Effect of nasal cannula oxygen administration on oxygen concentration at facial and adjacent landmarks

An oxygen-enriched atmosphere enhances the potential for operating-room fires. We thus determined oxygen concentrations at various facial landmarks during oxygen administration via nasal cannulae. Thirteen supine volunteers were draped similarly to patients undergoing a cervical-node biopsy. Oxygen was delivered in random order through nasal cannulae at rates of 2, 4, and 6 l.min^-1. Oxygen concentration was measured at pre-determined facial landmarks and also distal to the drape at non-facial sites. At a flow of 2 l.min^-1, oxygen concentrations exceeded 23% only within a few centimetres of the nasal cannula. Concentration increased as a function of flow, but rarely exceeded 26%. At all flow rates, concentrations distal to the drape were < 24%. To reduce combustion risk, ignition sources should be kept at least 10 cm from the oxygen outlet when using nasal cannula at a flow rate ≥ 4 l.min^-1.