Patients with pulmonary fibrosis and associated usual interstitial pneumonia that require mechanical ventilation for acute respiratory failure experience poor clinical outcomes. This may be influenced by the unfavorable interaction between the fibrotic lung and the stress and strain stimuli generated during controlled ventilation. Although there is no consensus on how to ventilate these patients, much of the recommendations followed in clinical practice are taken from the experience on patients with acute respiratory distress syndrome. Among these, measuring the esophageal pressures and adjusting positive-end expiatory pressure to make trans-pulmonary pressures positive can decrease atelectasis, derecruitment of lung, and cyclical opening and closing of airways and alveoli, thus optimizing lung mechanics and oxygenation. The effect of this strategy on the fibrotic lung has not yet been documented. With this observational study we aim at documenting the effect of PEEP titration maneuver based on end-expiratory trans-pulmonary pressure on lung mechanics of patients with pulmonary fibrosis and UIP pattern,