Video surveillance of oxygen administration by mask in postoperative patients

Patients may not receive prescribed oxygen because the oxygen face mask becomes displaced. Using video, we have observed the position of the face mask in 20 postoperative patients and recorded the timing and the events associated with mask displacement. Correct placement of the mask was confirmed at the start of the 8-h study period from 22:00 on the first night after operation. The mask remained on continuously and positioned correctly in only one patient. In the other 19 patients, it was removed 64 times (range 1-10 times per patient). The mask was removed 45 times for nursing tasks such as mouth care and temperature measurement and these represented 70% of the total number of times that the mask was not in position. Other reasons for removal were vomiting, retching and removal by the patient. The mask remained off a median time of 6 min 55 s per episode (range 46 s to 7 h 46 min 57 s) and per patient a median of 1 h 6 min 48 s (range 1 min to 7 h 46 min 57 s). Mask removal resulted in an average decrease in oxygen saturation of 4%. Oxygen by mask at 4 litre min-1 maintained an average saturation > or = 95% in most, but not all, of the patients.