In COVID-19-related acute respiratory distress syndrome (ARDS), there is no evidence of patients who have distinct respiratory system static compliance (CRS)-based clinical phenotypes and who would thus need individualized lung-protective ventilation strategies, according to meta-analysis findings published in The Lancet Respiratory Medicine.
Previous research has suggested that among those with COVID-19-related ARDS, some patients might have distinct phenotypes based on CRS and might thus require individualized ventilation strategies. In an effort to determine whether such phenotypes exist, investigators conducted a systematic review and meta-analysis of patients with COVID-19-related ARDS to uncover any potential patterns or trends with respect to basic respiratory system mechanics, ventilator parameters, gas exchange parameters, and clinical outcomes that might be indicative of (CRS)-based clinical phenotypes.
The study authors performed a literature search for relevant studies published from December 1, 2019 (the start of the pandemic period), to March 14, 2022 (when the review was initiated). Eligible studies included adult patients who received mechanical ventilation and reported ventilator parameters within hours to days after the initiation of invasive mechanical ventilation.
The investigators identified 51 observational studies with 12,095 patients who received invasive ventilation for COVID-19-related ARDS. Of this group, 37 unselected ARDS studies with 11,356 patients (8861 male) were used for the primary analysis.
The pooled reported CRS of patients from studies of unselected COVID-19-related ARDS was 35.8 mL/cm H2O (95% CI, 33.9-37.8; I² = 96.9%; τ² = 32.6; high certainty). CRS dispersion was not significantly different vs a normal distribution (Shapiro-Wilk test, P =.92). The pooled CRS for all patients from studies of selected and unselected COVID-19-related ARDS was 34.7 mL/cm H2O (32.8-36.6; 97.2%, 43.6; high certainty).
Overall, the mean ratio of partial pressure of oxygen to fraction of inspired oxygen (PaO2/FiO2) in patients from unselected studies was 149.1 mm Hg (95% CI, 135.4-162.9; 34 studies). Increasing COVID-19-related ARDS severity as assessed with PaO2/FiO2 was associated with a decrease in CRS (Pinteraction <.0001): CRS was progressively reduced from 39.3 mL/cm H2O (95% CI, 36.6-42.0) in patients with mild ARDS, to 34.9 mL/cm H2O (95% CI, 32.8–36.9) in those with moderate ARDS, and to 27.3 mL/cm H2O (95% CI, 23.3-31.2) in those with severe ARDS.
Among patients who had moderate-to-severe ARDS (PaO2/FiO2 ratio ≤200 mm Hg), increased positive end-expiratory pressure (PEEP) was associated with greater compliance compared with patients with mild ARDS (PaO2/FiO2 ratio >200 to 300 mm Hg).
Univariable meta-regression analyses showed a statistically significant positive correlation between CRS and PaO2/FiO2 ratio (β = 0.06; 95% CI, 0.02-0.11), between CRS and PEEP (0.88; 95% CI, 0.07-1.68), and between CRS and VT (6.28; 95% CI, 3.37-9.19). In addition, CRS had a statistically significant negative association with driving pressure (-2.49; 95% CI, -3.12 to -1.86), plateau pressure (-0.77; 95% CI, -1.53 to -0.02), and PaCO2 (-0.39; 95% CI, -0.71 to -0.07).
No significant correlation was observed between CRS and cumulative morality (β = -0.005; 95% CI, -0.01 to 0.002).
Among several limitations, substantial heterogeneity was observed in patient management with mechanical ventilation and in reporting of the analyzed variables in the included studies. Also, there was wide variation in the studies’ sample sizes and individual patient data were unavailable.
“Our study suggests that ventilatory strategies used in patients with non-COVID-19-related ARDS should be used in patients with COVID-19-related ARDS until there is evidence to the contrary; future research should focus on how best to individualize ventilatory strategy to the patient’s specific respiratory mechanics and hemodynamic status,” the investigators commented.
Reddy MP, Subramaniam A, Chua C, et al. Respiratory system mechanics, gas exchange, and outcomes in mechanically ventilated patients with COVID-19-related acute respiratory distress syndrome: a systematic review and meta-analysis. Lancet Respir Med. Published online November 3, 2022. doi:10.1016/S2213-2600(22)00393-9