Operationalizing the New Global Definition of ARDS: A Retrospective Cohort Study From South Africa

Abstract

Background: A proposed new global definition of ARDS seeks to update the Berlin definition and account for nonintubated ARDS and ARDS diagnoses in resource-variable settings.

Research question: How do ARDS epidemiologic characteristics change with operationalizing the new global definition of ARDS in a resource-limited setting?

Study design and methods: We performed a real-use retrospective cohort study among adult patients meeting criteria for the Berlin definition of ARDS or the global definition of ARDS at ICU admission in two public hospitals in the KwaZulu-Natal Department of Health, South Africa, from January 2017 through June 2022.

Results: Among 5,760 adults (aged ≥ 18 years) admitted to the ICU, 2,027 patients (35.2%) met at least one ARDS definition, including 1,218 patients meeting the Berlin definition of ARDS (60.1% of all ARDS diagnoses) and 809 new diagnoses of the global definition of ARDS that were not captured by the Berlin definition alone (39.9% of all ARDS diagnoses and 14.0% of all ICU admissions). After adjustment for hospital-level factors, patients who met only the global definition of ARDS criteria (ie, who would not have been captured by the Berlin definition) showed no statistically significant ICU mortality difference vs patients with ARDS according to the Berlin definition (21.7% [95% CI, 18.9%-24.4%] vs 23.8% [95% CI, 21.5%-26.2%]; OR, 0.88 [95% CI, 0.70-1.10]; P = .25). In prespecified exploratory subgroup analyses, patients without COVID-19 who met only the criteria for the global definition of ARDS showed reduced ICU mortality (14.2% [95% CI, 11.6%-16.9%] vs 22.2% [95% CI, 19.8%-24.6%]; OR, 0.58 [95% CI, 0.45-0.75]; P < .0005) compared with patients without COVID-19 who met the Berlin definition for ARDS.

Interpretation: The new global definition of ARDS captures a significant proportion of patients who would not have been included by the Berlin definition alone. These additional patients with ARDS may have heterogenous patterns of outcomes among diagnostic subgroups, including by COVID-19 status, compared with patients with ARDS according to the Berlin definition.

Keywords: ARDS; COVID-19; global health; low-income and middle-income countries; resource-limited settings.

Figure 1 –

Forest plot showing ICU mortality according to only the global definition ARDS vs the Berlin definition of ARDS by subgroups. After adjustment for hospital-level factors, patients who met only the global definition of ARDS criteria (ie, who would not have been captured by the Berlin definition) showed no statistically significant different ICU mortality vs patients meeting the Berlin definition of ARDS criteria (21.7% [95% CI, 18.9%−24.4%] vs 23.8% [95% CI, 21.5%−26.2%]; OR, 0.88 [95% CI, 0.70–1.10]; P = .25). However, prespecified exploratory subgroup analyses revealed heterogeneity. Patients without COVID-19 meeting only the global definition of ARDS criteria showed reduced ICU mortality (14.2% [95% CI, 11.6%−16.9%] vs 22.2% [95% CI, 19.8%−24.6%]; OR, 0.58 [95% CI, 0.45–0.75]; P < .0005) compared with patients without COVID-19 and meeting the Berlin definition of ARDS, whereas patients with COVID-19 meeting only the global definition of ARDS criteria showed a suggestion of increased ICU mortality that did not reach statistical significance (58.6% [95% CI, 51.0%−66.2%] vs 48.7% [95% CI, 34.1%−63.3%]; OR, 1.55 [95% CI, 0.74–3.24]; P = .25) compared with patients with COVID-19 meeting the Berlin definition of ARDS. ^aPrimary refers to the primary indication for ICU admission as determined by the admitting ICU team as part of real-time routine care. ^bAny refers to acute active diagnoses and processes present at the time of ICU admission (but not necessarily the primary indication for ICU admission) as determined by the admitting ICU team as part of real-time routine care. *P < .05.

Figure 2 –

Graph showing ICU mortality across ARDS cohorts and oxygenation severity levels. In the Berlin definition of ARDS cohort, and consistent with prior literature, worsening ARDS oxygenation severity classification was associated with increased ICU mortality after adjustment for hospital-level factors. ICU mortality across ARDS classifications showed a narrowing between mild and moderate levels and a worsening in the severe level in the global definition-only ARDS cohort. Figure symbols represent point estimates and 95% CIs.

Figure 3 –

A-C, Graphs showing ICU mortality by the global definition of ARDS subcohorts, oxygenation severity levels, and COVID-19 status. A, Intubated patients in the global definition of ARDS cohort, similar to the highly overlapping the Berlin definition of ARDS cohort, showed worsening ARDS oxygenation severity classification associated with increased ICU mortality, and the global definition resource-limited settings modification ARDS cohort, similar to the substantially overlapping global definition-only ARDS cohort, showed a decrease and narrowing of ICU mortality outcomes between the mild and moderate levels and a widening and worsening of the severe level ICU mortality outcomes. Nonintubated patients in the global definition of ARDS cohort were too few for meaningful precision. B, C, Stratification by COVID-19 status showed the increased mortality of the severe level driven by patients with COVID-19 (B) and the decreased mortality in the mild and moderate levels driven by patients without COVID-19 (C).