Impaired ventilation is not independently associated with 28-day mortality in coronavirus disease 2019 (COVID19) acute respiratory distress syndrome (ARDS)

ABSTRACT

INTRODUCTION Surrogates for impaired ventilation such as estimated dead-space fractions and the ventilatory ratio are independently associated with an increased risk of mortality in the acute respiratory distress syndrome (ARDS) and small case series of COVID-19 related ARDS. METHODS This study aimed to quantify the dynamics and determine the prognostic value of surrogate markers of impaired ventilation in patients with COVID-19 related ARDS. The present study is a secondary analysis of the PRactice Of VENTilation in COVID-19 patients (PROVENT-COVID) in 22 intensive care unit hospitals in the Netherlands. Surrogates of impaired ventilation such as the estimated dead space fraction (by Harris-Benedict-VD/VT HB and direct method-VD/VT DIR), ventilatory ratio (VR), and end-tidal-to-arterial PCO2 ratio (PETCO2/PaCO2) were used. RESULTS 927 consecutive patients admitted with COVID-19 related ARDS were included in this study. Surrogates of impaired ventilation were significantly higher in non-survivors than survivors at baseline and during the following days of mechanical ventilation (p <0.001). As ARDS severity increased, mortality increased with successive tertiles for VD/VT HB and VD/VT DIR, and VR, and decreased with successive tertiles for PETCO2/PaCO2. Mortality over the first 28 days was higher in patients in the high group of dead space fraction by VD/VT HB (16.4% vs. 12.3%;p = 0.003), but similar in the groups considering the dead space fraction by VD/VT DIR (15.4% vs. 13.3%;p = 0.100), and VR (15.5% vs. 13.2%;p = 0.080) (Figure 2). After adjustment for a base risk model that included chronic comorbidities, ventilation and oxygenation parameters, none of the surrogates of impaired ventilation measured at the start of ventilation or the following days were significantly associated with 28-day mortality. CONCLUSION Surrogate markers for impaired ventilation are abnormal at the start of invasive ventilation in patients with COVID-19 related ARDS and worsen during consequent days. Ventilation impairment seems to be more extensive in non-survivors than in survivors, but they do not yield prognostic information when added to a baseline risk model. In the absence of bedside capnography, surrogates of impaired ventilation may serve as an important tool to assess the severity of COVID-19 related ARDS along with other variables such as oxygenation abnormalities and respiratory mechanics.