For a study, the researchers sought to compare the effective inspired oxygen concentrations given by several low-flow oxygen treatment systems when they were tested in an experimental lung model with different oxygen flows and breathing patterns. Different breathing patterns were simulated using an adult lung model ventilated in volume control mode to generate mean inspiratory flows of 22.5, 30.0, 37.5, or 45.0 L/min. The oxygen concentration inside the lung model was measured using a nasal cannula, a simple face mask, a non-rebreather mask, and a double-trunk mask atop the nasal cannula at oxygen flows of 10, 12.5, and 15 L/min. The 3 masks were tightened around the model’s airway opening. They were also put to the test with standardized leakage to find how well they performed in the clinic. Regardless of the respiratory pattern, all oxygen delivery methods delivered higher oxygen concentrations as oxygen flows increased. When utilizing the nasal cannula (P=.03), the simple face mask (P=.03), but not the non-rebreather mask (P=.051) or the double-trunk mask (P=.13), increasing inspiratory flow lowered oxygen concentration. The double-trunk mask beat the non-rebreather mask and simple face mask in a sealed environment (P<.001); mean oxygen concentrations were 84.2%, 68.5%, and 60.8%, respectively. The oxygen delivery was reduced by 4.6% with a single face mask (95% CI 3.1–6.1%, P<.001), 7.8% with a non-rebreather mask (95% CI 6.3–9.3%, P<.001), and 2.5 with a double-trunk mask (95% CI 1–4%, P=.002). The oxygen concentration provided by the simple face mask and the non-rebreather mask was identical (P=.15) when there were leaks. When leaks were present, the lung oxygen concentrations given by the double-trunk mask were higher than those delivered by alternative oxygen delivery methods.