Advanced Ventilatory Strategies in ARDS

Alex Yartsev, Dec 2010

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

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•

The gospel of ARDS net

• Massive protocol derived from multiple trials

• “lung protective ventilation” with low tidal volume– Aim PaO2 55-80– 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 SienaSaint of those with lungand respiratory problemsPetrucci et al, 2007 Lung protective ventilation strategy for the acute respiratory distress

syndrome, Cochrane Database of Systematic Reviews 2007, Issue 3. Art. No.: CD003844.

What can you do with a Drager Evita XL?• Quite a lot• SIMV• PCV (pressure control ventilation)

• APRV (airway pressure-release ventilation)

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

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. 6 1690-1696 Lessard et.al. 1994 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, 1994 80:983-991Rappaport et a. 1994 Randomized prospective trial of pressure-limited versus volume-controlled ventilation in severe respiratory failure. Crit care Med 1994 22:22-32

Airway Pressure Release Ventilation• Similar to inverse ratio ventilation• Patient breathes spontaneously at high pressure support,

with short breaks of low support

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—731Liu 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. 2009 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: A1691Putensen et al. Long term effects of APRV. AJRCCM 2001;164:43.

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

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; 166:801–808Bollen 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; 9:430–439Papazian 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; 33:2162–2171Krishnan et al 2000 High-frequency ventilation for acute lung injury and ARDS. Chest 2000;118,795-807

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.

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

ECMO in ARDS• Early trials:

• Zapol, 1979: – 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, 4:156-168Zapol WM, Snider MT, Hill JD, et al.: Extracorporeal membrane oxygenation in severe acute respiratory failure. A randomized prospective study.JAMA 1979 , 242:2193-2196Morris 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 , 149:295-305.

ECMO in ARDS• More recently:

• 2009 CESAR trial: 180 pts– Survival: 63% (VV ECMO) vs 47% (standard)

Peek et.al. 2009 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 1351 - 1363, 17 October 2009

Experimental strategies

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. http://archive.rubicon-foundation.org/4257. Wolfson et al. Multicenter comparative study of conventional mechanical gas ventilation to tidal liquid ventilation in oleic acid injured sheep 54(3):236-269, 2008.Yoxall et al, Liquid Ventilation in the Preterm neonateThorax 1997;52:3- doi:10.1136/thx.52.2008.S3

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.: CD003707.

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 reviewPerfusion November 2010 vol. 25 no. 6 363-367

No further questions, please.

References• Esteban et.al, 2000 Prospective Randomized Trial Comparing Pressure-Controlled Ventilation and

Volume-Controlled Ventilation in ARDS CHEST June 2000 vol. 117 no. 6 1690-1696 • Kenneth et. al. 2007 High-Frequency Oscillatory Ventilation for Adult Patients With ARDS CHEST June

2007 vol. 131 no. 6 1907-1916 • Krishnan et al 2000 High-frequency ventilation for acute lung injury and ARDS. Chest 2000;118,795-807• 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. 2009 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.: CD003844.• 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. 6 1907-1916 • Lewandowski K, Extracorporeal membrane oxygenation for severe acute respiratory failure Critical Care

2000, 4:156-168