ABSTRACT
BACKGROUND: Previous studies linked a high intensity of ventilation, measured as mechanical power, to mortality in patients suffering from "classic" ARDS. By contrast, mechanically ventilated patients with a diagnosis of COVID-19 may present with intact pulmonary mechanics while undergoing mechanical ventilation for longer periods of time. We investigated whether an association between higher mechanical power and mortality is modified by a diagnosis of COVID-19. METHODS: This retrospective study included critically ill, adult patients who were mechanically ventilated for at least 24 h between March 2020 and December 2021 at a tertiary healthcare facility in Boston, Massachusetts. The primary exposure was median mechanical power during the first 24 h of mechanical ventilation, calculated using a previously validated formula. The primary outcome was 30-day mortality. As co-primary analysis, we investigated whether a diagnosis of COVID-19 modified the primary association. We further investigated the association between mechanical power and days being alive and ventilator free and effect modification of this by a diagnosis of COVID-19. Multivariable logistic regression, effect modification and negative binomial regression analyses adjusted for baseline patient characteristics, severity of disease and in-hospital factors, were applied. RESULTS: 1,737 mechanically ventilated patients were included, 411 (23.7%) suffered from COVID-19. 509 (29.3%) died within 30 days. The median mechanical power during the first 24 h of ventilation was 19.3 [14.6-24.0] J/min in patients with and 13.2 [10.2-18.0] J/min in patients without COVID-19. A higher mechanical power was associated with 30-day mortality (ORadj 1.26 per 1-SD, 7.1J/min increase; 95% CI 1.09-1.46; p = 0.002). Effect modification and interaction analysis did not support that this association was modified by a diagnosis of COVID-19 (95% CI, 0.81-1.38; p-for-interaction = 0.68). A higher mechanical power was associated with a lower number of days alive and ventilator free until day 28 (IRRadj 0.83 per 7.1 J/min increase; 95% CI 0.75-0.91; p < 0.001, adjusted risk difference - 2.7 days per 7.1J/min increase; 95% CI - 4.1 to - 1.3). CONCLUSION: A higher mechanical power is associated with elevated 30-day mortality. While patients with COVID-19 received mechanical ventilation with higher mechanical power, this association was independent of a concomitant diagnosis of COVID-19.
ABSTRACT
PURPOSE: Acute Respiratory Distress Syndrome (ARDS) secondary to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has demonstrated variable oxygenation and respiratory-system mechanics without investigation of transpulmonary and chest-wall mechanics. This study describes lung, chest wall and respiratory-system mechanics in patients with SARS-CoV-2 and ARDS. METHODS: Data was collected from forty patients with confirmed SARS-CoV-2 and ARDS at Beth Israel Deaconess Medical Center in Boston, Massachusetts. Esophageal balloons were placed to estimate pleural and transpulmonary pressures. Clinical characteristics, respiratory-system, transpulmonary, and chest-wall mechanics were measured over the first week. RESULTS: Patients had moderate-severe ARDS (PaO2/FiO2 123[98-149]) and were critically ill (APACHE IV 108 [94-128] and SOFA 12 [11-13]). PaO2/FiO2 improved over the first week (150 mmHg [122.9-182] to 185 mmHg [138-228] (p = 0.035)). Respiratory system (30-35 ml/cm H2O), lung (40-50 ml/cm H2O) and chest wall (120-150 ml/cm H2O) compliance remained similar over the first week. Elevated basal pleural pressures correlated with BMI. Patients required prolonged mechanical ventilation (14.5 days [9.5-19.0]), with a mortality of 32.5%. CONCLUSIONS: Patients displayed normal chest-wall mechanics, with increased basal pleural pressure. Respiratory system and lung mechanics were similar to known existing ARDS cohorts. The wide range of respiratory system mechanics illustrates the inherent heterogeneity that is consistent with typical ARDS.