An improved pocket rescue mask incorporating a novel visual breathing indicator.
The difficulties inherent in the 'Look, Listen and Feel' method of identifying respiratory arrest prompted the authors to develop a simple mechanical breathing indicator that can show clearly, at a glance, whether or not a patient is breathing. The novel indicator was designed to be highly visible so that its interpretation should be obvious to medical personnel and the lay public, and yet sufficiently simple so that it could be easily and inexpensively incorporated into the type of pocket rescue masks currently in use. The indicator needs no power source, works indoors and outdoors and does not interfere with the delivery of rescue breaths during resuscitation. A prototype of the improved pocket mask incorporating the new indicator was made and was tested for its ability to detect breaths over a range of inspiratory flow rates and inspiratory pressures. The authors found that the indicator responded to peak inspiratory flow rates of between 15 and 120 l/min, inspiratory pressures as low as 0.18 cm H(2)O with no supplemental oxygen flowing to the mask and 0.22 cm H(2)O with supplemental oxygen flowing at 9 l/min, minute ventilation volumes between 7.1 and 21.8 l/min, tidal volumes between 0.36 and 2.92 l and a respiratory rate range of 7-24 breaths per min. The authors conclude that the new indicator, when attached to a pocket rescue mask, is sensitive enough to identify clearly and reliably those patients at the scene of collapse who have stopped breathing. Additionally it may assist rescuers in timing the delivery of assisted rescue breaths in those patients with poor respiratory effort.