title: Esophageal pressure measurements under different conditions of intrathoracic pressure. An in vitro study of second generation balloon catheters.
abstract: BACKGROUND
  The aim of this study was to evaluate in vitro the accuracy of second generation esophageal catheters at different surrounding pressures and filling volumes and to suggest appropriate catheter management in clinical practice.
  
  
  METHODS
  Six different esophageal catheters were placed in an experimental chamber at four chamber pressures (0, 10, 20 and 30 cmH2O) and at filling volumes ranging from 0 to 10 mL. The working volume was defined as the volume range between the maximum (Vmax) and minimum (Vmin) volumes achieving acceptable accuracy (defined by a balloon transmural pressure ± 1 cmH2O). Accuracy was evaluated for a standard volume of 0.5 mL and for volumes recommended by manufacturers. Data are shown as median and interquartile range.
  
  
  RESULTS
  In the four conditions of chamber pressure Vmin, Vmax and working volume were 1.0 (0.5, 1.5), 5.3 (3.8, 7.1), and 3.5 (2.9, 6.1) mL. Increasing chamber pressure increased Vmin (rho=0.9; P<0.0001), that reached 2.0 mL (1.6-2.0) at 30 cmH2O. Vmax and working volumes differed among catheters, whereas Vmin did not. By injecting 0.5 mL and the minimum recommended volume by manufacturer, balloon transmural pressure was <-1 cmH2O in 71% and 53% of cases, it was negatively related to chamber pressure (rho=-0.97 and -0.71; P<0.0001) and reached values of -10.4 (-12.4, -9.7) and -9.8 (-10.6, -3.4) at 30 cmH2O.
  
  
  CONCLUSIONS
  Measuring positive esophageal pressures needs higher injected volumes than usually recommended. The range of appropriate filling volumes is catheter-specific. Both absolute values and respiratory changes of esophageal pressure can be underestimated by an underfilled balloon.
authors: Sezione di Anestesia Rianimazione e Terapia Antalgica, Dipartimento di Scienze Clinico-chirurgiche, Diagnostiche e Pediatriche, SC Anestesia e Rianimazione 1, Università degli Studi di Pavia, Fondazione IRCCS Policlinico S. Matteo, Pavia, Italy - chiumello@libero.it.
authors: F
authors: F
authors: Mojoli
authors: D
authors: D
authors: Chiumello
authors: M
authors: M
authors: Pozzi
authors: I
authors: I
authors: Algieri
authors: S
authors: S
authors: Bianzina
authors: S
authors: S
authors: Luoni
authors: C A
authors: CA
authors: Volta
authors: A
authors: A
authors: Braschi
authors: L
authors: L
authors: Brochard
mesh_terms: D002404:Catheterization / Q000379:methods*; D057785:Catheters; D004947:Esophagus; D006801:Humans; D011312:Pressure; D015203:Reproducibility of Results; D015656:Respiratory Mechanics