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Fig. 2 | BMC Pulmonary Medicine

Fig. 2

From: Efficacy and safety of oxygen-sparing nasal reservoir cannula for treatment of pediatric hypoxemic pneumonia in Uganda: a pilot randomized clinical trial

Fig. 2

Design of oxygen-sparing nasal reservoir cannula (OSNRC) based on oxygen sparing and CO2 retention. a-c. The fraction of inspired oxygen (FiO2) was higher at a given flow rate for the OSNRC (circle, solid line) compared to the SNC (square, dashed). The breathing simulator used a flow waveform resembling a patient with pneumonia. The tidal volume approximated that of an 8 kg (a), 12 kg (b) and 16 kg child (c), respectively. Two OSNRC sizes were used: 30 mL (a and b) and 50 mL (c). Data shown represent results from a single simulation at each condition. The flow savings ratio (FSR) was calculated to be 1.8 to 2.6. d. FSR as a function of OSNRC volume to tidal volume ratio. e. End-tidal CO2 (ETCO2), measured at the outlet of the simulated respiratory circuit, as a function of OSNRC volume to tidal volume ratio, using constant age-appropriate CO2 production in the circuit. f. OSNRC sizes (30 mL and 50 mL) were designed for patients from 8 kg to 26 kg. Sizes were bounded by minimum FSR of 1.8 (horizontal dashed line), maximum ETCO2 of 9% (vertical dashed lines), and maximum FSR observed (solid lines). Colored regions represent the range of operating states of the OSNRC

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