1. Advanced Ventilatory Strategies in ARDS
Alex Yartsev, Dec 2010

2. Whats the problem in ARDS
Thickened diffusion membrane
Inflamed exudate-filled alveoli
Collapsed bronchioles
Lost elasticity of parenchyma
Massive shunt
Thus, severe hypoxia

3. Challenge to ventilation in ARDS
Lung is inelastic: compliance is poor
Poor cokpliance = small tidal volume = poor ventilation
Poor ventilation = hypercapnoea, acidosis
Normal ventilation requires larger volumes…
Small changes in volume = large changes in pressure
Large changes in pressure = barotrauma
Severe hypoxia = high FiO2 requirements
High FiO2 for long periods = O2 toxicity

4. The gospel of ARDS net Massive protocol derived from multiple trials
“lung protective ventilation” with low tidal volume
Aim PaO
Tidal volume of ONLY 6ml/kg
Pplat to be kept under 30
pH to be kept over 7.30
- ANY ventilator mode
Saint Bernadine of Siena Saint of those with lung and respiratory problems
Petrucci et al, 2007 Lung protective ventilation strategy for the acute respiratory distress syndrome, Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD

5. What can you do with a Drager Evita XL?
Quite a lot
SIMV
PCV (pressure control ventilation)
APRV (airway pressure-release ventilation)

6. Pressure control ventilation
The target pressure is set, and never exceeded by the machine
Tidal volume and minute volume may vary depending on lung compliance and resistance
Does not guarantee minute ventilation; guarantees pressure instead

7. Evidence for pressure control ventilation
Any better than standard volume control?
According to Esteban and co (2000, 79 pts), there was lower mortality in the PCV group… but not because of ventilation (!)
Refractory hypoxia was the same, VCV or PCV; but VCV patients died more frequently, … of non-respiratory organ failures.
Other trials:
Lessard et al. (9 pts, no difference)
Rappaport et al (27 patients, fewer ventilated days on PCV)
General consensus: studies are underpowered,
but trend favours PCV
Esteban et.al, 2000 Prospective Randomized Trial Comparing Pressure-Controlled Ventilation and Volume-Controlled Ventilation in ARDS CHEST June 2000 vol. 117 no
Lessard et.al Effects of pressure-controlled with different I:E ratios versus volume-controlled ventilation on respiratory mechanics, gas exchange and hemodynamics in patients with adult respiratory distress syndrome. Anaesthesiology, :
Rappaport et a Randomized prospective trial of pressure-limited versus volume-controlled ventilation in severe respiratory failure. Crit care Med :22-32

8. Airway Pressure Release Ventilation
Similar to inverse ratio ventilation
Patient breathes spontaneously at high pressure support, with short breaks of low support

9. APRV vs standard modes Is it any better than SIMV+PSV?
Varpula and c o. (2004) – 58 pts randomised APRV or SIMV;
NO DIFFERENCE in ventilated days, gas exchange, cardiac output or mortality (18% vs 19%)
Liu et al (2009) – also 58 pts – APRV vs SIMV
PaO2/FiO2 ratios were better, APRV mortality 31% vs SIMV mortality 59%
Kyle et al (2010) – trial in progress
Alex couldn’t afford the journal access, findings were presented at the annual meeting in 2010
Is it any better than PCV?
Putensen’s 30 pt prospective trial (2001) – 15 to PCV, 15 to APRV
PCV stayed ventilated for longer (21 vs 15)
mortality essentially the same (12 vs 11)
Varpula et al, Airway pressure release ventilation as a primary ventilatory mode in acute respiratory distress syndrome Acta Anaesthesiol Scand 2004; 48: 722—731
Liu et al, Practical use of airway pressure release ventilation for severe ARDS--a preliminary report in comparison with a conventional ventilatory support. Hiroshima J Med Sci Dec;58(4):83-8.
Kyle et al 2010, APRV Vs. ARDSnet Protocol Ventilation For ARDS/ALI m. J. Respir. Crit. Care Med..2010; 181: A1691
Putensen et al. Long term effects of APRV. AJRCCM 2001;164:43.

10. High Frequency Oscillatory Ventilation
Tiny volumes, high frequency.
Generally, generates tidal volumes less than the dead space of the lung
Pressure oscillates around the mean airway pressure
There are several theories as to how gas mixing leads to oxygenation in the alveoli with a tidal volume this low
Higher pressure, lower peak pressure, thus better oxygenation with less barotrauma, …theoretically

11. HFOV vs standard modes in ARDS
RCTs:
Derdak et al. High-frequency oscillatory ventilation for acute respiratory distress syndrome in adults: a randomized, controlled trial. Am J Respir Crit Care Med 2002; 166:801–808
Bollen CW, van Well GT, Sherry T, et al. High frequency oscillatory ventilation compared with conventional mechanical ventilation in adult respiratory distress syndrome: a randomized controlled trial. Crit Care 2005; 9:430–439
Papazian L, Gainnier M, Marin V, et al. Comparison of prone positioning and high-frequency oscillatory ventilation in patients with acute respiratory distress syndrome. Crit Care Med 2005; 33:2162–2171
Krishnan et al High-frequency ventilation for acute lung injury and ARDS. Chest 2000;118,

12. HFOV vs standard modes in ARDS
Also lots of prospective and retrospective studies
Consensus:
Looks like mortality is lower in HFO group
However, trials are old
New, good outcomes being published with standard modes; is HFOV any better? No trials to compare.

13. Extra-Corporal Membrane Oxygenation
Veno-venous or veno-arterial (VA also provides pump support a’la cardiopulmonary bypass)
Patients blood is sucked through a membrane which acts as a gas exchange surface; blood is returned to the lung or to the tissues

14. ECMO in ARDS Early trials: Zapol, 1979: Morris, 1994
90 pts, 10% survival on ECMO(VA)- no difference
Morris, 1994
34% survival on ECMO (VV) – no difference
Lewandowski K, Extracorporeal membrane oxygenation for severe acute respiratory failure Critical Care 2000, 4:
Zapol WM, Snider MT, Hill JD, et al.: Extracorporeal membrane oxygenation in severe acute respiratory failure. A randomized prospective study.JAMA 1979 , 242:
Morris AH, Wallace CJ, Menlove RL, et al.: Randomized clinical trial of pressure-controlled inverse ratio ventilation and extracorporeal CO2 removal for adult respiratory distress syndrome.Am J Respir Crit Care Med 1994 , 149:

15. ECMO in ARDS More recently: 2009 CESAR trial: 180 pts
Survival: 63% (VV ECMO) vs 47% (standard)
Peek et.al Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial The Lancet, Volume 374, Issue 9698, Pages , 17 October 2009

16. Experimental strategies

17. Total Liquid Ventilation
Ventilator pushes fluid through a gas-exchange membrane into the lungs
Liquid is a perfluorocarbon
Used with variable success in preterm neomates
No adult human trials
Numerours sheep have died
Kylstra JA (1977). The Feasibility of Liquid Breathing in Man.. Report to the US Office of Naval Research. Durham, NC: Duke University.
Wolfson et al. Multicenter comparative study of conventional mechanical gas ventilation to tidal liquid ventilation in oleic acid injured sheep 54(3): , 2008.
Yoxall et al, Liquid Ventilation in the Preterm neonateThorax 1997;52:3- doi: /thx S3

18. Partial Liquid Ventilation
Unlike TLV, does not require a whole new ventilator
Only the functional residual capacity is full of liquid
A conventional ventilator delivers breaths on top of it
No mortality benefoit according to Cochrane
Davies MW, Fraser JF. Partial liquid ventilation for preventing death and morbidity in adults with acute lung injury and acute respiratory distress syndrome. Cochrane Database of Systematic Reviews 2004, Issue 4. Art. No.: CD

19. DOUBLE ECMO! Single case report from a month ago
49 yo M with severe HSV pneumonia – AND a fall from significant height,  aortic dissection
Had a veno-venous ECMO circuit AS WELL as a veno-arterial ECMO circuit
Survived, somehow.
Litmathe J., Double ECMO in severe ARDS: report of an outstanding case and literature review
Perfusion November 2010 vol. 25 no

20. No further questions, please.

21. References
Esteban et.al, 2000 Prospective Randomized Trial Comparing Pressure-Controlled Ventilation and Volume-Controlled Ventilation in ARDS CHEST June 2000 vol. 117 no
Kenneth et. al High-Frequency Oscillatory Ventilation for Adult Patients With ARDS CHEST June 2007 vol. 131 no
Krishnan et al High-frequency ventilation for acute lung injury and ARDS. Chest 2000;118,
Varpula et al, Airway pressure release ventilation as a primary ventilatory mode in acute respiratory distress syndrome Acta Anaesthesiol Scand 2004; 48: 722—731
Liu et al, Practical use of airway pressure release ventilation for severe ARDS--a preliminary report in comparison with a conventional ventilatory support. Hiroshima J Med Sci Dec;58(4):83-8.
Petrucci et al, 2007 Lung protective ventilation strategy for the acute respiratory distress syndrome, Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD
Kyle et al 2010, APRV Vs. ARDSnet Protocol Ventilation For ARDS/ALI m. J. Respir. Crit. Care Med..2010; 181: A1691
Putensen et al. Long term effects of APRV. AJRCCM 2001;164:43.
Kenneth et al, High-Frequency Oscillatory Ventilation for Adult Patients With ARDS CHEST June 2007 vol. 131 no
Lewandowski K, Extracorporeal membrane oxygenation for severe acute respiratory failure Critical Care 2000, 4: