Repeated distal airway closure occurs during tidal ventilation in a significant proportion of mechanically ventilated ARDS patients due to a narrowing of the distal airways and surfactant depletion. It may cause damage to the distal airways and induce inflammation.
In the case of complete airway closure, the total PEEP measured and the related calculations of driving pressures, static compliance, and recruitment-to-inflation ratio are misleading. Therefore, it is important to detect airway closure and set PEEP above the airway opening pressure.
Complete airway closure may be apparent on the inflation limb of a low-flow PV curve.
Using the P/V Tool® Pro on Hamilton Medical ventilators*, normal settings for the PV curve are as follows: Pstart = 0–5 cmH2O, Ptop = 40 cmH2O, End PEEP= 0-5 cmH2O, Ramp speed = 2 cmH2O/s, Tpause = 0.
If the volume increases immediately in the first part of the inflation limb, there is no airway closure (Figure 1).
If the initial part of the inflation limb is flat, with an increase in pressure but no increase in volume, this suggests complete airway closure. The blue arrow shows the start of inflation which occurs when airway pressure equals the airway opening pressure (AOP). AOP should be measured with the cursor, in order to set PEEP above that value (Figure 2).
* Available as an option on HAMILTON-G5 and HAMILTON-C3/C6 ventilators; standard on the HAMILTON-S1. Not all ventilators available in all markets.
Chen L, Del Sorbo L, Grieco DL, Shklar O, Junhasavasdikul D, Telias I, Fan E, Brochard L. Airway Closure in Acute Respiratory Distress Syndrome: An Underestimated and Misinterpreted Phenomenon. Am J Respir Crit Care Med. 2018 Jan 1;197(1):132-136
Hedenstierna G, Chen L, Brochard L. Airway closure, more harmful than atelectasis in intensive care? Intensive Care Med. 2020 Dec;46(12):2373-2376.
Coudroy R, Lu C, Chen L, Demoule A, Brochard L. Mechanism of airway closure in acute respiratory distress syndrome: a possible role of surfactant depletion. Intensive Care Med. 2019 Feb;45(2):290-291.
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