Comparing the Effects of Tidal Volume, Driving Pressure, and Mechanical Power on Mortality in Trials of Lung-Protective Mechanical Ventilation

BACKGROUND: The unifying goal of lung-protective ventilation strategies in ARDS is to minimize the strain and stress applied by mechanical ventilation to the lung to reduce ventilator-induced lung injury (VILI). The relative contributions of the magnitude and frequency of mechanical stress and the end-expiratory pressure to the development of VILI is unknown. Consequently, it is uncertain whether the risk of VILI is best quantified in terms of tidal volume (V-T), driving pressure (Delta P), or mechanical power. METHODS: The correlation between differences in V-T, Delta P, and mechanical power and the magnitude of mortality benefit in trials of lung-protective ventilation strategies in adult subjects with ARDS was assessed by meta-regression. Modified mechanical power was computed including PEEP (Power(elastic)), excluding PEEP (Power(dynamic)), and using Delta P (Power(driving)). The primary analysis incorporated all included trials. A secondary subgroup analysis was restricted to trials of lower versus higher PEEP strategies. RESULTS: We included 9 trials involving 4,731 subjects in the analysis. Odds ratios for moderation derived from meta-regression showed that variations in V-T, Delta P, and Power(dynamic) were associated with increased mortality with odds ratios of 1.24 (95% CI 1.03-1.49), 1.31 (95% CI 1.03-1.66), and 1.37 (95% CI 1.05-1.78), respectively. In trials comparing higher versus lower PEEP strategies, Power(elastic) was increased in the higher PEEP arm (24 +/- 1.7 vs 20 +/- 1.5 J/min, respectively), whereas the other parameters were not affected on average by a higher PEEP ventilation strategy. CONCLUSIONS: In trials of lung-protective ventilation strategies, V-T, Delta P, Power(elastic), Power(dynamic), and Power(driving) exhibited similar moderation of treatment effect on mortality. In this study, modified mechanical power did not add important information on the risk of death from VILI in comparison to V-T or Delta P.

Automated summary

In trials of lung-protective ventilation strategies, tidal volume, driving pressure, mechanical power all exhibit similar effects on mortality.