporation of PEEP into the PaO2/FiO2 ratio for prognostication and classification of acute respiratory distress syndrome

Deciphering Oxygenation Metrics in ARDS: A Deep Dive into the OXIVA-CARDS Study

Gangireddy S, Kambagiri P, Jindal A. Deciphering Oxygenation Metrics in ARDS: A Deep Dive into the OXIVA-CARDS Study. Indian J Crit Care Med 2025;29(3):282.

Metabolic Regulation in Acute Respiratory Distress Syndrome: Implications for Inflammation and Oxidative Stress

Acute respiratory distress syndrome (ARDS) is a severe and life-threatening pulmonary condition characterized by intense inflammation and disrupted oxygen exchange, which can lead to multiorgan failure. Recent findings have established ARDS as a systemic inflammatory disorder involving complex interactions between lung injury, systemic inflammation, and oxidative stress. This review examines the pivotal role of metabolic disturbances in the pathogenesis of ARDS, emphasizing their influence on inflammatory responses and oxidative stress. Common metabolic abnormalities in ARDS patients, including disruptions in carbohydrate, amino acid, and lipid metabolism, contribute significantly to the disease's severity. These metabolic dysfunctions interplay with systemic inflammation and oxidative stress, further exacerbating lung injury and worsening patient outcomes. By analyzing the regulatory mechanisms of various metabolites implicated in ARDS, we underscore the potential of targeting metabolic pathways as a therapeutic approach. Such interventions could help attenuate inflammation and oxidative stress, presenting a promising strategy for ARDS treatment. Additionally, we review potential drugs that modulate metabolic pathways, providing valuable insights into the etiology of ARDS and potential therapeutic directions. This comprehensive analysis enhances our understanding of ARDS and highlights the importance of metabolic regulation in the development of effective treatment strategies. Key findings from this review demonstrate that metabolic disturbances, particularly those affecting carbohydrate, amino acid, and lipid metabolism, play critical roles in amplifying inflammation and oxidative stress, underscoring the potential of metabolic-targeted therapies to improve patient outcomes.

Association between PaO2/(FiO2*PEEP) ratio and in-hospital mortality in COVID-19 patients: A reanalysis of published data from Peru using PaO2/(FiO2*PEEP) ratio in place of PaO2/FaO2 ratio

P/FP [PaO2/(FiO2*PEEP)] is associated with in-hospital mortality in patients with acute respiratory distress syndrome (ARDS). However, to the best of our knowledge, the association between P/FP after 24 hours of invasive mechanical ventilation (IMV) and in-hospital mortality in patients with ARDS due to Coronavirus Disease 2019 (COVID-19) remained unclear. This study aimed to evaluate the relationship between the P/FP after 24 hours of IMV and in-hospital mortality in patients with ARDS due to COVID-19. We reanalyzed previously published data from Peru. Hueda-Zavaleta et al conducted a retrospective cohort study between April 2020 and April 2021 in southern Peru. A total of 200 hospitalized COVID-19 patients requiring IMV were included in this analysis. We used Cox proportional hazard regression models and Kaplan-Meier survival analysis to investigate the effect of P/FP after 24 hours of IMV on in-hospital mortality. We used a restricted cubic spline regression and a two-piecewise Cox proportional hazards model to explore the relationship between P/FP after 24 hours of IMV and in-hospital mortality in patients with ARDS due to COVID-19. Of the 200 patients, 51 (25.50%) died in hospital. The median P/FP was 20.45 mm Hg/cmH2O [interquartile range 15.79-25.21 mm Hg/cmH2O], with a range of 5.67 mm Hg/cmH2O to 51.21 mm Hg/cmH2O. Based on the P/FP ratio, patients were equally divided into 2 groups (low group [P/FP < 20.50 mm Hg/cmH2O] and high group [P/FP ≥ 20.50 mm Hg/cmH2O]). In-hospital mortality was lower in the high P/FP group than in the low P/FP group (12 [12%] vs 39 [39%]; unadjusted hazard ratio [HR]: 0.33, 95% confidence interval [CI]: 0.17-0.63; adjusted HR: 0.10, 95% CI: 0.02-0.47). We also found a nonlinear relationship between P/FP and in-hospital mortality. After adjusting for potential confounders, the HR was 0.67 (95% CI: 0.56-0.79) for P/FP ≤ 22 mm Hg/cmH2O and 1.10 (95% CI: 0.83-1.47) for P/FP > 22 mm Hg/cmH2O. In addition, lymphocytes ≤ 1 × 109/L and acute kidney failure had a higher risk of death. After adjusting for potential confounders, the P/FP after 24 hours of IMV was nonlinearly associated with in-hospital mortality in patients with ARDS due to COVID-19.

Oxygenation Index, Oxygen Saturation Index vs PaO2/FiO2 *PEEP: A Secondary Analysis of OXIVA-CARDS Study

Background

The classification of Berlin definition is based on the PaO2/FiO2 ratio, which has been found to have a poor association with mortality. Airway pressures reflect lung compliance and the settings of mechanical ventilators. In this study, we aimed to investigate the change in the severity of COVID-19-associated acute respiratory distress syndrome (ARDS) classification using [PaO2/FiO2 × PEEP] (P/FP) ratio compared to the traditional P/F ratio, and whether the P/FP ratio improves the predictive validity of in-hospital mortality.

Methods

Our study sample included patients from the OXIVA-CARDS study. In this secondary analysis, we examined the oxygenation index and oxygen saturation index in relation to the P/FP ratio, as well as the risk of P/FP in mortality. We used Pearson's correlation to assess the relationships between various parameters. Receiver operating characteristic analysis with Youden's index was used to compare the prognostic value of the oxygenation index (OI), oxygen saturation index (OSI), P/F ratio, P/FP ratio, and SaO2/FiO2 ratio for predicting overall mortality. Multiple logistic regression was also performed to determine the impact of mean airway pressure (Pmean), S/F ratio, OI, and P/FP ratio on mortality.

Results

A total of 201 patients (with 1543 measurements) were included in the analysis. Overall, 522 (34%) were reclassified into either more or less severe categories. Patients who were classified as having severe ARDS based on the P/FP ratio had significantly lower P/FP ratio, oxygenation index, and A-a O2 gradient as compared to those classified as having severe ARDS based on the P/F ratio (p < 0.05) at all levels of ARDS severity. On multivariate regression analysis, only the OI significantly impacted mortality (p < 0.05).

Conclusion

We observed that the oxygen index and oxygen saturation index were more sensitive than the PaO2/FiO2 ratio and P/FP ratio. Additionally, only the oxygenation index had a significant impact on mortality. By including airway pressures in the calculation of the OI, its predictive ability is enhanced compared to using the S/F ratio, P/F ratio, or P/FP ratio.

Highlights

The sensitivity of mortality by including Pmean is higher as compared to when only PEEP is taken into consideration. P/FP is a weak predictor of mortality as compared to OI and OSI.

How to cite this article

Vadi SMR, Sanwalka N, Suthar D. Oxygenation Index, Oxygen Saturation Index vs PaO2/FiO2 *PEEP: A Secondary Analysis of OXIVA-CARDS Study. Indian J Crit Care Med 2024;28(10):917-922.

Oxygenation Indices in Adult COVID ARDS Patients

How to cite this article: Palanidurai S, Phua J, Mukhopadhyay A. Oxygenation Indices in Adult COVID ARDS Patients. Indian J Crit Care Med 2024;28(9):887-888.

Evaluation of the combined predictive value of multiple indicators based on diaphragmatic ultrasound using logistic regression and ROC curve in weaning from mechanical ventilation in pediatric patients

Background

Conventional single indicators have low sensitivity and specificity for predicting weaning from mechanical ventilation in pediatric patients, necessitating the establishment of a combined prediction model for predicting weaning outcomes.

Objectives

To explore the combined predictive value of PaO2/FiO2 Ratio (P/F ratio), diaphragm excursion-rapid shallow breathing index (DE-RSBI), diaphragm thickening fraction-rapid shallow breathing index (DTF-RSBI), and Pediatric Critical Illness Score (PCIS) in weaning from mechanical ventilation in pediatric patients.

Methods

Sixty critically ill pneumonia pediatric patients requiring mechanical ventilation treatment from July 2022 to June 2023 at the Second Affiliated Hospital of Jiaxing University were selected. They all underwent a spontaneous breathing trial (SBT) and were divided into the weaning success group (42 cases) and weaning failure group (18 cases) based on the weaning outcome. Parameters including total duration of illness, mechanical ventilation duration, heart rate (HR), P/F ratio, diaphragm excursion (DE), DE-RSBI, diaphragm thickening fraction (DTF), DTF-RSBI, and PCIS were included in univariate and multivariate logistic regression analyses to determine independent factors affecting pediatric weaning success. Receiver operating characteristic (ROC) curves were plotted to evaluate the predictive value of P/F ratio, DE-RSBI, DTF-RSBI, PCIS alone or in combination for weaning success.

Results

Comparing P/F ratio, DE, DE-RSBI, DTF, DTF-RSBI and PCIS, there were statistically significant differences (P < 0.05). Through collinearity analysis and binary logistic regression analysis,P/F ratio [OR = 0.777, 95% CI (0.641,0.941)], DE-RSBI [OR = 1.694, 95% CI (1.172, 2.447)], DTF-RSBI [OR = 1.057, 95% CI (1.002, 1.114)], and PCIS [OR = 0.661, 95% CI (0.445, 0.982)] were identified as independent factors affecting successful weaning(P < 0.05).The regression equation was: LogitP = 73.299-0.253 P/F ratio + 0.525DE-RSBI + 0.055DTF-RSBI-0.43PCIS.The sensitivity of the combined indicator Logit(P) in predicting successful weaning from mechanical ventilation in pediatric patients was 88.9%, with a specificity of 95.2% (optimal cutoff value of 0.511), and the area under the ROC curve (AUC) was 0.960 [95% CI (0.915, 1.000)]. The AUC of the combined prediction model for predicting pediatric weaning was greater than that of P/F ratio, DE-RSBI, DTF-RSBI and PCIS alone (Z values = 9.129, 2.061, 2.075, 8.326, P < 0.05).

Conclusions

In mechanically ventilated pediatric patients, the combined prediction model has better predictive value for weaning success compared to using P/F ratio, DE-RSBI, DTF-RSBI, or PCIS alone.

Progressive changes in pulmonary gas exchange during invasive respiratory support for COVID-19 associated acute respiratory failure: A retrospective study of the association with 90-day mortality

BACKGROUND

Ratio of arterial pressure of oxygen and fraction of inspired oxygen (P/F ratio) together with the fractional dead space (Vd/Vt) provides a global assessment of pulmonary gas exchange. The aim of this study was to assess the potential value of these variables to prognosticate 90-day survival in patients with COVID-19 associated ARDS admitted to the Intensive Care Unit (ICU) for invasive ventilatory support.

METHODS

In this single-center observational, retrospective study, P/F ratios and Vd/Vt were assessed up to 4 weeks after ICU-admission. Measurements from the first 2 weeks were used to evaluate the predictive value of P/F ratio and Vd/Vt for 90-day mortality and reported by the adjusted hazard ratio (HR) and 95% confidence intervals [95%CI] by Cox proportional hazard regression.

RESULTS

Almost 20,000 blood gases in 130 patients were analyzed. The overall 90-day mortality was 30% and using the data from the first ICU week, the HR was 0.85 [0.77-0.94] for every 10 mmHg increase in P/F ratio and 1.61 [1.20-2.16] for every 0.1 increase in Vd/Vt. In the second week, the HR for 90-day mortality was 0.82 [0.75-0.89] for every 10 mmHg increase in P/F ratio and 1.97 [1.42-2.73] for every 0.1 increase in Vd/Vt.

CONCLUSION

The progressive changes in P/F ratio and Vd/Vt in the first 2 weeks of invasive ventilatory support for COVID-19 ARDS were significant predictors for 90-day mortality.

Novel Oxygenation and Saturation Indices for Mortality Prediction in COVID-19 ARDS Patients: The Impact of Driving Pressure and Mechanical Power

Background: The oxygenation index (OI) and oxygen saturation index (OSI) are proven mortality predictors in pediatric and adult patients, traditionally using mean airway pressure (Pmean). We introduce novel indices, replacing Pmean with DP (ΔPinsp), MPdyn, and MPtot, assessing their potential for predicting COVID-19 acute respiratory distress syndrome (ARDS) mortality, comparing them to traditional indices. Methods: We studied 361 adult COVID-19 ARDS patients for 7 days, collecting ΔPinsp, MPdyn, and MPtot, OI-ΔPinsp, OI-MPdyn, OI-MPtot, OSI-ΔPinsp, OSI-MPdyn, and OSI-MPtot. We compared these in surviving and non-surviving patients over the first 7 intensive care unit (ICU) days using Mann-Whitney U test. Logistic regression receiver operating characteristic (ROC) analysis assessed AUC and CI values for ICU mortality on day three. We determined cut-off values using Youden's method and conducted multivariate Cox regression on parameter limits. Results: All indices showed significant differences between surviving and non-surviving patients on the third day of ICU care. The AUC values of OI-ΔPinsp were significantly higher than those of P/F and OI-Pmean (P values .0002 and <.0001, respectively). Similarly, AUC and CI values of OSI-ΔPinsp and OSI-MPdyn were significantly higher than those of SpO2/FiO2 and OSI-Pmean values (OSI-ΔPinsp: P < .0001, OSI-MPdyn: P values .047 and .028, respectively). OI-ΔPinsp, OSI-ΔPinsp, OI-MPdyn, OSI-MPdyn, OI-MPtot, and OSI-MPtot had AUC values of 0.72, 0.71, 0.69, 0.68, 0.66, and 0.64, respectively, with cut-off values associated with hazard ratios and P values of 7.06 (HR = 1.84, P = .002), 8.04 (HR = 2.00, P ≤ .0001), 7.12 (HR = 1.68, P = .001), 5.76 (HR = 1.70, P ≤ .0001), 10.43 (HR = 1.52, P = .006), and 10.68 (HR = 1.66, P = .001), respectively. Conclusions: Critical values of all indices were associated to higher ICU mortality rates and extended mechanical ventilation durations. The OI-ΔPinsp, OSI-ΔPinsp, and OSI-MPdyn indices displayed the strongest predictive capabilities for ICU mortality. These novel indices offer valuable insights for intensivists in the clinical management and decision-making process for ARDS patients.

Association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality in patients with COVID-19 pneumonia: A secondary analysis

BACKGROUND

The arterial pressure of oxygen (PaO2)/inspiratory fraction of oxygen (FiO2) is associated with in-hospital mortality in patients with Coronavirus Disease 2019 (COVID-19) pneumonia. ΔPaO2/FiO2 [the difference between PaO2/FiO2 after 24 h of invasive mechanical ventilation (IMV) and PaO2/FiO2 before IMV] is associated with in-hospital mortality. However, the value of PaO2 can be influenced by the end-expiratory pressure (PEEP). To the best of our knowledge, the relationship between the ratio of (ΔPaO2/FiO2)/PEEP and in-hospital mortality remains unclear. This study aimed to evaluate their association.

METHODS

The study was conducted in southern Peru from April 2020 to April 2021. A total of 200 patients with COVID-19 pneumonia requiring IMV were included in the present study. We analyzed the association between (ΔPaO2/FiO2)/PEEP and in-hospital mortality by Cox proportional hazards regression models.

RESULTS

The median (ΔPaO2/FiO2)/PEEP was 11.78 mmHg/cmH2O [interquartile range (IQR) 8.79-16.08 mmHg/cmH2O], with a range of 1 to 44.36 mmHg/cmH2O. Patients were divided equally into two groups [low group (< 11.80 mmHg/cmH2O), and high group (≥ 11.80 mmHg/cmH2O)] according to the (ΔPaO2/FiO2)/PEEP ratio. In-hospital mortality was lower in the high (ΔPaO2/FiO2)/PEEP group than in the low (ΔPaO2/FiO2)/PEEP group [18 (13%) vs. 38 (38%)]; hazard ratio (HR), 0.33 [95% confidence intervals (CI), 0.17-0.61, P < 0.001], adjusted HR, 0.32 (95% CI, 0.11-0.94, P = 0.038). The finding that the high (ΔPaO2/FiO2)/PEEP group exhibited a lower risk of in-hospital mortality compared to the low (ΔPaO2/FiO2)/PEEP group was consistent with the results from the sensitivity analysis. After adjusting for confounding variables, we found that each unit increase in (ΔPaO2/FiO2)/PEEP was associated with a 12% reduction in the risk of in-hospital mortality (HR, 0.88, 95%CI, 0.80-0.97, P = 0.013).

CONCLUSIONS

The (ΔPaO2/FiO2)/PEEP ratio was associated with in-hospital mortality in patients with COVID-19 pneumonia. (ΔPaO2/FiO2)/PEEP might be a marker of disease severity in COVID-19 patients.

Changes in Driving Pressure vs Oxygenation as Predictor of Mortality in Moderate to Severe Acute Respiratory Distress Syndrome Patients Receiving Prone Position Ventilation

Background

Prone position ventilation (PPV) causes improvement in oxygenation, nevertheless, mortality in severe acute respiratory distress syndrome (ARDS) remains high. The changes in the driving pressure (DP) and its role in predicting mortality in moderate to severe ARDS patients receiving PPV is unexplored.

Methods

A prospective observational study, conducted between September 2020 and February 2023 on moderate-severe ARDS patients requiring PPV. The values of DP and oxygenation (ratio of partial pressure of arterial oxygen to fraction of inspired oxygen [PaO2/FiO2]) before, during, and after PPV were recorded. The aim was to compare the DP and oxygenation before, during and after PPV sessions among moderate- severe ARDS patients, and determine the best predictor of mortality.

Results

Total of 52 patients were included; 28-day mortality was 57%. Among the survivors, DP prior to PPV as compared to post-PPV session reduced significantly, from 16.36 ± 2.57 cmH2O to 13.91 ± 1.74 cmH2O (p-value < 0.001), whereas DP did not reduce in the non-survivors (19.43 ± 3.16 to 19.70 ± 3.15 cmH2O (p-value = 0.318)]. Significant improvement in PaO2/FiO2 before PPV to post-PPV among both the survivors [92.75 [67.5-117.75]) to [205.50 (116.25-244.50)], (p-value < 0.001) and also among the non-survivors [87.90 (67.75-100.75)] to [112 (88.00-146.50)], (p-value < 0.001) was noted. Logistic regression analysis showed DP after PPV session as best predictor of mortality (p-value = 0.044) and its AUROC to predict mortality was 0.939, cut-off ≥16 cmH2O, 90% sensitivity, 82% specificity. The Kaplan-Meier curve of DP after PPV ≥16 cmH2O and <16 cmH2O was significant (Log-rank Mantel-Cox p-value < 0.001).

Conclusion

Prone position ventilation-induced decrease in DP is prognostic marker of survival than the increase in PaO2/FiO2. There is a primacy of DP, rather than oxygenation, in predicting mortality in moderate-severe ARDS. Post-PPV session DP ≥16 cmH2O was an independent predictor of mortality.

How to cite this article

Todur P, Nileshwar A, Chaudhuri S, Shanbhag V, Cherisma C. Changes in Driving Pressure vs Oxygenation as Predictor of Mortality in Moderate to Severe Acute Respiratory Distress Syndrome Patients Receiving Prone Position Ventilation. Indian J Crit Care Med 2024;28(2):134-140.

Comparing COVID-19 and influenza: Epidemiology, clinical characteristics, outcomes and mortality in the ICU

RATIONALE

Several authors have compared COVID-19 infection with influenza in the ICU.

OBJECTIVE

This study aimed to compare the baseline clinical profiles, care procedures, and mortality outcomes of patients admitted to the intensive care unit, categorized by infection status (Influenza vs. COVID-19).

METHODS

Retrospective observational study. Data were extracted from the Toulouse University Hospital from March 2014 to March 2021. To compare survival curves, we plotted the survival at Day-90 using the Kaplan-Meier curve and conducted a log-rank test. Additionally, we performed propensity score matching to adjust for confounding factors between the COVID-19 and influenza groups. Furthermore, we use the CART model for multivariate analysis.

RESULTS

The study included 363 patients admitted to the ICU due to severe viral pneumonia: 152 patients (41.9 %) with influenza and 211 patients (58.1 %) with COVID-19. COVID-19 patients exhibited a higher prevalence of cardiovascular risk factors, whereas influenza patients had significantly higher severity scores (SOFA: 10 [6-12] vs. 6 [3-9], p<0.01 and SAPS II: 51 [35-67] vs. 37 [29-50], p<0.001). Overall mortality rates were comparable between the two groups (27.6 % (n = 42) in the influenza group vs. 21.8 % (n = 46) in the COVID-19 group, p=NS). Mechanical ventilation was more commonly employed in the influenza group (76.3 % (n = 116) vs. 59.7 % (n = 126), p<0.001); however, COVID-19 patients required longer durations of mechanical ventilation (18 [9-29] days vs. 13 [5-24] days, p<0.006) and longer hospital stays (23 [13-34] days vs. 18.5 [9-34.5] days, p = 0.009). The CART analysis revealed that the use of extra renal replacement therapy was the most influential prognostic factor in the influenza group, while the PaO2/FiO2-PEEP ratio played a significant role in the COVID-19 group.

CONCLUSIONS

Despite differences in clinical presentation and prognostic factors, the mortality rates at 90 days, after adjusting for confounding factors, were similar between COVID-19 and influenza patients.

Physiologic Markers of Disease Severity in ARDS

Despite its significant limitations, the PaO2 /FIO2 remains the standard tool to classify disease severity in ARDS. Treatment decisions and research enrollment have depended on this parameter for over 50 years. In addition, several variables have been studied over the past few decades, incorporating other physiologic considerations such as ventilation efficiency, lung mechanics, and right-ventricular performance. This review describes the strengths and limitations of all relevant parameters, with the goal of helping us better understand disease severity and possible future treatment targets.

Management of severe acute respiratory distress syndrome: a primer

This narrative review explores the physiology and evidence-based management of patients with severe acute respiratory distress syndrome (ARDS) and refractory hypoxemia, with a focus on mechanical ventilation, adjunctive therapies, and veno-venous extracorporeal membrane oxygenation (V-V ECMO). Severe ARDS cases increased dramatically worldwide during the Covid-19 pandemic and carry a high mortality. The mainstay of treatment to improve survival and ventilator-free days is proning, conservative fluid management, and lung protective ventilation. Ventilator settings should be individualized when possible to improve patient-ventilator synchrony and reduce ventilator-induced lung injury (VILI). Positive end-expiratory pressure can be individualized by titrating to best respiratory system compliance, or by using advanced methods, such as electrical impedance tomography or esophageal manometry. Adjustments to mitigate high driving pressure and mechanical power, two possible drivers of VILI, may be further beneficial. In patients with refractory hypoxemia, salvage modes of ventilation such as high frequency oscillatory ventilation and airway pressure release ventilation are additional options that may be appropriate in select patients. Adjunctive therapies also may be applied judiciously, such as recruitment maneuvers, inhaled pulmonary vasodilators, neuromuscular blockers, or glucocorticoids, and may improve oxygenation, but do not clearly reduce mortality. In select, refractory cases, the addition of V-V ECMO improves gas exchange and modestly improves survival by allowing for lung rest. In addition to VILI, patients with severe ARDS are at risk for complications including acute cor pulmonale, physical debility, and neurocognitive deficits. Even among the most severe cases, ARDS is a heterogeneous disease, and future studies are needed to identify ARDS subgroups to individualize therapies and advance care.

Assessing Humoral Immuno-Inflammatory Pathways Associated with Respiratory Failure in COVID-19 Patients

All severe cases of SARS-CoV-2 infections are characterized by a high risk of disease progression towards ARDS, leading to a bad outcome. Respiratory symptoms in COVID-19 patients often do not correspond to disease's worsening. In our sample, median age was 74 years (72-75) and 54% were men. The median period of hospitalization was 9 days. Firstly, we observed a significant asynchronous trend of neutrophil-to-lymphocyte ratio (NLR) and C-reactive protein (CRP) in 764 selected among 963 patients, who were consecutively recruited in two hospitals (Cannizzaro, S. Marco) in Catania, Italy. NLR values in deceased patients showed an increase from baseline over time. By contrast, CRP tended to fall from baseline to median day of hospitalization in all three subgroups, but steeply increased at the end of hospitalization only in ICU-admitted patients. Then, we evaluated the relationships between NLR and CRP as continuous variables with PaO₂/FiO₂ ratio (P/F). NLR was an independent predictor of mortality (HR: 1.77, p < 0.0001), while ICU admission was more significantly associated with CRP (HR: 1.70, p < 0.0001). Finally, age, neutrophils, CRP, and lymphocytes are significantly and directly linked to P/F, while the influence of inflammation on P/F, reflected by CRP, was also mediated by neutrophils.

Epidemiological profile and risk factors associated with death in patients receiving invasive mechanical ventilation in an adult intensive care unit from Brazil: a retrospective study

Introduction

Understanding the epidemiological profile and risk factors associated with invasive mechanical ventilation (IMV) is essential to manage the patients better and to improve health services. Therefore, our objective was to describe the epidemiological profile of adult patients in intensive care that required IMV in-hospital treatment. Also, to evaluate the risks associated with death and the influence of positive end-expiratory pressure (PEEP) and arterial oxygen pressure (PaO2) at admission in the clinical outcome.

Methods

We conducted an epidemiological study analyzing medical records of inpatients who received IMV from January 2016 to December 2019 prior to the Coronavirus Disease (COVID)-19 pandemic in Brazil. We considered the following characteristics in the statistical analysis: demographic data, diagnostic hypothesis, hospitalization data, and PEEP and PaO2 during IMV. We associated the patients' features with the risk of death using a multivariate binary logistic regression analysis. We adopted an alpha error of 0.05.

Results

We analyzed 1,443 medical records; out of those, 570 (39.5%) recorded the patients' deaths. The binary logistic regression was significant in predicting the patients' risk of death [X2(9) = 288.335; p < 0.001]. Among predictors, the most significant in relation to death risk were: age [elderly ≥65 years old; OR = 2.226 (95%CI = 1.728-2.867)]; male sex (OR = 0.754; 95%CI = 0.593-0.959); sepsis diagnosis (OR = 1.961; 95%CI = 1.481-2.595); need for elective surgery (OR = 0.469; 95%CI = 0.362-0.608); the presence of cerebrovascular accident (OR = 2.304; 95%CI = 1.502-3.534); time of hospital care (OR = 0.946; 95%CI = 0.935-0.956); hypoxemia at admission (OR = 1.635; 95%CI = 1.024-2.611), and PEEP >8 cmH2O at admission (OR = 2.153; 95%CI = 1.426-3.250).

Conclusion

The death rate of the studied intensive care unit was equivalent to that of other similar units. Regarding risk predictors, several demographic and clinical characteristics were associated with enhanced mortality in intensive care unit patients under mechanical ventilation, such as diabetes mellitus, systemic arterial hypertension, and older age. The PEEP >8 cmH2O at admission was also associated with increased mortality since this value is a marker of initially severe hypoxia.

SPP1 exacerbates ARDS via elevating Th17/Treg and M1/M2 ratios through suppression of ubiquitination-dependent HIF-1α degradation

BACKGROUND

Acute respiratory distress syndrome (ARDS) is a severe inflammatory pulmonary condition that leads to respiratory failure. The imbalance of Th17/Treg and M1/M2 is implicated in ARDS. A better understanding of the regulation of the balance of Th17/Treg and M1/M2 may provide novel therapeutic targets for ARDS.

METHODS

Plasma and BALF samples were collected from ARDS patients. Inflammatory cytokines were examined by ELISA. Th17, Treg, M1 and M2 were identified via immunofluorescence staining of RORγt, Foxp3, iNOS and Arg-1. H&E and Masson's trichrome staining were applied for evaluating pulmonary damage and fibrosis. A mouse model of ARDS was established through LPS administration. HIF-1α was immunoprecipitated and subjected to ubiquitination analysis via western blotting. The expression of SPP1, VHL and HIF-1α was examined by RT-qPCR and western blotting.

RESULTS

ARDS patients showed elevated levels of inflammatory cytokines and ratios of Th17/Treg and M1/M2. SPP1 was upregulated in ARDS mice, and silencing of SPP1 alleviated lung injury and fibrosis. SPP1 inhibited VHL expression to reduce the ubiquitination and degradation of HIF-1α in ARDS. Overexpression of SPP1 facilitated Th17, Treg and M1 polarization but inhibited M2 polarization through upregulation of HIF-1α.

CONCLUSION

SPP1 elevates Th17/Treg and M1/M2 ratio by suppressing VHL expression and ubiquitination-dependent HIF-1α degradation, thus exacerbating ARDS. Our study provides novel mechanistic insights into ARDS pathogenesis and promising therapeutic targets.

A Clarion Call for a More Comprehensive Approach to Acute Respiratory Distress Syndrome Severity Categorization

How to cite this article: Magoon R, Suresh V. A Clarion Call for a More Comprehensive Approach to Acute Respiratory Distress Syndrome Severity Categorization. Indian J Crit Care Med 2022;26(12):1308-1309.

Prognostic value of the novel P/FPE index to classify ARDS severity: A cohort study

OBJECTIVE

To evaluate the impact of the novel P/FP_E index to classify ARDS severity on mortality of patients with ARDS.

DESIGN

A retrospective cohort study.

SETTING

Twelve-bed medical and surgical intensive care unit from January 2018 to December 2020.

PATIENTS

A total of 217 ARDS patients managed with invasive mechanical ventilation >48h.

INTERVENTIONS

None.

VARIABLES

ARDS severity on day 1 and day 3 was measured based on PaO₂/FiO₂ ratio and P/FP_E index [PaO₂/(FiO₂×PEEP)]. Primary outcome was the hospital mortality.

RESULTS

Hospital mortality rate was 59.9%. Relative to PaO₂/FiO₂ ratio, 31.8% of patients on day 1 and 77.0% on day 3 were reclassified into a different category of ARDS severity by P/FP_E index. The level of PEEP was lower by P/FP_E index-based ARDS severity classification than by using PaO₂/FiO₂ ratio. The performance for predicting mortality of P/FP_E index was superior to PaO₂/FiO₂ ratio in term of AROC (day 1: 0.72 vs. 0.62; day 3: 0.87 vs. 0.68) and CORR (day 1: 0.370 vs. 0.213; day 3: 0.634 vs. 0.301). P/FP_E index improved prediction of risk of death compared to PaO₂/FiO₂ ratio as showed by the qNRI (day 1: 72.0%, p<0.0001; day 3: 132.4%, p<0.0001) and IDI (day 1: 0.09, p<0.0001; day 3: 0.31, p<0.0001).

CONCLUSIONS

Assessment of ARDS severity based on P/FP_E index seems better than PaO₂/FiO₂ ratio for predicting mortality. The value of P/FP_E index for clinical decision-making requires confirmation by randomized controlled trials.

Acute Respiratory Distress Syndrome and Shunt Detection With Bubble Studies: A Systematic Review and Meta-Analysis

Acute respiratory distress syndrome (ARDS) is a life-threatening respiratory injury with multiple physiological sequelae. Shunting of deoxygenated blood through intra- and extrapulmonary shunts may complicate ARDS management. Therefore, we conducted a systematic review to determine the prevalence of sonographically detected shunts, and their association with oxygenation and mortality in patients with ARDS.

DATA SOURCES

Medical literature analysis and retrieval system online, Excerpta Medica dataBASE, Cochrane Library, and database of abstracts of reviews of effects databases on March 26, 2021.

STUDY SELECTION

Articles relating to respiratory failure and sonographic shunt detection.

DATA EXTRACTION

Articles were independently screened and extracted in duplicate. Data pertaining to study demographics and shunt detection were compiled for mortality and oxygenation outcomes. Risk of bias was appraised using the Joanna-Briggs Institute and the Newcastle-Ottawa Scale tools with evidence rating certainty using Grading of Recommendations Assessment, Development and Evaluation methodology.

DATA SYNTHESIS

From 4,617 citations, 10 observational studies met eligibility criteria. Sonographic detection of right-to-left shunt was present in 21.8% of patients (range, 14.4-30.0%) among included studies using transthoracic, transesophageal, and transcranial bubble Doppler ultrasonographies. Shunt prevalence may be associated with increased mortality (risk ratio, 1.22; 95% CI, 1.01-1.49; p = 0.04, very low certainty evidence) with no difference in oxygenation as measured by Pao2:Fio2 ratio (mean difference, -0.7; 95% CI, -18.6 to 17.2; p = 0.94, very low certainty).

CONCLUSIONS

Intra- and extrapulmonary shunts are detected frequently in ARDS with ultrasound techniques. Shunts may increase mortality among patients with ARDS, but its association with oxygenation is uncertain.

Comparison of Clinical Characteristics and Predictors of Mortality between Direct and Indirect ARDS

Background and Objectives: Acute Respiratory Distress Syndrome (ARDS) is a heterogeneous syndrome that encompasses lung injury from a direct pulmonary or indirect systemic insult. Studies have shown that direct and indirect ARDS differ in their pathophysiologic process. In this study, we aimed to compare the different clinical characteristics and predictors of 28-day mortality between direct and indirect ARDS. Materials and Methods: The data of 1291 ARDS patients from September 2012 to December 2021 at the Second Affiliated Hospital of Chongqing Medical University were reviewed. We enrolled 451 ARDS patients in our study through inclusion and exclusion criteria. According to the risk factors, each patient was divided into direct (n = 239) or indirect (n = 212) ARDS groups. The primary outcome was 28-day mortality. Results: The patients with direct ARDS were more likely to be older (p < 0.001) and male (p = 0.009) and have more comorbidity (p < 0.05) and higher 28-day mortality (p < 0.001) than those with indirect ARDS. Age and multiple organ dysfunction syndrome (MODS) were predictors of 28-day mortality in the direct ARDS group, while age, MODS, creatinine, prothrombin time (PT), and oxygenation index (OI) were independent predictors of 28-day mortality in the indirect ARDS group. Creatinine, PT, and OI have interactions with ARDS types (all p < 0.01). Conclusions: The patients with direct ARDS were more likely to be older and male and have worse conditions and prognoses than those with indirect ARDS. Creatinine, PT, and OI were predictors of 28-day mortality only in the indirect ARDS group. The differences between direct and indirect ARDS suggest the need for different management strategies of ARDS.

Utility of Pulse Oximetry Oxygen Saturation (SpO2) with Incorporation of Positive End-Expiratory Pressure (SpO2 ∗ 10/FiO2 ∗ PEEP) for Classification and Prognostication of Patients with Acute Respiratory Distress Syndrome

Background. Conventionally, PaO2/FiO2 (P/F ratio) has been used to categorize severity of acute respiratory distress syndrome (ARDS) and prognostication of outcome. Recent literature has shown that incorporation of positive end-expiratory pressure (PEEP) into the P/F ratio (PaO2 $\ast$ 10/FiO2 $\ast$ PEEP or P/FP $\ast$ 10) has a much better prognostic ability in ARDS as compared to P/F ratio. The aim of this study was to correlate SpO2 $\ast$ 10/FiO2 $\ast$ PEEP (S/FP $\ast$ 10) to PaO2 $\ast$ 10/FiO2 $\ast$ PEEP (P/FP $\ast$ 10) and evaluate the utility of S/FP $\ast$ 10 as a reliable noninvasive indicator of oxygenation in ARDS to avoid repeated arterial blood sampling. Aim. To evaluate if pulse oximetry is a reliable indicator of oxygenation in ARDS patients by calculating SpO2 $\ast$ 10/FiO2 $\ast$ PEEP (S/FP $\ast$ 10). The primary objective was to determine the correlation of S/FP $\ast$ 10 to P/FP $\ast$ 10 ratio in ARDS patients. The secondary objective was to determine the cut-off value of S/FP $\ast$ 10 ratio to predict severe ARDS and survival. Methods. Patients aged 18–80 years on invasive mechanical ventilation (MV) diagnosed with ARDS as defined by the Berlin definition were included. The values of PaO2, FiO2, and SpO2 were collected at three different time points. They were at baseline, i.e., after intubation and initiation of MV (within one hour of intubation), day one (1–24 hours of MV), and day three (48–72 hours of MV). The primary outcome was survival at the end of intensive care unit (ICU) stay. Results. A total of 85 patients with ARDS on invasive MV were included. The data points were obtained at baseline, day one, and day three of MV. S/FP $\ast$ 10 ratio has an excellent correlation to P/FP $\ast$ 10 ratio at baseline and day three of invasive MV (r = 0.831 and 0.853, respectively; $p<0.001$ ) and has a strong correlation on day one of invasive MV (r = 0.733, $p<0.001$ ). S/FP $\ast$ 10 ratio ≤116 at baseline has excellent discriminant function to be categorized as severe ARDS as per Berlin definition (AUC: 0.925, $p<0.001$ , 90% sensitivity, 93% specificity, CI: [0.862–0.988]). The increase in S/FP $\ast$ 10 ratio by ≥64.40 from baseline to day three of MV is a good predictor of survival (AUC: 0.877, $p<0.001$ , 73.5% sensitivity, 97% specificity, CI: [0.803–0.952]). Conclusion. S/FP $\ast$ 10 has a strong correlation to P/FP $\ast$ 10 in ARDS patients. S/FP $\ast$ 10 ≤116 has an excellent discriminant function to be categorized as severe ARDS. The S/FP $\ast$ 10 ratio on day three of MV and the change in S/FP $\ast$ 10 ratio from baseline and day one to day three of MV are good predictors of survival in ARDS patients. This trial is registered with CTRI/2020/04/024940.

The RALE Score Versus the CT Severity Score in Invasively Ventilated COVID-19 Patients-A Retrospective Study Comparing Their Prognostic Capacities

BACKGROUND

Quantitative radiological scores for the extent and severity of pulmonary infiltrates based on chest radiography (CXR) and computed tomography (CT) scan are increasingly used in critically ill invasively ventilated patients. This study aimed to determine and compare the prognostic capacity of the Radiographic Assessment of Lung Edema (RALE) score and the chest CT Severity Score (CTSS) in a cohort of invasively ventilated patients with acute respiratory distress syndrome (ARDS) due to COVID-19.

METHODS

Two-center retrospective observational study, including consecutive invasively ventilated COVID-19 patients. Trained scorers calculated the RALE score of first available CXR and the CTSS of the first available CT scan. The primary outcome was ICU mortality; secondary outcomes were duration of ventilation in survivors, length of stay in ICU, and hospital-, 28-, and 90-day mortality. Prognostic accuracy for ICU death was expressed using odds ratios and Area Under the Receiver Operating Characteristic curves (AUROC).

RESULTS

A total of 82 patients were enrolled. The median RALE score (22 [15-37] vs. 26 [20-39]; p = 0.34) and the median CTSS (18 [16-21] vs. 21 [18-23]; p = 0.022) were both lower in ICU survivors compared to ICU non-survivors, although only the difference in CTSS reached statistical significance. While no association was observed between ICU mortality and RALE score (OR 1.35 [95%CI 0.64-2.84]; p = 0.417; AUC 0.50 [0.44-0.56], this was noticed with the CTSS (OR, 2.31 [1.22-4.38]; p = 0.010) although with poor prognostic capacity (AUC 0.64 [0.57-0.69]). The correlation between the RALE score and CTSS was weak (r2 = 0.075; p = 0.012).

CONCLUSIONS

Despite poor prognostic capacity, only CTSS was associated with ICU mortality in our cohort of COVID-19 patients.

Mild Hypothermia via External Cooling Improves Lung Function and Alleviates Pulmonary Inflammatory Response and Damage in Two-Hit Rabbit Model of Acute Lung Injury

OBJECTIVES

Targeted temperature management (TTM) with therapeutic hypothermia (TH) has an organ-protective effect by mainly reducing inflammatory response. Here, our objective was to determine, for the first time, whether mild TH with external cooling, a simple and inexpensive method, could be safe or even beneficial in two-hit rabbit model of acute lung injury/acute respiratory distress syndrome (ALI/ARDS).

METHODS

Twenty-two New Zealand rabbits (6-month-old) were randomly divided into healthy control (HC) with conventional ventilation, but without injury, model group (ALI), and hypothermia group with external cooling (ALI-HT). After induction of ALI/ARDS through mild lung-lavages followed by non-protective ventilation, mild hypothermia was started in ALI-HT group (body temperature of 33-34 °C). All rabbits were conventionally ventilated for an additional 6-h by recording respiratory parameters. Finally, lung histopathology and inflammatory response were evaluated.

RESULTS

Hypothermia was associated with higher oxygen saturation, resulting in partial improvement in the P/F ratio (PaO2/FiO2), oxygenation index, mean airway pressure, and PaCO2, but did not affect lactate levels. The ALI-HT group had lower histopathological injury scores (hyperemia, edema, emphysema, atelectasis, and PMN infiltration). Further, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and -8 levels in lung tissue and serum samples markedly reduced due to hypothermia.

CONCLUSION

Mild TH with external cooling reduced lung inflammation and damage, whereas it resulted in partial improvement in gas exchanges. Our findings highlight that body temperature control may be a potentially supportive therapeutic option for regulating cytokine production and respiratory parameters in ALI/ARDS.

Monitoring Lung Injury Severity and Ventilation Intensity during Mechanical Ventilation

Acute respiratory distress syndrome (ARDS) is a severe form of respiratory failure burden by high hospital mortality. No specific pharmacologic treatment is currently available and its ventilatory management is a key strategy to allow reparative and regenerative lung tissue processes. Unfortunately, a poor management of mechanical ventilation can induce ventilation induced lung injury (VILI) caused by physical and biological forces which are at play. Different parameters have been described over the years to assess lung injury severity and facilitate optimization of mechanical ventilation. Indices of lung injury severity include variables related to gas exchange abnormalities, ventilatory setting and respiratory mechanics, ventilation intensity, and the presence of lung hyperinflation versus derecruitment. Recently, specific indexes have been proposed to quantify the stress and the strain released over time using more comprehensive algorithms of calculation such as the mechanical power, and the interaction between driving pressure (DP) and respiratory rate (RR) in the novel DP multiplied by four plus RR [(4 × DP) + RR] index. These new parameters introduce the concept of ventilation intensity as contributing factor of VILI. Ventilation intensity should be taken into account to optimize protective mechanical ventilation strategies, with the aim to reduce intensity to the lowest level required to maintain gas exchange to reduce the potential for VILI. This is further gaining relevance in the current era of phenotyping and enrichment strategies in ARDS.