Inspiratory Effort and Respiratory Mechanics in Patients with Acute Exacerbation of Idiopathic Pulmonary fibrosis: A Preliminary Matched Control Study

Background: Patients with acute exacerbation of idiopathic pulmonary fibrosis (AE-IPF) may experience severe acute respiratory failure, even requiring ventilatory assistance. Physiological data on lung mechanics during these events are lacking.

Methods: Patients with AE-IPF admitted to Respiratory Intensive Care Unit to receive non-invasive ventilation (NIV) were retrospectively analyzed. Esophageal pressure swing (ΔP_es) and respiratory mechanics before and after 2 hours of NIV were collected as primary outcome. The correlation between positive end-expiratory pressure (PEEP) levels and changes of in dynamic compliance (dynC_RS) and PaO₂/FiO₂ ratio was assessed. Further, an exploratory comparison with a historical cohort of ARDS patients matched 1:1 by age, sequential organ failure assessment score, body mass index and PaO₂/FiO₂ level was performed.

Results: At baseline, AE-IPF patients presented a high respiratory drive activation with ΔPes = 27 (21-34) cmH2O, respiratory rate (RR) = 34 (30-39) bpm and minute ventilation (VE) = 21 (20-26) L/min. Two hours after NIV application, ΔPes, RR and VE values showed a significant reduction (16 [14-24] cmH2O, p<0.0001, 27 [25-30] bpm, p=0.001, and 18 [17-20] L/min, p=0.003, respectively) while no significant change was found in dynamic transpulmonary pressure, expiratory tidal volume (Vte), dynCRS and dynamic mechanical power. PEEP levels negatively correlated with PaO₂/FiO₂ ratio and dynC_RS (r=-0.67, p=0.03 and r=-0.27, p=0.4, respectively). When compared to AE-IPF, ARDS patients presented lower baseline ΔP_es, RR, VE and dynamic mechanical power. Differently from AE-IPF, in ARDS both Vte and dynC_RS increased significantly following NIV (p=0.01 and p=0.004 respectively) with PEEP levels directly associated with PaO₂/FiO₂ ratio and dynC_RS (r=0.24, p=0.5 and r=0.65, p=0.04, respectively).

Conclusions: In this study, patients with AE-IPF showed a high inspiratory effort, whose intensity was reduced by NIV application without a significant improvement in respiratory mechanics. In an exploratory analysis, AE-IPF patients showed a different mechanical behavior under spontaneous unassisted and assisted breathing compared with ARDS patients of similar severity.