ConclusionsĮstimated methods for dead space calculation and the ventilatory ratio during the early course of ARDS are associated with mortality at day 30 and add statistically significant but limited improvement in the predictive accuracy to indices of oxygenation and respiratory system mechanics at the second day of mechanical ventilation. The predicted validity of the estimated dead space fraction and the ventilatory ratio improved the baseline model based on PEEP, PaO 2/FiO 2, driving pressure and compliance of the respiratory system at day 2 (AUROCC 0.72 vs. Dead space fraction calculation using the estimate from physiological variables and the ventilatory ratio at day 2 showed independent association with mortality at 30 days (odds ratio 1.28, p < 0.03 and 1.20, p < 0.03, respectively) whereas, the Harris–Benedict and Penn State estimations were not associated with mortality. Estimated dead space fraction and the ventilatory ratio at days 1 and 2 were significantly higher among non-survivors ( p < 0.01). Individual patient data from 940 ARDS patients were analyzed. The present study is a post hoc analysis of a prospective observational cohort study of ICUs of two tertiary care hospitals in the Netherlands. This study aimed to compare various methods for dead space estimation and the ventilatory ratio in patients with acute respiratory distress syndrome (ARDS) and to determine their independent values for predicting death at day 30. Indirect indices for measuring impaired ventilation, such as the estimated dead space fraction and the ventilatory ratio, have been shown to be independently associated with an increased risk of mortality.

How to calculate alveolar dead space