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The following is a summary of “Inter-lung asymmetrical airway closure cause insufflation delay between lungs in acute hypoxemic respiratory failure,” published in the October 2024 issue of Critical Care by Rozé et al. 

Electrical Impedance Tomography (EIT) quantified ventilation in both lungs and measured the airway opening pressure (AOP) for each lung, with asymmetrical AOPs potentially causing inter-lung insufflation delays.  

Researchers conducted a retrospective study to examine the association between AOP asymmetry and inter-lung insufflation delay at varying levels of positive end-expiratory pressure (PEEP).  

They included individuals with acute hypoxemic respiratory failure and airway closure. Low-flow pressure-volume curves and EIT signals were recorded during controlled ventilation and, for some individuals, during pressure support ventilation.  

The results showed that 23 individuals were studied, with 22 diagnosed with ARDS, among these, 9 had asymmetrical airway closure, exhibiting an AOP of 10 [6–13] cmH₂O in the affected lung (AOP_sicker) compared to 5 [3–9] cmH₂O in the healthier lung. During low-flow inflation, the inter-lung inflation delay was 0 [0-112] ms for those without asymmetry vs 1450 [375–2400] ms for individuals with asymmetrical AOPs (P < 0.0001). This delay significantly correlated with the AOP difference between the 2 lungs (Spearman R² = 0.800, P < 0.0001). During tidal ventilation, the median delay was 0 [0–62] ms in patients without asymmetry vs 150 [50–355] ms in those with asymmetry (P = 0.019), adjusting PEEP at the decremental EIT-based PEEP trial crossing point reduced inter-lung insufflation delay. In patients with asymmetrical lung injury, insufflation delay was measurable during pressure support and decreased by increasing PEEP from 5 to 10 cmH₂O.  

They concluded that in asymmetrical airway closure, titrating PEEP can minimize inter-lung insufflation delay and can be monitored by EIT. Additionally, this approach can reduce ventilation asymmetry during pressure support ventilation, even in the absence of low-flow inflation curves. 

Source: annalsofintensivecare.springeropen.com/articles/10.1186/s13613-024-01379-y