[The practicability, patient comfort and efficiency of the pre-oxygenation device NasOral]

We examined the new NasOral-System (NOS; Logomed, Germany), which is designed for a fasten and more complete denitrogenization when compared to the use of a contemporary face-mask. The patient inhales oxygen via a nose mask and exhales via mouthpiece. Nose mask and mouthpiece have built-in one-way valves, resulting in an unidirectional gas flow (nasal-oral).

With approval of the local ethic committee, pre-oxygenation with both the NOS and a face mask (Laerdal) was studied in 50 adult patients. Midazolam 3.75-7.5 mg p.os was given for premedication. The NOS was studied in two different ways: the nose mask fastened by rubberband and with the nose mask held by hand. Prior to induction every patient received every system in a randomised manner. Semi-closed-anaesthetic circle-systems with a fresh-gas-flow of 10 litres/min were used. The FEO2 over 5 min of pre-oxygenation were recorded (AS-3, Datex). Speed and degree of the denitrogenization was documented by an external digital data-acquisition system. Practicability of the systems regarding the anaesthesists (n = 27) and patient comfort were evaluated by means of a standardized postoperative questionnaire.

The hand-held NOS is definitely more effective and reliable than both the NOS fastened by rubber-band and the classical face mask: 80% of the hand-held NOS were able to achieve a FEO2 of > or = 0.8 compared to only 36% of the NOS fixed by rubber-band, face mask: 48%. FEO2 of > or = 0.8 was achieved with 52% of the hand-held NOS in 90 s, a time we consider practical for daily routine, whereas only 10% of the NOS fixed by rubberband and 14% of the face masks accomplished this threshold. A cooperative patient is an important condition when using the NOS: a strong premedication effect, absence of dentures, and patients who can not inspire via nose and expire via mouth involve impairment of the positive effects of the NOS. 21% of the anaesthesists felt disturbed by the NOS. 72% do not believe, that induction of anaesthesia will become more safe with the NOS. For 8 patients, breathing with the NOS was disagreeable (face-mask: 3 patients), 15 were disturbed by the nose part/mouth piece (face-mask: no patient).

An acceptable FEO2 of > or = 0.8 can be achieved only without leakage of both the NOS and the face-mask. Therefore, routine FEO2-monitoring seems highly desirable. Efficiency of the hand-held NOS is much better than with the NOS fastened by rubberband or the face mask. However, even the hand-held NOS cannot guarantee for optimal denitrogenization. Practicability in daily use was poor, because a test of airway patency by manual ventilation prior to relaxation/intubation is not possible with the NOS. Using the device as a help in apnoic oxygenation seems useful.