title: Lung Recruitment Assessed by Respiratory Mechanics and Computed Tomography in Patients with Acute Respiratory Distress Syndrome. What Is the Relationship?
abstract: The assessment of lung recruitability in patients with acute respiratory distress syndrome (ARDS) may be important for planning recruitment maneuvers and setting positive end-expiratory pressure (PEEP).
  
  
  
  To determine whether lung recruitment measured by respiratory mechanics is comparable with lung recruitment measured by computed tomography (CT).
  
  
  
  In 22 patients with ARDS, lung recruitment was assessed at 5 and 15 cm H2O PEEP by using respiratory mechanics-based methods: (1) increase in gas volume between two pressure-volume curves (P-Vrs curve); (2) increase in gas volume measured and predicted on the basis of expected end-expiratory lung volume and static compliance of the respiratory system (EELV-Cst,rs); as well as by CT scan: (3) decrease in noninflated lung tissue (CT [not inflated]); and (4) decrease in noninflated and poorly inflated tissue (CT [not + poorly inflated]).
  
  
  
  The P-Vrs curve recruitment was significantly higher than EELV-Cst,rs recruitment (423 ± 223 ml vs. 315 ± 201 ml; P < 0.001), but these measures were significantly related to each other (R(2) = 0.93; P < 0.001). CT (not inflated) recruitment was 77 ± 86 g and CT (not + poorly inflated) was 80 ± 67 g (P = 0.856), and these measures were also significantly related to each other (R(2) = 0.20; P = 0.04). Recruitment measured by respiratory mechanics was 54 ± 28% (P-Vrs curve) and 39 ± 25% (EELV-Cst,rs) of the gas volume at 5 cm H2O PEEP. Recruitment measured by CT scan was 5 ± 5% (CT [not inflated]) and 6 ± 6% (CT [not + poorly inflated]) of lung tissue.
  
  
  
  Respiratory mechanics and CT measure-under the same term, "recruitment"-two different entities. The respiratory mechanics-based methods include gas entering in already open pulmonary units that improve their mechanical properties at higher PEEP. Consequently, they can be used to assess the overall improvement of inflation. The CT scan measures the amount of collapsed tissue that regains inflation. Clinical trial registered with www.clinicaltrials.gov (NCT00759590).
authors.affiliation: 1 Dipartimento di Anestesia, Rianimazione ed Emergenza-Urgenza, Fondazione IRCCS Cà Granda - Ospedale Maggiore Policlinico, Milano, Italy.|2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Davide
authors.initials: D
authors.lastname: Chiumello
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Antonella
authors.initials: A
authors.lastname: Marino
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Matteo
authors.initials: M
authors.lastname: Brioni
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Irene
authors.initials: I
authors.lastname: Cigada
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Federica
authors.initials: F
authors.lastname: Menga
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Andrea
authors.initials: A
authors.lastname: Colombo
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Francesco
authors.initials: F
authors.lastname: Crimella
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Algieri
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Massimo
authors.initials: M
authors.lastname: Cressoni
authors.affiliation: 2 Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy; and.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Carlesso
authors.affiliation: 3 Department of Anesthesiology and Intensive Care Medicine, Georg-August-University of Goettingen, Goettingen, Germany.
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D008170:Lung Compliance; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D012128:Respiratory Distress Syndrome / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D015656:Respiratory Mechanics / Q000502:physiology*; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: acute respiratory distress syndrome; lung computed tomographic scan; lung recruitment; pressure–volume curve; respiratory system compliance