Improvement of arterial oxygenation using the double trunk mask above low flow nasal cannula: a pilot study
Letter to the Editor
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To the Editor,
The Double Trunk Mask (DTM) is an original mask (Fig. 1) which boosts the Fraction inspired in Oxygen (FiO 2) during oxygen therapy with high flow nasal oxygen (HFNO) [ 1]. In a previous study, the association of the DTM over HFNO showed an increase of the PaO 2 without PaCO 2 increase despite an added dead space of 210 mL due to the mask and the trunks. It can be explained principally by the washing of the trunks by the high flow (until 60 L/min). However, few studies have examined the effect of DTM on PaO 2 and PaCO 2 during oxygen therapy at low flow. Indeed, the use of low flow oxygen should lead to a risk of CO 2 rebreathing [ 2]. In fact, during expiration, the additional oxygen does not escape but is collected in the two trunks. During inspiration, the patient receives this oxygen-enriched gas mixture from the trunks instead of the air in the room. The DTM thus acts like a “reservoir” and results in increased FiO 2. However, thanks to its dead space volume, the DTM could...
Compliance with ethical standards
Conflict of interest
The authors declare no conflicts of interest.
The study protocol has been approved by the Erasmes Hospital (Brussels) Ethics Committee.
Written consent was obtained from all the participants before inclusion.
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