The percentage of potentially recruitable lung varies widely among ARDS patients, and zones of collapsed and consolidated alveoli in the most dependent lung frequently require airway opening pressures of more than 35–40 cmH2O to recruit (1).
Knowledge of the percentage of potentially recruitable lung may be important for establishing the therapeutic efficacy of PEEP. Setting levels of PEEP independently of that knowledge may reduce the possible benefits of PEEP, while use of high PEEP levels in patients with a low percentage of potentially recruitable lung provides little benefit and may actually be harmful (2).
Assessing lung recruitability before changing the patient’s position from supine to prone helps you predict the outcome of the prone positioning and determine the strategy. If the assessment shows low recruitability, the patient can be changed to the prone position and no recruitment maneuver is performed. If the assessment shows high recruitability, the patient remains in the supine position and a recruitment maneuver is performed.
The P/V Tool on Hamilton Medical ventilators can be used to assess lung recruitability (3, 4).
1. Use the following settings to generate a low-flow P/V curve:
|End PEEP||0 cmH2O
Note: When prompted whether to change the PEEP setting after the maneuver, touch No.
|Ramp speed||2 cmH2O|
2. Use the following criteria to help you assess the patient‘s potential for lung recruitment.
a. Determine the shape of the inspiratory curve.
b. Assess the volume difference at 20 cmH2O. The difference must be > 500 ml (5).
3. If either one or both of these two criteria is met, a recruitment maneuver is warranted.
4. If neither criteria is met, the patient‘s lung is not recruitable. In this case:
- Keep PEEP < 10 cm H2O
- Consider prone positioning
- Borges JB, Okamoto VN, Matos GF, Caramez MP, Arantes PR, Barros F, … Amato MB. Reversibility Of Lung Collapse And Hypoxemia In Early Acute Respiratory Distress Syndrome. Am J Respir Crit Care Med 174.3 (2006):268-278.
- Gattinoni L, Caironi P, Cressoni M, Chiumello D, Ranieri VM, Quintel M, … Bugedo G. Lung Recruitment In Patients With The Acute Respiratory Distress Syndrome. New England Journal of Medicine 354.17(2006): 1775-1786.
- Maggiore SM, Jonson B, Richard JC, Jaber S, Lemaire F, Brochard L. Alveolar Derecruitment at Decremental Positive End-Expiratory Pressure Levels in Acute Lung Injury. Am J Respir Crit Care Med 164.5(2001): 795-801. Web.
- Grasso S, Fanelli V, Cafarelli A, Anaclerio R, Amabile M, Ancona G, Fiore T. Effects Of High Versus Low Positive End-Expiratory Pressures In Acute Respiratory Distress Syndrome. Am J Respir Crit Care Med 171.9 (2005): 1002-1008.
- Demory D, Arnal JM, Wysocki M, Donati S, Granier I, Corno G, Durand-Gasselin J. Recruitability Of The Lung Estimated By The Pressure Volume Curve Hysteresis In ARDS Patients. Intensive Care Med 24.11 (2008): 2019-2025.
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