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The following is a summary of “Distribution of airway pressure opening in the lungs measured with electrical impedance tomography (POET): a prospective physiological study,” published in the January 2025 issue of Critical Care by Sun et al. 

Change in pressure slope during low-flow insufflation in patients with acute hypoxemic respiratory failure (AHRF) on mechanical ventilation indicates the global airway opening pressure (AOP) needed to reopen collapsed airways and can be used to titrate positive end-expiratory pressure.  

Researchers conducted a retrospective study to determine whether airways opened homogeneously or significant regional AOP variations existed and if pressure slope changes during low-flow insufflation indicated such variations.  

They recorded low-flow insufflation maneuvers (<10 L/min) starting from end-expiratory positive pressure of 0–5 cmH₂O using electrical impedance tomography. Global (AOP_global) and regional AOPs were measured from pressure-impedance curves across 4 lung quadrants, comparing AOP_global with the highest quadrantal AOP (AOP_highest). The slope change of the pressure-time curve during low-flow inflation was classified into 3 patterns: no change, progressive change, and abrupt change.  

The results showed that, among 36 individuals analyzed, 9 (25%) had AOP_global ≥5 cmH₂O, while 19 (53%) showed regional AOP_highest ≥5 cmH₂O. The AOP_global was similar to the AOP of the upper right quadrant (P=0.182) but lower than the other 3 quadrants (P <0.01 for each). AOP_global was significantly lower than AOP_highest: 3.0 [2.0–4.3] vs 5.0 [2.8–8.3] cmH₂O, P <0.001,  AOP was higher in the dependent than non-dependent lung (4.0 [2.0–6.3] vs 3.0 [2.0–5.0] cmH₂O, P <0.001) and 17 (47%) individuals had a ‘progressive change’ pattern in the pressure-time curve, showing a larger difference between AOP_highest and AOP_global (3.0 [2.0–4.0] cmH₂ O, max 8 cmH₂O) compared to the ‘no change’ (1.0 [0–1.0] cmH₂ O, P <0.001) and ‘abrupt change’ patterns (1.0 [0–2.0] cmH₂O, P =0.003).  

Investigators concluded that AOP_global primarily reflected the lowest opening pressure within the lung and often underestimated the highest regional AOP in patients with AHRF on mechanical ventilation, while a progressive slope change during the low-flow pressure-time curve suggested the presence of multiple and higher regional AOPs. 

Source: ccforum.biomedcentral.com/articles/10.1186/s13054-025-05264-3