Research

Electrical impedance tomography compared to positron emission tomography for the measurement of regional lung ventilation: an experimental study

JC Richard^1,2,3 , C Pouzot^2,4 , A Gros¹ , C Tourevieille⁵ , D Lebars⁵ , F Lavenne⁵ , I Frerichs⁶ and C Guérin^1,2,3

¹Service de Réanimation Médicale et d'Assistance Respiratoire, Hôpital de la Croix Rousse 103 Grande Rue de la Croix Rousse, Lyon, 69004, France

²Creatis, Centre National de la Recherche Scientifique Unité Mixte de Recherche 5220 and Institut National de la Santé et de l'Enseignement et de la Recherche Médicale U 630, 7 avenue Jean Capelle, Villeurbanne, 69621 Cedex, France

³Université de Lyon, Université Claude Bernard Lyon 1, 8 avenue Rockefeller, Lyon, 69008, France

⁴Service de Soins Intensifs Animaux et Medecine d'Urgence, Ecole Nationale Vétérinaire de Lyon, 1 Avenue Bourgelat, Marcy L'Etoile, 69280, France

⁵Centre de Recherche Médicale par Emission de Positrons, Imagerie du vivant, 59 Boulevard Pinel, 69003, Lyon, France

⁶Anaesthesiology and Intensive Care Medicine, University Medical Centre Schleswig-Holstein, Kiel, Germany

author email corresponding author email

Critical Care 2009, 13:R82doi:10.1186/cc7900

Published:	29 May 2009

Abstract

Introduction

Electrical impedance tomography (EIT), which can assess regional lung ventilation at the bedside, has never been compared with positron-emission tomography (PET), a gold-standard to quantify regional ventilation. This experiment systematically compared both techniques in injured and non-injured lungs.

Methods

The study was performed in six mechanically ventilated female piglets. In normal lungs, tidal volume (V_T) was randomly changed to 6, 8, 10 and 15 ml/kg on zero end-expiratory pressure (ZEEP), then, at V_T 10 ml/kg, positive end-expiratory pressure (PEEP) was randomly changed to 5, 10 and 15 cmH₂O. Afterwards, acute lung injury (ALI) was subsequently created in three animals by injecting 3 ml/kg hydrochloric acid into the trachea. Then at PEEP 5 cmH₂O, V_T was randomly changed to 8 and 12 ml/kg and PEEP of 10 and 15 cmH₂O applied at V_T 10 ml/kg. EIT and PET examinations were performed simultaneously. EIT ventilation (V_TEIT) and lung volume (V_L) were measured in the anterior and posterior area of each lung. On the same regions of interest, ventilation (V_PET) and aerated lung volume (VA_atten) were determined with PET.

Results

On ZEEP, V_TEIT and V_PET significantly correlated for global (V_TEIT = VPET - 2E-13, R² = 0.95, P < 0.001) and regional (V_TEIT = 0.81V_PET+7.65, R² = 0.63, P < 0.001) ventilation over both conditions. For ALI condition, corresponding R² were 0.91 and 0.73 (P < 0.01). Bias was = 0 and limits of agreement were -37.42 and +37.42 ml/min for global ventilation over both conditions. These values were 0.04 and -29.01 and +29.08 ml/min, respectively, for regional ventilation. Significant correlations were also found between V_L and VA_atten for global (V_L = VA_atten+1E-12, R² = 0.93, P < 0.0001) and regional (V_L = 0.99VA_atten+0.92, R² = 0.65, P < 0.001) volume. For ALI condition, corresponding R² were 0.94 (P < 0.001) and 0.54 (P < 0.05). Bias was = 0 and limits of agreement ranged -38.16 and +38.16 ml for global ventilation over both conditions. These values were -0.24 and -31.96 to +31.48 ml, respectively, for regional ventilation.

Conclusions

Regional lung ventilation and volume were accurately measured with EIT in healthy and injured lungs and validated by simultaneous PET imaging.