1. Contemporary Ventilator Management in Patients with and at risk of ALI/ARDS
Carl Hinkson, MS, RRT-ACCS, NPS, FAARC
Respiratory Care Department
Harborview Medical Center
Seattle, WA

2. Program Objectives Identify the research question of the study.
Identify the study design.
Discuss the main results of the study.
Discuss the implication of the study on patient care.

3. April 2013 RESPIRATORY CARE Journal Webcast
This webcast and any accompanying materials are copyrighted by the American Association for Respiratory Care (AARC).  Any public display, sale, copy or distribution of the video or materials may only be undertaken with the prior written consent of the AARC. Copyright 2013

4. Background
Patients with ALI/ARDS benefit from low tidal volume ventilation with limitation of plateau pressures
Despite several studies, the strategy to best manage PEEP in ALI/ARDS remains elusive
It is unclear if there is any benefit to ventilating patients without ALI/ARDS with low tidal volume ventilation

5. Background What is the research question? Any concerns about COI?
What variables impact administered tidal volume
What is the impact of ALI/ARDS on outcomes
Whether or not clinicians are consistently using low tidal volume ventilation after the 2000 ARDS Network study
The authors hypothesized ventilating with a low tidal volume would be associated with less post intubation ALI/ARDS
Any concerns about COI?
This research was not directly funded. Nor did any authors have any direct conflict of interests. Some authors reported receiving research funds or consulting fee not related to this topic

6. Methods
Secondary analysis of the Lung Injury Prevention Score (LIPS) study
Observational, 22 center cohort
Conducted between March to August 2009
19 centers prospectively collected data
3 centers retrospectively collected data

7. Methods Inclusion criteria > 18 years of age
1 or more risk factor for ALI/ARDS
Sepsis
Shock
Pancreatitis
Pneumonia
Aspiration
High-risk trauma
High-risk surgery
Admitted through ED or operating rooms

8. Methods Exclusion criteria
Excluded if they developed ALI/ARDS within six hours of assessment
Transferred from an outside institution
Died in the ED
Admitted for palliation (comfort care)
Re-admitted during the study period
Patients who never received mechanical ventilation or received mechanical ventilation for < 1 day

9. Methods Data collected
Baseline characteristics
Sociodemographics
Comorbidities
Data was collected within first 6 hours of evaluation
Initial ventilator settings, parameters, volumes, and pressures
For subjects that developed post intubation ALI/ARDS the first set of ventilator data was collected after the diagnosis was made.

10. Methods Outcomes Primary Secondary Initial tidal volume & PEEP in:
Patients who never developed ALI/ARDS,
Patients intubated because of ALI/ARDS
Patients who developed ALI/ARDS after intubation
Researchers used the American-European Consensus Conference definition
Secondary
Development of ALI/ARDS after initial intubation
Hospital outcomes: ventilator free days & mortality

11. Methods Statistical Analysis
Kolmogorov-Sminov test for normal distribution
Student’s t-test or Mann-Whitney for continuous variables
Categorical variables compared using Chi-squared or Fischer’s exact test
One-way ANOVA for variation in tidal volume settings
Multivariate analysis was done with logistic regression (one for tidal volume, one for PEEP)
Significance (alpha/α) was 0.05, all test were two-sided
Data was expressed as median with interquartile ranges

12. Results

13. Results
Baseline characteristics one

14. Results
Baseline characteristics two

15. Results
Initial ventilator settings and inspiratory pressures

16. Results
Comparison of Subjects Without ALI/ARDS at Onset of Mechanical Ventilation, Initially Treated with tidal Volume of <8 mL/kg PBW versus ≥ 8 mL/kg PBW

17. Results
Comparison of Subjects Without ALI/ARDS at Onset of Mechanical Ventilation, Initially Treated with tidal Volume of <8 mL/kg PBW versus ≥ 8 mL/kg PBW

18. Results
Factors Associated with Greater Odds of Receiving ≥ mL/kg PBW on Initial Ventilation in the subjects Without ALI/ARDS at Onset of Mechanical Ventilation; after adjusting for center.
About Odds Ratios

19. Results
Clinical Outcomes of Subjects Without ALI/ARDS at Onset of Ventilation (Based on Tidal Volume)

20. Results
Initial Ventilator Settings and Pressures Among the 722 Subjects Without ALI/ARDS at Onset of Mechanical Ventilation

21. Results
Ventilator Settings and Parameters Before and After Development of ALI/ARDS in the 161 Subjects who Developed ALI/ARDS After the Onset of Mechanical Ventilation

22. Results
Hospital Outcomes

23. Results – Inter-center variation in VT among all MV pts
ARDSnet target VT
Inter-center variation in initial tidal volume settings among all intubated and mechanically ventilated patients (n=829)

24. Results – Inter-center variation in VT among MV pts that did not develop ALI/ARDS
ARDSnet target VT

25. Results – Inter-center variation in VT among MV pts intubated for ALI/ARDS
ARDSnet target VT

26. Results – Inter-center variation in VT among MV pts with post-intubation ALI/ARDS
ARDSnet target VT

27. Discussion What do these finding mean?
Application of low tidal volume is variable, but clinicians are getting better about using low tidal volume ventilation for ALI/ARDS
Sicker patients were more likely to receive low VT ventilation
Ventilator settings and delivering VT < 8mL/kg PBW is not associated with development of post-intubation ALI/ARDS or outcomes
Development of post-intubation ALI/ARDS was associated with more resource utliziation
Subjects were more likely to receive low VT if they were male, taller, and less obese.
Shorter & heavier subjects tended to receive VT ≥8mL/kg PBW

28. Discussion What are the study limitations?
Analysis is based from initial ventilator check
The study was under-powered to detect outcome differences
Study limited by observational nature
What additional work is needed in this area?
Why patients who develop ARDS post intubation consume more resources
Prospective research the role of ventilator settings on post-intubation ARDS

29. Editorial From Robert P Dickson, MD
Main limitation of this study “snapshot” nature of the ventilator data
Difficult to ascertain if subjects received low VT ventilation based only on ventilator data
The absolute difference between the “at intubation” and “post-intubation” ALI/ARDS was small
Message of lower tidal volume from ARDSnet trial seems to have gotten out
Difficult to measure patient initially?

30. Conclusions What are the authors’ conclusions?
Improved, but not ideal adherence to lower VT ventilation
Variation in ventilator management did not affect outcomes
Post-intubation ARDS was associated with greater resource utilization
What is the take-home message?
You should still use low VT ventilation for ARDS pts
Assure that VT is calculated from PBW not ABW