Reviewed and revised 10 February 2014
- protective lung ventilation with low tidal volumes is now the standard of care in ARDS
- the open lung ventilation approach involves increasing the level of Positive End Expiratory Pressure (PEEP) in combination with protective ventilation
- a universally accepted protocol for open lung ventilation does not exist
- the use of PEEP, at what level and how to set it is controversial
- Recruitment manoeuvres in ARDS and novel ventilation modes (e.g. Airway Pressure Release Ventilation (APRV)) may also be incorporated into the open lung approach
Potential benefits of PEEP and the open lung approach in ARDS
- maximises recruitment of alveoli (by preventing de-recruitment)
- minimises cyclic atelectasis and atelectotrauma
- decreases biotrauma from alveolar collapse (e.g. release of inflammatory mediators)
- minimises denitrogenation atelectasis and oxygen toxicity (by allowing lower FiO2)
DETERMINING OPTIMAL PEEP
Optimal PEEP level ultimately represents a balance between regional areas of overstretching and regional derecruitment
- no agreed upon method of determination
- optimal PEEP may change over time
- ‘best’ PEEP maybe independent of oxygenation effects (e.g. due to hyperinflation injury)
- ‘best’ PEEP may be independent of respiratory mechanics
There are a number of methods suggested to determine the optimum PEEP setting:
- perform staircase recruitment manouvre (SRM) (see Recruitment manouvres in ARDS)
- adjust according to FiO2 requirements (e.g. as per ARDSNet protocol)
- higher than the upper or the lower infection point on a pressure-volume loop (experts argue over which inflection point is preferable to use)
- adjust PEEP to maximise static compliance: TV / (Pplat – PEEP) (increased risk of alveolar stretch above this)
- thoracic tomography
- lowest intra-pulmonary shunt (highest SvO2)
- esophageal balloon directed estimation of pleural pressures to calculate transpulmonary pressures and guide PEEP titration
- model-based methods
- in asthma, can use either ZEEP (PEEP = 0) or 2/3 of measured auto-PEEP (no high level evidence for either)
A clinical trial has been registered that plans to compared the ARDSNest approach to 3 different methods of determining optimal PEEP (see here)
PROS AND CONS OF PEEP
- Three major studies have assessed high versus low PEEP in combination with protective lung ventilation at low tidal volumes
- ALVEOLI trial in 2004 — no difference between high and low PEEP
- LOVS trial in 2008 — improved oxygenation and less need for rescue interventions (e.g. ECMO), no difference in mortality
- EXPRESS trial in 2008 — more ventilator-free days and more organ failure-free days, no difference in mortality
- Briel et al (2010) meta-analysis — used the data from the above 3 trials ( 2299 patients) and showed that higher levels of PEEP were associated with improved survival among ARDS but not ALI patients (i.e. if PF ratios <200 there was 34.1% versus 39.1% mortality with adjusted RR, 0.90; 95% CI, 0.81-1.00; P = .049)
The effect of low VT ventilation with higher levels of PEEP in patients without ARDS is uncertain
- an open lung approach to ventilation is safe
- Higher PEEP (>15 cmH20) is a reasonable approach in patients with the highest lung recruitability and in the most hypoxemic patients
- Determination of optimal PEEP is controversial, I usually use the staircase recruitment manoevre (SRM) approach in my practice
- A meta-analysis suggests a possible mortality benefit of protective lung ventilation with high PEEP in patients with moderate-to-severe ARDS (PF ratio <200)
References and Links
- CCC — Positive End Expiratory Pressure (PEEP)
- CCC — Protective Lung Ventilation
- CCC — Recruitment manoeuvres in ARDS
- CCC — Airway Pressure Release Ventilation (APRV)
- Briel M, Meade M, Mercat A, Brower RG, Talmor D, Walter SD, Slutsky AS, Pullenayegum E, Zhou Q, Cook D, Brochard L, Richard JC, Lamontagne F, Bhatnagar N, Stewart TE, Guyatt G. Higher vs lower positive end-expiratory pressure in patients with acute lung injury and acute respiratory distress syndrome: systematic review and meta-analysis. JAMA. 2010 Mar 3;303(9):865-73. doi: 10.1001/jama.2010.218. Review. PubMed PMID: 20197533.
- Brower RG, Lanken PN, MacIntyre N, Matthay MA, Morris A, Ancukiewicz M, Schoenfeld D, Thompson BT; National Heart, Lung, and Blood Institute ARDS Clinical Trials Network. Higher versus lower positive end-expiratory pressures in patients with the acute respiratory distress syndrome. N Engl J Med. 2004 Jul 22;351(4):327-36. PubMed PMID: 15269312.
- Dueck R. Alveolar recruitment versus hyperinflation: A balancing act. Curr Opin Anaesthesiol. 2006 Dec;19(6):650-4. Review. PubMed PMID: 17093370.
- Guerin C. The preventive role of higher PEEP in treating severely hypoxemic ARDS. Minerva Anestesiol. 2011 Aug;77(8):835-45. Review. PubMed PMID: 21730932. [Free Full Text]
- Meade MO, Cook DJ, Guyatt GH, Slutsky AS, Arabi YM, Cooper DJ, Davies AR, Hand LE, Zhou Q, Thabane L, Austin P, Lapinsky S, Baxter A, Russell J, Skrobik Y, Ronco JJ, Stewart TE; Lung Open Ventilation Study Investigators. Ventilation strategy using low tidal volumes, recruitment maneuvers, and high positive end-expiratory pressure for acute lung injury and acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2008 Feb 13;299(6):637-45. doi: 10.1001/jama.299.6.637. PubMed PMID: 18270352.
- Mercat A, Richard JC, Vielle B, Jaber S, Osman D, Diehl JL, Lefrant JY, Prat G, Richecoeur J, Nieszkowska A, Gervais C, Baudot J, Bouadma L, Brochard L; Expiratory Pressure (Express) Study Group. Positive end-expiratory pressure setting in adults with acute lung injury and acute respiratory distress syndrome: a randomized controlled trial. JAMA. 2008 Feb 13;299(6):646-55. doi: 10.1001/jama.299.6.646. PubMed PMID: 18270353.
- Rouby JJ, Ferrari F, Bouhemad B, Lu Q. Positive end-expiratory pressure in acute respiratory distress syndrome: should the ‘open lung strategy’ be replaced by a ‘protective lung strategy’? Crit Care. 2007;11(6):180. Review. PubMed PMID: 18086329; PubMed Central PMCID: PMC2246215
- Rubenfeld GD. How much PEEP in acute lung injury. JAMA. 2010 Mar 3;303(9):883-4. doi: 10.1001/jama.2010.226. PubMed PMID: 20197538.
- Santa Cruz R, Rojas JI, Nervi R, Heredia R, Ciapponi A. High versus low positive end-expiratory pressure (PEEP) levels for mechanically ventilated adult patients with acute lung injury and acute respiratory distress syndrome. Cochrane Database Syst Rev. 2013 Jun 6;6:CD009098. doi: 10.1002/14651858.CD009098.pub2. PubMed PMID: 23740697.
- Suter PM, Fairley B, Isenberg MD. Optimum end-expiratory airway pressure in patients with acute pulmonary failure. N Engl J Med. 1975 Feb 6;292(6):284-9. PubMed PMID: 234174.
- Villar J, Kacmarek RM, Pérez-Méndez L, Aguirre-Jaime A. A high positive end-expiratory pressure, low tidal volume ventilatory strategy improves outcome in persistent acute respiratory distress syndrome: a randomized, controlled trial. Crit Care Med. 2006 May;34(5):1311-8. PubMed PMID: 16557151.