University of Michigan
Department of Pediatrics
Evidence-Based Pediatrics Web Site

Question

• Are High Frequency Oscillatory Ventilation (HFOV) strategies safe to use in an adolescent population with acute respiratory distress syndrome?

Clinical Bottom Lines

1. HFOV using the “open-lung” approach is a safe ventilatory option with no significant increased risk of hemodynamic adverse events when compared to CV.
2. This study showed a non-statistically significant trend towards reduced mortality at 30 days and 6 months in patients ventilated using HFOV compared to CV.
3. Although Oxygen Index (OI) trend is the most statistically significant predictor of 30 day mortality, it is not advisable to use this as a clinical guideline until it is prospectively validated.
4. Further studies are needed to better elucidate ideal patients, optimal settings, and to further document the safety profile of HFOV.

Summary of Key Evidence

1. Randomized, controlled trial comparing “lung protective” strategies on conventional ventilation to “open lung” strategies on high frequency oscillatory ventilation.  Study was unable to be blinded by nature of interventions being compared.¹
2. Inclusion Criteria: patients older than 16 years, mechanically ventilated, meeting ARDS criteria (PaO2/FiO2 <= 200mmHg, PEEP >= 10cmH2O, bilateral radiographic infiltrates)
3. Exclusion Criteria: left atrial hypertension, wt <= 35kg, severe COPD or asthma, intractable shock, severe airleak, non-pulmonary terminal diagnosis, FiO2 >= 0.8 for >48hr, recent participation in investigational study.
4. Data collected at baseline, 2hr, 24hr, 48hr, 72hr, 30days, and 60days after randomization.
5. Primary Outcomes: survival without need for mechanical ventilation at 30days after study entry.
6. Secondary Outcomes: New/worsening airleak, mucus plugging requiring ETT change, six month mortality, intractable hypotension, oxygen failure, ventilation failure.
7. Result: no statistically significant difference in primary or secondary outcomes between CV and HFOV.
8. Statistically significant predictors of survival at 30 days after study entry irrespective of assigned ventilator were identified as OI response at 16hr (p=0.001), >5days ventilation prior to study initiation (p=0.032), APACHE II (p=0.002), and baseline pH (p=0.049)

Additional Comments

• In animal models, High Frequency Oscillatory Ventilation (HFOV) strategies show improved gas exchange, more uniform lung inflation, and reduced histopathological evidence of ventilator-induced lung injury, as well as decreased levels of inflammatory mediators when compared to conventional ventilation (CV) strategies using similar peak airway pressures.²
• Neonatal studies have shown improvements in oxygenation using HFOV without increasing barotrauma.²
• Advantages of this Study
  • Large, multi-center randomized trial.
  • Included older adolescents in their study population.
  • Achieved excellent compliance with study protocol in both treatment arms.
• Limitations of this Study
  • Unable to be blinded secondary to the nature of the ventilator machinery.
  • This study was designed in the early days of ARDS Network recommendations, so patients were not stratified based on PIP at time of randomization.
  • The CV strategy was limited to use tidal volume algorithm on true weight rather than ideal body weight.

Citation

1. Derdak S, et al.  High-frequency oscillatory ventilation for acute respiratory distress syndrome in adults: A randomized controlled trial.  American Journal of Respiratory & Critical Care Medicine 2002166:801-808.
2. MacIntyre N. Ventilatory Management of ALI/ARDS. Seminars in Respiratory & Critical Care Medicine. 2006; 27:396-403.

CAT Author: Kristin M. Jensen, MD

CAT Appraisers: Francis McBee Orzulak, MD

Date appraised: March 7, 2007