Incorrect assembly of non‐return valve of an Oxylog ventilator

Abstract

We wish to report a critical incident during use of a Draeger Oxylog ventilator. Transfer was arranged for a burns victim whose lungs were mechanically ventilated. In preparation for the transfer he was changed to a Draeger Oxylog ventilator (Draeger Medical Ltd, Hertfordshire, UK) and the end-tidal carbon dioxide continually analysed. The initial end-tidal carbon dioxide measurement was 5.1 kPa, but within minutes this value increased to 11.0 kPa in association with a raised inspired concentration of carbon dioxide (1.5 kPa). Arterial blood gas analysis confirmed an elevated Paco2 of 13 kPa. The patient was reconnected to the ICU ventilator and ventilated to normocapnia. There appeared to be adequate chest expansion and appropriate movements of the pressure gauge on the ventilator were observed, but no gas flow could be detected from the PEEP valve situated on the expiratory port and the characteristic expiratory noise was absent. The Oxylog ventilator was examined closely and the non-return valve unit was discovered to have been incorrectly assembled such that the dark red ‘mushroom’ part of the valve had been inserted the wrong way around (see Figure 3). The result was that the patient was being ventilated predominantly with rebreathed gases. The correct assembly is shown in Figure 4. It is likely that the patient would have suffered an adverse event during the transfer had this error not been recognised at the bedside before departure. This was avoided by use of continuous end-tidal carbon dioxide monitoring to confirm the adequacy of ventilation on the new ventilator, as recommended by a number of professional organisations [1, 2]. The main learning point from this incident is that it is essential to confirm that the patient is stable on the transfer trolley and with the equipment that will be used for the transfer before leaving the relative safety of the parent unit. Incorrect assembly of non-return valve of Oxylog ventilator. Correct assembly of valve. We would like to thank Drs Thomas and Kuppurao for their report and for the opportunity to reply. From the information given in the letter we were not able to establish the exact model of Oxylog ventilator referred to. Therefore, we can only assume from studying the patient valve shown in the attachment sent to us that the Oxylog ventilator mentioned is either an Oxylog 1 or an Oxylog 1000. Our assumption is further supported by the fact that no mention or information is given in the article of any alarms being generated. This strongly suggests that an Oxylog 1 ventilator was being used and our following comments relate to this model. The Oxylog 1 ventilator is an early model in the ‘Dräger Oxylog family’ of emergency ventilators. It was first introduced into service in the 1980s and provided settings for minute volume, frequency, ‘air mix/no air mix’ and an on/off switch. Our initial concern with the letter is prompted by the fact that no reference is made to the manufacturer's Instructions for Use or the pre-use checks recommended in these [1]. Incorrect assembly of the check valve ‘dark red mushroom’ within the patient valve suggests that the valve was not assembled correctly as illustrated to users in the Instructions for Use. These instructions also have clear diagrams and explanations for cleaning, disinfecting, re-assembly and testing of the device. We would not disagree with the principle of the main learning point in the letter but consider it should be expanded further. To help ensure patient stability with the equipment and prior to leaving the safety of the parent unit, users should perform pre-use checks as detailed in the Instructions for Use before connecting the ventilator to the patient. M. S. RedpathDraeger Medical UK Ltd Hemel Hempstead HP2 7BW, UK E-mail: [email protected]