Hypoxemia in COVID-19–Related ARDS: Links to BMI, Prior Respiratory Disease

ARDS diagnosis
ARDS diagnosis
What are the determinants of oxygenation over time in patients with COVID-19 ARDS, and how do these determinants relate to Berlin ARDS definition categories?

The presence of hypoxemia in patients with COVID-19–related acute respiratory distress syndrome (ARDS) is associated with such risk factors as body mass index (BMI) and prior respiratory illness, according to clinical trial results recently published in the Journal of Critical Care.

Organized by the Argentine Society of Intensive Care Medicine, the SATICOVID19 clinical trial (ClinicalTrials.gov Identifier: NCT04611269), a prospective, multicenter cohort study, identified determinants of oxygenation over time (as measured by the ratio of arterial oxygen partial pressure to fractional inspired oxygen over days 1, 3, and 7 from ICU admission) among patients with COVID-19 ARDS. Study authors also analyzed the differences in physiological parameters, ventilation management, and outcomes over time associated with the 3 categories of ARDS severity outlined in the Berlin definition of ARDS

The researchers analyzed data on study participants requiring invasive mechanical ventilation (MV) who were admitted to Argentina hospitals with ARDS between March 20, 2020, and October 31, 2020. All participants in the current analysis fulfilled the criteria for ARDS — based on the 3 categories of the Berlin definition — on day 1 of MV in the intensive care unit (ICU). The researchers recorded patient data on date of hospitalization/ICU admission, type of hospital, gender, age, BMI, obesity, comorbidities, medications, prior use/duration of high-flow nasal cannula and noninvasive MV, APACHE II, Sequential Organ Failure Assessment (SOFA) scores, use of vasopressors, and laboratory variables. The investigators obtained physiologic respiratory and MV variables on days 1, 3, and 7, analyzing the data for the entire population as well as categorically for mild, moderate, and severe ARDS. 

ARDS was reported in a total of 1525 patients (79.9% of the entire SATICOVID-19 cohort) on MV on day 1 of admission to the ICU. Overall, 69% of the participants were male; the average patient age was 61±13 years; the average BMI was 32±8 kg/m2. On admission, the percentages of patients with mild, moderate, and severe ARDS were 21%, 56%, and 23%, respectively. All of these individuals received lung-protective ventilation (mean tidal volumes of 6.3 to 6.7 mL/kg predicted body weight [PBW]) and intermediate positive end-expiratory pressure (PEEP) levels of 10 to 11 cmH2O. Mortality rates among those with mild, moderate, and severe ARDS were 55%, 58%, and 70%, respectively. The most common comorbidities were obesity in 49% of participants, hypertension in 47%, diabetes in 30%, and prior respiratory illness in 14%. 

A major limitation of the current study is the fact that because patients were evaluated only on days 1, 3, and 7 after initiation of MV — which represents very precise time points — the possibility exists that gas-exchange and lung mechanical characteristics might have varied over time.

The researchers concluded that findings from the current study provide evidence that hypoxemia among individuals with COVID-19–related ARDS is associated with such risk factors as BMI and prior respiratory illness, which are separate from markers of disease severity, including activated coagulation, increased dead space, and levels of PEEP required.


Estenssoro E, Loudet CI, Dubin A, et al; SATI-COVID-19 Study Group. Clinical characteristics, respiratory management, and determinants of oxygenation in COVID-19 ARDS: a prospective cohort study.  J Crit Care. Published online March 26, 2022.