Double-lumen tubes and auto-PEEP during one-lung ventilation J. Spaeth, M. Ott, W. Karzai, A. Grimm, S. Wirth, S. Schumann, T. Loop  British Journal of Anaesthesia  Volume 116, Issue 1, Pages 122-130 (January 2016) DOI: 10.1093/bja/aev398 Copyright © 2016 The Author(s) Terms and Conditions

Fig 1 Clinical measurement setup during left-sided one-lung ventilation exemplarily. The right bronchial limb of the double-lumen tube (DLT) is disconnected to the ventilator and opened to atmosphere, while both tracheal and bronchial DLT-cuffs are inflated. Measuring sites for airway pressure (Paw) and flow are at the proximal end of the DLT. Bronchial pressure (Pbronch) is measured via an intraluminal placed bronchial pressure catheter (BPC) ending at the distal end of the DLT’s bronchial limb. Inserted box: Scheme of the manufactured connector for insertion of the BPC. 1+sleeve that fits on the DLT connector, 2+cylinder with internal screw thread and 5+screw with central canal all made of stainless steel; 3+silicon tube; 4+carbon ring. After insertion of the BPC closing of the screw applies circular pressure to the silicon tube which air tightly seals the system to the BPC without compression of the catheters lumen. British Journal of Anaesthesia 2016 116, 122-130DOI: (10.1093/bja/aev398) Copyright © 2016 The Author(s) Terms and Conditions

Fig 2 Assessment and allocation of patients according to the CONSORT (Consolidated Standards of Reporting Trials) Statement. A total of 94 patients awaiting thoracic surgery were assed preoperatively for study eligibility. 83 patients received intervention in one of the study groups referring to the outer diameter (35, 37 and 39 French) of the double-lumen tube (DLT). A total of 72 patients (24 patients in each group) were included in the data analysis. British Journal of Anaesthesia 2016 116, 122-130DOI: (10.1093/bja/aev398) Copyright © 2016 The Author(s) Terms and Conditions

Fig 3 Pressure, flow and volume curves of one representative breath at each applied inspiratory to expiratory ratio (I:E) measured in a male patient (77 kg, 177 cm) intubated with a left sided double-lumen tube (DLT) of 37 French outer diameter, during pressure controlled one-lung ventilation. Pressure-time curves are demonstrated for both airway pressure (Paw; green line) and bronchial pressure (Pbronch; blue line), superimposed by each other. Please note the following: (1) Paw and Pbronch differ by the pressure gradient across the DLT (+ΔPDLT); (2) Shortening of the expiratory time results in a more pronounced increase in end-expiratory Pbronch as compared with the increase in end-expiratory Paw; (3) tidal volume increases as inspiratory time increases until the expiratory time is too short to allow complete expiration. Resulting increased end-expiratory pressure reduces the expiratory driving pressure and thus reduces tidal volume again; (4) grey markers at the end of each breathing cycle indicate the time intervals (50 ms) within the end-expiratory measurements were performed. The levels of auto-PEEPcircuit and auto-PEEPDLT can be estimated within these time intervals from the pressure differences between Paw and PEEP (5 cm H2O) and Pbronch and Paw respectively. British Journal of Anaesthesia 2016 116, 122-130DOI: (10.1093/bja/aev398) Copyright © 2016 The Author(s) Terms and Conditions

Fig 4 Auto-PEEP calculated in double-lumen tubes (DLT) of 35, 37 and 39 French outer diameter at a certain inspiratory to expiratory ratio (I:E) during one-lung ventilation. Each bar represents mean (sd) based on data measured in 12 patients. Total auto-PEEP (auto-PEEPtotal) is demonstrated for DLT’s right (blue bars) and left (green bars) sided bronchial limb. Superimposed striped bars indicate the share of DLT-related auto-PEEP (auto-PEEPDLT) within the total auto-PEEP at the respective DLT and I:E ratio. *P<0.05; **P<0.001 compared with the corresponding values at I:E+1:2. British Journal of Anaesthesia 2016 116, 122-130DOI: (10.1093/bja/aev398) Copyright © 2016 The Author(s) Terms and Conditions