I would like to thank N Abeysinghe, K Laver and F Mason for their e- letter response to my reflective article. One of the aims of the reflection was to stimulate debate around this difficult subject and indeed the proposal of using a piece of equipment that has a dual purpose of triaging and supplying oxygen therapy has its merits. I welcome the opportunity to explain why I favour the use of the disposable End Tidal Carbon Dioxide (ETCO2) detector for responders in difficult and dangerous incidents over the Respi-check mask. With regard to the susceptibility of the disposable ETCO2 detector to atmospheric contaminants, it was acknowledged in the reflection that this is an area that requires investigation, but if the disposable ETCO2 detector were to react with contaminants, this may be useful. It should be remembered that during a multiple casualty Chemical Biological Radiological Nuclear (CBRN) or HAZMAT incident, not all of the responders may have access to portable Detection Identification and Monitoring (DIM) equipment such as the Gas Alert Quattro, which in itself only detects 4 gases without a Ph value. If a responder was to use the disposable ETCO2 and noted any changes to the colour before or during its use, this could help identify the contaminant or at least some of its characteristics. Any changes noted (or absent of changes) could assist in Personal Protection Equipment (PPE) choice, treatment of casualties (or expectant decision if there is an indication of the casualty has been exposed a contaminant at the extremes of Ph), possible 'scouting' Hot Zone treatment or collection areas. The ETCO2 apnoea detector may not only be used in large single site multiple casualty incidents but also at a chemical suicide to perform Recognition Of Life Extinct (ROLE) or the 'front door' of a NHS hospital away from the incident site where there may have been gross contamination. As for emesis and excessive secretions, it may not be advisable to use any mask as it may fill up rapidly and block any vents and increasing the risk of aspiration. It may be best to position the casualty in the recovery position allowing drainage and visualising evidence of respiratory effort from fluid movement from the mouth and/or bubbling. If any aerosolised fluids make it as far as the disposable ETCO2 detector during use, this may be seen as evidence of breathing. Also the Respi-check masks we currently use in my local ambulance service caution against getting moisture in the indicator tube as this may stop it from working. If I may take this opportunity to expand further on the ETCO2 apnoea detector use. It is envisaged that if possible and appropriate the casualty will be rolled into the supine position and apply the mask/ETCO2 detector combination. Whilst holding and applying the mask the responder may be able to open the airway by tilting the head back with the responder crouching and without directly touching the casualty's face. With the Respi-check mask there is a danger of crushing the mask, covering the indicator tube and blocking vents with the large PPE gloves and kneeling on the ground. Whereas it may be easier to get a good seal, without crushing the mask and clearly seeing if the casualty is breathing with the ETCO2 detector. Additions to the original ETCO2 set-up could include adding an in-line filter which may help protect the responder from any possible exhalation contamination, but of course increasing air resistance and dead air space. The addition of a catheter mount allowing the ETCO2 detector to be positioned to enable viewing may be used in trapped or difficult to reach casualties where their head is reachable. To assess the respiratory status of casualties wearing negative pressure respiratory protection (such as the Avon S10 respirator with the exhalation valve at the front) the same method may be deployed but replacing the adult translucent mask with a paediatric mask/ETCO2 monitor combination over the exhalation valve. In summary I feel that there are advantages of using the ETCO2 set-up over the Respi-check mask, with the ETCO2 possible susceptibility to contaminants may be an advantage.

Conflict of Interest:

None declared

Editor, We read with interest the article by M.Malpas [1] which cites the difficulty of assessing respiratory status in triaging those involved in a mass casualty chemical incident resulting from the use of personal protective equipment. However, we are concerned that the use of a calorimetric device to aid this assessment in a mass casualty CBRN incident will prove impractical. It is often difficult to ascertain early identification of the contaminant [2] which may result in false negative readings of the calorimetric device from acidic atmospheric agents. It is also well established that the effects of noxious chemical agents are highly variable but include emesis; itself of an acidic nature, and excessive secretions, which may impair the performance of the calorimetric device. We believe that a simpler device may have been overlooked. The Respi-check mask? is a high-flow reservoir oxygen mask with an adjustable clear plastic tube housing a highly-visible coloured ball, which moves with respiratory effort [3]. This gives a clear visual indication of a patient's respiratory status. Whilst we feel it unlikely that this device's performance will fail due to atmospheric contaminants, we acknowledge that patients will need to generate sufficient tidal volumes in order for the ball sensor to move. However, in a mass casualty triage incident this may help identify those which may be assigned to the 'expectant' category. Discussion with HART operatives has confirmed that oxygen can be delivered via these masks to patients within the hot zone. Whilst identification of a patient's respiratory effort does not require the mask to be connected to an oxygen supply, this could be attached later. The application of these masks whilst wearing a chemical protection suit has also been confirmed to be straightforward and practical. We suggest that this simple device offers the most convenient and practical method of determining respiratory status.

References 1. Malpas M. Prehospital reflections: diagnosing apnoea at a multiple casualty chemical, biological, radiological and nuclear incident. Emerg Med J 2011;28:1061-2. 2. Byers M, Russell M, Lockey DJ. Clinical care in the ''Hot Zone''. Emerg Med J 2008;25:108-12. 3. Breakell A, Townsend-Rose C. The clinical evaluation of the Respi-check mask: a new oxygen mask incorporating a breathing indicator Emerg Med J 2001;18:366-9

Conflict of Interest:

None declared