A comparison of the tissue oxygenation achieved using different oxygen delivery devices and flow rates.

INTRODUCTION: High-concentration normobaric oxygen (O2) administration is the first-aid priority in treating divers with suspected decompression illness. The best O2 delivery device and flow rate are yet to be determined. AIM: To determine whether administering O2 with a non-rebreather mask (NRB) at a flow rate of 10 or 15 L·min ⁻¹ or with a demand valve with oronasal mask significantly affects the tissue partial pressure of O2 (PtcO2) in healthy volunteer scuba divers. METHODS: Fifteen certified scuba divers had PtcO2 measured at six positions on the arm and leg. Measurements were taken with subjects lying supine whilst breathing O2 from a NRB at 10 or 15·L·min⁻¹, a demand valve with an adult Tru-Fit oronasal mask and, as a reference standard, an oxygen 'head hood'. End-tidal carbon dioxide was also measured. RESULTS: While none of the emergency delivery devices performed as well as the head hood, limb tissue oxygenation was greatest when O2 was delivered via the NRB at 15 L·min⁻¹. There were no clinically significant differences in end-tidal carbon dioxide regardless of the delivery device or flow rate. CONCLUSION: Based on transcutaneous oximetry values, of the commonly available emergency O2 delivery devices, the NRB at 15 L·min ⁻¹ is the device and flow rate that deliver the most O2 to body tissues and, therefore, should be considered as a first-line pre-hospital treatment in divers with suspected decompression illness.