Introduction Oesophageal balloon catheters (OBCs) are commonly used to measure oesophageal pressure as a surrogate of pleural pressure. This pressure is used to calculate trans- diaphragmatic or transpulmonary pressure and subse- quently derived parameters such as work of breathing or pressure-time product [1]. However, processing of very fast pressure signals (e. g., diaphragmatic response to phrenic nerve stimulation [2]) requires a fast pressure signal transmission for a correct calculation. To evaluate the accuracy of pressure transmission we measured the pressure transmission time (Tt) of five commercially available OBCs in a laboratory setting. Material and methods Commercially available OBCs from five manufacturers were test- ed: Bicore, USA (BI); International Medical, Netherlands (IN); Mallinckrodt, Ireland (MA); Morgan, Great Britain (MO); Rüsch, Germany (RÜ) (for product data see Table 1). The BI, RÜ and MA OBCs are integrated in a naso-gastric tube while the IN and MO OBCs are designed for measurement purposes only. The BI OBC is part of an automatic lung function monitoring system [4]. The RÜ OBC is the only one out of the OBCs tested which has a second balloon at its tip to allow the additional measurement of gastric pressure. Each OBC was connected via a 180-cm (4.0-mm diameter) plastic tube (the same as the control tube, see below) to a pressure transducer (Huba Control, Switzerland). After having been filled with 1 ml of air the OBC was placed in an airtight latex balloon. This balloon was filled with air up to a pressure of 17.5 cmH 2 O (P0). An identical pressure transducer with an identical connecting tube was attached directly to the latex balloon and served as con- H. Buscher P. Valta M. Sydow K. Thies H. Burchardi Pressure signal transmission of five commercially available oesophageal balloon catheters Received: 23 August 1999 Final revision received: 3 January 2000 Accepted: 1 February 2000 H. Buscher ( ) ) ´ M. Sydow ´ K. Thies ´ H. Burchardi Zentrum Anaesthesiologie, Rettungs- und Intensivmedizin, George-August Universität Göttingen, Robert-Koch Strasse 40, D-37 075 Göttingen, Germany e-mail: hbusche@gwdg.de Tel.: + 49-5 51-39 29 95 Fax: + 49-5 51-39 86 76 P. Valta Surgical Hospital, Helsinki University Central Hospital, Helsinki, Finland Abstract Objective: Five commer- cially available oesophageal balloon catheters (OBCs) were tested to evaluate the accuracy in transmit- ting fast-changing pressure signals which can be observed, for example, during phrenic nerve stimulation. Setting: Research laboratory of a university hospital. Method: The OBCs tested varied in length (900±1390 mm) and inner di- ameter (0.9±1.5 mm) as well as in balloon material [latex or polyvinyl- chloride (PVC)]. A 180-cm tube served as a control. A sudden pres- sure drop was generated by the ex- plosion of a pressurized latex bal- loon. The time between the pressure drop and 75, 50, 25 and 10 % of the maximal pressure was measured. Results: The time intervals required to transduce a pressure drop of 90 % varied between the different OBCs from 85 to 476 ms(control 32 ms). Transmission time was lower in OBCs with a larger inner diameter. Shortening the OBCs resulted in a further decrease in transmission time. Conclusion: The type of OBC used has an impact on signal processing. An OBCs with a short transmission time should be chosen, especially if fast pressure changes are to be eval- uated such as during phrenic nerve stimulation. Key words Phrenic nerve stimulation ´ Work of breathing ´ Oesophageal pressure Intensive Care Med (2000) 26: 462±465 Ó Springer-Verlag 2000 BRIEF REPORT