Comparison of tissue oxygenation achieved breathing oxygen using different delivery devices and flow rates.

INTRODUCTION: Divers with suspected decompression illness require high concentration oxygen (O2). There are many different O2 delivery devices, with few data comparing their performance. This study evaluated O2 delivery, using tissue O2 partial pressure (PtcO2), in healthy divers breathing O2 via three different delivery devices. METHODS: Twelve divers had PtcO2 measured at six limb sites. Participants breathed O2 from: a demand valve using an intraoral mask with a nose clip (NC); a medical O2 rebreathing system (MORS) with an oronasal mask and with an intraoral mask; and a non-rebreather mask (NRB) at 15 or 10 L·min⁻¹ O2 flow. In-line inspired O2 FIO2) and nasopharyngeal FIO2 were measured. Participants provided subjective ratings of device comfort, ease of breathing, and overall ease of use. RESULTS: PtcO2 values and nasopharyngeal FIO2 were similar with the demand valve with intraoral mask, MORS with both masks and the NRB at 15 L·min⁻¹. PtcO2 and nasopharyngeal FIO2 values were significantly lower with the NRB at 10 L·min⁻¹. The NRB was rated as the most comfortable to wear, easiest to breathe with, and overall the easiest to use. CONCLUSION: Of the commonly available devices promoted for O2 delivery to injured divers, similar PtcO2 and nasopharyngeal FIO2 values were obtained with the three devices tested: MORS with an oronasal or intraoral mask, demand valve with an intraoral mask and NRB at a flow rate of 15 L·min⁻¹. PtcO2 and nasopharyngeal FIO2 values were significantly lower when the flow rate using the NRB was decreased to 10 L·min⁻¹.

Comparison of tissue oxygenation achieved breathing oxygen from a demand valve with four different mask configurations.

INTRODUCTION: High concentration normobaric oxygen (O2) is a priority in treating divers with suspected decompression illness. The effect of different O2 mask configurations on tissue oxygenation when breathing with a demand valve was evaluated. METHODS: Sixteen divers had tissue oxygen partial pressure (PtcO2) measured at six limb sites. Participants breathed O2 from a demand valve using: an intraoral mask (IOM®) with and without a nose clip (NC), a pocket face mask and an oronasal mask. In-line inspired O2 (FIO2) and nasopharyngeal FIO2 were measured. Participants provided subjective ratings of mask comfort, ease of breathing and holding in position. RESULTS: PtcO2 values and nasopharyngeal FIO2 (median and range) were greatest using the IOM with NC and similar with the IOM without NC. O2 measurements were lowest with the oronasal mask which also was rated as the most difficult to breathe from and to hold in position. The pocket face mask was reported as the most comfortable to wear. The NC was widely described as uncomfortable. The IOM and pocket face mask were rated best for ease of breathing. The IOM was rated as the easiest to hold in position. CONCLUSION: Of the commonly available O2 masks for use with a demand valve, the IOM with NC achieved the highest PtcO2 values. PtcO2 and nasopharyngeal FIO2 values were similar between the IOM with and without NC. Given the reported discomfort of the NC, the IOM without NC may be the best option.