Comparison of 3 Methods of Detecting Acute Respiratory Distress Syndrome: Clinical Screening, Chart Review, and Diagnostic Coding

Evaluating construct validity of computable acute respiratory distress syndrome definitions in adults hospitalized with COVID-19: an electronic health records based approach

BACKGROUND

Evolving ARDS epidemiology and management during COVID-19 have prompted calls to reexamine the construct validity of Berlin criteria, which have been rarely evaluated in real-world data. We developed a Berlin ARDS definition (EHR-Berlin) computable in electronic health records (EHR) to (1) assess its construct validity, and (2) assess how expanding its criteria affected validity.

METHODS

We performed a retrospective cohort study at two tertiary care hospitals with one EHR, among adults hospitalized with COVID-19 February 2020-March 2021. We assessed five candidate definitions for ARDS: the EHR-Berlin definition modeled on Berlin criteria, and four alternatives informed by recent proposals to expand criteria and include patients on high-flow oxygen (EHR-Alternative 1), relax imaging criteria (EHR-Alternatives 2-3), and extend timing windows (EHR-Alternative 4). We evaluated two aspects of construct validity for the EHR-Berlin definition: (1) criterion validity: agreement with manual ARDS classification by experts, available in 175 patients; (2) predictive validity: relationships with hospital mortality, assessed by Pearson r and by area under the receiver operating curve (AUROC). We assessed predictive validity and timing of identification of EHR-Berlin definition compared to alternative definitions.

RESULTS

Among 765 patients, mean (SD) age was 57 (18) years and 471 (62%) were male. The EHR-Berlin definition classified 171 (22%) patients as ARDS, which had high agreement with manual classification (kappa 0.85), and was associated with mortality (Pearson r = 0.39; AUROC 0.72, 95% CI 0.68, 0.77). In comparison, EHR-Alternative 1 classified 219 (29%) patients as ARDS, maintained similar relationships to mortality (r = 0.40; AUROC 0.74, 95% CI 0.70, 0.79, Delong test P = 0.14), and identified patients earlier in their hospitalization (median 13 vs. 15 h from admission, Wilcoxon signed-rank test P < 0.001). EHR-Alternative 3, which removed imaging criteria, had similar correlation (r = 0.41) but better discrimination for mortality (AUROC 0.76, 95% CI 0.72, 0.80; P = 0.036), and identified patients median 2 h (P < 0.001) from admission.

CONCLUSIONS

The EHR-Berlin definition can enable ARDS identification with high criterion validity, supporting large-scale study and surveillance. There are opportunities to expand the Berlin criteria that preserve predictive validity and facilitate earlier identification.

Impact of Clinician Recognition of Acute Respiratory Distress Syndrome on Evidenced-Based Interventions in the Medical ICU

Acute respiratory distress syndrome is underrecognized in the ICU, but it remains uncertain if acute respiratory distress syndrome recognition affects evidence-based acute respiratory distress syndrome care in the modern era. We sought to determine the rate of clinician-recognized acute respiratory distress syndrome in an academic medical ICU and understand how clinician-recognized-acute respiratory distress syndrome affects clinical care and patient-centered outcomes.

DESIGN

Observational cohort study.

SETTING

Single medical ICU at an academic tertiary-care hospital.

PATIENTS

Nine hundred seventy-seven critically ill adults (381 with expert-adjudicated acute respiratory distress syndrome) enrolled from 2006 to 2015.

INTERVENTIONS

Clinician-recognized-acute respiratory distress syndrome was identified using an electronic keyword search of clinical notes in the electronic health record. We assessed the classification performance of clinician-recognized acute respiratory distress syndrome for identifying expert-adjudicated acute respiratory distress syndrome. We also compared differences in ventilator settings, diuretic prescriptions, and cumulative fluid balance between clinician-recognized acute respiratory distress syndrome and unrecognized acute respiratory distress syndrome.

MEASUREMENTS AND MAIN RESULTS

Overall, clinician-recognized-acute respiratory distress syndrome had a sensitivity of 47.5%, specificity 91.1%, positive predictive value 77.4%, and negative predictive value 73.1% for expert-adjudicated acute respiratory distress syndrome. Among the 381 expert-adjudicated acute respiratory distress syndrome cases, we did not observe any differences in ventilator tidal volumes between clinician-recognized-acute respiratory distress syndrome and unrecognized acute respiratory distress syndrome, but clinician-recognized-acute respiratory distress syndrome patients had a more negative cumulative fluid balance (mean difference, -781 mL; 95% CI, [-1,846 to +283]) and were more likely to receive diuretics (49.3% vs 35.7%, p = 0.02). There were no differences in mortality, ICU length of stay, or ventilator-free days.

CONCLUSIONS

Acute respiratory distress syndrome recognition was low in this single-center study. Although acute respiratory distress syndrome recognition was not associated with lower ventilator volumes, it was associated with differences in behaviors related to fluid management. These findings have implications for the design of future studies promoting evidence-based acute respiratory distress syndrome interventions in the ICU.

External Validation of an Acute Respiratory Distress Syndrome Prediction Model Using Radiology Reports

OBJECTIVES

Acute respiratory distress syndrome is frequently under recognized and associated with increased mortality. Previously, we developed a model that used machine learning and natural language processing of text from radiology reports to identify acute respiratory distress syndrome. The model showed improved performance in diagnosing acute respiratory distress syndrome when compared to a rule-based method. In this study, our objective was to externally validate the natural language processing model in patients from an independent hospital setting.

DESIGN

Secondary analysis of data across five prospective clinical studies.

SETTING

An urban, tertiary care, academic hospital.

PATIENTS

Adult patients admitted to the medical ICU and at-risk for acute respiratory distress syndrome.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The natural language processing model was previously derived and internally validated in burn, trauma, and medical patients at Loyola University Medical Center. Two machine learning models were examined with the following text features from qualifying radiology reports: 1) word representations (n-grams) and 2) standardized clinical named entity mentions mapped from the National Library of Medicine Unified Medical Language System. The models were externally validated in a cohort of 235 patients at the University of Chicago Medicine, among which 110 (47%) were diagnosed with acute respiratory distress syndrome by expert annotation. During external validation, the n-gram model demonstrated good discrimination between acute respiratory distress syndrome and nonacute respiratory distress syndrome patients (C-statistic, 0.78; 95% CI, 0.72-0.84). The n-gram model had a higher discrimination for acute respiratory distress syndrome when compared with the standardized named entity model, although not statistically significant (C-statistic 0.78 vs 0.72; p = 0.09). The most important features in the model had good face validity for acute respiratory distress syndrome characteristics but differences in frequencies did occur between hospital settings.

CONCLUSIONS

Our computable phenotype for acute respiratory distress syndrome had good discrimination in external validation and may be used by other health systems for case-identification. Discrepancies in feature representation are likely due to differences in characteristics of the patient cohorts.

Association of Economic Status and Mortality in Patients with Acute Respiratory Distress Syndrome

The high cost of treatment for acute respiratory distress syndrome (ARDS) is a concern for healthcare systems, while the impact of patients’ socio-economic status on the risk of ARDS-associated mortality remains controversial. This study investigated associations between patients’ income at the time of ARDS diagnosis and ARDS-specific mortality rate after treatment initiation. Data from records provided by the National Health Insurance Service of South Korea were used. Adult patients admitted for ARDS treatment from 2013 to 2017 were included in the study. Patients’ income in the year of diagnosis was evaluated. A total of 14,600 ARDS cases were included in the analysis. The 30-day and 1-year mortality rates were 48.6% and 70.3%, respectively. In multivariable Cox regression model, we compared income quartiles, showing that compared to income strata Q1, the Q2 (p = 0.719), Q3 (p = 0.946), and Q4 (p = 0.542) groups of income level did not affect the risk of 30-day mortality, respectively. Additionally, compared to income strata Q1, the Q2 (p = 0.762), Q3 (p = 0.420), and Q4 (p = 0.189) strata did not affect the risk of 1-year mortality. Patient income at the time of ARDS diagnosis did not affect the risk of 30-day or 1-year mortality in the present study based on South Korea’s health insurance data.

Recent advances in understanding and treating acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a clinically and biologically heterogeneous disorder associated with many disease processes that injure the lung, culminating in increased non-hydrostatic extravascular lung water, reduced compliance, and severe hypoxemia. Despite enhanced understanding of molecular mechanisms, advances in ventilatory strategies, and general care of the critically ill patient, mortality remains unacceptably high. The Berlin definition of ARDS has now replaced the American-European Consensus Conference definition. The recently concluded Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG-SAFE) provided worldwide epidemiological data of ARDS including prevalence, geographic variability, mortality, and patterns of mechanical ventilation use. Failure of clinical therapeutic trials prompted the investigation and subsequent discovery of two distinct phenotypes of ARDS (hyper-inflammatory and hypo-inflammatory) that have different biomarker profiles and clinical courses and respond differently to the random application of positive end expiratory pressure (PEEP) and fluid management strategies. Low tidal volume ventilation remains the predominant mainstay of the ventilatory strategy in ARDS. High-frequency oscillatory ventilation, application of recruitment maneuvers, higher PEEP, extracorporeal membrane oxygenation, and alternate modes of mechanical ventilation have failed to show benefit. Similarly, most pharmacological therapies including keratinocyte growth factor, beta-2 agonists, and aspirin did not improve outcomes. Prone positioning and early neuromuscular blockade have demonstrated mortality benefit, and clinical guidelines now recommend their use. Current ongoing trials include the use of mesenchymal stem cells, vitamin C, re-evaluation of neuromuscular blockade, and extracorporeal carbon dioxide removal. In this article, we describe advances in the diagnosis, epidemiology, and treatment of ARDS over the past decade.

Racial Differences in Mortality from Severe Acute Respiratory Failure in the United States, 2008-2012

RATIONALE

Racial disparities in health and healthcare in the United States are well documented and are increasingly recognized in acute critical illnesses such as sepsis and acute respiratory failure.

OBJECTIVES

Using a large, representative, U.S. nationwide database, we examined the hypothesis that black and Hispanic patients with severe acute respiratory failure have higher mortality rates when compared with non-Hispanic whites.

METHODS

This retrospective analysis used discharge data from the Agency for Healthcare Research and Quality, Nationwide Inpatient Sample, Healthcare Cost and Utilization Project, for the years 2008-2012. We identified hospitalizations with acute respiratory failure using a combination of International Classification of Diseases, Ninth Revision, Clinical Modification, codes. A logistic regression model was fitted to compare in-hospital mortality rates by race.

MEASUREMENTS AND MAIN RESULTS

After adjusting for sex, age, race, disease severity, type of hospital, and median household income for patient ZIP code, blacks had a greater odds ratio of in-hospital death when compared with non-Hispanic whites (odds ratio [OR], 1.13; 95% confidence interval [CI], 1.11-1.14; P < 0.001), and Hispanics also had a greater odds ratio of in-hospital death when compared with non-Hispanic whites (OR, 1.17; 95% CI, 1.15-1.19; P < 0.001), and so did Asian and Pacific Islanders (OR, 1.15; 95% CI, 1.12-1.18; P < 0.001) and Native Americans (OR, 1.08; 95% CI, 1.00-1.15; P < 0.001) when compared with non-Hispanic whites (OR, 1.0).

CONCLUSIONS

Blacks, Hispanics, and other racial minorities in the United States were observed to exhibit significantly higher in-hospital sepsis-related respiratory failure associated mortality when compared with non-Hispanic whites.

Fifty Years of Research in ARDS. The Epidemiology of Acute Respiratory Distress Syndrome. A 50th Birthday Review

Since its first description 50 years ago, no other intensive care syndrome has been as extensively studied as acute respiratory distress syndrome (ARDS). Despite this extensive body of research, many basic epidemiologic questions remain unsolved. The lack of gold standard tests jeopardizes accurate diagnosis and translational research. Wide variation in the population incidence has been reported, making even simple estimates of the burden of disease problematic. Despite these limitations, there has been an increase in the understanding of pathophysiology and important risk factors both for the development of ARDS and for important patient-centered outcomes like mortality. In this Critical Care Perspective, we discuss the historical context of ARDS description and attempts at its definition. We highlight the epidemiologic challenges of studying ARDS, as well as other intensive care syndromes, and propose solutions to address them. We update the current knowledge of ARDS trends in incidence and mortality, risk factors, and recently described endotypes.

Increased Risk of Post-Trauma Stroke after Traumatic Brain Injury-Induced Acute Respiratory Distress Syndrome

This study determines whether acute respiratory distress syndrome (ARDS) is an independent risk factor for an increased risk of post-traumatic brain injury (TBI) stroke during 3-month, 1-year, and 5-year follow-ups, respectively, after adjusting for other covariates. Clinical data for the analysis were from the National Health Insurance Database 2000, which covered a total of 2121 TBI patients and 101 patients with a diagnosis of TBI complicated with ARDS (TBI-ARDS) hospitalized between January 1, 2001 and December 31, 2005. Each patient was tracked for 5 years to record stroke occurrences after discharge from the hospital. The prognostic value of TBI-ARDS was evaluated using a multivariate Cox proportional hazard model. The main outcome found that stroke occurred in nearly 40% of patients with TBI-ARDS, and the hazard ratio for post-TBI stroke increased fourfold during the 5-year follow-up period after adjusting for other covariates. The increased risk of hemorrhagic stroke in the ARDS group was considerably higher than in the TBI-only cohort. This is the first study to report that post-traumatic ARDS yielded an approximate fourfold increased risk of stroke in TBI-only patients. We suggest intensive and appropriate medical management and intensive follow-up of TBI-ARDS patients during the beginning of the hospital discharge.

Understanding the global epidemiology of pediatric critical illness: the power, pitfalls, and practicalities of point prevalence studies

OBJECTIVE

The point prevalence methodology is a valuable epidemiological study design that can optimize patient enrollment, prospectively gather individual-level data, and measure practice variability across a large number of geographic regions and healthcare settings. The objective of this article is to review the design, implementation, and analysis of recent point prevalence studies investigating the global epidemiology of pediatric critical illness.

DATA SOURCES

Literature review and primary datasets.

STUDY SELECTION

Multicenter, international point prevalence studies performed in PICUs since 2007.

DATA EXTRACTION

Study topic, number of sites, number of study days, patients screened, prevalence of disease, use of specified therapies, and outcomes.

DATA SYNTHESIS

Since 2007, five-point prevalence studies have been performed on acute lung injury, neurologic disease, thromboprophylaxis, fluid resuscitation, and sepsis in PICUs. These studies were performed in 59-120 sites in 7-28 countries. All studies accounted for seasonal variation in pediatric disease by collecting data over multiple study days. Studies screened up to 6,317 patients and reported data on prevalence and therapeutic variability. Three studies also reported short-term outcomes, a valuable but atypical data element in point prevalence studies. Using these five studies as examples, the advantages and disadvantages and approach to designing, implementing, and analyzing point prevalence studies are reviewed.

CONCLUSIONS

Point prevalence studies in pediatric critical care can efficiently provide valuable insight on the global epidemiology of disease and practice patterns for critically ill children.

Outcome of pediatric acute myeloid leukemia patients receiving intensive care in the United States

OBJECTIVE

Children with acute myeloid leukemia are at risk for sepsis and organ failure. Outcomes associated with intensive care support have not been studied in a large pediatric acute myeloid leukemia population. Our objective was to determine hospital mortality of pediatric acute myeloid leukemia patients requiring intensive care.

DESIGN

Retrospective cohort study of children hospitalized between 1999 and 2010. Use of intensive care was defined by utilization of specific procedures and resources. The primary endpoint was hospital mortality.

SETTING

Forty-three children's hospitals contributing data to the Pediatric Health Information System database.

PATIENTS

Patients who are newly diagnosed with acute myeloid leukemia and who are 28 days through 18 years old (n = 1,673) hospitalized any time from initial diagnosis through 9 months following diagnosis or until stem cell transplant. A reference cohort of all nononcology pediatric admissions using the same intensive care resources in the same time period (n = 242,192 admissions) was also studied.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

One-third of pediatric patients with acute myeloid leukemia (553 of 1,673) required intensive care during a hospitalization within 9 months of diagnosis. Among intensive care admissions, mortality was higher in the acute myeloid leukemia cohort compared with the nononcology cohort (18.6% vs 6.5%; odds ratio, 3.23; 95% CI, 2.64-3.94). However, when sepsis was present, mortality was not significantly different between cohorts (21.9% vs 19.5%; odds ratio, 1.17; 95% CI, 0.89-1.53). Mortality was consistently higher for each type of organ failure in the acute myeloid leukemia cohort versus the nononcology cohort; however, mortality did not exceed 40% unless there were four or more organ failures in the admission. Mortality for admissions requiring intensive care decreased over time for both cohorts (23.7% in 1999-2003 vs 16.4% in 2004-2010 in the acute myeloid leukemia cohort, p = 0.0367; and 7.5% in 1999-2003 vs 6.5% in 2004-2010 in the nononcology cohort, p < 0.0001).

CONCLUSIONS

Pediatric patients with acute myeloid leukemia frequently required intensive care resources, with mortality rates substantially lower than previously reported. Mortality also decreased over the time studied. Pediatric acute myeloid leukemia patients with sepsis who required intensive care had a mortality comparable to children without oncologic diagnoses; however, overall mortality and mortality for each category of organ failure studied was higher for the acute myeloid leukemia cohort compared with the nononcology cohort.

Sex, race, and the development of acute lung injury

BACKGROUND

Prior studies suggest that mortality differs by sex and race in patients who develop acute lung injury (ALI). Whether differences in presentation account for these disparities remains unclear. We sought to determine whether sexual and racial differences exist in the rate of ALI development and ALI-related mortality after accounting for differences in clinical presentations.

METHODS

This was a multicenter, observational cohort study of 5,201 patients at risk for ALI. Multivariable logistic regression with adjustment for center-level effects was used to adjust for potential covariates.

RESULTS

The incidence of ALI development was 5.9%; in-hospital mortality was 5.0% for the entire cohort, and 24.4% for those patients who developed ALI. Men were more likely to develop ALI compared to women (6.9% vs 4.7%, P , .001) and had a nonsignificant increase in mortality when ALI developed (27.6% vs 18.5%, P 5 .08). However, after adjustment for baseline imbalances between sexes these differences were no longer significant. Black patients, compared to white patients, presented more frequently with pneumonia, sepsis, or shock and had higher severity of illness. Black patients were less likely to develop ALI than whites (4.5% vs. 6.5%, P 5 .014), and this association remained statistically significant after adjusting for differences in presentation (OR, 0.66; 95 % CI, 0.45-0.96).

CONCLUSIONS

Sex and race differences exist in the clinical presentation of patients at risk of developing ALI. After accounting for differences in presentation, there was no sex difference in ALI development and outcome. Black patients were less likely to develop ALI despite increased severity of illness on presentation.

Impact of acute lung injury and acute respiratory distress syndrome after traumatic brain injury in the United States

BACKGROUND

Traumatic brain injury (TBI) is a major cause of disability, morbidity, and mortality. The effect of the acute respiratory distress syndrome and acute lung injury (ARDS/ALI) on in-hospital mortality after TBI remains controversial.

OBJECTIVE

To determine the epidemiology of ARDS/ALI, the prevalence of risk factors, and impact on in-hospital mortality after TBI in the United States.

METHODS

Retrospective cohort study of admissions of adult patients>18 years with a diagnosis of TBI and ARDS/ALI from 1988 to 2008 identified through the Nationwide Inpatient Sample.

RESULTS

During the 20-year study period, the prevalence of ARDS/ALI increased from 2% (95% confidence interval [CI], 2.1%-2.4%) in 1988 to 22% (95% CI, 21%-22%) in 2008 (P<.001). ARDS/ALI was more common in younger age; males; white race; later year of admission; in conjunction with comorbidities such as congestive heart failure, hypertension, chronic obstructive pulmonary disease, chronic renal and liver failure, sepsis, multiorgan dysfunction; and nonrural, medium/large hospitals, located in the Midwest, South, and West continental US location. Mortality after TBI decreased from 13% (95% CI, 12%-14%) in 1988 to 9% (95% CI, 9%-10%) in 2008 (P<.001). ARDS/ALI-related mortality after TBI decreased from 33% (95% CI, 33%-34%) in 1988 to 28% (95% CI, 28%-29%) in 2008 (P<.001). Predictors of in-hospital mortality after TBI were older age, male sex, white race, cancer, chronic kidney disease, hypertension, chronic liver disease, congestive heart failure, ARDS/ALI, and organ dysfunctions.

CONCLUSION

Our analysis demonstrates that ARDS/ALI is common after TBI. Despite an overall reduction of in-hospital mortality, ARDS/ALI carries a higher risk of in-hospital death after TBI.

Trends in the incidence of noncardiogenic acute respiratory failure: the role of race

OBJECTIVE

We sought to examine trends in the race-specific incidence of acute respiratory failure in the United States.

DESIGN

Retrospective cohort study.

SETTING

We used the National Hospital Discharge Survey database (1992-2007), an annual survey of approximately 500 hospitals weighted to provide national hospitalization estimates.

PATIENTS

All incident cases of noncardiogenic acute respiratory failure hospitalized in the United States.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We identified noncardiogenic acute respiratory failure by the presence of International Classification of Diseases, Ninth Revision, codes for respiratory failure or pulmonary edema (518.4, 518.5, 518.81, and 518.82) and mechanical ventilation (96.7×), excluding congestive heart failure. Incidence rates were calculated using yearly census estimates standardized to the age and sex distribution of the 2000 census population. Annual cases of noncardiogenic acute respiratory failure increased from 86,755 in 1992 to 323,474 in 2007. Noncardiogenic acute respiratory failure among black Americans increased from 56.4 (95% confidence interval 39.7-73.1) to 143.8 (95% confidence interval 123.8-163.8) cases per 100,000 in 1992 and 2007, respectively. Among white Americans, the incidence of noncardiogenic acute respiratory failure increased from 31.2 (95% confidence interval 26.2-36.5) to 94.0 (95% confidence interval 86.7-101.2) cases per 100,000 in 1992 and 2007, respectively. The average annual incidence of noncardiogenic acute respiratory failure over the entire study period was 95.1 (95% confidence interval 93.9-96.4) cases per 100,000 for black Americans compared to 66.5 (95% confidence interval 65.8-67.2) cases per 100,000 for white Americans (rate ratio 1.43, 95% confidence interval 1.42-1.44). Overall in-hospital mortality was greater for other-race Americans, but only among patients with two or more organ failures (57% [95% confidence interval 56%-59%] for other race, 51% [95% confidence interval 50%-52%] for white, 50% [95% confidence interval 49%-51%] for black).

CONCLUSIONS

The incidence of noncardiogenic acute respiratory failure in the United States increased between 1992 and 2007. Black and other-race Americans are at greater risk of developing noncardiogenic acute respiratory failure compared to white Americans.

Macrolide antibiotics and survival in patients with acute lung injury

BACKGROUND

Animal models suggest that immunomodulatory properties of macrolide antibiotics have therapeutic value for patients with acute lung injury (ALI). We investigated the association between receipt of macrolide antibiotics and clinical outcomes in patients with ALI.

METHODS

Secondary analysis of multicenter, randomized controlled trial data from the Acute Respiratory Distress Syndrome Network Lisofylline and Respiratory Management of Acute Lung Injury Trial, which collected detailed data regarding antibiotic use among participants with ALI.

RESULTS

Forty-seven of 235 participants (20%) received a macrolide antibiotic within 24 h of trial enrollment. Among patients who received a macrolide, erythromycin was the most common (57%), followed by azithromycin (40%). The median duration of macrolide use after study enrollment was 4 days (interquartile range, 2-8 days). Eleven of the 47 (23%) patients who received macrolides died, compared with 67 of the 188 (36%) who did not receive a macrolide (P = .11). Participants administered macrolides were more likely to have pneumonia as an ALI risk factor, were less likely to have nonpulmonary sepsis or to be randomized to low tidal volume ventilation, and had a shorter length of stay prior to trial enrollment. After adjusting for potentially confounding covariates, use of macrolide was associated with lower 180-day mortality (hazard ratio [HR], 0.46; 95% CI, 0.23-0.92; P = .028) and shorter time to successful discontinuation of mechanical ventilation (HR, 1.93; 95% CI, 1.18-3.17; P = .009). In contrast, fluoroquinolone (n = 90) and cephalosporin antibiotics (n = 93) were not associated with improved outcomes.

CONCLUSIONS

Receipt of macrolide antibiotics was associated with improved outcomes in patients with ALI.

Doppler-defined pulmonary hypertension in medical intensive care unit patients: Retrospective investigation of risk factors and impact on mortality

Pulmonary hypertension (PH) is poorly characterized in the critically ill. No prior studies describe the burden of or outcomes associated with PH in a general medical intensive care unit population. We hypothesize that PH is an important comorbidity prevalent in the modern medical intensive care unit. We undertook a preliminary investigation to define the consequences of Doppler-defined PH in the critically ill. A single-center retrospective case–control study of medical intensive care patients admitted over a 1-year period was conducted. Eligible patients had an echocardiogram within 4 days of admission. PH was defined to include both pulmonary arterial and venous hypertension and required a tricuspid regurgitant jet velocity ≥3 m/sec. Cases and controls were compared for comorbidities, illness severity, diagnoses, and mortality. Multivariable regression was performed to identify clinical features associated with PH and mortality. 299 (21% of admissions) patients had an eligible echocardiogram. Patients with PH (N=126) had a higher unadjusted mortality than did controls (N=173) (37% vs. 25%, P=0.04) and PH remained significantly associated with mortality after controlling for other clinical factors (HR=1.59, 95% CI=1.03–2.44, P=0.036). Low ejection fraction (OR=2.21, 95% CI=1.19–4.11, P=0.012) and pulmonary embolism (OR=4.28, 95% CI=1.59–11.5, P=0.004) were independently associated with PH. Doppler-defined PH is associated with mortality in the critically ill. Prospective studies are needed to define the prevalence of pulmonary venous hypertension versus pulmonary arterial hypertension, and the clinical consequences of each, in a general medical intensive care unit population.

Epidemiology and Outcomes of Acute Lung Injury

Acute lung injury (ALI) and its presentation with more severe hypoxemia, the ARDS, is a challenging entity for clinical investigation because, like many critical illness syndromes, it lacks an accepted diagnostic test and relies on a constellation of clinical findings for diagnosis. Despite these barriers, there have been important advances in the clinical and population epidemiology of ALI. This article will review recent studies of the incidence, diagnosis, etiologic and prognostic factors, relevant disease subsets, mortality, and long-term outcomes of ALI. A detailed understanding of the epidemiology and outcomes of ALI is essential for future research on mechanisms of both the acute presentation and long-term sequelae, for designing studies to identify genetic risk factors for developing ALI, and to develop strategies to treat or prevent the morbidity encountered by survivors.