Prognostic Utility of Estimated Pulmonary Dead Space to Tidal Volume Fraction in Patients With COVID-19 Respiratory Failure Treated With Invasive Mechanical Ventilation

Abstract

Background: Multiple studies have previously identified measurements of pulmonary dead space fraction (Vd/Vt) as accurate predictors of clinical outcome for patients with acute respiratory distress syndrome (ARDS). The objective of this study was to evaluate the association of Vd/Vt calculations utilizing a validated equation using clinically available data with mortality in patients with severe COVID-19 lung disease requiring invasive mechanical ventilation.

Methods: Calculations of Vd/Vt were obtained based upon equation for dead space ventilation fraction (Vd/Vt = 0.320 + 0.0106 (PaCO₂ - ETCO₂) + (0.003 × RR) + (0.0015 × age)) on patients with RT-PCR-confirmed COVID-19 following initial endotracheal intubation and initiation of invasive mechanical ventilation. Clinical patient groups were stratified based upon outcome: 1) Survivors (n = 9); 2) Non-survivors resultant from withdrawal of care (n = 2); and 3) Non-survivors with lung-related death (n = 9).

Results: Comparison of Vd/Vt data for the clinical outcome study groups (survivors versus non-survivors related to lung disease progression) demonstrated: 1) No differences in first/initial Vd/Vt calculations (0.58 (0.06) vs. 0.62 (0.06), respectively; P = 0.311); and 2) Marked and statistically significant differences in final/last Vd/Vt calculations (0.52 (0.04) vs. 0.83 (0.07), respectively; P < 0.001).

Conclusion: The prediction equation for Vd/Vt reflects mortality in this study-specific population of patients with COVID-19 respiratory failure. In addition, the progressive worsening of lung disease severity in non-survivors is mirrored by changes in Vd/Vt calculations.

Clin Infect Immun. 2021;6(1):6-10
doi: https://doi.org/10.14740/cii126