Detecting complete airway closure in mechanically ventilated patients

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 (Available as an option on HAMILTON-G5 and HAMILTON-C3/C6 ventilatorsA​, Standard on the HAMILTON-S1B​), 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 (see Figure 1 below).

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 (see Figure 2 below).

Full citations see below: (Chen L, Del Sorbo L, Grieco DL, et al. Airway Closure in Acute Respiratory Distress Syndrome: An Underestimated and Misinterpreted Phenomenon. Am J Respir Crit Care Med. 2018;197(1):132-136. doi:10.1164/rccm.201702-0388LE1​, Hedenstierna G, Chen L, Brochard L. Airway closure, more harmful than atelectasis in intensive care?. Intensive Care Med. 2020;46(12):2373-2376. doi:10.1007/s00134-020-06144-w2​, 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;45(2):290-291. doi:10.1007/s00134-018-5501-53​)