Hfov in adult ards smith

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Hfov in adult ards smith

  1. 1. High-frequency oscillatory ventilation in adults Geoff Smith SICU July 2007
  2. 2. Trauma with Acute Respiratory Distress Syndrome <ul><li>JS: 19yo man drove car off embankment into water while intoxicated. Ambulatory at scene with GCS15. Presenting pH 6.9. Oxygen saturation dropped and respiratory distress ensued, prompting emergent intubation in the ED. </li></ul>
  3. 4. High-Frequency Oscillatory Ventilation (HFOV) <ul><li>“ Lung protective” ventilation that oscillates the lung around a constant mean airway pressure higher than conventional ventilation </li></ul><ul><li>Significant pressure swings in the endotracheal tube, but pressure fluctuations are attenuated at the alveoli </li></ul><ul><li>First established for use in pediatrics cases of neonatal ARDS </li></ul><ul><li>No mortality benefit yet demonstrated in children (multiple RCTs) or adults (Multicenter Oscillatory Ventilation for ARDS Trial [MOAT] 2002, Bollen et al. 2005) </li></ul>
  4. 5. Theoretical advantages of HFOV <ul><li>Smaller VT </li></ul><ul><ul><li>Limit alveolar overdistension </li></ul></ul><ul><li>Higher mean airway pressure (mPaw/Pmaw) </li></ul><ul><ul><li>More alveolar recruitment </li></ul></ul><ul><li>Constant mPaw during inspiration and expiration </li></ul><ul><ul><li>Preventing end-expiratory alveolar collapse </li></ul></ul>
  5. 6. Gas exchange during HFOV <ul><li>direct bulk flow </li></ul><ul><li>longitudinal (Taylor) dispersion </li></ul><ul><li>pendeluft </li></ul><ul><li>asymmetric velocity profiles </li></ul><ul><li>cardiogenic mixing </li></ul><ul><li>molecular diffusion </li></ul>
  6. 7. Biology of HFOV-Animal models <ul><li>Less evidence of injury in surfactant-depleted rabbit lungs vs. conventional mechanical ventilation (CV). </li></ul><ul><ul><li>Reduced inflammatory cytokine expression: IL-1b, IL-6, IL-8, IL-10, TGFb, TNF </li></ul></ul><ul><ul><li>Reduced pathological change: less alveolar leukocyte infiltration and airway epithelial damage </li></ul></ul>
  7. 8. Multicenter Oscillatory Ventilation for ARDS Trial (MOAT) - 2002 RCT <ul><li>13 university-affiliated medical centers, recruitment 1997-2000 </li></ul><ul><li>Eligibility: </li></ul><ul><ul><li>age >= 16 on mechanical ventilation </li></ul></ul><ul><ul><li>PaO2/FiO2 < 200 while on PEEP >= 10 </li></ul></ul><ul><ul><li>Bilateral pulmonary infiltrates on CXR </li></ul></ul><ul><ul><li>No evidence of left atrial HTN </li></ul></ul><ul><li>Exclusion: </li></ul><ul><ul><li>Weight < 35 kg </li></ul></ul><ul><ul><li>Severe COPD or asthma </li></ul></ul><ul><ul><li>Intractable shock </li></ul></ul><ul><ul><li>Severe airleak </li></ul></ul><ul><ul><li>Nonpulmonary terminal diagnosis </li></ul></ul><ul><ul><li>FiO2 > 0.80 for more than 2d </li></ul></ul>
  8. 9. MOAT - 2002 RCT <ul><li>n=148, mean age 50, APACHE II score 22, PaO2/FiO2 ratio 112, OI 25, mean CV prior to HFOV 2.8 d </li></ul>
  9. 10. MOAT - 2002 RCT
  10. 11. MOAT - 2002 RCT <ul><li>Survival trend for HFOV over CV, but underpowered for significance </li></ul>
  11. 12. MOAT - 2002 RCT <ul><li>Oxygenation Index a marker of survival irrespective of method </li></ul>
  12. 13. MOAT - 2002 RCT <ul><li>Criticisms: </li></ul><ul><ul><li>Not powered to evaluate mortality (would need n=199) </li></ul></ul><ul><ul><li>Higher VT (8 cc/kg measured wt, 10.6 cc/kg ideal wt) and peak Paw (38 cm H2O at 48h) in CV group than current ARDS Network trial standard of care for ARDS (6 cc/kg, 30 cm H2O) </li></ul></ul>
  13. 14. Bollen et al. HFOV RCT 2005 <ul><li>ICU in London, Cardiff, Paris, Mainz </li></ul><ul><li>Eligibility: </li></ul><ul><ul><li>PaO2/FiO2 < 200 </li></ul></ul><ul><ul><li>Bilateral pulmonary infiltrates on CXR </li></ul></ul><ul><ul><li>No evidence of atrial HTN </li></ul></ul><ul><li>Exclusion: </li></ul><ul><ul><li>Weight < 35 kg </li></ul></ul><ul><ul><li>Severe COPD or asthma </li></ul></ul><ul><ul><li>Non-pulmonary terminal disease </li></ul></ul><ul><ul><li>Grade 3 or 4 air-leak </li></ul></ul><ul><ul><li>FiO2 > 0.80 for 2d or CV > 10d </li></ul></ul>
  14. 15. Bollen 2005 RCT <ul><li>n=61 (37 and 24), mean age 51 and 55, APACHE II score 21 and 20, mean CV prior to HFOV 2.1 and 1.5 </li></ul><ul><li>Study stopped prematurely because of a low inclusion rate and the completion of the similar MOAT trial. </li></ul>
  15. 16. Bollen 2005 RCT <ul><li>No difference in 30 d mortality </li></ul>
  16. 17. Bollen 2005 RCT <ul><li>Oxygenation index response does not predict outcome in HFOV. </li></ul>
  17. 18. Bollen 2005 RCT <ul><li>Post-hoc analysis: better treatment effect of HFOV in patients with higher baseline OI. </li></ul>
  18. 19. Bollen 2005 RCT <ul><li>Criticisms: </li></ul><ul><ul><li>Small number of patients </li></ul></ul><ul><ul><li>Differences in baseline patient characteristics: </li></ul></ul><ul><ul><ul><li>OI (25 HFOV vs. 18 CV) </li></ul></ul></ul><ul><ul><ul><li>PaO2 (81 HFOV vs. 93 CV) </li></ul></ul></ul><ul><ul><li>Lack of explicit ventilation protocols </li></ul></ul><ul><ul><li>Underpowered to show differences in efficacy or safety </li></ul></ul>
  19. 20. Conclusions <ul><li>HFOV as safe and efficacious as lung protective CV in RCTs. </li></ul><ul><li>There is a trend of improved mortality with HFOV, but this needs to be repeated in a fully powered, properly controlled RCT (i.e., vs. lung protective CV) </li></ul><ul><li>HFOV may be more effective in patients with high baseline OI, but this should be studied directly. </li></ul>

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