- Overall, ICU mortality continues to improve
REASONS WHY MORTALITY IMPROVEMENT IS NOT FASTER
ARDS as an example:
- Major gains were made with the change to protective lung ventilation, gains since then have been slow
- A number of factors need to be considered, in particular the large amount of background noise making accurate assessment of improvements near impossible.
- Indeed, the studies that have actually shown benefit may not be extrapolatable to the majority of the ARDS population seen in Intensive Care.
- The mortality of ARDS is not usually due to respiratory disease per se, but instead to multiple organ dysfunction, which is due to a multiplicity of factors (including the underlying disease process that resulted in ARDS [eg. pancreatitis, sepsis, burns], inflammatory response due to ARDS, nosocomial infections. No single specific therapy is likely to prevent the cascade of events that result in inflammation. Insufficient studies have been performed to consistently demonstrate one technique has benefits, let alone which combinations of therapies may be useful.
- ARDS is also the end result of a large number of predisposing insults. The outcomes vary dramatically between subgroups (eg. trauma versus pneumonia). More specific classification or stratification may allow more accurate comparisons.
- As a result of better general supportive care, patients that would not previously been considered salvageable could now be going on to develop ARDS, and are more likely to have an adverse outcome
- Potential risk factors as they are discovered are continually being treated/corrected, decreasing the likelihood of less severe/complex cases developing ARDS
- It is probably impossible to accurately compare outcomes now with decades ago, given the inability to control for the many factors that influence outcome