Survey and evaluation of modified oxygen delivery devices used for suspected severe acute respiratory syndrome and other high-risk patients in Hong Kong.

1. Covering facemasks or nasal cannulae with surgical facemasks generally improved percentage of inspired oxygen (FiO2) but at a risk of increased CO2 rebreathing when a low oxygen flow rate was used. 2. We recommend that at least 5 L/min of oxygen be used for nasal cannula and at least 6 L/min of oxygen be used for facemask when these devices are covered with a surgical facemask. 3. Using a combination of several oxygen delivery devices is unlikely to increase the FiO2 significantly. 4. All the modifications described did not introduce any significant increase in airway resistance.