• J Spaeth, M Ott, W Karzai, A Grimm, S Wirth, S Schumann, and T Loop.
• Department of Anaesthesiology and Intensive Care Medicine, University Medical Center Freiburg, Hugstetter Str. 55, Freiburg 79106, Germany johannes.spaeth@uniklinik-freiburg.de.
• Br J Anaesth. 2016 Jan 1; 116 (1): 122-30.

BackgroundDouble-lumen tubes (DLT) are routinely used to enable one-lung-ventilation (OLV) during thoracic anaesthesia. The flow-dependent resistance of the DLT's bronchial limb may be high as a result of its narrow inner diameter and length, and thus potentially contribute to an unintended increase in positive end-expiratory pressure (auto-PEEP). We therefore studied the impact of adult sized DLTs on the dynamic auto-PEEP during OLV.MethodsIn this prospective clinical study, dynamic auto-PEEP was determined in 72 patients undergoing thoracic surgery, with right- and left-sided DLTs of various sizes. During OLV, air trapping was provoked by increasing inspiration to expiration ratio from 1:2 to 2:1 (five steps). Based on measured flow rate, airway pressure (Paw) and bronchial pressure (Pbronch), the pressure gradient across the DLT (ΔPDLT) and the total auto-PEEP in the respiratory system (i.e. the lungs, the DLT and the ventilator circuit) were determined. Subsequently the DLT's share in total auto-PEEP was calculated.ResultsΔPDLT was 2.3 (0.7) cm H2O over the entire breathing cycle. At the shortest expiratory time the mean total auto-PEEP was 2.9 (1.5) cm H2O (range 0-5.9 cm H2O). The DLT caused 27 to 31% of the total auto-PEEP. Size and side of the DLT's bronchial limb did not impact auto-PEEP significantly.ConclusionsAlthough the DLT contributes to the overall auto-PEEP, its contribution is small and independent of size and side of the DLT's bronchial limb. The choice of DLT does not influence the risk of auto-PEEP during OLV to a clinically relevant extent.Clinical Trial RegistrationDRKS00005648.© The Author 2015. Published by Oxford University Press on behalf of the British Journal of Anaesthesia. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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