Acute lung injury in the medical ICU: comorbid conditions, age, etiology, and hospital outcome

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.

Endotyping in ARDS: one step forward in precision medicine

BACKGROUND

The Berlin definition of acute respiratory distress syndrome (ARDS) includes only clinical characteristics. Understanding unique patient pathobiology may allow personalized treatment. We aimed to define and describe ARDS phenotypes/endotypes combining clinical and pathophysiologic parameters from a Canadian ARDS cohort.

METHODS

A cohort of adult ARDS patients from multiple sites in Calgary, Canada, had plasma cytokine levels and clinical parameters measured in the first 24 h of ICU admission. We used a latent class model (LCM) to group the patients into several ARDS subgroups and identified the features differentiating those subgroups. We then discuss the subgroup effect on 30 day mortality.

RESULTS

The LCM suggested three subgroups (n1 = 64, n2 = 86, and n3 = 30), and 23 out of 69 features made these subgroups distinct. The top five discriminating features were IL-8, IL-6, IL-10, TNF-a, and serum lactate. Mortality distinctively varied between subgroups. Individual clinical characteristics within the subgroup associated with mortality included mean PaO2/FiO2 ratio, pneumonia, platelet count, and bicarbonate negatively associated with mortality, while lactate, creatinine, shock, chronic kidney disease, vasopressor/ionotropic use, low GCS at admission, and sepsis were positively associated. IL-8 and Apache II were individual markers strongly associated with mortality (Area Under the Curve = 0.84).

PERSPECTIVE

ARDS subgrouping using biomarkers and clinical characteristics is useful for categorizing a heterogeneous condition into several homogenous patient groups. This study found three ARDS subgroups using LCM; each subgroup has a different level of mortality. This model may also apply to developing further trial design, prognostication, and treatment selection.

A Narrative Review on the Administration of Inhaled Prostaglandins in Critically Ill Adult Patients With Acute Respiratory Distress Syndrome

OBJECTIVE

To describe the effect of inhaled prostaglandins on both oxygenation and mortality in critically ill patients with acute respiratory distress syndrome (ARDS), with a focus on safety and efficacy in coronavirus disease 2019 (COVID-19)-associated ARDS and non-COVID-19 ARDS.

DATA SOURCES

A literature search of MEDLINE was performed using the following search terms: inhaled prostaglandins, inhaled epoprostenol, inhaled nitric oxide, ARDS, critically ill. All abstracts were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Relevant English-language reports and studies conducted in humans between 1980 and June 2023 were considered.

DATA SYNTHESIS

Data regarding inhaled prostaglandins and their effect on oxygenation are limited but show a benefit in patients who respond to therapy, and data pertaining to their effect on mortality is scarce. Concerns exist regarding the formulation of inhaled epoprostenol (iEPO) utilized in addition to modes of medication delivery; however, the limited data surrounding their use have shown a reasonable safety profile. Other avenues and beneficial effects may exist with inhaled prostaglandins, such as use in COVID-19-associated ARDS or non-COVID-19 ARDS patients undergoing noninvasive mechanical ventilation or during patient transport.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

The use of inhaled prostaglandins can be considered in critically ill patients with COVID-19-associated ARDS or non-COVID-19 ARDS who are experiencing difficulties with oxygenation refractory to nonpharmacologic strategies.

CONCLUSIONS

The use of iEPO and other inhaled prostaglandins requires further investigation to fully elucidate their effects on clinical outcomes, but it appears these medications may have a potential benefit in COVID-19-associated ARDS and non-COVID-19 ARDS patients with refractory hypoxemia but with little effect on mortality.

Hospital Outcomes in Patients Who Developed Acute Respiratory Distress Syndrome After Community-Acquired Pneumonia

Purpose: To identify risk factors for and outcomes in acute respiratory distress syndrome (ARDS) in patients hospitalized with community-acquired pneumonia (CAP). Methods: This is a retrospective study using the Premier Healthcare Database between 2016 and 2020. Patients diagnosed with pneumonia, requiring mechanical ventilation (MV), antimicrobial therapy, and hospital admission ≥2 days were included. Multivariable regression models were used for outcomes including in-hospital mortality, hospital length of stay (LOS), intensive care unit (ICU) LOS, and days on MV. Results: 1924 (2.7%) of 72 107 patients with CAP developed ARDS. ARDS was associated with higher mortality (33.7% vs 18.9%; adjusted odds ratio 2.4; 95% confidence interval [CI] 2.16-2.66), longer hospital LOS (13 vs 9 days; adjusted incidence risk ratio (aIRR) 1.24; 95% CI 1.20-1.27), ICU LOS (9 vs 5 days; aIRR 1.51; 95% CI 1.46-1.56), more MV days (8 vs 5; aIRR 1.54; 95% CI 1.48-1.59), and increased hospitalization cost ($46 459 vs $29 441; aIRR 1.50; 95% CI 1.45-1.55). Conclusion: In CAP, ARDS was associated with worse in-patient outcomes in terms of mortality, LOS, and hospitalization cost. Future studies are needed to explore outcomes in patients with CAP with ARDS and explore risk factors for development of ARDS after CAP.

Segmental Shielding: A Rare Case of Acute Respiratory Distress Syndrome with Middle Lobe Sparing

Acute respiratory distress syndrome (ARDS) presents a formidable challenge in critical care, often resulting in high mortality rates, particularly in severe cases or those compounded by preexisting conditions. Despite substantial advancements in critical care, the heterogeneous nature of ARDS necessitates nuanced clinical approaches. ARDS is generally diagnosed through clinical evaluation, radiographic imaging, and laboratory tests, as well as acute onset, bilateral lung infiltrates on imaging, and a partial pressure of oxygen in arterial blood (PaO2)/fraction of inspiratory oxygen concentration (FiO2) ratio of less than 300 mmHg. Management involves measurements to improve oxygenation and provide mechanical ventilation to assist breathing. The typical manifestation of ARDS is diffuse lung involvement, which affects multiple lobes symmetrically. Here, we report an unusual case of ARDS in a 53-year-old female who was brought into the hospital in an unresponsive state, exhibiting hypoxic and hypotension requiring intubation. Subsequent imaging revealed a distinctive pattern: the preservation of the right middle lobe, diverging from the conventional diffuse pulmonary affliction. This case underscores the need for clinical vigilance and adaptability, as such atypical presentations can confound diagnosis and management, posing unique clinical challenges. This case highlights the importance of recognizing ARDS' diverse presentations. Moreover, understanding the mechanisms behind the lobar sparing could provide greater insight into the disease heterogeneity and guide tailored therapeutic approaches. The imperative for further research into these uncommon presentations is clear, as it may be vital to improving outcomes for a broader spectrum of ARDS patients.

Pulmonary response prediction through personalized basis functions in a virtual patient model

BACKGROUND AND OBJECTIVE

Recruitment maneuvers with subsequent positive-end-expiratory-pressure (PEEP) have proven effective in recruiting lung volume and preventing alveoli collapse. However, determining a safe, effective, and patient-specific PEEP is not standardized, and this more optimal PEEP level evolves with patient condition, requiring personalised monitoring and care approaches to maintain optimal ventilation settings.

METHODS

This research examines 3 physiologically relevant basis function sets (exponential, parabolic, cumulative) to enable better prediction of elastance evolution for a virtual patient or digital twin model of MV lung mechanics, including novel elements to model and predict distension elastance. Prediction accuracy and robustness are validated against recruitment maneuver data from 18 volume-controlled ventilation (VCV) patients at 7 different baseline PEEP levels (0 to 12 cmH2O) and 14 pressure-controlled ventilation (PCV) patients at 4 different baseline PEEP levels (6 to 12 cmH2O), yielding 623 and 294 prediction cases, respectively. Predictions were made up to 12 cmH2O of added PEEP ahead, covering 6 × 2 cmH2O PEEP steps.

RESULTS

The 3 basis function sets yield median absolute peak inspiratory pressure (PIP) prediction error of 1.63 cmH2O for VCV patients, and median peak inspiratory volume (PIV) prediction error of 0.028 L for PCV patients. The exponential basis function set yields a better trade-off of overall performance across VCV and PCV prediction than parabolic and cumulative basis function sets from other studies. Comparing predicted and clinically measured distension prediction in VCV demonstrated consistent, robust high accuracy with R2 = 0.90-0.95.

CONCLUSIONS

The results demonstrate recruitment mechanics are best captured by an exponential basis function across different mechanical ventilation modes, matching physiological expectations, and accurately capture, for the first time, distension mechanics to within 5-10 % accuracy. Enabling the risk of lung injury to be predicted before changing ventilator settings. The overall outcomes significantly extend and more fully validate this digital twin or virtual mechanical ventilation patient model.

Outcomes and time trends of acute respiratory distress syndrome patients with and without liver cirrhosis: an observational cohort

BACKGROUND

In studies prior to lung-protective ventilation, liver cirrhosis in acute respiratory distress syndrome (ARDS) was associated with high mortality rates. Since patients with cirrhosis have been excluded from many trials on ARDS, their outcome when treated with lung-protective ventilation is unclear. The objectives were to assess whether cirrhosis is associated with mortality in ARDS and trends over time in mortality and severity.

METHODS

We conducted a retrospective analysis of a prospective observational cohort conducted in a 20-bed tertiary ICU from October 2003 to December 2021. All consecutive adult critically ill patients with ARDS were included. ARDS was defined by the Berlin criteria. The primary outcome was 90 day mortality, assessed with Kaplan-Meier curves and multivariate Cox analysis. Time trends were assessed on 90 day mortality, Sequential Organ-Function Assessment score (SOFA) and non-hepatic SOFA. Ventilation settings were compared between patients with and without cirrhosis.

RESULTS

Of the 7155 patients screened, 863 had a diagnosis of ARDS. Among these ARDS patients, 157(18%) had cirrhosis. The overall 90 day mortality was of 43% (378/863), 57% (90/157) in patients with cirrhosis and 41% (288/706) in patients without cirrhosis (p < 0.001). On survival curves, cirrhosis was associated with 90 day mortality (p < 0.001). Cirrhosis was independently associated with 90 day mortality in multivariate analysis (hazard ratio = 1.56, 95% confidence interval 1.20-2.02). There was no change in mortality over time in ARDS patients with and without cirrhosis. SOFA (p = 0.04) and non-hepatic SOFA (p = 0.02) increased over time in ARDS patients without cirrhosis, and remained stable in ARDS patients with cirrhosis. Tidal volume, positive end-expiratory pressure, plateau pressure and driving pressure were not different between ARDS patients with and without cirrhosis.

CONCLUSIONS

Although ARDS management improved over the last decades, the 90 day mortality remained high and stable over time for both ARDS patients with (57%) and without cirrhosis (41%). Nevertheless, the severity of patients without cirrhosis has increased over time, while the severity of patients with cirrhosis has remained stable.

Respiratory issues in patients with multiple sclerosis as a risk factor during SARS-CoV-2 infection: a potential role for exercise

Coronavirus disease-2019 (COVID-19) is associated with cytokine storm and is characterized by acute respiratory distress syndrome (ARDS) and pneumonia problems. The respiratory system is a place of inappropriate activation of the immune system in people with multiple sclerosis (MS), and this may cause damage to the lung and worsen both MS and infections.The concerns for patients with multiple sclerosis are because of an enhance risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The MS patients pose challenges in this pandemic situation, because of the regulatory defect of autoreactivity of the immune system and neurological and respiratory tract symptoms. In this review, we first indicate respiratory issues associated with both diseases. Then, the main mechanisms inducing lung damages and also impairing the respiratory muscles in individuals with both diseases is discussed. At the end, the leading role of physical exercise on mitigating respiratory issues inducing mechanisms is meticulously evaluated.

Considerations of Medical Preparedness to Assess and Treat Various Populations During a Radiation Public Health Emergency

During a radiological or nuclear public health emergency, given the heterogeneity of civilian populations, it is incumbent on medical response planners to understand and prepare for a potentially high degree of interindividual variability in the biological effects of radiation exposure. A part of advanced planning should include a comprehensive approach, in which the range of possible human responses in relation to the type of radiation expected from an incident has been thoughtfully considered. Although there are several reports addressing the radiation response for special populations (as compared to the standard 18-45-year-old male), the current review surveys published literature to assess the level of consideration given to differences in acute radiation responses in certain sub-groups. The authors attempt to bring clarity to the complex nature of human biology in the context of radiation to facilitate a path forward for radiation medical countermeasure (MCM) development that may be appropriate and effective in special populations. Consequently, the focus is on the medical (as opposed to logistical) aspects of preparedness and response. Populations identified for consideration include obstetric, pediatric, geriatric, males, females, individuals of different race/ethnicity, and people with comorbidities. Relevant animal models, biomarkers of radiation injury, and MCMs are highlighted, in addition to underscoring gaps in knowledge and the need for consistent and early inclusion of these populations in research. The inclusion of special populations in preclinical and clinical studies is essential to address shortcomings and is an important consideration for radiation public health emergency response planning. Pursuing this goal will benefit the population at large by considering those at greatest risk of health consequences after a radiological or nuclear mass casualty incident.

Extracorporeal Carbon Dioxide Removal: From Pathophysiology to Clinical Applications; Focus on Combined Continuous Renal Replacement Therapy

Lung-protective ventilation (LPV) with low tidal volumes can significantly increase the survival of patients with acute respiratory distress syndrome (ARDS) by limiting ventilator-induced lung injuries. However, one of the main concerns regarding the use of LPV is the risk of developing hypercapnia and respiratory acidosis, which may limit the clinical application of this strategy. This is the reason why different extracorporeal CO₂ removal (ECCO₂R) techniques and devices have been developed. They include low-flow or high-flow systems that may be performed with dedicated platforms or, alternatively, combined with continuous renal replacement therapy (CRRT). ECCO₂R has demonstrated effectiveness in controlling PaCO₂ levels, thus allowing LPV in patients with ARDS from different causes, including those affected by Coronavirus disease 2019 (COVID-19). Similarly, the suitability and safety of combined ECCO₂R and CRRT (ECCO₂R-CRRT), which provides CO₂ removal and kidney support simultaneously, have been reported in both retrospective and prospective studies. However, due to the complexity of ARDS patients and the limitations of current evidence, the actual impact of ECCO₂R on patient outcome still remains to be defined. In this review, we discuss the main principles of ECCO₂R and its clinical application in ARDS patients, in particular looking at clinical experiences of combined ECCO₂R-CRRT treatments.

Gram-negative bacteremia in solid organ transplant recipients: Clinical characteristics and outcomes as compared to immunocompetent non-transplant recipients

BACKGROUND

Outcomes from Gram-negative bacteremia (GNB) in solid organ transplant (SOT) recipients are poorly understood.

METHODS

This is a single center prospective cohort study comparing the clinical characteristics and outcomes of SOT recipients with GNB to immunocompetent non-SOT patients with GNB between 1/1/2002 through 12/31/2018. Outcomes of interest included incidence of septic shock, respiratory failure, and time to death. A multivariable logistic regression model was used to determine factors associated with incidence of septic shock and respiratory failure. Time to death was evaluated using Cox proportional hazard models.

RESULTS

A total of 297 SOT and 1245 immunocompetent non-SOT patients were included. Incidence of septic shock did not significantly differ between the groups (SOT 25.3% vs. non-SOT 24.6%, p = .8225). Overall survival did not significantly differ by transplant status (30-day survival: SOT 76%, 95% confidence interval [CI] 70, 92, non-SOT 74%, 95% CI 71, 77: log rank: p = .76). SOT recipients taking three immunosuppressive medications had significantly lower odds of developing septic shock or respiratory failure requiring intubation and mechanical ventilation than those taking ≤1 agent (shock: adjusted odds ratio [aOR] 0.29, 95% CI 0.09, 0.90, p = .0316; respiratory failure: aOR 0.14, 95% CI: 0.04, 0.49, p = .0020).

CONCLUSIONS

SOT recipients with GNB do not experience higher rates of septic shock, respiratory failure, or mortality than immnon-SOT recipients with GNB. Among SOT recipients, a greater number of immunosuppressive medications may be associated with improved outcomes during GNB. Future studies are needed to understand the potential relationship between levels of immunosuppression and clinical outcome in SOT recipients with GNB.

Electrical impedance tomography for titration of positive end-expiratory pressure in acute respiratory distress syndrome patients with chronic obstructive pulmonary disease

Background

Chronic obstructive pulmonary disease (COPD) is one of most common comorbidities in acute respiratory distress syndrome (ARDS). There are few specific studies on the appropriate ventilation strategy for patients with ARDS comorbid with COPD, especially regarding on positive end-expiratory pressure (PEEP) titration.

Methods

To compare the respiratory mechanics in mechanical ventilated ARDS patients with or without COPD and to determine whether titration of PEEP based on electrical impedance tomography (EIT) is superior to the ARDSnet protocol. This is a single center, perspective, repeated measure study. ARDS patients requiring mechanical ventilation who were admitted to the intensive care unit between August 2017 and December 2020 were included. ARDS patients were divided according to whether they had COPD into a COPD group and a non-COPD group. Respiratory mechanics, gas exchange, and hemodynamics during ventilation were compared between the groups according to whether the PEEP level was titrated by EIT or the ARDSnet protocol.

Results

A total of twenty-seven ARDS patients including 14 comorbid with and 13 without COPD who met the study eligibility criteria were recruited. The PEEP levels titrated by EIT and the ARDSnet protocol were lower in the COPD group than in the non-COPD group (6.93 ± 1.69 cm H₂O vs. 12.15 ± 2.40 cm H₂O, P < 0.001 and 10.43 ± 1.20 cm H₂O vs. 14.0 ± 3.0 cm H₂O, P < 0.001, respectively). In the COPD group, the PEEP level titrated by EIT was lower than that titrated by the ARDSnet protocol (6.93 ± 1.69 cm H₂O vs. 10.43 ± 1.20 cm H₂O, P < 0.001), as was the global inhomogeneity (GI) index (0.397 ± 0.040 vs. 0.446 ± 0.052, P = 0.001), plateau airway pressure (16.50 ± 4.35 cm H₂O vs. 20.93 ± 5.37 cm H₂O, P = 0.001), dead space ventilation ratio (48.29 ± 6.78% vs. 55.14 ± 8.85%, P < 0.001), ventilation ratio (1.63 ± 0.33 vs. 1.87 ± 0.33, P < 0.001), and mechanical power (13.92 ± 2.18 J/min vs. 15.87 ± 2.53 J/min, P < 0.001). The cardiac index was higher when PEEP was treated by EIT than when it was titrated by the ARDSnet protocol (3.41 ± 0.50 L/min/m² vs. 3.02 ± 0.43 L/min/m², P < 0.001), as was oxygen delivery (466.40 ± 71.08 mL/min/m² vs. 411.10 ± 69.71 mL/min/m², P = 0.001).

Conclusion

Titrated PEEP levels were lower in patients with ARDS with COPD than in ARDS patients without COPD. In ARDS patient comorbid with COPD, application of PEEP titrated by EIT was lower than those titrated by the ARDSnet protocol, which contributed to improvements in the ventilation ratio, mechanical energy, cardiac index, and oxygen delivery with less of an adverse impact on hemodynamics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-04201-y.

A Case of Severe Acute Respiratory Distress Syndrome Secondary to Atypical Amniotic Fluid Embolism

Acute respiratory distress syndrome (ARDS) is a noncardiogenic pulmonary edema that leads to acute respiratory distress. It remains one of the major diagnoses requiring ICU admission and mechanical ventilation. We present a case of a 25-year-old gravida 3 para 2 female who was admitted for uncomplicated 38-week pregnancy and delivered a healthy male infant but developed acute onset dyspnea six hours after vaginal delivery. She required mechanical ventilation four hours after the onset of respiratory distress and had to be transferred to a higher level facility for extracorporeal membrane oxygenation (ECMO) within 24 hours of the symptom onset. She was diagnosed with severe ARDS. Even though she missed the other typical feature of amniotic fluid embolism, atypical amniotic fluid embolism remained the most likely explanation for her symptoms after the other causes of ARDS were excluded.

Immune Infiltration and N(6)-Methyladenosine ncRNA Isoform Detection in Acute Lung Injury

Acute lung injury (ALI) is a severe form of sepsis that is associated with a high rate of morbidity and death in critically ill individuals. The emergence of ALI is the result of several factors at work. Case mortality rates might range from 40% to 70%. Researchers have discovered that epigenetic alterations are important in the pathophysiology of ALI and that using epigenetic inhibitors may help reduce symptoms. In embryonic development, circadian rhythm, the cell cycle, and cancer, methylation of m6A seems to be relevant all along the way. According to recent research, posttranscriptional methylation is a key player in the development of alveolar lymphoma. In this study, we clustered ALI based on m6A-related factors, analyzed different classes of immune cell enrichment and inflammatory cytokine expression, screened clustered differential genes for ALI to construct coexpression networks, screened key ALI genes potentially regulated by m6A modifications, and then typed the disease based on key genes to compare the consistency of different clustering results. Our findings have revealed a hitherto undiscovered prognostic sign and a therapeutic target for ALI therapy in m6A and immune invading cells, respectively.

The Impact of Chronic Medical Conditions on Mortality in Acute Respiratory Distress Syndrome

PURPOSE

To examine the impact of chronic comorbidities on mortality in Acute Respiratory Distress Syndrome (ARDS).

MATERIALS AND METHODS

Retrospective cohort study of adults with ARDS (ICD-10-CM code J80) from the National Inpatient Sample between January, 2016 and December, 2018. For the primary outcome of mortality, we conducted weighted logistic regression adjusting for factors identified on univariate analysis as potentially significant or differing between the two groups at baseline. We used negative binomial regression adjusting for the same comorbidities to identify risk factors for longer length of stay (LOS) among ARDS survivors.

RESULTS

After exclusions, 1046 records were analyzed (3355 ARDS survivors and 1875 non-survivors.) The comorbidities examined included hypertension, diabetes mellitus, obesity, hypothyroidism, alcohol and drug use, chronic kidney disease (CKD), cardiovascular disease, chronic liver disease, chronic pulmonary disease and malignancy. In multivariate analysis, we found that malignancy (OR 2.26, 95% CI 1.84-2.78, p < 0.001), cardiovascular disease (OR 1.54, 95% CI 1.23-1.92, p < 0.001), and CKD (OR 1.75, 95% CI 1.22-2.50, p  =  0.002) increased the risk of death. In interaction analyses, cardiovascular disease combined with either malignancy or CKD conferred higher odds of death compared to either risk factor alone.

CONCLUSIONS

The comorbidity of malignancy confers the most reliable risk of poor outcomes in ARDS with higher odds of hospital death and a simultaneous association with longer hospital LOS among survivors.

Patient Information Items Needed to Guide the Allocation of Scarce Life-Sustaining Resources: A Delphi Study of Multidisciplinary Experts

OBJECTIVE

Plans for allocation of scarce life-sustaining resources during the coronavirus disease 2019 (COVID-19) pandemic often include triage teams, but operational details are lacking, including what patient information is needed to make triage decisions.

METHODS

A Delphi study among Washington state disaster preparedness experts was performed to develop a list of patient information items needed for triage team decision-making during the COVID-19 pandemic. Experts proposed and rated their agreement with candidate information items during asynchronous Delphi rounds. Consensus was defined as ≥80% agreement. Qualitative analysis was used to describe considerations arising in this deliberation. A timed simulation was performed to evaluate feasibility of data collection from the electronic health record.

RESULTS

Over 3 asynchronous Delphi rounds, 50 experts reached consensus on 24 patient information items, including patients' age, severe or end-stage comorbidities, the reason for and timing of admission, measures of acute respiratory failure, and clinical trajectory. Experts weighed complex considerations around how information items could support effective prognostication, consistency, accuracy, minimizing bias, and operationalizability of the triage process. Data collection took a median of 227 seconds (interquartile range = 205, 298) per patient.

CONCLUSIONS

Experts achieved consensus on patient information items that were necessary and appropriate for informing triage teams during the COVID-19 pandemic.

Clinical risk factors for early mortality in patients with community-acquired septic shock. The importance of adequate source control

OBJECTIVE

To evaluate the incidence and risk factors for early mortality (EM) in the ICU in patients with community-acquired septic shock (CASS).

DESIGN

A retrospective cohort study of patients with CASS admitted to the ICU (2003-2016).

SETTING

ICU at a University Hospital in Spain.

PATIENTS

All consecutive patients admitted to the ICU with CASS.

INTERVENTIONS

None.

MAIN VARIABLES OF INTEREST

CASS was defined according to the Sepsis-3 definitions. EM were defined as occurring within of 72h following ICU admission. A multinomial logistic regression analysis was performed to identify the risk factors associated with early deaths.

RESULTS

During the study period, 625 patients met the Sepsis-3 criteria and admitted with CASS. 14.4% of all patients died within the first 72h. Of 161 patients who died in the ICU, 90 (55.9%) died within the first 72h. The percentage of early and late mortality did not vary significantly during the study period. The need and adequacy of source control were significantly lower in patients with EM. In the multivariate analysis, ARDS, non-respiratory infections, bacteremia and severity at admission were variables independently associated with EM. The only factor that decreased EM was adequate source control in patients with infections amenable to source control.

CONCLUSIONS

The incidence of EM has remained stable over time, which means that more than half of the patients who die from CASS do so within the first 72h. Infections where adequate source control can be performed have lower EM.

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Inflammation plays an important role in the development of acute lung injury (ALI). Severe pulmonary inflammation can cause acute respiratory distress syndrome (ARDS) or even death. Expression of proinflammatory interleukin-‍1β (IL-‍1β) and inducible nitric oxide synthase (iNOS) in the process of pulmonary inflammation will further exacerbate the severity of ALI. The purpose of this study was to explore the effect of Palrnatine (Pa) on lipopolysaccharide (LPS)-induced mouse ALI and its underlying mechanism. Pa, a natural product, has a wide range of pharmacological activities with the potential to protect against lung injury. Western blotting and quantitative real-time polymerase chain reaction (qRT-PCR) assays were performed to detect the expression and translation of inflammatory genes and proteins in vitro and in vivo. Immunoprecipitation was used to detect the degree of P65 translocation into the nucleus. We also used molecular modeling to further clarify the mechanism of action. The results showed that Pa pretreatment could significantly inhibit the expression and secretion of the inflammatory cytokine IL-1β, and significantly reduce the protein level of the proinflammatory protease iNOS, in both in vivo and in vitro models induced by LPS. Further mechanism studies showed that Pa could significantly inhibit the activation of the protein kinase B (Akt)/nuclear factor-κB (NF-κB) signaling pathway in the LPS-induced ALI mode and in LPS-induced RAW264.7 cells. Through molecular dynamics simulation, we observed that Pa was bound to the catalytic pocket of Akt and effectively inhibited the biological activity of Akt. These results indicated that Pa significantly relieves LPS-induced ALI by activating the Akt/NF-κB signaling pathway.

The Risk Factors for Weaning Failure of Mechanically Ventilated Patients With COVID-19: A Retrospective Study in National Medical Team Work

Purpose: This study aimed to describe the clinical and laboratory characteristics and the parameters of the respiratory mechanics of mechanically ventilated patients with confirmed COVID-19 pneumonia and to clarify the risk or protective factors for weaning failure. Methods: Patients diagnosed with COVID-19 pneumonia were selected from the special intensive care unit (ICU) of the Sino-French New City Branch of Tong Ji Hospital, Wuhan, and treated by the National Medical Team Work. They were divided into successful weaning (SW) group (N = 15) and unsuccessful weaning (USW) group (N = 18) according to the prognosis. Information of these patients was analyzed. Results: There were 33 patients included in this study. Patients in the USW group were associated with a poor outcome; the 28-day mortality rate was higher than in the SW group (86.7 vs. 16.7% p < 0.001). By comparison, we found that the initial plateau pressure (Pplat) and driving pressure (DP) of the USW group were higher and that compliance was lower than that of the SW group, but there was no difference between positive end-expiratory pressure (PEEP), partial pressure of carbon dioxide (PCO₂), and the ratio of partial pressure arterial oxygen and fraction of inspired oxygen (P/F ratio). Comparing the worst respiratory mechanics parameters of the two groups, the results of the Pplat, DP, compliance, and PEEP were the same as the initial data. The PCO₂ of the USW group was higher, while the P/F ratio was lower. A logistic regression analysis suggested that higher Pplat might be an independent risk factor and that higher compliance and lower DP might be protective factors for weaning failure of invasive mechanically ventilated patients with COVID-19 pneumonia. Conclusions: Patients with USW were associated with a poor outcome, higher Pplat might be a risk factor, and a higher compliance and a lower DP might be protective factors for the weaning failure of ventilated COVID-19 patients. Mechanical ventilation settings will affect the patient's prognosis.

Survival of COVID-19 Patients With Respiratory Failure is Related to Temporal Changes in Gas Exchange and Mechanical Ventilation

Background: Respiratory failure due to coronavirus disease of 2019 (COVID-19) often presents with worsening gas exchange over a period of days. Once patients require mechanical ventilation (MV), the temporal change in gas exchange and its relation to clinical outcome is poorly described. We investigated whether gas exchange over the first 5 days of MV is associated with mortality and ventilator-free days at 28 days in COVID-19. Methods: In a cohort of 294 COVID-19 patients, we used data during the first 5 days of MV to calculate 4 daily respiratory scores: PaO₂/FiO₂ (P/F), oxygenation index (OI), ventilatory ratio (VR), and Murray lung injury score. The association between these scores at early (days 1-3) and late (days 4-5) time points with mortality was evaluated using logistic regression, adjusted for demographics. Correlation with ventilator-free days was assessed (Spearman rank-order coefficients). Results: Overall mortality was 47.6%. Nonsurvivors were older (P < .0001), more male (P = .029), with more preexisting cardiopulmonary disease compared to survivors. Mean PaO₂ and PaCO₂ were similar during this timeframe. However, by days 4 to 5 values for all airway pressures and FiO₂ had diverged, trending lower in survivors and higher in nonsurvivors. The most substantial between-group difference was the temporal change in OI, improving 15% in survivors and worsening 11% in nonsurvivors (P < .05). The adjusted mortality OR was significant for age (1.819, P = .001), OI at days 4 to 5 (2.26, P = .002), and OI percent change (1.90, P = .02). The number of ventilator-free days correlated significantly with late VR (-0.166, P < .05), early and late OI (-0.216, P < .01; -0.278, P < .01, respectively) and early and late P/F (0.158, P < .05; 0.283, P < .01, respectively). Conclusion: Nonsurvivors of COVID-19 needed increasing intensity of MV to sustain gas exchange over the first 5 days, unlike survivors. Temporal change OI, reflecting both PaO₂ and the intensity of MV, is a potential marker of outcome in respiratory failure due to COVID-19.

A randomized, controlled, multicenter clinical study of the "improved sitting Wuqinxi" intervention for mechanically ventilated patients in the intensive care unit

INTRODUCTION

Mechanical ventilation is a powerful tool for the treatment of various critical emergencies. However, surviving critically ill patients often have poor psychological and physiological outcomes. Prevention of various complications and adverse outcomes of mechanical ventilation is a priority and a challenge in the intensive care unit (ICU). Early intervention is the key to reducing complications and improving outcomes of mechanical ventilation in the ICU. As an auxiliary rehabilitation treatment, the improved sitting Wuqinxi intervention has recognized unique advantages. It has achieved beneficial therapeutic effects during early intervention in clinical practice. It can reduce the incidence of delirium, shorten the duration of mechanical ventilation, and prevent complications and secondary damages related to mechanical ventilation in the ICU. Therefore, the purpose of this study will be to explore the effect of improved sitting Wuqinxi on the clinical outcomes of mechanically ventilated ICU patients.

METHODS

This prospective, multicenter, randomized, single-blinded, parallel controlled clinical study will involve 160 patients who met the inclusion criteria. The patients will be randomly divided into the experimental and control groups. Both groups will be given standardized comprehensive western medicine treatment (including mechanical ventilation) and routine care in the ICU. Management of the experimental group will also include "improved sitting Wuqinxi," with the treatment objective to observe the effect of the improved sitting Wuqinxi intervention on the clinical outcomes in mechanically ventilated ICU patients. The outcome measures will include the incidence of complications, duration of mechanical ventilation, length of ICU stay, and cost of hospitalization. In addition, the effect of the improved sitting Wuqinxi intervention on the safety indexes of mechanically ventilated ICU patients will be assessed and the clinical effects of the improved sitting Wuqinxi intervention will be comprehensively evaluated.

DISCUSSION

The purpose of this study will be to evaluate the effect of the improved sitting Wuqinxi intervention on the incidence of complications, duration of mechanical ventilation, length of ICU stay, cost of hospitalization, and safety indicators. If successful, it will provide a reliable, simple, and feasible auxiliary rehabilitation treatment scheme for mechanically ventilated ICU patients.

Etiology and Outcomes of ARDS in the Elderly Population in an Intensive Care Unit in North India

Background

Whether age would impact the outcomes in subjects with acute respiratory distress syndrome (ARDS) remains unclear. Herein, we study the effect of age as a predictor of mortality in ARDS.

Materials and methods

We categorized consecutive subjects with ARDS as either ARDS_elderly (age >65 years) or ARDSnon_elderly (age ≤65 years) admitted to the respiratory intensive care unit (ICU) of a tertiary care hospital in North India between January 2007 and December 2019. We compared the baseline clinical and demographic characteristics, lung mechanics, and mortality between the two groups. We also analyzed the factors predicting ICU survival using multivariate logistic regression analysis.

Results

We included 625 patients (ARDS_elderly, 140 [22.4%] and ARDS_nonelderly, 485 [77.6%]) with a mean (standard deviation) age (56.3% males) of 40.6 (17.8) years. The ARDS_elderly were more likely (p = 0.0001) to have the presence of any comorbid illness compared to ARDS_nonelderly. The elderly subjects had significantly higher pulmonary ARDS than the younger group. The severity of ARDS was however, similarly distributed between the two study arms. There were 224 (35.8%) deaths, and the mortality was significantly higher (p = 0.012) in the ARDS_elderly than the to ARDS_nonelderly (ARDS_elderly vs ARDS_nonelderly, 45 vs 33.2%). On multivariate logistic regression analysis, the baseline sequential organ failure assessment scores, presence of pulmonary ARDS, and the development of new organ dysfunction were the independent predictors of mortality.

Conclusion

The outcomes in subjects with ARDS are dependent on the severity of illness at admission and the etiology of ARDS rather than the age alone.

How to cite this article

Sehgal IS, Agarwal R, Dhooria S, Prasad KT, Muthu V, Aggarwal AN. Etiology and Outcomes of ARDS in the Elderly Population in an Intensive Care Unit in North India. Indian J Crit Care Med 2021;25(6):648–654.

A cross-sectional study of early mobility practice in intensive care units in Sarawak Hospitals, Malaysia

Aims

To determine the prevalence, characteristics of EM activities, the relationship between level of activity and mode of ventilation and adherence rate of EM protocol.

Background

Mobilizing ICU patients remains a challenge, despite its safety, feasibility and positive short-term outcomes.

Design

A cross-sectional point prevalence study.

Methods

All patients who were eligible and admitted to the adult ICUs during March 2018 were recruited. Data were analysed by using the Statistical Package for Social Sciences version 24 for Windows.

Results

The prevalence of EM practice was 65.6%. The most frequently reported avoidable and unavoidable factors inhibit mobility were deep sedation and vasopressor infusion, respectively. Level II of activity was the most common level of activity performed in ICU patients. The invasive ventilated patient had 12.53 the odds to stay in bed as compared to non-invasive ventilated patient. An average adherence rate of EM protocol was 52.5%.

Diagnosis and Management of Acute Respiratory Distress Syndrome in a Time of COVID-19

Acute respiratory distress syndrome (ARDS) remains a serious illness with significant morbidity and mortality, characterized by hypoxemic respiratory failure most commonly due to pneumonia, sepsis, and aspiration. Early and accurate diagnosis of ARDS depends upon clinical suspicion and chest imaging. Coronavirus disease 2019 (COVID-19) is an important novel cause of ARDS with a distinct time course, imaging and laboratory features from the time of SARS-CoV-2 infection to hypoxemic respiratory failure, which may allow diagnosis and management prior to or at earlier stages of ARDS. Treatment of ARDS remains largely supportive, and consists of incremental respiratory support (high flow nasal oxygen, non-invasive respiratory support, and invasive mechanical ventilation), and avoidance of iatrogenic complications, all of which improve clinical outcomes. COVID-19-associated ARDS is largely similar to other causes of ARDS with respect to pathology and respiratory physiology, and as such, COVID-19 patients with hypoxemic respiratory failure should typically be managed as other patients with ARDS. Non-invasive respiratory support may be beneficial in avoiding intubation in COVID-19 respiratory failure including mild ARDS, especially under conditions of resource constraints or to avoid overwhelming critical care resources. Compared to other causes of ARDS, medical therapies may improve outcomes in COVID-19-associated ARDS, such as dexamethasone and remdesivir. Future improved clinical outcomes in ARDS of all causes depends upon individual patient physiological and biological endotyping in order to improve accuracy and timeliness of diagnosis as well as optimal targeting of future therapies in the right patient at the right time in their disease.

Clinical risk factors for early mortality in patients with community-acquired septic shock. The importance of adequate source control

OBJECTIVE

To evaluate the incidence and risk factors for early mortality (EM) in the ICU in patients with community-acquired septic shock (CASS).

DESIGN

A retrospective cohort study of patients with CASS admitted to the ICU (2003-2016).

SETTING

ICU at a University Hospital in Spain.

PATIENTS

All consecutive patients admitted to the ICU with CASS.

INTERVENTIONS

None.

MAIN VARIABLES OF INTEREST

CASS was defined according to the Sepsis-3 definitions. EM were defined as occurring within of 72h following ICU admission. A multinomial logistic regression analysis was performed to identify the risk factors associated with early deaths.

RESULTS

During the study period, 625 patients met the Sepsis-3 criteria and admitted with CASS. 14.4% of all patients died within the first 72h. Of 161 patients who died in the ICU, 90 (55.9%) died within the first 72h. The percentage of early and late mortality did not vary significantly during the study period. The need and adequacy of source control were significantly lower in patients with EM. In the multivariate analysis, ARDS, non-respiratory infections, bacteremia and severity at admission were variables independently associated with EM. The only factor that decreased EM was adequate source control in patients with infections amenable to source control.

CONCLUSIONS

The incidence of EM has remained stable over time, which means that more than half of the patients who die from CASS do so within the first 72h. Infections where adequate source control can be performed have lower EM.

Association between age and acute respiratory distress syndrome development and mortality following trauma

BACKGROUND

Improved understanding of the relationship between patient age and acute respiratory distress syndrome (ARDS) development and mortality following traumatic injury may help facilitate generation of new hypotheses about ARDS pathophysiology and the role of novel treatments to improve outcomes across the age spectrum.

METHODS

We conducted a retrospective cohort study of trauma patients included in the National Trauma Data Bank who were admitted to an intensive care unit from 2007 to 2016. We determined ARDS incidence and mortality across eight age groups for the entire 10-year study period and by year. We used generalized linear Poisson regression models adjusted for underlying mortality risk (injury mechanism, Injury Severity Score, admission Glasgow Coma Scale score, admission heart rate, and admission hypotension).

RESULTS

Acute respiratory distress syndrome occurred in 3.1% of 1,297,190 trauma encounters. Acute respiratory distress syndrome incidence was lowest among pediatric patients and highest among adults aged 35 to 64 years. Acute respiratory distress syndrome mortality was highest among patients 80 years or older (43.9%), followed by 65 to 79 years (30.6%) and 4 years or younger (25.3%). The relative risk of mortality associated with ARDS was highest among the pediatric age groups, with an adjusted relative risk (aRR) of 2.06 (95% confidence interval [CI], 1.72-2.70) among patients 4 years or younger compared with an aRR of 1.51 (95% CI, 1.42-1.62) for the entire cohort. Acute respiratory distress syndrome mortality increased over the 10-year study period (aRR, 1.03 per year; 95% CI, 1.02-1.05 per year), whereas all-cause mortality decreased (aRR, 0.98 per year; 95% CI, 0.98-0.99 per year).

CONCLUSIONS

While ARDS development following traumatic injury was most common in middle-aged adults, patients 4 years or younger and 65 years or older with ARDS experienced the highest burden of mortality. Children 4 years or younger were disproportionately affected by ARDS relative to their low underlying mortality following trauma that was not complicated by ARDS. Acute respiratory distress syndrome-associated mortality following trauma has worsened over the past decade, emphasizing the need for new prevention and treatment strategies.

LEVEL OF EVIDENCE

Prognostic/epidemiological study, level III.

Prognostic relevance and inter-observer reliability of chest-imaging in pediatric ARDS: a pediatric acute respiratory distress incidence and epidemiology (PARDIE) study

Purpose

Definitions of acute respiratory distress syndrome (ARDS) include radiographic criteria, but there are concerns about reliability and prognostic relevance. This study aimed to evaluate the independent relationship between chest imaging and mortality and examine the inter-rater variability of interpretations of chest radiographs (CXR) in pediatric ARDS (PARDS).

Methods

Prospective, international observational study in children meeting Pediatric Acute Lung Injury Consensus Conference (PALICC) criteria for PARDS, which requires new infiltrate(s) consistent with pulmonary parenchymal disease, without mandating bilateral infiltrates. Mortality analysis focused on the entire cohort, whereas inter-observer variability used a subset of patients with blinded, simultaneous interpretation of CXRs by intensivists and radiologists.

Results

Bilateral infiltrates and four quadrants of alveolar consolidation were associated with mortality on a univariable basis, using CXRs from 708 patients with PARDS. For patients on either invasive (IMV) or non-invasive ventilation (NIV) with PaO₂/FiO₂ (PF) ratios (or SpO₂/FiO₂ (SF) ratio equivalent) > 100, neither bilateral infiltrates (OR 1.3 (95% CI 0.68, 2.5), p = 0.43), nor 4 quadrants of alveolar consolidation (OR 1.6 (0.85, 3), p = 0.14) were associated with mortality. For patients with PF ≤ 100, bilateral infiltrates (OR 3.6 (1.4, 9.4), p = 0.01) and four quadrants of consolidation (OR 2.0 (1.14, 3.5), p = 0.02) were associated with higher mortality. A subset of 702 CXRs from 233 patients had simultaneous interpretations. Interobserver agreement for bilateral infiltrates and quadrants was “slight” (kappa 0.31 and 0.33). Subgroup analysis showed agreement did not differ when stratified by PARDS severity but was slightly higher for children with chronic respiratory support (kappa 0.62), NIV at PARDS diagnosis (kappa 0.53), age > 10 years (kappa 0.43) and fluid balance > 40 ml/kg (kappa 0.48).

Conclusion

Bilateral infiltrates and quadrants of alveolar consolidation are associated with mortality only for those with PF ratio ≤ 100, although there is high- inter-rater variability in these chest-x ray parameters.

Electronic supplementary material

The online version of this article (10.1007/s00134-020-06074-7) contains supplementary material, which is available to authorized users.

Design and Study of a Portable High-frequency Ventilator for Clinical Applications

Treatment costs for ventilator-dependent patients are a substantial burden not only for their family but also for medical systems in general. Recently, using high-frequency ventilators have been shown to reduce the risk of lung injury through low-volume airflow. However, the machines used today remain bulky, costly, and only for use in hospital settings. To provide intermediate therapy for patients between hospitalization and complete discharge, a portable, light-weight high-frequency ventilator is an urgent need. This work presents the design of a portable high-frequency ventilator and a study of its practicality for further clinical medical applications. Through the integration of advanced electronics and mechanical instruments, we develop a portable high-frequency ventilator with reconfigurable oxygen flow rate, applied pressure, and air volume for the needs of individual patients. A miniaturized portable high-frequency ventilator with digital controller and feedback system for stabilization and precision control is implemented. The efficiency of CO₂ washout using the proposed ventilator has been demonstrated in animal trials.

Association of Intraoperative Ventilator Management With Postoperative Oxygenation, Pulmonary Complications, and Mortality

BACKGROUND

"Lung-protective ventilation" describes a ventilation strategy involving low tidal volumes (VTs) and/or low driving pressure/plateau pressure and has been associated with improved outcomes after mechanical ventilation. We evaluated the association between intraoperative ventilation parameters (including positive end-expiratory pressure [PEEP], driving pressure, and VT) and 3 postoperative outcomes: (1) PaO2/fractional inspired oxygen tension (FIO2), (2) postoperative pulmonary complications, and (3) 30-day mortality.

METHODS

We retrospectively analyzed adult patients who underwent major noncardiac surgery and remained intubated postoperatively from 2006 to 2015 at a single US center. Using multivariable regressions, we studied associations between intraoperative ventilator settings and lowest postoperative PaO2/FIO2 while intubated, pulmonary complications identified from discharge diagnoses, and in-hospital 30-day mortality.

RESULTS

Among a cohort of 2096 cases, the median PEEP was 5 cm H2O (interquartile range = 4-6), median delivered VT was 520 mL (interquartile range = 460-580), and median driving pressure was 15 cm H2O (13-19). After multivariable adjustment, intraoperative median PEEP (linear regression estimate [B] = -6.04; 95% CI, -8.22 to -3.87; P < .001), median FIO2 (B = -0.30; 95% CI, -0.50 to -0.10; P = .003), and hours with driving pressure >16 cm H2O (B = -5.40; 95% CI, -7.2 to -4.2; P < .001) were associated with decreased postoperative PaO2/FIO2. Higher postoperative PaO2/FIO2 ratios were associated with a decreased risk of pulmonary complications (adjusted odds ratio for each 100 mm Hg = 0.495; 95% CI, 0.331-0.740; P = .001, model C-statistic of 0.852) and mortality (adjusted odds ratio = 0.495; 95% CI, 0.366-0.606; P < .001, model C-statistic of 0.820). Intraoperative time with VT >500 mL was also associated with an increased likelihood of developing a postoperative pulmonary complication (adjusted odds ratio = 1.06/hour; 95% CI, 1.00-1.20; P = .042).

CONCLUSIONS

In patients requiring postoperative intubation after noncardiac surgery, increased median FIO2, increased median PEEP, and increased time duration with elevated driving pressure predict lower postoperative PaO2/FIO2. Intraoperative duration of VT >500 mL was independently associated with increased postoperative pulmonary complications. Lower postoperative PaO2/FIO2 ratios were independently associated with pulmonary complications and mortality. Our findings suggest that postoperative PaO2/FIO2 may be a potential target for future prospective trials investigating the impact of specific ventilation strategies for reducing ventilator-induced pulmonary injury.

Aetiology and Short-Term Outcome of Acute Respiratory Distress Syndrome: A Real-World Experience from a Medical Intensive Care Unit in Southern India

Background

Acute respiratory distress syndrome (ARDS) is a highly fatal syndrome especially in resource constrained settings. In this study we prospectively studied the aetiology of ARDS and its short-term outcome.

Methods

Consecutive adults with suspected ARDS were screened. ARDS was diagnosed by the Berlin criteria. Aetiology was determined clinically, and by imaging and microbiological investigations. Patients presenting with fever, prominent cough and expectoration had a throat swab tested for influenza H1N1 virus. Outcome was discharge from hospital or death.

Results

A total of 42 patients, mean age 42.6 years, were studied. All received mechanical ventilation. Thirteen (31%) had pulmonary ARDS: H1N1 virus infection (n = 5), pneumonia (n = 7) and tuberculosis (n = 1). Twenty nine (69%) had extrapulmonary ARDS: sepsis (n = 16) and scrub typhus (n = 8). Thirty three (79%) died, of the nine survivors scrub typhus was diagnosed in seven patients.

Conclusion

The aetiology of ARDS in tropical medical setting is infection related. ARDS due to scrub typhus appeared to be mild with good outcome.

Acute Respiratory Distress Syndrome Definition, Causes, and Pathophysiology

First successfully described in 1967, acute respiratory distress syndrome has since garnered much interest and debate. Extensive studies and clinical trials have been carried out in efforts to address the associated high mortality; however, it remains a significant burden on health care. Despite the heterogeneous etiologies that lead to the development of acute respiratory distress syndrome, this rapidly progressing form of respiratory failure, characterized by severe hypoxemia and nonhydrostatic pulmonary edema, has a recognizable pattern of lung injury. In this chapter, we will review the clinical manifestations, definitions, causes, and a brief overview of the pathophysiology of this complex syndrome.

Pre-Treatment with Ten-Minute Carbon Dioxide Inhalation Prevents Lipopolysaccharide-Induced Lung Injury in Mice via Down-Regulation of Toll-Like Receptor 4 Expression

Various animal studies have shown beneficial effects of hypercapnia in lung injury. However, in patients with acute respiratory distress syndrome (ARDS), there is controversial information regarding the effect of hypercapnia on outcomes. The duration of carbon dioxide inhalation may be the key to the protective effect of hypercapnia. We investigated the effect of pre-treatment with inhaled carbon dioxide on lipopolysaccharide (LPS)-induced lung injury in mice. C57BL/6 mice were randomly divided into a control group or an LPS group. Each LPS group received intratracheal LPS (2 mg/kg); the LPS groups were exposed to hypercapnia (5% carbon dioxide) for 10 min or 60 min before LPS. Bronchoalveolar lavage fluid (BALF) and lung tissues were collected to evaluate the degree of lung injury. LPS significantly increased the ratio of lung weight to body weight; concentrations of BALF protein, tumor necrosis factor-α, and CXCL2; protein carbonyls; neutrophil infiltration; and lung injury score. LPS induced the degradation of the inhibitor of nuclear factor-κB-α (IκB-α) and nuclear translocation of NF-κB. LPS increased the surface protein expression of toll-like receptor 4 (TLR4). Pre-treatment with inhaled carbon dioxide for 10 min, but not for 60 min, inhibited LPS-induced pulmonary edema, inflammation, oxidative stress, lung injury, and TLR4 surface expression, and, accordingly, reduced NF-κB signaling. In summary, our data demonstrated that pre-treatment with 10-min carbon dioxide inhalation can ameliorate LPS-induced lung injury. The protective effect may be associated with down-regulation of the surface expression of TLR4 in the lungs.

Trends in the incidence and mortality of patients with community-acquired septic shock 2003-2016

PURPOSE

To evaluate the incidence and mortality of adult patients with community-acquired septic shock (CASS) and the influence of source control (SC) and other risk factors on the outcome.

MATERIAL AND METHODS

The study included patients with CASS admitted to the ICU at a university hospital (2003-2016). Multivariate analyses were performed to identify risk factors of ICU mortality.

RESULTS

A total of 625 patients were included. The incidence showed an average annual increase of 4.9% and the mortality an average annual decrease of 1.4%. The patients who required SC showed a lower mortality (20.4%) than patients who did not require SC (31.3%) (p = 0.002). However, the evolution in mortality was different: Mortality decreased in patients who did not require SC (from 56.3% to 20%; p = 0.02), but did not differ in those who required SC (from 21.4% to 27.6%; p = 0.43). In the multivariate analysis, severity at admission, age, alcoholism, cirrhosis, ARDS, neutropenia and thrombocytopenia were associated with worse outcome, whereas appropriate antibiotic treatment and adequate SC were independently associated with better survival.

CONCLUSIONS

The incidence of CASS increased and the ICU mortality decreased during the study period. The mortality was mainly due to a decrease in mortality in infections not requiring SC.

Platelets inhibit apoptotic lung epithelial cell death and protect mice against infection-induced lung injury

Thrombocytopenia is associated with worse outcomes in patients with acute respiratory distress syndrome, which is most commonly caused by infection and marked by alveolar-capillary barrier disruption. However, the mechanisms by which platelets protect the lung alveolar-capillary barrier during infectious injury remain unclear. We found that natively thrombocytopenic Mpl ^-/- mice deficient in the thrombopoietin receptor sustain severe lung injury marked by alveolar barrier disruption and hemorrhagic pneumonia with early mortality following acute intrapulmonary Pseudomonas aeruginosa (PA) infection; barrier disruption was attenuated by platelet reconstitution. Although PA infection was associated with a brisk neutrophil influx, depletion of airspace neutrophils failed to substantially mitigate PA-triggered alveolar barrier disruption in Mpl ^-/- mice. Rather, PA cell-free supernatant was sufficient to induce lung epithelial cell apoptosis in vitro and in vivo and alveolar barrier disruption in both platelet-depleted mice and Mpl ^-/- mice in vivo. Cell-free supernatant from PA with genetic deletion of the type 2 secretion system, but not the type 3 secretion system, mitigated lung epithelial cell death in vitro and lung injury in Mpl ^-/- mice. Moreover, platelet releasates reduced poly (ADP ribose) polymerase cleavage and lung injury in Mpl ^-/- mice, and boiling of platelet releasates, but not apyrase treatment, abrogated PA supernatant-induced lung epithelial cell cytotoxicity in vitro. These findings indicate that while neutrophil airspace influx does not potentiate infectious lung injury in the thrombocytopenic host, platelets and their factors protect against severe pulmonary complications from pathogen-secreted virulence factors that promote host cell death even in the absence of overt infection.

Survival and new-onset morbidity after critical care admission for acute pancreatitis in Scotland: a national electronic healthcare record linkage cohort study

INTRODUCTION

Severe acute pancreatitis (AP) requiring critical care admission (ccAP) impacts negatively on long-term survival.

OBJECTIVE

To document organ-specific new morbidity and identify risk factors associated with premature mortality after an episode of ccAP.

DESIGN

Cohort study.

SETTING

Electronic healthcare registries in Scotland.

PARTICIPANTS

The ccAP cohort included 1471 patients admitted to critical care with AP between 1 January 2008 and 31 December 2010 followed up until 31 December 2014. The population cohort included 3450 individuals from the general population of Scotland frequency-matched for age, sex and social deprivation.

METHODS

Record linkage of routinely collected electronic health data with population matching.

PRIMARY AND SECONDARY OUTCOME MEASURES

Patient demographics, comorbidity (Charlson Comorbidity Index), acute physiology, organ support and other critical care data were linked to records of mortality (death certificate data) and new-onset morbidity. Kaplan-Meier and Cox regression analyses were used to identify risk factors associated with mortality.

RESULTS

310 patients with AP died during the index admission. Outcomes were not ascertained for five patients, and the deprivation quintile was not known for six patients. 340 of 1150 patients in the resulting postdischarge ccAP cohort died during the follow-up period. Greater comorbidity measured by the Charlson score, prior to ccAP, negatively influenced survival in the hospital and after discharge. The odds of developing new-onset diabetes mellitus after ccAP compared with the general population were 10.70 (95% CI 5.74 to 19.94). A new diagnosis of myocardial infarction, stroke, heart failure, liver disease, peptic ulcer, renal failure, cancer, peripheral vascular disease and lung disease was more frequent in the ccAP cohort than in the general population.

CONCLUSIONS

The persistent deleterious impact of severe AP on long-term outcome and survival is multifactorial in origin, influenced by pre-existing patient characteristics and acute episode features. Further mechanistic and epidemiological investigation is warranted.

Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS) is a well-described disease process that can have numerous underlying causes, is commonly seen in the critical care setting, and is often under-recognized. ARDS is characterized by pulmonary edema with refractory hypoxemia, and was traditionally associated with a high mortality rate. The past few decades have generated many studies examining therapeutic interventions for ARDS; however, there are few Level 1 evidence-based interventions to this day that have been shown to improve mortality and outcomes. Lung protective ventilation remains the most studied and evidence-based intervention for the treatment of ARDS.

Biomedical engineer's guide to the clinical aspects of intensive care mechanical ventilation

Background

Mechanical ventilation is an essential therapy to support critically ill respiratory failure patients. Current standards of care consist of generalised approaches, such as the use of positive end expiratory pressure to inspired oxygen fraction (PEEP–FiO₂) tables, which fail to account for the inter- and intra-patient variability between and within patients. The benefits of higher or lower tidal volume, PEEP, and other settings are highly debated and no consensus has been reached. Moreover, clinicians implicitly account for patient-specific factors such as disease condition and progression as they manually titrate ventilator settings. Hence, care is highly variable and potentially often non-optimal. These conditions create a situation that could benefit greatly from an engineered approach. The overall goal is a review of ventilation that is accessible to both clinicians and engineers, to bridge the divide between the two fields and enable collaboration to improve patient care and outcomes. This review does not take the form of a typical systematic review. Instead, it defines the standard terminology and introduces key clinical and biomedical measurements before introducing the key clinical studies and their influence in clinical practice which in turn flows into the needs and requirements around how biomedical engineering research can play a role in improving care. Given the significant clinical research to date and its impact on this complex area of care, this review thus provides a tutorial introduction around the review of the state of the art relevant to a biomedical engineering perspective.

Discussion

This review presents the significant clinical aspects and variables of ventilation management, the potential risks associated with suboptimal ventilation management, and a review of the major recent attempts to improve ventilation in the context of these variables. The unique aspect of this review is a focus on these key elements relevant to engineering new approaches. In particular, the need for ventilation strategies which consider, and directly account for, the significant differences in patient condition, disease etiology, and progression within patients is demonstrated with the subsequent requirement for optimal ventilation strategies to titrate for patient- and time-specific conditions.

Conclusion

Engineered, protective lung strategies that can directly account for and manage inter- and intra-patient variability thus offer great potential to improve both individual care, as well as cohort clinical outcomes.

Etiology and Outcomes of ARDS in a Resource Limited Urban Tropical Setting

BACKGROUND

Several studies have been published in the western literature on the incidence, clinical course and outcome of patients with ARDS. However, there is limited data about ARDS in the tropics and moreover, the etiology and outcomes of ARDS in tropical countries are different from those of western nations. In tropical countries like India, resources are limited and costs of therapy play a major role in deciding treatment options. This prospective observational study was designed to analyze the clinical profile, outcomes and predictors of mortality of patients with ARDS in an urban tropical setting.

METHODS

75 patients ≥13 years, admitted in the medical intensive care unit of a teaching hospital in Kerala, India between March 2013 and February 2014, satisfying Berlin definition for ARDS were enrolled in the study. Lung protective ventilation strategy as laid by ARDS Network protocol was followed for every patient on mechanical ventilation. Due to scarcity of ventilators in our institution, invasive ventilation could not be provided for all ARDS patients. The criteria used for patient selection for non-invasive ventilation were hemodynamic stability, well compliant to the use of NIV mask and PaO2/FiO2 ratio >180 at the time of admission.

RESULTS

Out of the 75 patients, 51% were females and the mean age of the study population was 39.8 ± 3.3 years. Common aetiologies were leptospirosis (18.7%), bronchopneumonia (17.3%), scrub typhus and dengue (12% each). Lung injury score and sequential organ failure assessment score scores had statistically significant association with the severity of ARDS. Forty patients (53.3%) received invasive mechanical ventilation and 35 patients were managed with non-invasive ventilation at the time of admission. The mortality in our study was 45%. Altered sensorium (p-0.002), central cyanosis (p-0.024), elevated creatinine (p-0.036), acidosis (p < 0.001), hypotension (p < 0.001), multiorgan dysfunction (p-0.017), PEEP >12 cm H2O (p-0.036), days on ventilator <7 (p-0.014), PaO2/FiO2 Ratio <100 (p < 0.001), LIS>2.5 (p < 0.001) and SOFA score>11 (p < 0.001) were individual predictors of mortality.

CONCLUSION

Tropical infections form a major etiological component of ARDS in a developing country like India. More studies are required for determining criteria for using NIV in mild ARDS patients which would be helpful in resource limited countries. Timely administration of effective antimicrobial therapy in patients in the rural tropics may help to reduce mortality and financial burden due to ARDS.

Management and outcomes of acute respiratory distress syndrome patients with and without comorbid conditions

Rationale

The standard of care for patients with acute respiratory distress syndrome (ARDS) has been developed based on studies that usually excluded patients with major comorbidities.

Objectives

To describe treatments and outcomes according to comorbidities in patients with ARDS admitted to 19 ICUs (1997–2014).

Methods

Patients were grouped based on comorbidities. Determinants of day-28 mortality were identified by multivariable Cox analysis stratified on center.

Measurements and main results

Among 4953 ARDS patients, 2545 (51.4%) had major comorbidities; the proportion with major comorbidities increased after 2008. Hematological malignancy was associated with severe ARDS and rescue therapies for refractory hypoxemia. COPD, HIV infection, and hematological malignancy were associated with a lower likelihood of invasive mechanical ventilation on the admission day. Admission-day SOFA score was higher in patients with major comorbidities, who more often received vasopressors, dialysis, or treatment-limitation decisions. Day-28 mortality was 33.7% overall, 27.2% in patients without major comorbidities, and 31.1% (COPD) to 56% (hematological malignancy) in patients with major comorbidities. By multivariable analysis, mortality was lower in patients with COPD and higher in those with chronic heart failure, solid tumors, or hematological malignancies. Mortality was independently associated with P_aO₂/F_iO₂ and PaCO₂ on day 1, ARDS of pulmonary origin, worse SOFA score, and ICU-acquired events.

Conclusions

Half the patients with ARDS had major comorbidities, which were associated with severe ARDS, multiple organ dysfunction, and day-28 mortality. These findings do not support the exclusion of ARDS patients with severe comorbidities from randomized clinical trials. Trials in ARDS patients with whatever comorbidities are warranted.

Electronic supplementary material

The online version of this article (10.1007/s00134-018-5209-6) contains supplementary material, which is available to authorized users.

Characterization of the seven-day course of pulmonary response following unilateral lung acid injury in rats

BACKGROUND

Aspiration of gastric acid is an important cause of acute lung injury. The time course of the pulmonary response to such an insult beyond the initial 48 hours is incompletely characterized. The purpose of this study was to comprehensively describe the pulmonary effects of focal lung acid injury over a seven day period in both directly injured and not directly injured lung tissue.

METHODS

Male Wistar rats underwent left-endobronchial instillation with hydrochloric acid and were sacrificed at 4, 24, 48, 96 or 168 h after the insult. Healthy non-injured animals served as controls. We assessed inflammatory cell counts and cytokine levels in right and left lung lavage fluid and blood, arterial oxygen tension, alterations in lung histology, lung wet-to-dry weight ratio and differential lung perfusion.

RESULTS

Lung acid instillation induced an early strong inflammatory response in the directly affected lung, peaking at 4-24 hours, with only partial resolution after 7 days. A less severe response with complete resolution after 4 days was seen in the opposite lung. Alveolar cytokine levels, with exception of IL-6, only partially reflected the localization of lung injury and the time course of the functional and histologic alterations. Alveolar leucocyte subpopulations exhibited different time courses in the acid injured lung with persistent elevation of alveolar lymphocytes and macrophages. After acid instillation there was an early transient decrease in arterial oxygen tension and lung perfusion was preferentially distributed to the non-injured lung.

CONCLUSION

These findings provide a basis for further research in the field of lung acid injury and for studies exploring effects of mechanical ventilation on injured lungs. Incomplete recovery in the directly injured lung 7 days after acid instillation suggests that increased vulnerability and susceptibility to further noxious stimuli are still present at that time.

The Incremental Burden of Acute Respiratory Distress Syndrome: Long-term Follow-up of a Population-Based Nested Case-Control Study

OBJECTIVE

To evaluate the long-term survival of patients at similar risk for hospital-acquired acute respiratory distress syndrome (ARDS) who did and did not develop ARDS.

METHODS

We conducted long-term follow-up of a population-based nested case-control study in a consecutive cohort of adult Olmsted County, Minnesota, patients admitted from January 1, 2001, through December 31, 2010. Patients in whom ARDS developed during their hospital stay (cases) were matched to similar-risk patients without ARDS (controls) by 6 characteristics: age, sex, sepsis, high-risk surgery, ratio of oxygen saturation to fraction of inspired oxygen, and ARDS risk according to the Lung Injury Prediction Score. Hospital mortality, discharge disposition, and long-term survival were compared.

RESULTS

Patients who developed hospital-acquired ARDS (n=400) had higher hospital mortality than at-risk controls (n=400) (35% vs 5%; P<.001). Among hospital survivors (252 matched pairs), ARDS cases were more likely to be discharged to rehabilitation (13% vs 4%) and long-term care (30% vs 15%) facilities, whereas more controls were discharged home (71% vs 41%). After discharge, differences in survival persisted beyond 90 days (adjusted hazard ratio [HR], 1.76; 95% CI, 1.2-2.5; P=.002) and 6 months (adjusted HR, 1.73; 95% CI, 1.2-2.6; P<.001).

CONCLUSION

These results suggest that in a population-based matched case-control study of patients with similar characteristics at the time of hospital admission, those who developed hospital-acquired ARDS had worse long-term survival.

Factors determining outcomes in adult patient undergoing mechanical ventilation: A "real-world" retrospective study in an Indian Intensive Care Unit

Background:

Characteristics of patients admitted to intensive care units with respiratory failure (RF) and undergoing mechanical ventilation (MV) have been described for particular indications and diseases, but there are few studies in the general Intensive Care Unit (ICU) population and even lesser from developing countries.

Objective:

This study aims to study clinical characteristics, outcomes, and factors affecting outcomes in adult patients with RF on MV admitted to ICU.

Methods:

A retrospective study of medical records of all patients admitted to ICU between January 1, 2015, and March 31, 2016. Patients receiving MV for more than 6 h were included in the study. Patients younger than 12 years were excluded. Data were recorded of all patients receiving MV during this period regarding demographics, indications for MV, type and characteristics of ventilation, concomitant complications and treatment, and outcomes. Data were recorded at the initiation of MV and daily all throughout the course of MV. The main outcome measure was all-cause mortality at the end of ICU stay.

Results:

Of the 500 patients admitted to the ICU during the period of the study, a total of 122 patients received MV (and were included in study) for mean (standard deviation [SD]) duration of 4 (3.4) days. The mean (SD) stay in ICU and hospital was 4.49 (3.52) and 6.4 (3.6), respectively. Overall mortality for the unselected general ICU patients on MV was 67.21% while that for ARDS patients was 76.1%. The main factors independently associated with increased mortality were (i) pre-MV factors: age, Apache II scores, heart failure (odds ratio [OR], 1.42; 95% confidence interval [CI], 0.54–3.73; P < 0.001); (ii) patient management factors: positive end-expiratory pressure (OR, 2.69; 95% CI, 0.84–8.61; P < 0.001); (iii) Factors occurring over the course of MV: PaO₂/FiO₂ ratio < 100 (OR, 1.66; 95% CI, 0.67–4.11; P < 0.001) and development of renal failure (OR, 2.33; 95% CI, 2.05–2.42; P < 0.001) and hepatic failure (OR, 2.07; 95% CI, 1.91–2.24; P < 0.001) after initiation of MV.

Conclusions:

Outcomes of patients undergoing MV are dependent on various factors (including patient demographics, nature of associated morbidity, characteristics of the MV received, and conditions developing over course of MV) and these factors may be present before or develop after initiation of MV.

α-bisabolol-loaded lipid-core nanocapsules reduce lipopolysaccharide-induced pulmonary inflammation in mice

Acute respiratory distress syndrome (ARDS) is a severe clinical condition of respiratory failure due to an intense inflammatory response with different etiologies. Despite all efforts, therapy remains limited, and ARDS is still associated with high mortality and morbidity. Plants can provide a vast source of active natural products for the discovery of new drugs. α-bisabolol (α-bis), a constituent of the essential oil from chamomile, has elicited pharmacological interest. However, the molecule has some limitations to its biological application. This study was conducted to develop a drug delivery system using lipid-core nanocapsules (LNCs) to improve the anti-inflammatory effects of orally administered α-bis. α-bis-loaded LNCs (α-bis-LNCs) were prepared by interfacial deposition of poly(ε-caprolactone) and orally administered in a mouse model of ARDS triggered by an intranasal administration of lipopolysaccharide (LPS). We found that α-bis-LNCs (30, 50, and 100 mg kg^-1) significantly reduced airway hyperreactivity (AHR), neutrophil infiltration, myeloperoxidase activity, chemokine levels (KC and MIP-2), and tissue lung injury 18 hours after the LPS challenge. By contrast, free α-bis failed to modify AHR and neutrophil accumulation in the bronchoalveolar lavage effluent and lung parenchyma and inhibited elevation in the myeloperoxidase and MIP-2 levels only at the highest dose. Furthermore, only α-bis-LNCs reduced LPS-induced changes in mitogen-activated protein kinase signaling, as observed by a significant reduction in phosphorylation levels of ERK1/2, JNK, and p38 proteins. Taken together, our results clearly show that by using LNCs, α-bis was able to decrease LPS-induced inflammation. These findings may be explained by the robust increase of α-bis concentration in the lung tissue that was achieved by the LNCs. Altogether, these results indicate that α-bis-LNCs should further be investigated as a potential alternative for the treatment of ARDS.

Clinical characteristics of acute respiratory distress syndrome survived patients at a tertiary hospital in Jakarta

Background: While a good deal of research on characteristic the different characteristics between surviving and dying patient with ARDS has been conducted globally, such research is scarce in developing countries. This study aimed to obtain clinical profile of ARDS survivors during hospitalization.Methods: This was a prospective, observational study conducted at a tertiary hospital in Jakarta from October 2015 to April 2016. Primary data was collected from ARDS patients based on Berlin Definition admitted to emergency room, ICU, HCU, ICCU, and all other wards. The patients were followed until they discharged. We only included survivors on the analysis. Descriptive analysis was done using SPSS 21.0.Results: A total of 43 patients were survived during study period. The majority were below 65 years of age (69.8%) and were male (53.5%). ARDS was mainly mild in severity (62.8%) and early onset (55.8%). Sepsis was the most common causes of ARDS (97.7%). Most of the patients had comorbidities (74.4%). Majority of the patients had APACHE II score <20 (77.3%) with mean 15.6±4.8. The mean of albumin was 2.9±0.6 and the median of procalcitonin was 3 (0.1-252.3.Conclusion: The clinical profile of ARDS survivors in our study were mostly similar with other studies conducted in developed and other developing countries.

Low Molecular Weight Heparin Nebulization Attenuates Acute Lung Injury

BACKGROUND

As acute lung injury (ALI) caused high mortality rate, it is important to explore the protection and treatment of ALI. The aim of the current study is to evaluate the effect of low molecular weight heparin (LMWH) nebulization on attenuating acute lung injury and the associated mechanism.

METHODS

The arterial blood gas, total protein content in bronchoalveolar lavage fluid, lung wet/dry weight ratio, malondialdehyde (MDA) content, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity, and Akt phosphorylation were evaluated after the ALI rabbits were treated with or without LMWH nebulization.

RESULTS

PaO₂ was increased and lung wet/dry weight ratio as well as total protein content in BALF was decreased after LMWH nebulization. After the application of LMWH nebulization therapy, the SOD and GSH-Px activity was rebounded and the increase of MDA content was significantly inhibited. The Akt protein phosphorylation level was decreased after LMWH nebulization therapy.

CONCLUSIONS

LMWH nebulization treatment can relieve the traumatic ALI in rabbits and inhibit oxidative stress possibly by suppressing the Akt phosphorylation.

The effect of demographics and patient location on the outcome of patients with acute respiratory distress syndrome

OBJECTIVE

Outcome of acute respiratory distress syndrome (ARDS) in relation to age, gender, race, pre-Intensive Care Unit (ICU) location, and type of ICU.

METHODS

Retrospective cohort study of patients enrolled in the ARDS network randomized controlled trials.

RESULTS

A total of 2914 patients were included in these trials. Outcomes were adjusted to baseline covariates including APACHE III score, vasopressor use, cause of lung injury, lung injury score, diabetes, cancer status, body mass index, and study ID. Older patients had significantly higher mortality at both 28- and 60-day (odds ratio [OR] 2.59 [95% confidence interval [CI]: 2.12-3.18] P < 0.001 and 2.79, 95% CI: 2.29-3.39, P < 0.001, respectively); less ICU and ventilator free days (relative risk [RR] 0.92, 95% CI: 0.87-0.96, P < 0.001 and 0.92, 95% CI: 0.88-0.96, P < 0.001, respectively). For preadmission location, the 28- and 60-day mortality were lower if the patient was admitted from the operating room (OR)/recovery room (OR 0.65, 95% CI: 0.44-0.95, P = 0.026; and OR = 0.66, 95% CI: 0.46-0.95, P = 0.025, respectively) or emergency department (OR = 0.78, 95% CI: 0.61-0.99, P = 0.039; and OR = 0.71, 95% CI: 0.56-0.89, P = 0.004, respectively), but no statistical differences in ICU and ventilator free days between different preadmission locations. Races other than white and black had a statistically higher mortality (28- and 60-day mortality: OR = 1.47, 95% CI: 1.09-1.98, P = 0.011; and OR 1.53, 95% CI: 1.15-2.04, P = 0.004, respectively). Between whites and blacks, females and males there were no statistically significant differences in all outcomes.

CONCLUSION

Older patients and races other than blacks and whites have higher mortality associated with ARDS. Mortality is affected by patients preadmission location. There are no differences in outcome in relation to the type of ICU, gender, or between blacks and whites.

Critical Illness in the Elderly: Review of Pathophysiology of Aging and Outcome of Intensive Care

The goal of this article is to review the literature on age and its influence on the pathophysiology of critical illness, outcome after critical illness, and end of life decision making in critically ill elderly patients. Sources for this review included the MEDLINE database and bibliographies of original articles, reviews, and book chapters. The population is aging and the need for medical care and its costs increase with increasing age. A majority of the elderly lead independent lives, although some need help with various functional activities related to daily living. It is difficult to separate the effects of aging from the effects of the comorbidities that develop with increasing age. The physiologic reserve decreases in the elderly and they may not be able to tolerate a critical injury or illness as well as a younger individual. As the elderlyare usually on multiple medications, they are prone to have more drug interactions and side effects, and need close monitoring of the drugs and adjustment of the dosage. Mortality after a critical illness in the elderly is higher compared to younger patients, and it is more related to the acuity of physiologic disturbance than age alone. The effect of age alone on long-term outcome is not well studied, but individuals with poor functional status and/or increased comorbidities have a poor short-term outcome. Functional status usually deteriorates after critical illness, but the long-term survivors usually recover functional abilities, and they are satisfied with their quality of life. Decision making at the end of life is difficult because of the paucity of data on long-term mortality and quality of life, lack of information about patient wishes, and the uncertainty of the prognosis. Because many elderly patients survive critical illness and may return to their previous lifestyle, age alone should not weigh heavily in end of life decisions. As with other age groups, end of life decisions in the elderly should be made after considering long-term outcomes, patient goals, and the benefits and burdens of life-sustaining technology.