Physiological effects of lung-protective ventilation in patients with lung fibrosis and usual interstitial pneumonia pattern versus primary ARDS: a matched-control study

Background: Although patients with interstitial pneumonia pattern (ILD-UIP) and acute exacerbation (AE) leading to severe acute respiratory failure may require invasive mechanical ventilation (MV), physiological data on lung mechanics during MV are lacking. We aimed at describing the physiological effect of lung-protective ventilation in patients with AE-ILD-UIP compared with primary ARDS. Methods: Partitioned lung and chest wall mechanics were assessed in a series of AE-ILD-UIP patients matched 1:1 with primary ARDS as controls (based on BMI and PaO2/FiO2 ratio). Three PEEP levels (zero = ZEEP, 4–8 cmH2O = PEEP LOW, and titrated to achieve positive end-expiratory transpulmonary pressure P L,EE = PEEP TITRATED) were used for measurements. Results: Ten AE-ILD-UIP patients and 10 matched ARDS were included. In AE-ILD-UIP median P L,EE at ZEEP was − 4.3 [− 7.6– − 2.3] cmH2O and lung elastance (E L) 44 [40–51] cmH2O/L. At PEEPLOW, P L,EE remained negative and E L did not change (p = 0.995) versus ZEEP. At PEEPTITRATED, P L,EE increased to 0.8 [0.3–1.5] cmH2O and E L to 49 [43–59] (p = 0.004 and p < 0.001 compared to ZEEP and PEEPLOW, respectively). ΔP L decreased at PEEPLOW (p = 0.018) and increased at PEEPTITRATED (p = 0.003). In matched ARDS control PEEP titration to obtain a positive P L,EE did not result in significant changes in E L and ΔP L. Conclusions: In mechanically ventilated AE-ILD-UIP patients, differently than in patients with primary ARDS, PEEP titrated to obtain a positive P L,EE significantly worsened lung mechanics.