• Michael Dreher, Emelie Ekkernkamp, Stephan Walterspacher, Claudia Schmoor, Jan H Storre, Wolfram Windisch, and Sophie E Huttmann.
• Department of Pneumology, University Hospital, Freiburg, Germany.
• Respir Care. 2014 Jan 1;59(1):113-20.

BackgroundWhen supplemental oxygen is added to noninvasive ventilation using a non-ICU ventilator, it is usually introduced with a preset flow into the circuit near the ventilator; however, the impact of different CO2 exhalation systems and leaks on the actual FIO2 and gas exchange has not been elucidated.MethodsIn a randomized, open-label, 4-treatment (2-by-2), 4-period crossover design, 4 daytime measurements (60 min each) were performed in 20 subjects receiving home mechanical noninvasive ventilation plus supplemental oxygen (≥ 2 L/min) inserted near the ventilator: active valve circuit or leak port circuit with or without artificial leakage (4 mm inner diameter). Oxygen concentration near the ventilator, oxygen concentration at the mask, and blood gases were measured.ResultsOverall, oxygen concentration at the mask (29 ± 5%) was lower than oxygen concentration at the ventilator (34 ± 4%), with a mean difference of 5.1% (95% CI 4.2-5.9%, P < .001)%. With the leak port circuit, oxygen concentration at the mask decreased by 3.2% (95% CI 2.6 to 3.9%, P < .001), compared to the active valve circuit. When artificial leakage was introduced into the circuit, oxygen concentration at the mask decreased by 5.7% (95% CI 5.1 to 6.4%, P < .001)%, PaO2 by 10.4 mm Hg (95% CI 3.1 to 17.7 mm Hg, P = .006), and PaCO2 increased by 1.8 mm Hg (95% CI 0.5 to 3.1 mm Hg, P = .008).ConclusionsThe use of a leak port circuit and the occurrence of leak around the interface significantly reduced oxygen concentration at the mask and negatively impacted gas exchange in subjects receiving home noninvasive ventilation and supplemental oxygen. (German Clinical Trials Registry, www.drks.de, DRKS00000449).

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