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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 PaO 2 /FiO 2 ratio). Three PEEP levels (zero = ZEEP, 4-8 cmH 2 O = 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] cmH 2 O and lung elastance (E L ) 44 [40-51] cmH 2 O/L. At PEEP LOW , P L,EE remained negative and E L did not change (p = 0.995) versus ZEEP. At PEEP TITRATED , P L,EE increased to 0.8 [0.3-1.5] cmH 2 O and E L to 49 [43-59] (p = 0.004 and p < 0.001 compared to ZEEP and PEEP LOW , respectively). ΔP L decreased at PEEP LOW (p = 0.018) and increased at PEEP TITRATED (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., (© 2023. BioMed Central Ltd., part of Springer Nature.)

Background: In acute respiratory distress syndrome (ARDS), response to positive end-expiratory pressure (PEEP) is variable according to different degrees of lung recruitability. The search for a tool to individualize PEEP based on patients' individual response is warranted. End-expiratory lung volume (EELV) assessment by nitrogen washing-washout aids bedside estimation of PEEP-induced alveolar recruitment and may therefore help titrate PEEP on patient's individual recruitability. We designed a randomized trial to test whether an individualized PEEP setting protocol driven by EELV measurement may improve a composite clinical outcome in patients with moderate-to-severe ARDS (IPERPEEP trial)., Methods: IPERPEEP is an open-label, multicenter, randomized trial that will be conducted in 10 intensive care units in Italy and will enroll 132 ARDS patients showing PaO 2 /FiO 2 ratio ≤ 150 mmHg within 24 h from endotracheal intubation while on mechanical ventilation with PEEP 5 cmH 2 O. To standardize lung volumes at study initiation, all patients will undergo mechanical ventilation with tidal volume of 6 ml/kg of predicted body weight and PEEP set to obtain a plateau pressure within 28 and 30 cmH 2 O for 30 min (EXPRESS PEEP). Afterwards, a 5-step decremental PEEP trial will be conducted (EXPRESS PEEP to PEEP 5 cmH 2 O), and EELV will be measured at each step. Recruitment-to-inflation ratio will be calculated for each PEEP range from EELV difference. Patients will be then randomized to receive mechanical ventilation with PEEP set according to the optimal recruitment observed in the PEEP trial (IPERPEEP arm) trial or to achieve a plateau pressure of 28-30 cmH 2 O (control arm, EXPRESS strategy). In both groups, tidal volume size, use of prone positioning and neuromuscular blocking agents, and weaning from PEEP and from mechanical ventilation will be standardized. The primary endpoint of the study is a composite clinical outcome incorporating in-ICU mortality, 60-day ventilator-free days, and serum interleukin-6 concentration over the course of the initial 72 h of treatment., Discussion: The IPERPEEP study is a randomized trial powered to elucidate whether an individualized PEEP setting protocol based on bedside assessment of lung recruitability can improve a composite clinical outcome during moderate-to-severe ARDS., Trial Registration: ClinicalTrials.gov NCT04012073 . Registered 9 July 2019., (© 2022. The Author(s).)

Objectives: Clinical observation suggests that early acute respiratory distress syndrome induced by the severe acute respiratory syndrome coronavirus 2 may be "atypical" due to a discrepancy between a relatively unaffected static respiratory system compliance and a significant hypoxemia. This would imply an "atypical" response to the positive end-expiratory pressure., Design: Single-center, unblinded, crossover study., Setting: ICU of Bari Policlinico Academic Hospital (Italy), dedicated to care patients with confirmed diagnosis of novel coronavirus disease 2019., Patients: Eight patients with early severe acute respiratory syndrome coronavirus 2 acute respiratory distress syndrome and static respiratory compliance higher than or equal to 50 mL/cm H2O., Interventions: We compared a "lower" and a "higher" positive end-expiratory pressure approach, respectively, according to the intervention arms of the acute respiratory distress syndrome network and the positive end-expiratory pressure setting in adults with acute respiratory distress syndrome studies., Measurements and Main Results: Patients were ventilated with the acute respiratory distress syndrome network and, subsequently, with the ExPress protocol. After 1 hour of ventilation, for each protocol, we recorded arterial blood gas, respiratory mechanics, alveolar recruitment, and hemodynamic variables. Comparisons were performed with analysis of variance for repeated measures or Friedman test as appropriate. Positive end-expiratory pressure was increased from 9 ± 3.5 to 17.7 ± 1.7 cm H2O (p < 0.01). Alveolar recruitment was 450 ± 111 mL. Static respiratory system compliance decreased from 58.3 ± 7.6 mL/cm H2O to 47.4 ± 14.5 mL/cm H2O (p = 0.018) and the "stress index" increased from 0.97 ± 0.03 to 1.22 ± 0.07 (p < 0.001). The PaO2/FIO2 ratio increased from 131 ± 22 to 207 ± 41 (p < 0.001), and the PaCO2 increased from 45.9 ± 12.7 to 49.8 ± 13.2 mm Hg (p < 0.001). The cardiac index went from 3.6 ± 0.4 to 2.9 ± 0.6 L/min/m (p = 0.01)., Conclusions: Our data suggest that the "higher" positive end-expiratory pressure approach in patients with severe acute respiratory syndrome coronavirus 2 acute respiratory distress syndrome and high compliance improves oxygenation and lung aeration but may result in alveolar hyperinflation and hemodynamic alterations.

Objectives: Quantification of potential for lung recruitment may guide the ventilatory strategy in acute respiratory distress syndrome. However, there are no quantitative data on recruitability in patients with severe acute respiratory distress syndrome who require extracorporeal membrane oxygenation. We sought to quantify potential for lung recruitment and its relationship with outcomes in this cohort of patients., Design: A single-center, retrospective, observational cohort study., Setting: Tertiary referral severe respiratory failure center in a university hospital in the United Kingdom., Patients: Forty-seven adults with severe acute respiratory distress syndrome requiring extracorporeal membrane oxygenation., Intervention: None., Measurements and Main Results: In patients with severe acute respiratory distress syndrome-mainly of pulmonary origin (86%)-the potential for lung recruitment and the weight of nonaerated, poorly aerated, normally aerated, and hyperaerated lung tissue were assessed at low (5 cmH2O) and high (45 cmH2O) airway pressures. Patients were categorized as high or low potential for lung recruitment based on the median potential for lung recruitment value of the study population. The median potential for lung recruitment was 24.3% (interquartile range = 11.4-37%) ranging from -2% to 76.3% of the total lung weight. Patients with potential for lung recruitment above the median had significantly shorter extracorporeal membrane oxygenation duration (8 vs 13 d; p = 0.013) and shorter ICU stay (15 vs 22 d; p = 0.028), but mortality was not statistically different (24% vs 46%; p = 0.159)., Conclusions: We observed significant variability in potential for lung recruitment in patients with severe acute respiratory distress syndrome requiring extracorporeal membrane oxygenation. Patients with high potential for lung recruitment had a shorter ICU stay and shorter extracorporeal membrane oxygenation duration.