Reclassifying Acute Respiratory Distress Syndrome

Association of obesity on short- and long-term survival in patients with moderate to severe pneumonia-related ARDS: a retrospective cohort study

BACKGROUND

The incidence of obesity among patients admitted to the intensive care unit (ICU) is increasing, and pneumonia remains the leading cause of acute respiratory distress syndrome (ARDS). The association of obesity on both short- and long-term outcomes in patients with pneumonia-induced ARDS has been the subject of only limited research.

METHODS

We conducted a retrospective analysis of a prospective cohort consisting of ARDS patients who had microbiologically confirmed pneumonia and a PaO2/FiO2 ratio ≤ 150 mmHg. Patients were assessed for mortality at 28 days, 90 days, and at 1 year from the diagnosis of ARDS and compared between obese defined by a body mass index (BMI) ≥ 30 kg.m2 and non-obese patients. Models were adjusted for age, sex, COPD, coronary artery disease, immunodepression, severity score and acute kidney injury on admission to the ICU, severity of ARDS (PaO2/FiO2 ratio ≤ 100 mmHg), severe hypercapnia (PaCO2 ≥ 50 mmHg), ventilatory ratio and plateau pressure the first day of ARDS, influenza, COVID-19, pneumocystosis, and bacteria involved in pneumonia. We also investigated the continuous spectrum of BMI on the risk of mortality.

RESULTS

Of 603 patients, 227 patients (37.6%) were obese. Obesity was associated with female gender (p = 0.009), hypertension (p < 0.001), diabetes mellitus (p < 0.001), COVID-19 pneumonia (p = 0.008), and PaO2/FiO2 ratio ≤ 100 mmHg (p = 0.006). Obesity was independently associated with lower mortality at 28 days (adjusted Odds Ratio (OR) 0.55, 95% confident interval (CI) 0.33-0.90, p = 0.02) but not at 90 days (adjusted OR 0.70, 95% CI 0.45-1.09, p = 0.11) nor at 1 year from the diagnosis of ARDS (adjusted OR 0.73, 95% CI 0.47-1.13, p = 0.16). Mortality at 28 days was significantly lower in obese patients than in non-obese patients when propensity score matching was used (15.2% versus 22%, p = 0.04). BMI was also independently associated with lower mortality at 28 days (p = 0.038) but not with mortality at 90 days (p = 0.12) and 1 year (p = 0.12).

CONCLUSION

Our results suggest that in patients with pneumonia-related ARDS, obesity is independently associated with better survival at 28 days but not at 90 days and 1 year from the diagnosis of ARDS.

Mechanical Power: Using Ideal Body Weight to Identify Injurious Mechanical Ventilation Thresholds

Identifying the mechanisms of ventilator/ventilation-induced lung injury requires an understanding of the pulmonary physiology involved in the mechanical properties of the lung along with the involvement of the inflammatory cascade. Accurately measuring parameters that represent physiologic lung stress and lung strain at the bedside can be clinically challenging. Although surrogates for lung stress and strain have been proposed, such as plateau pressure and driving pressure, these values only represent a static variable in the ventilator breath. It has been proposed that a single variable could be used as a unifying parameter to identify a threshold for the safe application of mechanical ventilation. The concept of "mechanical power" applies an energy load transfer designation to the ventilator settings and output of tidal volume, airway pressures, and flow. However, there is a potential disconnect between the use of "absolute" mechanical power and the variability of body weight throughout a mixed medical population. Using ideal body weight as an influential factor to express mechanical power can potentially allow for a more accurate depiction of energy applied to the lungs and a potentially reliable injurious mechanical ventilation threshold indicator.

Ventilatory variables and computed tomography features in COVID-19 ARDS and non-COVID-19-related ARDS: a prospective observational cohort study

BACKGROUND

This study compared the ventilatory variables and computed tomography (CT) features of patients with coronavirus disease 2019 (COVID-19) versus those of patients with pulmonary non-COVID-19-related acute respiratory distress syndrome (ARDS) during the early phase of ARDS.

METHODS

This prospective, observational cohort study of ARDS patients in Taiwan was performed between February 2017 and June 2018 as well as between October 2020 and January 2024. Analysis was performed on clinical characteristics, including consecutive ventilatory variables during the first week after ARDS diagnosis. Analysis was also performed on CT scans obtained within one week after ARDS onset.

RESULTS

A total of 222 ARDS patients were divided into a COVID-19 ARDS group (n = 44; 19.8%) and a non-COVID-19 group (all pulmonary origin) (n = 178; 80.2%). No significant difference was observed between the two groups in terms of all-cause hospital mortality (38.6% versus 47.8%, p = 0.277). Pulmonary non-COVID-19 patients presented higher values for mechanical power (MP), MP normalized to predicted body weight (MP/PBW), MP normalized to compliance (MP/compliance), ventilatory ratio (VR), peak inspiratory pressure (Ppeak), and dynamic driving pressure (∆P) as well as lower dynamic compliance from day 1 to day 7 after ARDS onset. In both groups, non-survivors exceeded survivors and presented higher values for MP, MP/PBW, MP/compliance, VR, Ppeak, and dynamic ∆P with lower dynamic compliance from day 1 to day 7 after ARDS onset. The CT severity score for each of the five lung lobes and total CT scores were all significantly higher in the non-COVID-19 group (all p < 0.05). Multivariable logistic regression models revealed that Sequential Organ Failure Assessment (SOFA) score was independently associated with mortality in the COVID-19 group. In the non-COVID-19 group, body mass index, immunocompromised status, SOFA score, MP/PBW and total CT severity scores were independently associated with mortality.

CONCLUSIONS

In the early course of ARDS, physicians should be aware of the distinctions between COVID-19-related ARDS and non-COVID-19-related ARDS in terms of ventilatory variables and CT imaging presentations. It is also important to tailor the mechanical ventilation settings according to these distinct subsets of ARDS.

Rethinking ARDS classification: oxygenation impairment fails to predict VILI risk

PURPOSE

The selection and intensity of respiratory support for ARDS are guided by PaO2/FiO2. However, ventilator-induced lung injury (VILI) is linked to respiratory mechanics and ventilator settings. We explored whether the VILI risk is related to ARDS severity based on oxygenation.

METHODS

We analysed data on 228 ARDS subjects with PaO2/FiO2 < 200 mmHg, categorized into three severity groups: one based on PaO2/FiO2 ratio, and the others based on tertiles of predictors of VILI: mechanical power ratio (MPR) and driving pressure (DP). In each group of oxygenation-based ARDS severity and MPR and DP tertiles, we measured CT anatomy, gas exchange, respiratory mechanics, VILI prerequisites (lung elastance and lung gas volume), and VILI determinants (tidal volume, PEEP, airway pressures).

RESULTS

Predictors of VILI, such as MPR and DP, were similar across ARDS severity groups based on PaO2/FiO2 ratio, while oxygenation remained comparable across different levels of VILI risk defined by MPR and DP. Oxygenation impairment was associated with increased lung weight, recruitability, and reduced well-inflated tissue. In contrast, MPR and DP tertiles affected variables associated with the baby lung size, such as lung gas volume and well-inflated tissue. Mechanical ventilation intensity increased progressively across MPR and DP tertiles, but remained similar across PaO2/FiO2 severity groups.

CONCLUSIONS

ARDS severity based on oxygenation impairment does not reflect the prerequisites and determinants of VILI. This should prompt a reconsideration of recommending respiratory support based on oxygenation impairment, rather than VILI determinants.

Subphenotypes in Acute Respiratory Distress Syndrome: Universal Steps Toward Treatable Traits

Patients with acute respiratory distress syndrome (ARDS) have severe respiratory impairment requiring mechanical ventilation resulting in high mortality. Despite extensive research, no effective pharmacological interventions have been identified in unselected ARDS, which has been attributed to the considerable heterogeneity. The identification of more homogeneous subgroups through phenotyping has provided a novel method to improve our pathophysiological understanding, trial design, and, most importantly, patient care through targeted interventions. The objective of this article is to outline a structured, stepwise approach toward identifying and classifying heterogeneity within ARDS and subsequently derive, validate, and integrate targeted treatment options. We present a 6-step roadmap toward the identification of effective phenotype-targeted treatments: development of distinct and reproducible subphenotypes, derivation of a possible parsimonious bedside classification method, identification of possible interventions, prospective validation of subphenotype classification, testing of subphenotype-targeted intervention prospectively in randomized clinical trial (RCT), and finally implementation of subphenotype classification and intervention in guidelines and clinical practice. Based on this framework, the current literature was reviewed. Respiratory physiology, lung morphology, and systemic inflammatory biology subphenotypes were identified. Currently, lung morphology and systemic inflammatory biology subphenotypes are being tested prospectively in RCTs.

[Ventilatory management of SARS-CoV-2 acute respiratory failure]

COVID-19 pneumonia presents several particularities in its clinical presentation (cytokine storm, silent hypoxemia, thrombo-embolic risk) and may lead to a number of acute respiratory distress syndrome (ARDS) phenotypes. While the optimal oxygenation strategy in cases of hypoxemic acute respiratory failure (ARF) is still under debate, ventilatory management of COVID-19-related ARF has confirmed the efficacy of high-flow oxygen therapy and restored interest in other ventilatory approaches such as continuous positive airway pressure (CPAP) and noninvasive ventilation involving a helmet, which due to patient overflow are sometimes implemented outside of critical care units. However, further studies are still needed to determine which patients should be given which oxygenation technique, and under which conditions they require invasive mechanical ventilation, given that delayed initiation potentially burdens prognosis. During invasive mechanical ventilation, ventral decubitus and extracorporeal membrane oxygenation have become increasingly prevalent. While innovative therapies such as awake prone position or lung transplantation have likewise been developed, their indications, modalities and efficacy remain to be determined.

Significance of Pyroptosis in Immunoregulation and Prognosis of Patients with Acute Respiratory Distress Syndrome: Evidence from RNA-Seq of Alveolar Macrophages

Objective

This study aimed to investigate the role of pyroptosis in alveolar macrophages regarding the immune microenvironment of acute respiratory distress syndrome (ARDS) and its prognosis.

Methods

ARDS Microarray data were downloaded from Gene Expression Omnibus (GEO). Support vector machine (SVM) and random forest (RF) models were applied to identify hub pyroptosis-related genes (PRGs) with prognostic significance in ARDS. RT-PCR was used to detect the relative expression of PRGs mRNA in alveolar macrophages of ARDS mice. Consensus clustering analysis was conducted based on the expression of the PRGs to identify pyroptosis modification patterns. Bioinformatic algorithms were used to study the immune traits and biological functions of the pyroptosis patterns. Finally, protein-protein interaction (PPI) networks were established to identify hub regulatory proteins with implications for the pyroptosis patterns.

Results

In our study, a total of 12 PRGs with differential expression were obtained. Four hub PRGs, including GPX4, IL6, IL18 and NLRP3, were identified and proven to be predictive of ventilator-free days (VFDS) in ARDS patients. The AUC values of the 4 PRGs were 0.911 (GPX4), 0.879 (IL18), 0.851 (IL6) and 0.841 (NLRP3), respectively. In ARDS mice, GPX4 mRNA decreased significantly, while IL6, IL18, and NLRP3 mRNA increased. Functional analysis revealed that IL6 had the strongest positive correlation with the CCR pathway, while GPX4 exhibited the strongest negative correlation with the T co-inhibition pathway. Based on the expression of the 4 PRGs, three pyroptosis modification patterns representing different immune states were obtained, and pattern C might represent immune storm.

Conclusion

The results showed that pyroptosis plays an important regulatory role in the immune microenvironment of ARDS. This finding provides new insights into the pathogenesis, diagnosis, and treatment of ARDS.

Mechanical power of ventilation and driving pressure: two undervalued parameters for pre extracorporeal membrane oxygenation ventilation and during daily management?

The current ARDS guidelines highly recommend lung protective ventilation which include plateau pressure (P_plat < 30 cm H₂O), positive end expiratory pressure (PEEP > 5 cm H₂O) and tidal volume (V_t of 6 ml/kg) of predicted body weight. In contrast, the ELSO guidelines suggest the evaluation of an indication of veno-venous extracorporeal membrane oxygenation (ECMO) due to hypoxemic or hypercapnic respiratory failure or as bridge to lung transplantation. Finally, these recommendations remain a wide range of scope of interpretation. However, particularly patients with moderate-severe to severe ARDS might benefit from strict adherence to lung protective ventilation strategies. Subsequently, we discuss whether extended physiological ventilation parameter analysis might be relevant for indication of ECMO support and can be implemented during the daily routine evaluation of ARDS patients. Particularly, this viewpoint focus on driving pressure and mechanical power.

Integrating biology into clinical trial design

PURPOSE OF REVIEW

Critical care medicine revolves around syndromes, such as acute respiratory distress syndrome (ARDS), sepsis and acute kidney injury. Few interventions have shown to be effective in large clinical trials, likely because of between-patient heterogeneity. Translational evidence suggests that more homogeneous biological subgroups can be identified and that differential treatment effects exist. Integrating biological considerations into clinical trial design is therefore an important frontier of critical care research.

RECENT FINDINGS

The pathophysiology of critical care syndromes involves a multiplicity of processes, which emphasizes the difficulty of integrating biology into clinical trial design. Biological assessment can be integrated into clinical trials using predictive enrichment at trial inclusion, time-dependent variation to better understand treatment effects and biological markers as surrogate outcomes.

SUMMARY

Integrating our knowledge on biological heterogeneity into clinical trial design, which has revolutionized other medical fields, could serve as a solution to implement personalized treatment in critical care syndromes. Changing the trial design by using predictive enrichment, incorporation of the evaluation of time-dependent changes and biological markers as surrogate outcomes may improve the likelihood of detecting a beneficial effect from targeted therapeutic interventions and the opportunity to test multiple lines of treatment per patient.

Association of the C-terminal 42-peptide fragment of alpha-1 antitrypsin with the severity of ARDS: A pilot study

BACKGROUND

Acute respiratory distress syndrome is a life-threatening condition with a hospital mortality rate of up to 40%. Biomarkers related to the pathophysiology of ARDS may not only identify patients at risk but may also serve as potential therapeutic targets. This study examined the association between the proteolytic C-terminal 42-peptide fragment of alpha-1 antitrypsin and ARDS severity.

METHODS

The 42-peptide fragment and interleukin-6 levels were measured in 21 patients with mild-to-moderate ARDS and 47 patients with moderate-to-severe ARDS on days 1, 3, and 5 after diagnosis/admission to the intensive care unit. To elucidate the association between both biomarkers and the PaO₂/FiO₂ ratio, the concentrations of both biomarkers were compared between the two groups, and a multivariate regression analysis was performed.

RESULTS

The concentrations of both biomarkers were higher in patients with moderate-to-severe ARDS. While the PaO₂/FiO₂ ratio increased from day 1 to day 3, the concentrations of both biomarkers decreased. Multivariate regression analysis revealed negative associations between the PaO₂/FiO₂ ratio and both the C-terminal 42-peptide of alpha-1 antitrypsin and interleukin-6 on day 1 (beta: -0.138, p = 0.052; beta: -0.096, p = 0.004) and on day 3 (beta: -0.157, p = 0.045; beta: -0.106, p = 0.043).

INTERPRETATION

The C-terminal 42-peptide of alpha-1 antitrypsin is a new biomarker associated with ARDS severity. Its predictive value in identifying patients at risk of developing moderate-to-severe ARDS must be investigated in additional, independent prospective studies.

Prone position: how understanding and clinical application of a technique progress with time

Historical background

The prone position was first proposed on theoretical background in 1974 (more advantageous distribution of mechanical ventilation). The first clinical report on 5 ARDS patients in 1976 showed remarkable improvement of oxygenation after pronation. 

Pathophysiology

The findings in CT scans enhanced the use of prone position in ARDS patients. The main mechanism of the improved gas exchange seen in the prone position is nowadays attributed to a dorsal ventilatory recruitment, with a substantially unchanged distribution of perfusion. Regardless of the gas exchange, the primary effect of the prone position is a more homogenous distribution of ventilation, stress and strain, with similar size of pulmonary units in dorsal and ventral regions. In contrast, in the supine position the ventral regions are more expanded compared with the dorsal regions, which leads to greater ventral stress and strain, induced by mechanical ventilation.

Outcome in ARDS

The number of clinical studies paralleled the evolution of the pathophysiological understanding. The first two clinical trials in 2001 and 2004 were based on the hypothesis that better oxygenation would lead to a better survival and the studies were more focused on gas exchange than on lung mechanics. The equations better oxygenation = better survival was disproved by these and other larger trials (ARMA trial). However, the first studies provided signals that some survival advantages were possible in a more severe ARDS, where both oxygenation and lung mechanics were impaired. The PROSEVA trial finally showed the benefits of prone position on mortality supporting the thesis that the clinical advantages of prone position, instead of improved gas exchange, were mainly due to a less harmful mechanical ventilation and better distribution of stress and strain. In less severe ARDS, in spite of a better gas exchange, reduced mechanical stress and strain, and improved oxygenation, prone position was ineffective on outcome.

Prone position and COVID-19

The mechanisms of oxygenation impairment in early COVID-19 are different than in typical ARDS and relate more on perfusion alteration than on alveolar consolidation/collapse, which are minimal in the early phase. Bronchial shunt may also contribute to the early COVID-19 hypoxemia. Therefore, in this phase, the oxygenation improvement in prone position is due to a better matching of local ventilation and perfusion, primarily caused by the perfusion component. Unfortunately, the conditions for improved outcomes, i.e. a better distribution of stress and strain, are almost absent in this phase of COVID-19 disease, as the lung parenchyma is nearly fully inflated. Due to some contradictory results, further studies are needed to better investigate the effect of prone position on outcome in COVID-19 patients.

Graphical Abstract

High rates of impaired quality of life and social and economic problems at 6 months after COVID-19-related ARDS

Purpose

Assess long-term quality of life (HR-QoL) and socio-economic impact in COVID-19-related ARDS (C-ARDS) survivors.

Methods

C-ARDS survivors were followed up at 6 months in this prospective, cohort study. HR-QoL was assessed using SF-36 and EQ-5D-5L, and the socio-economic burden of COVID-19 was evaluated with a dedicated questionnaire. Clinical data were prospectively recorded.

Results

Seventy-nine survivors, age 63 [57-71], 84% male, were enrolled. The frequency of EQ-5D-5L reported problems was significantly higher among survivors compared to normal, in mobility, usual activities, and self-care; anxiety and depression and pain were not different. SF-36 scores were lower than the reference population, and physical and mental summary scores were below normal in 52% and 33% of the subjects, respectively. In the multivariable analysis, prolonged hospital length of stay (OR 1.45; p 0.02) and two or more comorbidities on admission (OR 7.42; p 0.002) were significant predictors of impaired “physical” and “mental” HR-QoL, respectively. A total of 38% subjects worsened social relations, 42% changed their employment status, and 23% required personal care support.

Conclusions

C-ARDS survivors have long-term impairment in HR-QoL and socio-economic problems. Prolonged hospital stay and previous comorbidities are risk factors for developing health-related issues.

Supplementary Information

The online version contains supplementary material available at. 10.1186/s44158-022-00048-5

Mechanical power is associated with weaning outcome in critically ill mechanically ventilated patients

Several single-center studies have evaluated the predictive performance of mechanical power (MP) on weaning outcomes in prolonged invasive mechanical ventilation (IMV) patients. The relationship between MP and weaning outcomes in all IMV patients has rarely been studied. A retrospective study was conducted on MIMIC-IV patients with IMV for more than 24 h to investigate the correlation between MP and weaning outcome using logistic regression model and subgroup analysis. The discriminative ability of MP, MP normalized to dynamic lung compliance (C_dyn-MP) and MP normalized to predicted body weight (PBW-MP) on weaning outcome were evaluated by analyzing the area under the receiver-operating characteristic (AUROC). Following adjustment for confounding factors, compared with the reference group, the Odds Ratio of weaning failure in the maximum MP, C_dyn-MP, and PBW-MP groups increased to 3.33 [95%CI (2.04-4.53), P < 0.001], 3.58 [95%CI (2.27-5.56), P < 0.001] and 5.15 [95%CI (3.58-7.41), P < 0.001], respectively. The discriminative abilities of C_dyn-MP (AUROC 0.760 [95%CI 0.745-0.776]) and PBW-MP (AUROC 0.761 [95%CI 0.744-0.779]) were higher than MP (AUROC 0.745 [95%CI 0.730-0.761]) (P < 0.05). MP is associated with weaning outcomes in IMV patients and is an independent predictor of the risk of weaning failure. C_dyn-MP and PBW-MP showed higher ability in weaning failure prediction than MP.

Respiratory Subsets in Patients with Moderate to Severe Acute Respiratory Distress Syndrome for Early Prediction of Death

Introduction: In patients with acute respiratory distress syndrome (ARDS), the PaO2/FiO2 ratio at the time of ARDS diagnosis is weakly associated with mortality. We hypothesized that setting a PaO2/FiO2 threshold in 150 mm Hg at 24 h from moderate/severe ARDS diagnosis would improve predictions of death in the intensive care unit (ICU). Methods: We conducted an ancillary study in 1303 patients with moderate to severe ARDS managed with lung-protective ventilation enrolled consecutively in four prospective multicenter cohorts in a network of ICUs. The first three cohorts were pooled (n = 1000) as a testing cohort; the fourth cohort (n = 303) served as a confirmatory cohort. Based on the thresholds for PaO2/FiO2 (150 mm Hg) and positive end-expiratory pressure (PEEP) (10 cm H2O), the patients were classified into four possible subsets at baseline and at 24 h using a standardized PEEP-FiO2 approach: (I) PaO2/FiO2 ≥ 150 at PEEP < 10, (II) PaO2/FiO2 ≥ 150 at PEEP ≥ 10, (III) PaO2/FiO2 < 150 at PEEP < 10, and (IV) PaO2/FiO2 < 150 at PEEP ≥ 10. Primary outcome was death in the ICU. Results: ICU mortalities were similar in the testing and confirmatory cohorts (375/1000, 37.5% vs. 112/303, 37.0%, respectively). At baseline, most patients from the testing cohort (n = 792/1000, 79.2%) had a PaO2/FiO2 < 150, with similar mortality among the four subsets (p = 0.23). When assessed at 24 h, ICU mortality increased with an advance in the subset: 17.9%, 22.8%, 40.0%, and 49.3% (p < 0.0001). The findings were replicated in the confirmatory cohort (p < 0.0001). However, independent of the PEEP levels, patients with PaO2/FiO2 < 150 at 24 h followed a distinct 30-day ICU survival compared with patients with PaO2/FiO2 ≥ 150 (hazard ratio 2.8, 95% CI 2.2−3.5, p < 0.0001). Conclusions: Subsets based on PaO2/FiO2 thresholds of 150 mm Hg assessed after 24 h of moderate/severe ARDS diagnosis are clinically relevant for establishing prognosis, and are helpful for selecting adjunctive therapies for hypoxemia and for enrolling patients into therapeutic trials.

Venovenous extracorporeal CO2 removal to support ultraprotective ventilation in moderate-severe acute respiratory distress syndrome: A systematic review and meta-analysis of the literature

BACKGROUND

A strategy that limits tidal volumes and inspiratory pressures, improves outcomes in patients with the acute respiratory distress syndrome (ARDS). Extracorporeal carbon dioxide removal (ECCO₂R) may facilitate ultra-protective ventilation. We conducted a systematic review and meta-analysis to evaluate the efficacy and safety of venovenous ECCO₂R in supporting ultra-protective ventilation in moderate-to-severe ARDS.

METHODS

MEDLINE and EMBASE were interrogated for studies (2000-2021) reporting venovenous ECCO₂R use in patients with moderate-to-severe ARDS. Studies reporting ≥10 adult patients in English language journals were included. Ventilatory parameters after 24 h of initiating ECCO₂R, device characteristics, and safety outcomes were collected. The primary outcome measure was the change in driving pressure at 24 h of ECCO₂R therapy in relation to baseline. Secondary outcomes included change in tidal volume, gas exchange, and safety data.

RESULTS

Ten studies reporting 421 patients (PaO₂:FiO₂ 141.03 mmHg) were included. Extracorporeal blood flow rates ranged from 0.35-1.5 L/min. Random effects modelling indicated a 3.56 cmH₂O reduction (95%-CI: 3.22-3.91) in driving pressure from baseline (p < .001) and a 1.89 mL/kg (95%-CI: 1.75-2.02, p < .001) reduction in tidal volume. Oxygenation, respiratory rate and PEEP remained unchanged. No significant interactions between driving pressure reduction and baseline driving pressure, partial pressure of arterial carbon dioxide or PaO₂:FiO₂ ratio were identified in metaregression analysis. Bleeding and haemolysis were the commonest complications of therapy.

CONCLUSIONS

Venovenous ECCO₂R permitted significant reductions in ∆P in patients with moderate-to-severe ARDS. Heterogeneity amongst studies and devices, a paucity of randomised controlled trials, and variable safety reporting calls for standardisation of outcome reporting. Prospective evaluation of optimal device operation and anticoagulation in high quality studies is required before further recommendations can be made.

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.

Histopathological and molecular links of COVID-19 with novel clinical manifestations for the management of coronavirus-like complications

Coronavirus disease 2019 (COVID-19) causes transmissible viral illness of the respiratory tract prompted by the SARS-CoV-2 virus. COVID-19 is one of the worst global pandemics affecting a large population worldwide and causing catastrophic loss of life. Patients having pre-existing chronic disorders are more susceptible to contracting this viral infection. This pandemic virus is known to cause notable respiratory pathology. Besides, it can also cause extra-pulmonary manifestations. Multiple extra-pulmonary tissues express the SARS-CoV-2 entry receptor, hence causing direct viral tissue damage. This insightful review gives a brief description of the impact of coronavirus on the pulmonary system, extra-pulmonary systems, histopathology, multiorgan consequences, the possible mechanisms associated with the disease, and various potential therapeutic approaches to tackle the manifestations.

Comparison of COVID-19 Induced Respiratory Failure and Typical ARDS: Similarities and Differences

Coronavirus disease 2019 (COVID-19) is a predominantly respiratory infectious disease caused by novel coronavirus infection (SARS-CoV-2), respiratory failure is the main clinical manifestation and the leading cause of death. Even though it can meet the acute respiratory distress syndrome (ARDS) Berlin definition, only some clinical features of COVID-19 are consistent with typical ARDS, and which has its own peculiar phenotypes. When compared with typical ARDS, in addition to the typical diffuse alveolar injury, COVID-19 has unique pathological and pathophysiological features, such as endothelial injury, extensive microthrombus, and pulmonary capillary hyperplasia. The clinical features of patients with respiratory failure caused by COVID-19 are heterogeneous and can be generally divided into two phenotypes: progressive respiratory distress and unique "silent hypoxemia". The "H-type" characteristics of reduced lung volume, decreased lung compliance, and unmatched ventilator-perfusion ratio. While some patients may have close to normal lung compliance, that is "L-type". Identifying the exact phenotype in whom are suffered with COVID-19 is crucial to guide clinicians to adopt appropriate treatment strategies. This review discussed the similarities and differences in the pathogenesis, pathophysiology, clinical features and treatment strategies of COVID-19 induced acute respiratory failure and typical ARDS.

Fraction of Inspired Oxygen With Low-Flow Versus High-Flow Devices: A Simulation Study

Purpose: The fraction of inspired oxygen while administering oxygen to patients must be measured as it represents the alveolar oxygen concentration, which is important from a respiratory physiology viewpoint. Therefore, the purpose of this study was to compare the fractions of inspired oxygen obtained through different oxygen delivery devices.

Methods: A simulation model of spontaneous respiration was used. The fractions of inspired oxygen obtained through low- and high-flow nasal cannulas and a simple oxygen mask were measured. The fraction of inspired air was measured every second for 30 s after 120 s of oxygen administration. This was measured three times under each condition.

Results: With a low-flow nasal cannula, airflow reduced both the intratracheal fraction of inspired oxygen and extraoral oxygen concentration, indicating that exhalatory respiration occurred during rebreathing and may be involved in increasing the intratracheal fraction of inspired oxygen.

Conclusion: Oxygen administration during expiratory flow may lead to an increased oxygen concentration in the anatomical dead space, which may be involved in the increase in the fraction of inspired oxygen. With a high-flow nasal cannula, a high fraction of inspired oxygen can be achieved even at a flow rate of 10 L/min. When determining the optimum amount of oxygen, it is necessary to set an appropriate flow rate for patients and specific conditions without being bound by the fraction of inspired oxygen values alone. It might be difficult to estimate the fraction of inspired oxygen while using a low-flow nasal cannula and simple oxygen mask in clinical situations.

Impact of cytidine diphosphocholine on oxygenation in client-owned dogs with aspiration pneumonia

BACKGROUND

New drugs for veterinary patients with acute respiratory distress syndrome (ARDS) are urgently needed. Early or late postinfection treatment of influenza-infected mice with the liponucleotide cytidine diphosphocholine (CDP-choline) resulted in decreased hypoxemia, pulmonary edema, lung dysfunction, and inflammation without altering viral replication. These findings suggested CDP-choline could have benefit as adjunctive treatment for ARDS in veterinary patients (VetARDS).

OBJECTIVES

Determine if parenterally administered CDP-choline can attenuate mild VetARDS in dogs with aspiration pneumonia.

ANIMALS

Dogs admitted to a veterinary intensive care unit (ICU) for aspiration pneumonia.

METHODS

Subjects were enrolled in a randomized, double-blinded, placebo-controlled trial of treatment with vehicle (0.1 mL/kg sterile 0.9% saline, IV; n = 8) or CDP-choline (5 mg/kg in 0.1 mL/kg 0.9% saline, IV; n = 9) q12h over the first 48 hours after ICU admission.

RESULTS

No significant differences in signalment or clinical findings were found between placebo- and CDP-choline-treated dogs on admission. All dogs exhibited tachycardia, tachypnea, hypertension, hypoxemia, hypocapnia, lymphopenia, and neutrophilia. CDP-choline administration resulted in rapid, progressive, and clinically relevant increases in oxygenation as determined by pulse oximetry and ratios of arterial oxygen partial pressure (Pa O2 mmHg) to fractional inspired oxygen (% Fi O2 ) and decreases in alveolar-arterial (A-a) gradients that did not occur in placebo (saline)-treated animals. Treatment with CDP-choline was also associated with less platelet consumption over the first 48 hours, but had no detectable detrimental effects.

CONCLUSIONS AND CLINICAL IMPORTANCE

Ctyidine diphosphcholine acts rapidly to promote gas exchange in dogs with naturally occurring aspiration pneumonia and is a potential adjunctive treatment in VetARDS patients.

Influence of mechanical power and its components on mechanical ventilation in SARS-CoV-2

OBJECTIVE

To analyze the influence of mechanical power and its components on mechanical ventilation for patients infected with SARS-CoV-2; identify the values of the mechanical ventilation components and verify their correlations with each other and with the mechanical power and effects on the result of the Gattinoni-S and Giosa formulas.

METHODS

This was an observational, longitudinal, analytical and quantitative study of respirator and mechanical power parameters in patients with SARS-CoV-2.

RESULTS

The mean mechanical power was 26.9J/minute (Gattinoni-S) and 30.3 J/minute (Giosa). The driving pressure was 14.4cmH2O, the plateau pressure was 26.5cmH2O, the positive end-expiratory pressure was 12.1cmH2O, the elastance was 40.6cmH2O/L, the tidal volume was 0.36L, and the respiratory rate was 32 breaths/minute. The correlation between the Gattinoni and Giosa formulas was 0.98, with a bias of -3.4J/minute and a difference in the correlation of the resistance pressure of 0.39 (Gattinoni) and 0.24 (Giosa). Among the components, the correlations between elastance and driving pressure (0.88), positive end-expiratory pressure (-0.54) and tidal volume (-0.44) stood out.

CONCLUSION

In the analysis of mechanical ventilation for patients with SARS-CoV-2, it was found that the correlations of its components with mechanical power influenced its high momentary values and and that the correlations of its components with each other influenced their behavior throughout the study period. Because they have specific effects on the Gatinnoni-S and Giosa formulas, the mechanical ventilation components influenced their calculations and caused divergence in the mechanical power values.

High-Flow Nasal Oxygen for Severe Hypoxemia: Oxygenation Response and Outcome in Patients with COVID-19

Rationale: The "Berlin definition" of acute respiratory distress syndrome (ARDS) does not allow inclusion of patients receiving high-flow nasal oxygen (HFNO). However, several articles have proposed that criteria for defining ARDS should be broadened to allow inclusion of patients receiving HFNO. Objectives: To compare the proportion of patients fulfilling ARDS criteria during HFNO and soon after intubation, and 28-day mortality between patients treated exclusively with HFNO and patients transitioned from HFNO to invasive mechanical ventilation (IMV). Methods: From previously published studies, we analyzed patients with coronavirus disease (COVID-19) who had PaO2/FiO2 of ⩽300 while treated with ⩾40 L/min HFNO, or noninvasive ventilation (NIV) with positive end-expiratory pressure of ⩾5 cm H2O (comparator). In patients transitioned from HFNO/NIV to invasive mechanical ventilation (IMV), we compared ARDS severity during HFNO/NIV and soon after IMV. We compared 28-day mortality in patients treated exclusively with HFNO/NIV versus patients transitioned to IMV. Measurements and Main Results: We analyzed 184 and 131 patients receiving HFNO or NIV, respectively. A total of 112 HFNO and 69 NIV patients transitioned to IMV. Of those, 104 (92.9%) patients on HFNO and 66 (95.7%) on NIV continued to have PaO2/FiO2 ⩽300 under IMV. Twenty-eight-day mortality in patients who remained on HFNO was 4.2% (3/72), whereas in patients transitioned from HFNO to IMV, it was 28.6% (32/112) (P < 0.001). Twenty-eight-day mortality in patients who remained on NIV was 1.6% (1/62), whereas in patients who transitioned from NIV to IMV, it was 44.9% (31/69) (P < 0.001). Overall mortality was 19.0% (35/184) and 24.4% (32/131) for HFNO and NIV, respectively (P = 0.2479). Conclusions: Broadening the ARDS definition to include patients on HFNO with PaO2/FiO2 ⩽300 may identify patients at earlier stages of disease but with lower mortality.

Accuracy and Acceptability of Wrist-Wearable Activity-Tracking Devices: Systematic Review of the Literature

Background

Numerous wrist-wearable devices to measure physical activity are currently available, but there is a need to unify the evidence on how they compare in terms of acceptability and accuracy.

Objective

The aim of this study is to perform a systematic review of the literature to assess the accuracy and acceptability (willingness to use the device for the task it is designed to support) of wrist-wearable activity trackers.

Methods

We searched MEDLINE, Embase, the Cochrane Central Register of Controlled Trials, and SPORTDiscus for studies measuring physical activity in the general population using wrist-wearable activity trackers. We screened articles for inclusion and, for the included studies, reported data on the studies’ setting and population, outcome measured, and risk of bias.

Results

A total of 65 articles were included in our review. Accuracy was assessed for 14 different outcomes, which can be classified in the following categories: count of specific activities (including step counts), time spent being active, intensity of physical activity (including energy expenditure), heart rate, distance, and speed. Substantial clinical heterogeneity did not allow us to perform a meta-analysis of the results. The outcomes assessed most frequently were step counts, heart rate, and energy expenditure. For step counts, the Fitbit Charge (or the Fitbit Charge HR) had a mean absolute percentage error (MAPE) <25% across 20 studies. For heart rate, the Apple Watch had a MAPE <10% in 2 studies. For energy expenditure, the MAPE was >30% for all the brands, showing poor accuracy across devices. Acceptability was most frequently measured through data availability and wearing time. Data availability was ≥75% for the Fitbit Charge HR, Fitbit Flex 2, and Garmin Vivofit. The wearing time was 89% for both the GENEActiv and Nike FuelBand.

Conclusions

The Fitbit Charge and Fitbit Charge HR were consistently shown to have a good accuracy for step counts and the Apple Watch for measuring heart rate. None of the tested devices proved to be accurate in measuring energy expenditure. Efforts should be made to reduce the heterogeneity among studies.

Safety and efficacy of multipotent adult progenitor cells in acute respiratory distress syndrome (MUST-ARDS): a multicentre, randomised, double-blind, placebo-controlled phase 1/2 trial

PURPOSE

Bone marrow-derived, allogeneic, multipotent adult progenitor cells demonstrated safety and efficacy in preclinical models of acute respiratory distress syndrome (ARDS).

METHODS

This phase 1/2 trial evaluated the safety and tolerability of intravenous multipotent adult progenitor cells in patients with moderate-to-severe ARDS in 12 UK and USA centres. Cohorts 1 and 2 were open-label, evaluating acute safety in three subjects receiving 300 or 900 million cells, respectively. Cohort 3 was a randomised, double-blind, placebo-controlled parallel trial infusing 900 million cells (n = 20) or placebo (n = 10) within 96 h of ARDS diagnosis. Primary outcomes were safety and tolerability. Secondary endpoints included clinical outcomes, quality of life (QoL) and plasma biomarkers.

RESULTS

No allergic or serious adverse reactions were associated with cell therapy in any cohort. At baseline, the cohort 3 cell group had less severe hypoxia. For cohort 3, 28-day mortality was 25% for cell vs. 45% for placebo recipients. Median 28-day free from intensive care unit (ICU) and ventilator-free days in the cell vs. placebo group were 12.5 (IQR 0,18.5) vs. 4.5 (IQR 0,16.8) and 18.5 (IQR 0,22) vs. 6.5 (IQR 0,18.3), respectively. A prospectively defined severe ARDS subpopulation (PaO₂/FiO₂ < 150 mmHg (20 kPa); n = 16) showed similar trends in mortality, ICU-free days and ventilator-free days favouring cell therapy. Cell recipients showed greater recovery of QoL through Day 365.

CONCLUSIONS

Multipotent adult progenitor cells were safe and well tolerated in ARDS. The clinical outcomes warrant larger trials to evaluate the therapeutic efficacy and optimal patient population.

COVID-19 pneumonia: pathophysiology and management

Coronavirus disease 2019 (COVID-19) pneumonia is an evolving disease. We will focus on the development of its pathophysiologic characteristics over time, and how these time-related changes determine modifications in treatment. In the emergency department: the peculiar characteristic is the coexistence, in a significant fraction of patients, of severe hypoxaemia, near-normal lung computed tomography imaging, lung gas volume and respiratory mechanics. Despite high respiratory drive, dyspnoea and respiratory rate are often normal. The underlying mechanism is primarily altered lung perfusion. The anatomical prerequisites for PEEP (positive end-expiratory pressure) to work (lung oedema, atelectasis, and therefore recruitability) are lacking. In the high-dependency unit: the disease starts to worsen either because of its natural evolution or additional patient self-inflicted lung injury (P-SILI). Oedema and atelectasis may develop, increasing recruitability. Noninvasive supports are indicated if they result in a reversal of hypoxaemia and a decreased inspiratory effort. Otherwise, mechanical ventilation should be considered to avert P-SILI. In the intensive care unit: the primary characteristic of the advance of unresolved COVID-19 disease is a progressive shift from oedema or atelectasis to less reversible structural lung alterations to lung fibrosis. These later characteristics are associated with notable impairment of respiratory mechanics, increased arterial carbon dioxide tension (P_aCO2), decreased recruitability and lack of response to PEEP and prone positioning.

COVID-19 pneumonia cannot be correctly described, analysed and treated if the time-factor is not taken into accounthttps://bit.ly/3AOKxc4

Role of advanced respiratory support in acute respiratory failure in clinically frail patients with COVID-19

Background: The main aim of this study was to assess the efficacy of advanced respiratory support (ARS) for acute respiratory failure in do-not-attempt cardiopulmonary resuscitation order (DNACPR) COVID-19 patients. Methods: In this single-center study, the impact of different types of ARS modality, PaO₂/FiO₂ (PF) ratio, clinical frailty score (CFS) and 4C score on mortality was evaluated. Results: There was no significant difference in age, type of ARS modality, PF ratio and 4C scores between those who died and those who survived. Overall survival rates/hospital discharge of patients still requiring ARS at 5 and 7 days post admission were 20 and 17%, respectively. Conclusion: Our study showed that ARS can be a useful tool in frail, elderly and high-risk COVID-19 patients irrespective of high 4C mortality score.

Mechanical Ventilation during Extracorporeal Membrane Oxygenation in Acute Respiratory Distress Syndrome: A Narrative Review

Acute respiratory distress syndrome (ARDS) is a life-threatening condition involving acute hypoxemic respiratory failure. Mechanical ventilation remains the cornerstone of management for ARDS; however, potentially injurious mechanical forces introduce the risk of ventilator-induced lung injury, multiple organ failure, and death. Extracorporeal membrane oxygenation (ECMO) is a salvage therapy aimed at ensuring adequate gas exchange for patients suffering from severe ARDS with profound hypoxemia where conventional mechanical ventilation has failed. ECMO allows for lower tidal volumes and airway pressures, which can reduce the risk of further lung injury, and allow the lungs to rest. However, the collateral effect of ECMO should be considered. Recent studies have reported correlations between mechanical ventilator settings during ECMO and mortality. In many cases, mechanical ventilation settings should be tailored to the individual; however, researchers have yet to establish optimal ventilator settings or determine the degree to which ventilation load can be decreased. This paper presents an overview of previous studies and clinical trials pertaining to the management of mechanical ventilation during ECMO for patients with severe ARDS, with a focus on clinical findings, suggestions, protocols, guidelines, and expert opinions. We also identified a number of issues that have yet to be adequately addressed.

Inhaled β2 Adrenergic Agonists and Other cAMP-Elevating Agents: Therapeutics for Alveolar Injury and Acute Respiratory Disease Syndrome?

Inhaled long-acting β-adrenergic agonists (LABAs) and short-acting β-adrenergic agonists are approved for the treatment of obstructive lung disease via actions mediated by β2 adrenergic receptors (β2-ARs) that increase cellular cAMP synthesis. This review discusses the potential of β2-AR agonists, in particular LABAs, for the treatment of acute respiratory distress syndrome (ARDS). We emphasize ARDS induced by pneumonia and focus on the pathobiology of ARDS and actions of LABAs and cAMP on pulmonary and immune cell types. β2-AR agonists/cAMP have beneficial actions that include protection of epithelial and endothelial cells from injury, restoration of alveolar fluid clearance, and reduction of fibrotic remodeling. β2-AR agonists/cAMP also exert anti-inflammatory effects on the immune system by actions on several types of immune cells. Early administration is likely critical for optimizing efficacy of LABAs or other cAMP-elevating agents, such as agonists of other Gs-coupled G protein-coupled receptors or cyclic nucleotide phosphodiesterase inhibitors. Clinical studies that target lung injury early, prior to development of ARDS, are thus needed to further assess the use of inhaled LABAs, perhaps combined with inhaled corticosteroids and/or long-acting muscarinic cholinergic antagonists. Such agents may provide a multipronged, repurposing, and efficacious therapeutic approach while minimizing systemic toxicity. SIGNIFICANCE STATEMENT: Acute respiratory distress syndrome (ARDS) after pulmonary alveolar injury (e.g., certain viral infections) is associated with ∼40% mortality and in need of new therapeutic approaches. This review summarizes the pathobiology of ARDS, focusing on contributions of pulmonary and immune cell types and potentially beneficial actions of β2 adrenergic receptors and cAMP. Early administration of inhaled β2 adrenergic agonists and perhaps other cAMP-elevating agents after alveolar injury may be a prophylactic approach to prevent development of ARDS.

Role of total lung stress on the progression of early COVID-19 pneumonia

Purpose

We investigated if the stress applied to the lung during non-invasive respiratory support may contribute to the coronavirus disease 2019 (COVID-19) progression.

Methods

Single-center, prospective, cohort study of 140 consecutive COVID-19 pneumonia patients treated in high-dependency unit with continuous positive airway pressure (n = 131) or non-invasive ventilation (n = 9). We measured quantitative lung computed tomography, esophageal pressure swings and total lung stress.

Results

Patients were divided in five subgroups based on their baseline PaO₂/FiO₂ (day 1): non-CARDS (median PaO₂/FiO₂ 361 mmHg, IQR [323–379]), mild (224 mmHg [211–249]), mild-moderate (173 mmHg [164–185]), moderate-severe (126 mmHg [114–138]) and severe (88 mmHg [86–99], p < 0.001). Each subgroup had similar median lung weight: 1215 g [1083–1294], 1153 [888–1321], 968 [858–1253], 1060 [869–1269], and 1127 [937–1193] (p = 0.37). They also had similar non-aerated tissue fraction: 10.4% [5.9–13.7], 9.6 [7.1–15.8], 9.4 [5.8–16.7], 8.4 [6.7–12.3] and 9.4 [5.9–13.8], respectively (p = 0.85).

Treatment failure of CPAP/NIV occurred in 34 patients (24.3%). Only three variables, at day one, distinguished patients with negative outcome: PaO₂/FiO₂ ratio (OR 0.99 [0.98–0.99], p = 0.02), esophageal pressure swing (OR 1.13 [1.01–1.27], p = 0.032) and total stress (OR 1.17 [1.06–1.31], p = 0.004). When these three variables were evaluated together in a multivariate logistic regression analysis, only the total stress was independently associated with negative outcome (OR 1.16 [1.01–1.33], p = 0.032).

Conclusions

In early COVID-19 pneumonia, hypoxemia is not linked to computed tomography (CT) pathoanatomy, differently from typical ARDS. High lung stress was independently associated with the failure of non-invasive respiratory support.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-021-06519-7.

Progress of mechanical power in the intensive care unit

Mechanical power of ventilation, currently defined as the energy delivered from the ventilator to the respiratory system over a period of time, has been recognized as a promising indicator to evaluate ventilator-induced lung injury and predict the prognosis of ventilated critically ill patients. Mechanical power can be accurately measured by the geometric method, while simplified equations allow an easy estimation of mechanical power at the bedside. There may exist a safety threshold of mechanical power above which lung injury is inevitable, and the assessment of mechanical power might be helpful to determine whether the extracorporeal respiratory support is needed in patients with acute respiratory distress syndrome. It should be noted that relatively low mechanical power does not exclude the possibility of lung injury. Lung size and inhomogeneity should also be taken into consideration. Problems regarding the safety limits of mechanical power and contribution of each component to lung injury have not been determined yet. Whether mechanical power-directed lung-protective ventilation strategy could improve clinical outcomes also needs further investigation. Therefore, this review discusses the algorithms, clinical relevance, optimization, and future directions of mechanical power in critically ill patients.

Latent class analysis to predict intensive care outcomes in Acute Respiratory Distress Syndrome: a proposal of two pulmonary phenotypes

Background

Acute respiratory distress syndrome remains a heterogeneous syndrome for clinicians and researchers difficulting successful tailoring of interventions and trials. To this moment, phenotyping of this syndrome has been approached by means of inflammatory laboratory panels. Nevertheless, the systemic and inflammatory expression of acute respiratory distress syndrome might not reflect its respiratory mechanics and gas exchange.

Methods

Retrospective analysis of a prospective cohort of two hundred thirty-eight patients consecutively admitted patients under mechanical ventilation presenting with acute respiratory distress syndrome. All patients received standardized monitoring of clinical variables, respiratory mechanics and computed tomography scans at predefined PEEP levels. Employing latent class analysis, an unsupervised structural equation modelling method, on respiratory mechanics, gas-exchange and computed tomography-derived gas- and tissue-volumes at a PEEP level of 5cmH₂O, distinct pulmonary phenotypes of acute respiratory distress syndrome were identified.

Results

Latent class analysis was applied to 54 respiratory mechanics, gas-exchange and CT-derived gas- and tissue-volume variables, and a two-class model identified as best fitting. Phenotype 1 (non-recruitable) presented lower respiratory system elastance, alveolar dead space and amount of potentially recruitable lung volume than phenotype 2 (recruitable). Phenotype 2 (recruitable) responded with an increase in ventilated lung tissue, compliance and PaO₂/FiO₂ ratio (p < 0.001), in addition to a decrease in alveolar dead space (p < 0.001), to a standardized recruitment manoeuvre. Patients belonging to phenotype 2 (recruitable) presented a higher intensive care mortality (hazard ratio 2.9, 95% confidence interval 1.7–2.7, p = 0.001).

Conclusions

The present study identifies two ARDS phenotypes based on respiratory mechanics, gas-exchange and computed tomography-derived gas- and tissue-volumes. These phenotypes are characterized by distinctly diverse responses to a standardized recruitment manoeuvre and by a diverging mortality. Given multicentre validation, the simple and rapid identification of these pulmonary phenotypes could facilitate enrichment of future prospective clinical trials addressing mechanical ventilation strategies in ARDS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03578-6.

Novel criteria to classify ARDS severity using a machine learning approach

Background

Usually, arterial oxygenation in patients with the acute respiratory distress syndrome (ARDS) improves substantially by increasing the level of positive end-expiratory pressure (PEEP). Herein, we are proposing a novel variable [PaO₂/(FiO₂xPEEP) or P/FP_E] for PEEP ≥ 5 to address Berlin’s definition gap for ARDS severity by using machine learning (ML) approaches.

Methods

We examined P/FP_E values delimiting the boundaries of mild, moderate, and severe ARDS. We applied ML to predict ARDS severity after onset over time by comparing current Berlin PaO₂/FiO₂ criteria with P/FP_E under three different scenarios. We extracted clinical data from the first 3 ICU days after ARDS onset (N = 2738, 1519, and 1341 patients, respectively) from MIMIC-III database according to Berlin criteria for severity. Then, we used the multicenter database eICU (2014–2015) and extracted data from the first 3 ICU days after ARDS onset (N = 5153, 2981, and 2326 patients, respectively). Disease progression in each database was tracked along those 3 ICU days to assess ARDS severity. Three robust ML classification techniques were implemented using Python 3.7 (LightGBM, RF, and XGBoost) for predicting ARDS severity over time.

Results

P/FP_E ratio outperformed PaO₂/FiO₂ ratio in all ML models for predicting ARDS severity after onset over time (MIMIC-III: AUC 0.711–0.788 and CORR 0.376–0.566; eICU: AUC 0.734–0.873 and CORR 0.511–0.745).

Conclusions

The novel P/FP_E ratio to assess ARDS severity after onset over time is markedly better than current PaO₂/FiO₂ criteria. The use of P/FP_E could help to manage ARDS patients with a more precise therapeutic regimen for each ARDS category of severity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-021-03566-w.

End-tidal to arterial PCO2 ratio: a bedside meter of the overall gas exchanger performance

Background

The physiological dead space is a strong indicator of severity and outcome of acute respiratory distress syndrome (ARDS). The “ideal” alveolar PCO₂, in equilibrium with pulmonary capillary PCO₂, is a central concept in the physiological dead space measurement. As it cannot be measured, it is surrogated by arterial PCO₂ which, unfortunately, may be far higher than ideal alveolar PCO₂, when the right-to-left venous admixture is present. The “ideal” alveolar PCO₂ equals the end-tidal PCO₂ (P_ETCO₂) only in absence of alveolar dead space. Therefore, in the perfect gas exchanger (alveolar dead space = 0, venous admixture = 0), the P_ETCO₂/PaCO₂ is 1, as P_ETCO₂, P_ACO₂ and PaCO₂ are equal. Our aim is to investigate if and at which extent the P_ETCO₂/PaCO₂, a comprehensive meter of the “gas exchanger” performance, is related to the anatomo physiological characteristics in ARDS.

Results

We retrospectively studied 200 patients with ARDS. The source was a database in which we collected since 2003 all the patients enrolled in different CT scan studies. The P_ETCO₂/PaCO₂, measured at 5 cmH₂O airway pressure, significantly decreased from mild to mild–moderate moderate–severe and severe ARDS. The overall populations was divided into four groups (~ 50 patients each) according to the quartiles of the P_ETCO₂/PaCO₂ (lowest ratio, the worst = group 1, highest ratio, the best = group 4). The progressive increase P_ETCO₂/PaCO₂ from quartile 1 to 4 (i.e., the progressive approach to the “perfect” gas exchanger value of 1.0) was associated with a significant decrease of non-aerated tissue, inohomogeneity index and increase of well-aerated tissue. The respiratory system elastance significantly improved from quartile 1 to 4, as well as the PaO₂/FiO₂ and PaCO₂. The improvement of P_ETCO₂/PaCO₂ was also associated with a significant decrease of physiological dead space and venous admixture. When PEEP was increased from 5 to 15 cmH₂O, the greatest improvement of non-aerated tissue, PaO₂ and venous admixture were observed in quartile 1 of P_ETCO₂/PaCO₂ and the worst deterioration of dead space in quartile 4.

Conclusion

The ratio P_ETCO₂/PaCO₂ is highly correlated with CT scan, physiological and clinical variables. It appears as an excellent measure of the overall “gas exchanger” status.

Extracellular histones aggravate inflammation in ARDS by promoting alveolar macrophage pyroptosis

Extracellular histones have been discovered to play a pathogenic role in ARDS, but the underlying mechanisms are yet to be fully defined. Alveolar macrophage (AM) is essential for the initiation and progression of lung inflammation; of note, AM pyroptosis has been suggested contributing to ARDS-associated inflammation. Here we aimed to investigate whether extracellular histones promote ARDS by triggering AM pyroptosis. The BALF samples of ARDS patients were collected and AMs were further isolated. Extracellular histones, AM pyroptosis, and pyroptosis-associated mediators were measured. Furthermore, the effects of extracellular histones on AM pyroptosis and the underlying mechanisms were investigated. It showed that extracellular histones were markedly elevated in the BALF of ARDS patients and correlated with the increased AM pyroptosis. ARDS patient's BALF induced pronounced pyroptosis in cultured human monocytes, which could be prevented by neutralizing extracellular histones with heparin. In addition, exogenous histones induced pyroptosis of MH-S cells in a dose- and time-dependent manner, which acted through the NLRP3 inflammasome signaling pathway. Inhibition of NLRP3 inflammasome signaling substantially reduced cell pyroptosis. In a murine model of LPS-induced ARDS, extracellular histones were increased in the BALF and its increase was associated with enhanced AM pyroptosis and exaggerated lung inflammation. Blockade of extracellular histones or NLPR3 inflammasome equally inhibited macrophage pyroptosis, whereas targeting histones appeared more effective in alleviating lung inflammation. This study suggested that extracellular histones promote AM pyroptosis through NLRP3 inflammasome pathway, which in turn aggravates lung inflammation in ARDS. Pharmacological manipulation of extracellular histones or AM pyroptosis may become promising strategies for the treatment of ARDS.

Current views on the potentials of convalescent plasma therapy (CPT) as Coronavirus disease 2019 (COVID-19) treatment: A systematic review and meta-analysis based on recent studies and previous respiratory pandemics

Convalescent plasma therapy (CPT) has been investigated as a treatment for COVID-19. This review evaluates CPT in COVID-19 and other viral respiratory diseases, including severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS) and influenza. PubMed and Google scholar databases were used to collect eligible publications until 8 December 2020. Meta-analysis used Mantel-Haenszel risk ratio (RR) with 95% confidence interval (CI) and pooled analysis for individual patient data with inverse variance weighted average. The study is registered at PROSPERO with the number of CRD4200270579. Forty-four studies with 36,716 participants were included in the pooled analysis and 20 studies in the meta-analysis. Meta-analysis showed reduction of mortality (RR 0.57, 95% CI [0.43, 0.76], z = 3.86 [p < 0.001], I²  = 44% [p = 0.03]) and higher number of discharged patients (RR 2.53, 95% CI [1.72, 3.72], z = 4.70 [p < 0.001], I²  = 3% [p = 0.39]) in patients receiving CPT compared to standard care alone. A possible mechanism of action is prompt reduction in viral titre. Serious transfusion-related adverse events were reported to be less than 1% of cases, suggesting the overall safety of CPT; nevertheless, the number of patients participating in the studies was still limited. It is also important to notice that in all the studies, the majority of patients were also given other medications, such as antivirals, antibiotics and corticosteroid; furthermore, randomized controlled studies involving more patients and in combination with other treatment modalities are urgently needed.

Continuous positive airway pressure in COVID-19 patients with moderate-to-severe respiratory failure

Noninvasive ventilation (NIV) and continuous positive airway pressure (CPAP) are recommended for acute hypoxaemic respiratory failure (AHRF) due to cardiogenic pulmonary oedema but no recommendation has been made for viral pandemics, because of the lack of randomised studies showing their efficacy and concerns of infection dissemination [1]. Early after the coronavirus disease 2019 (COVID-19) outbreak in Italy, there was an expert consensus in favour of CPAP and NIV as first-line treatments for the associated AHRF [2]. However, few studies used unspecified NIV in a minority of patients without detailed results [3–5]. CPAP was the object of two short reports with differing results [6, 7]. Thus, their value in COVID-19 remains to be established.

CPAP can be successfully used in a number of COVID-19 patients with hypoxaemic respiratory failure and gas exchange and radiological findings similar to those generally considered to be indications for invasive mechanical ventilationhttps://bit.ly/2GpBx6a

Lung ultrasound and computed tomography to monitor COVID-19 pneumonia in critically ill patients: a two-center prospective cohort study

BACKGROUND

Lung ultrasound can adequately monitor disease severity in pneumonia and acute respiratory distress syndrome. We hypothesize lung ultrasound can adequately monitor COVID-19 pneumonia in critically ill patients.

METHODS

Adult patients with COVID-19 pneumonia admitted to the intensive care unit of two academic hospitals who underwent a 12-zone lung ultrasound and a chest CT examination were included. Baseline characteristics, and outcomes including composite endpoint death or ICU stay > 30 days were recorded. Lung ultrasound and CT images were quantified as a lung ultrasound score involvement index (LUSI) and CT severity involvement index (CTSI). Primary outcome was the correlation, agreement, and concordance between LUSI and CTSI. Secondary outcome was the association of LUSI and CTSI with the composite endpoints.

RESULTS

We included 55 ultrasound examinations in 34 patients, which were 88% were male, with a mean age of 63 years and mean P/F ratio of 151. The correlation between LUSI and CTSI was strong (r = 0.795), with an overall 15% bias, and limits of agreement ranging - 40 to 9.7. Concordance between changes in sequentially measured LUSI and CTSI was 81%. In the univariate model, high involvement on LUSI and CTSI were associated with a composite endpoint. In the multivariate model, LUSI was the only remaining independent predictor.

CONCLUSIONS

Lung ultrasound can be used as an alternative for chest CT in monitoring COVID-19 pneumonia in critically ill patients as it can quantify pulmonary involvement, register changes over the course of the disease, and predict death or ICU stay > 30 days.

TRIAL REGISTRATION

NTR, NL8584. Registered 01 May 2020-retrospectively registered, https://www.trialregister.nl/trial/8584.

Mechanical power during extracorporeal membrane oxygenation and hospital mortality in patients with acute respiratory distress syndrome

Background

Mechanical power (MP) refers to the energy delivered by a ventilator to the respiratory system per unit of time. MP referenced to predicted body weight (PBW) or respiratory system compliance have better predictive value for mortality than MP alone in acute respiratory distress syndrome (ARDS). Our objective was to assess the potential impact of consecutive changes of MP on hospital mortality among ARDS patients receiving extracorporeal membrane oxygenation (ECMO).

Methods

We performed a retrospective analysis of patients with severe ARDS receiving ECMO in a tertiary care referral center in Taiwan between May 2006 and October 2015. Serial changes of MP during ECMO were recorded.

Results

A total of 152 patients with severe ARDS rescued with ECMO were analyzed. Overall hospital mortality was 53.3%. There were no significant differences between survivors and nonsurvivors in terms of baseline values of MP or other ventilator settings. Cox regression models demonstrated that mean MP alone, MP referenced to PBW, and MP referenced to compliance during the first 3 days of ECMO were all independently associated with hospital mortality. Higher MP referenced to compliance (HR 2.289 [95% CI 1.214–4.314], p = 0.010) was associated with a higher risk of death than MP itself (HR 1.060 [95% CI 1.018–1.104], p = 0.005) or MP referenced to PBW (HR 1.004 [95% CI 1.002–1.007], p < 0.001). The 90-day hospital mortality of patients with high MP (> 14.4 J/min) during the first 3 days of ECMO was significantly higher than that of patients with low MP (≦ 14.4 J/min) (70.7% vs. 46.8%, p = 0.004), and the 90-day hospital mortality of patients with high MP referenced to compliance (> 0.53 J/min/ml/cm H₂O) during the first 3 days of ECMO was significantly higher than that of patients with low MP referenced to compliance (≦ 0.53 J/min/ml/cm H₂O) (63.6% vs. 29.7%, p < 0.001).

Conclusions

MP during the first 3 days of ECMO was the only ventilatory variable independently associated with 90-day hospital mortality, and MP referenced to compliance during ECMO was more predictive for mortality than was MP alone.

SARS-CoV-2 pathophysiology and its clinical implications: An integrative overview of the pharmacotherapeutic management of COVID-19

Common manifestations of COVID-19 are respiratory and can extend from mild symptoms to severe acute respiratory distress. The severity of the illness can also extend from mild disease to life-threatening acute respiratory distress syndrome (ARDS). SARS-CoV-2 infection can also affect the gastrointestinal tract, liver and pancreatic functions, leading to gastrointestinal symptoms. Moreover, SARS-CoV-2 can cause central and peripheral neurological manifestations, affect the cardiovascular system and promote renal dysfunction. Epidemiological data have indicated that cancer patients are at a higher risk of contracting the SARS-CoV-2 virus. Considering the multitude of clinical symptoms of COVID-19, the objective of the present review was to summarize their pathophysiology in previously healthy patients, as well as in those with comorbidities. The present review summarizes the current, though admittedly fluid knowledge on the pathophysiology and symptoms of COVID-19 infection. Although unclear issues still remain, the present study contributes to a more complete understanding of the disease, and may drive the direction of new research. The recognition of the severity of the clinical symptoms of COVID-19 is crucial for the specific therapeutic management of affected patients.

Diaphragmatic thickening fraction as a potential predictor of response to continuous positive airway pressure ventilation in Covid-19 pneumonia: A single-center pilot study

BACKGROUND

In a variable number of Covid-19 patients with acute respiratory failure, non-invasive breathing support strategies cannot provide adequate oxygenation, thus making invasive mechanical ventilation necessary. Factors predicting this unfavorable outcome are unknown, but we hypothesized that diaphragmatic weakness may contribute.

METHODS

We prospectively analyzed the data of 27 consecutive patients admitted to the general Intensive Care Unit (ICU) from March 19, 2020, to April 20, 2020 and submitted to continuous positive airway pressure (CPAP) before considering invasive ventilation. Diaphragmatic thickening fraction (DTF) inferred by ultrasound was determined before applying CPAP.

RESULTS

Eighteen patients recovered with CPAP, whereas nine required invasive mechanical ventilation with longer stay in ICU (p < 0.001) and hospital (p = 0.003). At univariate logistic regression analysis, CPAP failure was significantly associated with low DTF [β: -0.396; OR: 0.673; p < 0.001] and high respiratory rate [β: 0.452; OR: 1.572; p < 0.001] but only DTF reached statistical significance at multivariate analysis [β: -0.384; OR: 0.681; p < 0.001]. The DTF best threshold predicting CPAP failure was 21.4 % (AUC: 0.944; sensitivity: 94.4 %, specificity: 88.9 %).

CONCLUSIONS

In critically ill patients with Covid-19 respiratory failure admitted to ICU, a reduced DTF could be a potential predictor of CPAP failure and requirement of invasive ventilation.

A quantitative CT parameter for the assessment of pulmonary oedema in patients with acute respiratory distress syndrome

Objectives

The aim of this study was to establish quantitative CT (qCT) parameters for pathophysiological understanding and clinical use in patients with acute respiratory distress syndrome (ARDS). The most promising parameter is introduced.

Materials and methods

28 intubated patients with ARDS obtained a conventional CT scan in end-expiratory breathhold within the first 48 hours after admission to intensive care unit (ICU). Following manual segmentation, 137 volume- and lung weight-associated qCT parameters were correlated with 71 clinical parameters such as blood gases, applied ventilation pressures, pulse contour cardiac output measurements and established status and prognosis scores (SOFA, SAPS II).

Results

Of all examined qCT parameters, excess lung weight (ELW), i.e. the difference between a patient’s current lung weight and the virtual lung weight of a healthy person at the same height, displayed the most significant results.

ELW correlated significantly with the amount of inflated lung tissue [%] (p<0.0001; r = -0.66) and was closely associated with the amount of extravascular lung water (EVLW) (p<0.0001; r = 0.72). More substantially than the oxygenation index (PaO₂/FiO₂) or any other clinical parameter it correlated with the patients’ mean SOFA- (p<0.0001, r = 0.69) and SAPS II-Score (p = 0.0005, r = 0.62). Patients who did not survive intensive care treatment displayed higher values of ELW in the initial CT scans.

Conclusions

ELW could serve as a non-invasive method to quantify the amount of pulmonary oedema. It might serve as an early radiological marker of severity in patients with ARDS.

Timing of Intubation and Mortality Among Critically Ill Coronavirus Disease 2019 Patients: A Single-Center Cohort Study

OBJECTIVES

Increasing time to mechanical ventilation and high-flow nasal cannula use may be associated with mortality in coronavirus disease 2019. We examined the impact of time to intubation and use of high-flow nasal cannula on clinical outcomes in patients with coronavirus disease 2019.

DESIGN

Retrospective cohort study.

SETTING

Six coronavirus disease 2019-specific ICUs across four university-affiliated hospitals in Atlanta, Georgia.

PATIENTS

Adults with laboratory-confirmed severe acute respiratory syndrome coronavirus 2 infection who received high-flow nasal cannula or mechanical ventilation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 231 patients admitted to the ICU, 109 (47.2%) were treated with high-flow nasal cannula and 97 (42.0%) were intubated without preceding high-flow nasal cannula use. Of those managed with high-flow nasal cannula, 78 (71.6%) ultimately received mechanical ventilation. In total, 175 patients received mechanical ventilation; 44.6% were female, 66.3% were Black, and the median age was 66 years (interquartile range, 56-75 yr). Seventy-six patients (43.4%) were intubated within 8 hours of ICU admission, 57 (32.6%) between 8 and 24 hours of admission, and 42 (24.0%) greater than or equal to 24 hours after admission. Patients intubated within 8 hours were more likely to have diabetes, chronic comorbidities, and higher admission Sequential Organ Failure Assessment scores. Mortality did not differ by time to intubation (≤ 8 hr: 38.2%; 8-24 hr: 31.6%; ≥ 24 hr: 38.1%; p = 0.7), and there was no association between time to intubation and mortality in adjusted analysis. Similarly, there was no difference in initial static compliance, duration of mechanical ventilation, or ICU length of stay by timing of intubation. High-flow nasal cannula use prior to intubation was not associated with mortality.

CONCLUSIONS

In this cohort of critically ill patients with coronavirus disease 2019, neither time from ICU admission to intubation nor high-flow nasal cannula use were associated with increased mortality. This study provides evidence that coronavirus disease 2019 respiratory failure can be managed similarly to hypoxic respiratory failure of other etiologies.

Can mesenchymal stem cells be used to treat COVID-19-induced pneumonia? (Review)

The novel severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) which has resulted in the COVID-19 pandemic, infection by which is commonly characterized by a sore throat, fever and cough, was first reported in Wuhan, China on 31^st December 2019. This novel disease is mild in certain individuals, usually younger healthy individuals, whereas the elder and those with underlying health conditions develop severe symptoms and may die as a result of the disease or associated complications. Along with pneumonia, hypercytokinemia, also termed a cytokine storm, is one of the most common pathologies observed in patients with COVID-19. As patients react to the infection with the virus differently; in certain individuals, a cytokine storm may result in death. At present, there is no cure or widely available vaccine for the novel coronavirus. However, it has been hypothesized that mesenchymal stem cells may assist in the treatment/management of the cytokine storm due to their immunomodulating properties.

Short-term survival of acute respiratory distress syndrome patients due to influenza virus infection alone: a cohort study

Background

Influenza virus (IV)-related pathophysiology suggests that the prognosis of acute respiratory distress syndrome (ARDS) due to IV could be different from the prognosis of ARDS due to other causes. However, the impact of IV infection alone on the prognosis of ARDS patients compared to that of patients with other causes of ARDS has been poorly assessed.

Methods

We compared the 28-day survival from the diagnosis of ARDS with an arterial oxygen tension/inspiratory oxygen fraction ratio ≤150 mmHg between patients with and without IV infection alone. Data were collected prospectively and analysed retrospectively. We first performed survival analysis on the whole population; second, patients with IV infection alone were compared with matched pairs using propensity score matching.

Results

The cohort admitted from October 2009 to March 2020 consisted of 572 patients, including 73 patients (13%) with IV alone. On the first 3 days of mechanical ventilation, nonpulmonary Sequential Organ Failure Assessment scores were significantly lower in patients with IV infection than in the other patients. After the adjusted analysis, IV infection alone remained independently associated with lower mortality at day 28 (hazard ratio 0.51, 95% CI 0.26–0.99, p=0.047). Mortality at day 28 was significantly lower in patients with IV infection alone than in other patients when propensity score matching was used (20% versus 38%, p=0.02).

Conclusions

Our results suggest that patients with ARDS following IV infection alone have a significantly better prognosis at day 28 and less severe nonpulmonary organ dysfunction than do those with ARDS from causes other than IV infection alone.

Influenza virus infection alone is associated with a better short-term prognosis than are other causes of ARDShttps://bit.ly/31W2Mh2

Alveolar CCN1 is associated with mechanical stretch and acute respiratory distress syndrome severity

The cellular communication network factor 1 (CCN1) is a matricellular protein that can modulate multiple tissue responses, including inflammation and repair. We have previously shown that adenoviral overexpression of Ccn1 is sufficient to cause acute lung injury in mice. We hypothesized that CCN1 is present in the airspaces of lungs during the acute phase of lung injury, and higher concentrations are associated with acute respiratory distress syndrome (ARDS) severity. We tested this hypothesis by measuring 1) CCN1 in bronchoalveolar lavage fluid (BALF) and lung homogenates from mice subjected to ventilation-induced lung injury (VILI), 2) Ccn1 gene expression and protein levels in MLE-12 cells (alveolar epithelial cell line) subjected to mechanical stretch, and 3) CCN1 in BALF from mechanically ventilated humans with and without ARDS. BALF CCN1 concentrations and whole lung CCN1 protein levels were significantly increased in mice with VILI (n = 6) versus noninjured controls (n = 6). Ccn1 gene expression and CCN1 protein levels were increased in MLE-12 cells cultured under stretch conditions. Subjects with ARDS (n = 77) had higher BALF CCN1 levels compared with mechanically ventilated subjects without ARDS (n = 45) (P < 0.05). In subjects with ARDS, BALF CCN1 concentrations were associated with higher total protein, sRAGE, and worse [Formula: see text]/[Formula: see text] ratios (all P < 0.05). CCN1 is present in the lungs of mice and humans during the acute inflammatory phase of lung injury, and concentrations are higher in patients with increased markers of severity. Alveolar epithelial cells may be an important source of CCN1 under mechanical stretch conditions.

Retour d’expérience sur les transports Smur des patients Covid-19

Dès la fin du mois de février 2020, les urgentistes français ont été confrontés à une situation inédite et complexe dans la gestion des cas les plus sévères d’infections pulmonaires associées au nouveau coronavirus (SARSCoV- 2). Les informations en provenance de Chine et les recommandations initiales de l’Organisation mondiale de la santé ont rapidement amené à considérer l’intubation et la ventilation mécanique précoce des malades atteints par la pneumonie de la Covid-19. Or, dès la fin du mois de mars 2020, grâce aux retours d’expérience et de prise en charge, d’abord de la part des réanimateurs et urgentistes italiens, puis espagnols, les pratiques et les recommandations concernant les modalités d’oxygénation et de ventilation des patients Covid-19 ont évolué. Le caractère exceptionnel de cette pandémie et la grande adaptabilité des services de Samu/Smur de France, en l’espace de quelques semaines, pour prendre en charge ces patients oxygénodépendants, justifient que nous en fassions le retour d’expérience, et ce, d’autant plus que nous sommes exposés à un risque de recrudescence d’infections respiratoires graves associées au SARS-CoV-2 à court terme, risquant de saturer une nouvelle fois notre système de santé. Nous détaillons donc ici le retour d’expérience des prises en charge médicales préhospitalières concernant principalement les supports d’oxygénation et de ventilation mécanique.

[COVID-19, an atypical acute respiratory distress syndrome]

L’infection au nouveau coronavirus Sars-Cov2 est responsable d’une forme sévère de pneumonie, la COVID-19 pouvant évoluer vers un tableau de syndrome de détresse respiratoire aiguë. Cependant, bien que les critères d’hypoxémie soient présents, ce SDRA diffère des formes classiques, notamment en raison d’une compliance pulmonaire le plus souvent normale au stade initial. Ceci suggère des mécanismes physiopathologiques spécifiques encore mal compris, qui aboutissent à des profils de la maladie devant faire repenser la ventilation protectrice, afin de limiter la genèse des lésions pulmonaires induites par la ventilation.

Respiratory and cardiovascular effects of COVID-19 infection and their management

The COVID-19 epidemic has put an enormous burden on the health-care system and the economy. The virus has very high infectivity and is crippling in patients developing severe disease. The disease caused by this infective agent, a novel RNA coronavirus (SARS-CoV-2), was named by the World Health Organization as COVID-19. SARS-CoV-2 usually enters the human body from the respiratory tract and gradually causes systemic disease. The disease is mild in 81% and severe in the balance. The virus causes multiorgan damage and primarily damages airway epithelium, small intestine epithelium, and vascular endothelium, which are organs with high angiotensin-converting enzyme (angiotensin-converting enzyme-2 [ACE2] expression). The most affected organ is the lungs, and the cardiovascular system follows it closely. Symptomatic hypoxic patients are initially treated with oxygen supplementation, but those with severe hypoxia need mechanical ventilation support. Patients with COVID-19 infection present as two phenotypes. The ventilation strategy should be based on the phenotype. The disease causes major hemodynamic disturbances in its invasion of the cardiovascular system. Strict personal protection protocols are needed to ensure the safety of health-care workers and nosocomial spread.