High-Frequency Oscillation: New Directions

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Presented by Dr.Nial Ferguson at Pulmonary Medicine Update Course held at Cairo, Egypt. Pulmonary Medicine Update Course is the leading Pulmonary Critical Care event in Egypt. Organized by Scribe www.scribeofegypt.com

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High-Frequency Oscillation: New Directions

  1. 1. High-Frequency Oscillation: New Directions for 2009 Niall D. Ferguson, MD, FRCPC, MSc Assistant Professor Interdepartmental Division of Critical Care Medicine University of Toronto
  2. 2. HFO: A Canadian Invention
  3. 3. Outline • Background on HFO • Ventilator-induced Lung Injury (VILI) • Implementing HFO to prevent VILI  Who  When  How  Oxygenation & Recruitment  Ventilation  Transition back to CV
  4. 4. Pressure-Time Curve CMV HFOV P r e s s u r e Time
  5. 5. Patient HFOV Gas-flow Circuit Humidified Bias Flow Active Expiration R Humidifier
  6. 6. HFOV - Setup Settings • PAW • P (Power) • Frequency • Bias Flow, I:E
  7. 7. In Adults – HFOV is safe & improves oxygenation - appropriate as rescue therapy
  8. 8. High-frequency oscillatory ventilation for adult respiratory distress syndrome: Let's get it right this time! AB Froese Crit Care Med 1997; 25:906-908
  9. 9. ARDS Network • High Stretch  VT: 11.8  PPLAT: 32-34  RR: 18  VMIN: 13  PEEP: 8 • Mortality 40% • Low Stretch  VT: 6.2 ml/kg  PPLAT: 25 cm H2O  RR: 29  VMIN: 13 L/min  PEEP: 9 cm H2O • Mortality 31%* *p=0.005 N Engl J Med 2000 342:1301-8
  10. 10. Can We Reduce VILI any Further?
  11. 11. Preventing VILI - Principles • Limit overdistention • Maintain EELV • Minimize oxygen toxicity • HFOV benefits:  margin of error for overdistention / derecruitment - Decoupling of ventilation & oxygenation - Improved oxygenation  FIO2 Employ early
  12. 12. Alveolar (In)stability JM Steinberg et al. AJRCCM 2004; 169:57-63 DiRocco, Nieman AARC 2005
  13. 13. 14/0 45/0 Experimental pulmonary edema due to intermittent positive pressure ventilation with high inflation pressures. Protection by positive end-expiratory pressure. HH Webb & DF Tierney ARRD 1974; 110:556-65
  14. 14. 14/0 45/10 45/0 Experimental pulmonary edema due to intermittent positive pressure ventilation with high inflation pressures. Protection by positive end-expiratory pressure. HH Webb & DF Tierney ARRD 1974; 110:556-65
  15. 15. HFO vs. Injurious CV in Animals
  16. 16. HFO vs. ‘protective’ CV in animals
  17. 17. Outcomes 30 Day Mortality HFOV: 37% CMV: 52% Absolute Risk Reduction: 15% Relative Risk Reduction: 29% p=0.102 p=0.057 30 d p=0.078 90 d HFOV in adults with ARDS is safe and may improve outcome – more study is needed
  18. 18. HFO
  19. 19. Background  HFO is theoretically ideal for lung protection  early RCTs suggest HFO is safe and may reduce deaths Design  multicentre RCT Population  72 patients with ARDS, at 12 participating sites Interventions  HFO  conventional ventilation - a low tidal volume, open lung approach Primary outcome  hospital mortality Pilot study goals  assess recruitment, and barriers to recruitment  assess adherence to explicit ventilation protocols  measure and understand reasons for crossovers
  20. 20. Outline • Ventilator-induced Lung Injury (VILI) • Background on HFO • Implementing HFO  Who  When  How  Oxygenation & Recruitment  Ventilation  Transition back to CV
  21. 21. HFOV compared with CMV for Respiratory Failure in Preterm Infants HIFI Group N Engl J Med 1989;320 673 preterms with respiratory failure within 12 hrs of CMV 346 CMV, 327 HFOV HFOV - MAP as with CMV, FiO2 was increased first Results: Similar Bronchopulmonary Dysplasia & Mortality Increased pneumoperitoneum, intracranial bleeds, periventricular leukomalacia
  22. 22. Reflections on HIFI Bryan & Froese Pediatrics 1991;87 1. Goals were not to increase lung volume. 2. PAW weaned before FiO2. 3. Cross centre differences in adverse events.
  23. 23. Volume-Pressure Curve CMV HFO V o l u m e Pressure Lower Inflection Point Upper Infection Point
  24. 24. RMs with Conventional Ventilation • Multiple studies – inconsistent results  Timing  Type of manoeuvre  Cause of lung injury  How PEEP was set afterwards • With HFO  Theoretically RMs may be of more use (because of lack of tidal recruitment)  and may be more effective (because of ability to set a very high PEEP)
  25. 25. PaO2 Time (min.) HFO - Recruitment Manoeuvres • Oleic Acid Lavaged Rabbits • Conventional Ventilation followed by HFOV  With and without Sustained Inflation (30 cm H2O for 10 s) Relationship Between PaO2 and Lung Volume During HFOV Suzuki et al. Acta Pedr Jpn 1992
  26. 26. > 0.6
  27. 27. 0 100 200 300 400 Standardized CMV HFOV + 1-3 RMs (1.5 Hours) PaO2/FIO2 Individual & Mean PaO2/FIO2 Values
  28. 28. HFO Prone
  29. 29. Conclusions • HFO theoretically ideal for preventing VILI – if used with a strategy to maintain EELV • On balance the potential for benefit with RMs in HFO seems to outweigh downsides • Lung recruitment is a good thing - If it can be achieved  Ineffective attempts at lung recruitment: no benefit vs. harmful
  30. 30. Outline • Ventilator-induced Lung Injury (VILI) • Background on HFO • Implementing HFO  Who  When  How  Oxygenation & Recruitment  Ventilation  Transition back to CV
  31. 31. High-frequency oscillatory ventilation for adult respiratory distress syndrome: Let's get it right this time! AB Froese Crit Care Med 1997; 25:906-908
  32. 32. HFOV - background • Respiratory frequencies 180-900 / min • Tidal volumes (VT) < dead space (VD) • Ventilation (CO2) dependent on:  VT  P frequency • Oxygenation dependent on:  PAW / lung volume  FIO2 Decoupling of O2 / CO2
  33. 33. Slutsky & Drazen NEJM 2002, 347:630-1
  34. 34. Crit Care Med 2003; 31:227-231 < 1.2 - 2 ml/kg ?
  35. 35. Crit Care Med 2006; 34:751-757 Hot-wire Anemometer
  36. 36. Conclusions • In addition to targeting lung recruitment we need to deliver the lowest VT possible  Higher frequencies (facilitated by higher power / delta P)  Controlled cuff leak?  Accept a ‘reasonable’ pH
  37. 37. Outline • Ventilator-induced Lung Injury (VILI) • Background on HFO • Implementing HFO  Who  When  How  Oxygenation & Recruitment  Ventilation  Transition back to CV
  38. 38. Implementing HFO 2009 • Who should we consider as candidates for HFO?  Sick ARDS patients in need of recruitment • When should we use HFO?  Rescue therapy for now  Maybe earlier rather than later • How we use HFO?  Oxygenation = Target lung recruitment  Ventilation = Keep tidal volume minimal
  39. 39. HFO
  40. 40. n.ferguson@utoronto.ca October 25 – 29, 2009 Metro Toronto Convention Centre
  41. 41. n.ferguson@utoronto.ca

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