Abstract

Background

Although patients with AE-ILD and UIP patternmay experience severe acute respiratory failure requiring invasive MV, physiological data on lung mechanics during these events are lacking. We aimed to describe the physiological effect of lung protective ventilation in patients with AE-ILD-UIP and to compare it with primary ARDS.

Methods

Partitioned lung and chest wall mechanics were compared between patients AE-ILD-UIP and 1:1 matched primary ARDS (based on BMI and PaO2/FiO2 ratio) within a PEEP trial performed within 24 h from intubation and comprising three levels of PEEP [(ZEEP), 4-8 cmH2O (PEEPLOW) and PEEP titrated to achieve positive end-expiratory transpulmonary pressure (PL,EE) (PEEPTITRATED)]

Results

Ten patients with AE-ILD-UIP and 10 matched with primary ARDS were included. In AE-ILD-UIP median PL,EEat ZEEP was - 4.3 [-7.6 ? -2.3] cmH2O and lung elastance (EL) 44 [40 ? 51] cmH2O/L. At PEEPLOW, PL,EEremained negative and EL did not change (p=0.995) versus ZEEP. At PEEPTITRATED, PL,EE increased to 0.8 [0.3 ? 1.5] cmH2O and EL to 49 [59 ? 43] (p=0.004 and p<0.001 compared to ZEEP and PEEPLOW, respectively). DPL decreased at PEEPLOW (p=0.018) and increased at PEEPTITRATED (p=0.003). Differently than AE-ILD-UIP, in ARDS matched controls PEEP titration to obtain a positive PL,EE did not result in changes in EL and DPL.

Conclusions
In mechanically ventilated AE-ILD-UIP, lower PEEP levels did not impact on EL and DPL whereas, differentlythan in patients with primary ARDSPEEP titrated to obtain a positive PL,EE worsened EL and DPL.