title: Drainage of pleural effusion in mechanically ventilated patients: time to measure chest wall compliance?
abstract: OBJECTIVE
  Pleural effusion (PE) is commonly encountered in mechanically ventilated, critically ill patients and is generally addressed with evacuation or by fluid displacement using increased airway pressure (P(AW)). However, except when massive or infected, clear evidence is lacking to guide its management. The aim of this study was to investigate the effect of recruitment maneuvers and drainage of unilateral PE on respiratory mechanics, gas exchange, and lung volume.
  
  
  METHODS
  Fifteen critically ill and mechanically ventilated patients with unilateral PE were enrolled. A 3-step protocol (baseline, recruitment, and effusion drainage) was applied to patients with more than 400 mL of PE, as estimated by chest ultrasound. Predefined subgroup analysis compared patients with normal vs reduced chest wall compliance (C(CW)). Esophageal and P(AW)s, respiratory system, lung and C(CW)s, arterial blood gases, and end-expiratory lung volumes were recorded.
  
  
  RESULTS
  In the whole case mix, neither recruitment nor drainage improved gas exchange, lung volume, or tidal mechanics. When C(CW) was normal, recruitment improved lung compliance (81.9 [64.8-104.1] vs 103.7 [91.5-111.7] mL/cm H2O, P < .05), whereas drainage had no significant effect on total respiratory system mechanics or gas exchange, although it measurably increased lung volume (1717 vs 2150 mL, P < .05). In the setting of reduced C(CW), however, recruitment had no significant effect on total respiratory system mechanics or gas exchange, whereas pleural drainage improved respiratory system and C(CW)s as well as lung volume (42.7 [38.9-50.0] vs 47.0 [43.8-63.3], P < .05 and 97.4 [89.3-97.9] vs 126.7 [92.3-153.8] mL/cm H2O, P < .05 and 1580 vs 1750 mL, P < .05, respectively).
  
  
  CONCLUSIONS
  Drainage of a moderate-sized effusion should not be routinely performed in unselected population of critically ill patients. We suggest that measurement of C(CW) may help in the decision-making process.
authors.affiliation: Unità Operativa di Anestesia e Rianimazione, Azienda Ospedaliera San Paolo-Polo Universitario, Milano, Italy. Electronic address: formenti.paolo80@gmail.com.
authors.forename: Paolo
authors.initials: P
authors.lastname: Formenti
authors.affiliation: Unità Operativa di Anestesia e Rianimazione, Azienda Ospedaliera San Paolo-Polo Universitario, Milano, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Umbrello
authors.affiliation: Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy.
authors.forename: Ilaria R
authors.initials: IR
authors.lastname: Piva
authors.affiliation: Unità Operativa di Anestesia e Rianimazione, Azienda Ospedaliera San Paolo-Polo Universitario, Milano, Italy; Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Mistraletti
authors.affiliation: Dipartimento di Neuroscienze, Azienda Ospedaliera Ospedale Niguarda Ca' Granda, Milano, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Zaniboni
authors.affiliation: Unità Operativa di Anestesia e Rianimazione, Azienda Ospedaliera San Paolo-Polo Universitario, Milano, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Spanu
authors.affiliation: Unità Operativa di Anestesia e Rianimazione, Azienda Ospedaliera San Paolo-Polo Universitario, Milano, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Noto
authors.affiliation: Department of Pulmonary and Critical Care, University of Minnesota, Regions Hospital, St Paul, MN, USA.
authors.forename: John J
authors.initials: JJ
authors.lastname: Marini
authors.affiliation: Unità Operativa di Anestesia e Rianimazione, Azienda Ospedaliera San Paolo-Polo Universitario, Milano, Italy; Dipartimento di Fisiopatologia Medico-Chirurgica e dei Trapianti, Università degli Studi di Milano, Milano, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Iapichino
mesh_terms: D000368:Aged; D001784:Blood Gas Analysis; D016638:Critical Illness; D004322:Drainage / Q000379:methods*; D005260:Female; D006801:Humans; D008170:Lung Compliance; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D010996:Pleural Effusion / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency / Q000503:physiopathology / Q000628:therapy; D015656:Respiratory Mechanics / Q000502:physiology*; D016683:Supine Position; D035441:Thoracic Wall / Q000503:physiopathology; D013990:Tidal Volume; D014463:Ultrasonography
keywords: Chest wall and lung compliance; End-expiratory lung volume; Esophageal pressure; Mechanical ventilation; Pleural effusion; Transpulmonary pressure