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Abstract
BACKGROUND: Numerous delivery systems are used to treat hypoxemia. It is unknown if FIO2 at the lips predicts oropharyngeal FIO2 for various oxygen mask systems. We tested whether FIO2 measurements differed between the lips and oropharynx, and whether this difference depends on the mask system.
METHODS: Ten healthy volunteers had one sampling catheter positioned at the lips and another catheter in the oropharynx. FIO2 was sampled at each location while the subjects breathed normal tidal volumes with oxygen at 15 L/min via 4 delivery devices: a simple mask, a non-rebreather mask, a face mask with a diffuser that concentrates and directs O2 toward the mouth and nose (mask with diffuser), and a closed mask with a Jackson-Rees circuit. Data were analyzed by using a linear mixed model to account for subject crossover in the repeated measures design.
RESULTS: FIO2 levels differed significantly for the 4 delivery mask systems (P < .001) and by sampling catheter location (P < .001). Differences in mean FIO2 between the lips and the oropharynx were observed for the mask with diffuser (difference 0.30, 95% CI 0.25–0.36; P < .001), and non-rebreather mask (difference 0.09, 95% CI 0.04–0.15; P = .001). The mean FIO2 at the oropharynx was highest for the closed mask (0.97, 95% CI 0.92–1.00), followed by the non-rebreather mask (0.76, 95% CI 0.72–0.81), simple mask (0.62, 95% CI 0.58–0.67), and the mask with diffuser (0.51, 95% CI 0.46–0.56). At the lips, the mean FIO2 was highest for the closed mask (0.97, 95% CI 0.92–1.00), followed by the non-rebreather mask (0.86, 95% CI 0.81- 0.90), OxyMask (0.81, 95% CI 0.76–0.86), and simple mask (0.67, 95% CI 0.62–0.71).
CONCLUSIONS: With high oxygen flows and normal tidal volume breathing, FIO2 measurements obtained at the oropharynx or at the lips depended on the device used, with the mask with diffuser showing the most significant discrepancies. FIO2 measures at the oropharynx and the lips were only consistent for the closed mask system.
- hypoxemia prevention and control
- oxygen inhalation
- therapy
- respiratory therapy
- perioperative
- critical care
- respiratory insufficiency
- equipment design
Footnotes
- Correspondence: N David Yanez PhD, Oregon Health and Science University, Oregon Health and Science University/PSU School of Public Health, Mailcode GH-230, 3181 SW Sam Jackson Park Rd, Portland, OR 97239. E-mail: yanezn{at}ohsu.edu.
The authors have disclosed no conflicts of interest.
- Copyright © 2019 by Daedalus Enterprises
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