Multivariate analysis identified OI at 24 h after HFOV initiation as the most significant posttreatment predictor of mortality. Derdak and colleagues also identified OI trend as the most significant posttreatment predictor of survival regardless of assigned ventilator, with the 16-h OI as the most discriminating time point. Fort and colleagues identified the fact that an OI of > 47 predicted mortality with a sensitivity and specificity of 100%. In a large retrospective assessment of HFOV therapy in 10 pediatric ICUs, OI at 24 h also was found to be an important predictor of survival. We found that a 24-h OI of 24 h was a reasonable predictor of survival, but that it was not as significant as the continuous OI value. In the ARDS population, with such an array of confounding risk factors, multivariate models may be more helpful than a single variable in predicting mortality. Nevertheless, OI may serve as an additional indicator of the probability of survival.
Four other parameters also significantly predicted 30-day mortality in our population, as follows: age; APACHE II score; number of days receiving CV prior to receiving HFOV; and baseline pH. Three previous studies also identified that a greater number of pretreatment CV days correlated directly with mortality. This observation from multiple studies highlights the importance of developing criteria for the early initiation of HFOV as rescue therapy.
The major limitation of our report is its retrospective nature. There was no standard protocol for HFOV initiation or titration, sedation, neuromuscular blockade, fluid administration, or vasopressor therapy. As such, practices varied among institutions, In addition, HFOV therapy was used primarily in a medical population.
HFOV has become the standard of care for the treatment of neonatal respiratory distress syndrome. Support for the use of HFOV therapy in adults with ARDS is more limited and awaits the performance of rigorous trials comparing HFOV to CV using low tidal volumes, evaluating outcomes such as mortality. Until then, HFOV therapy shows promise as rescue therapy to improve oxygenation in patients not responding to conventional therapy.