Copyright © European Society of Anaesthesiology. Unauthorized reproduction of this article is prohibited. Correspondence European Journal of Anaesthesiology 2012, 29:000–000 Recurrent false alarm of extracorporeal membrane oxygenation at high noon Daniel Dirkmann, Clemens J. Kehren, Michael Adamzik, Christian Hofer, Ju ¨ rgen Peters and Frank Herbstreit From the Klinik fu ¨r Ana ¨ sthesiologie und Intensivmedizin, Universita ¨ tsklinikum Essen, Essen, Germany Correspondence to Dr. med. Daniel Dirkmann, Klinik fu ¨r Ana ¨ sthesiologie und Intensivmedizin, Universita ¨ tsklinikum Essen, Hufelandstraße 55, D-45122 Essen, Germany Tel: +49 201 7238 4423; fax: +49 201 723 5949; e-mail: Daniel.Dirkmann@uk-essen.de Extracorporeal membrane oxygenation (ECMO) is an established treatment for patients with severe pulmonary and/or cardiac failure unresponsive to conventional treat- ment. Its goal is to provide time for treatment and recovery from the underlying disease process, as a bridge to decision-making 1 or to transplantation. 2 ECMO is complex both medically and technically, requires a specialised team and equipment and its complications can be devastating. Accordingly, extensive monitoring of patients undergoing ECMO is essential. We report the simultaneous and recurring malfunction of two new miniaturised ECMO devices due to environ- mental influences. During the 2010/2011 influenza A (H1N1) pandemic, 14 patients suffering from adult respiratory distress syn- drome (ARDS) due to community-acquired H1N1 infec- tion were treated in our ICU using ECMO. In February 2011, we introduced into clinical practice a new ECMO device (Cardiohelp; Maquet Cardiopulmonary AG, Hirr- lingen, Germany). This device is exceptionally small (315  255  427 mm), lightweight (<10 kg) and can be carried by a single person. Its cube-shaped disposable contains a centrifugal pump, a gas-exchanger/oxygenator and also provides several integrated pressure sensors and a blood temperature probe. Furthermore, an ultrasound flow sensor, which also serves as a sensitive bubble detector, and a sensor for continuous photometric measurement of haemoglobin concentration, haematocrit and venous oxygen saturation can be attached to the venous drainage line (Fig. 1). In March 2011, three patients in our ICU simultaneously underwent ECMO for H1N1-associated ARDS. On one day at about 12.00 h, we encountered simultaneous alarms of two of the three machines that were located in adjacent rooms. Both devices failed to measure haemo- globin concentration, haematocrit and venous oxygen saturation and no numbers were given for the respective measurements. One of the nurses in charge complained that both ECMO devices had given alarms for the same type of malfunction for a few days exactly 1 h before her shift changeover. The third ECMO device was in operation in a patient’s room on the other side of the ICU and did not malfunction. We unsuccessfully attempted to alleviate the problem by recalibration of the probes according to the manufacturer’s instructions. However, despite recalibration, the same malfunction occurred repeatedly around noon each day. Curiously, when a colleague by chance shaded the sensor of one device for a few seconds while trying to silence the alarm, this alone silenced the alarm and re-enabled measurements. The same malfunction was encountered a few weeks later during transfer of a patient with severe ARDS on ECMO from a referring hospital. When sunlight fell on the probe through the back window of the ambulance, alarms went off and measurements were disturbed. The problem was resolved by covering the window. The observed malfunction of the ECMO device’s photo- metric sensors occurred repeatedly around noon and was alleviated by shading the sensor. Our ICU is located on the ground floor of the medical centre and most of the windows face south (Fig. 2a). Although the windows are slightly opaque in their lower part to prevent pedestrians from looking into the ICU rooms, bright sunlight shines Fig. 1 The extracorporeal membrane oxygenation’s photometric detector (  ) attached to the venous drainage tubing of the device. 0265-0215 ß 2012 Copyright European Society of Anaesthesiology DOI:10.1097/EJA.0b013e3283598e7c