title: Respiratory mechanics and lung stress/strain in children with acute respiratory distress syndrome.
abstract: BACKGROUND
  In sedated and paralyzed children with acute respiratory failure, the compliance of respiratory system and functional residual capacity were significantly reduced compared with healthy subjects. However, no major studies in children with ARDS have investigated the role of different levels of PEEP and tidal volume on the partitioned respiratory mechanic (lung and chest wall), stress (transpulmonary pressure) and strain (inflated volume above the functional residual capacity).
  
  
  METHODS
  The end-expiratory lung volume was measured using a simplified closed circuit helium dilution method. During an inspiratory and expiratory pause, the airway and esophageal pressure were measured. Transpulmonary pressure was computed as the difference between airway and esophageal pressure.
  
  
  RESULTS
  Ten intubated sedated paralyzed healthy children and ten children with ARDS underwent a PEEP trial (4 and 12 cmH2O) with a tidal volume of 8, 10 and 12 ml/kgIBW. The two groups were comparable for age and BMI (2.5 [1.0-5.5] vs 3.0 [1.7-7.2] years and 15.1 ± 2.4 vs 15.3 ± 3.0 kg/m(2)). The functional residual capacity in ARDS patients was significantly lower as compared to the control group (10.4 [9.1-14.3] vs 16.6 [11.7-24.6] ml/kg, p = 0.04). The ARDS patients had a significantly lower respiratory system and lung compliance as compared to control subjects (9.9 ± 5.0 vs 17.8 ± 6.5, 9.3 ± 4.9 vs 16.9 ± 4.1 at 4 cmH2O of PEEP and 11.7 ± 5.8 vs 23.7 ± 6.8, 10.0 ± 4.9 vs 23.4 ± 7.5 at 12 cmH2O of PEEP). The compliance of the chest wall was similar in both groups (76.7 ± 30.2 vs 94.4 ± 76.4 and 92.6 ± 65.3 vs 90.0 ± 61.7 at 4 and 12 cmH2O of PEEP). The lung stress and strain were significantly higher in ARDS patients as compared to control subjects and were poorly related to airway pressure and tidal volume normalized for body weight.
  
  
  CONCLUSIONS
  Airway pressures and tidal volume normalized to body weight are poor surrogates for lung stress and strain in mild pediatric ARDS.
  
  
  BACKGROUND
  Clinialtrials.gov NCT02036801. Registered 13 January 2014.
authors: Dipartimento di Anestesia, Rianimazione (Intensiva e Subintensiva) e Terapia del Dolore, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Via F. Sforza 35, Milan, Italy. chiumello@libero.it.|Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy. chiumello@libero.it.
authors: Davide
authors: D
authors: Chiumello
authors: Terapia Intensiva Pediatrica, Dipartimento di Anestesia e Rianimazione, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milan, Italy.
authors: Giovanna
authors: G
authors: Chidini
authors: Terapia Intensiva Pediatrica, Dipartimento di Anestesia e Rianimazione, Fondazione IRCCS Ca' Granda - Ospedale Maggiore Policlinico, Milan, Italy.
authors: Edoardo
authors: E
authors: Calderini
authors: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors: Andrea
authors: A
authors: Colombo
authors: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors: Francesco
authors: F
authors: Crimella
authors: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milan, Italy.
authors: Matteo
authors: M
authors: Brioni
keywords: Acute respiratory distress syndrome; Functional residual capacity; Lung strain; Lung stress; PEEP; Tidal volume; Ventilator-induced lung injury