Có bốn loại khác nhau của giao diện: mũi mặt nạ, mặt nạ trên khuôn mặt bao gồm mũi và miệng, gối mũi, và mouthpieces. Mặt nạ mũi được sử dụng chủ yếu (10,16). Mouthpieces hiện nay cơ bản được chỉ ra trong trường hợp hệ thống thông gió vào ban ngày (17,18). Điều này có thể đủ khả năng một giao diện tuyệt vời | 174 Robert and Argaud an individually made interface is now seldom needed even if it remains probably the best interface 10-15 . There are currently four different types of interfaces nasal mask facial mask covering the nose and the mouth nasal pillows and mouthpieces. Nasal masks are predominantly used 10 16 . Mouthpieces are now essentially indicated in the case of daytime ventilation 17 18 . This may afford an excellent interface to adjunct daytime ventilation in neuromuscular patients who are unable to maintain acceptable diurnal arterial blood gases without frequent intermittent periods of assistance. The mouthpiece is positioned close to the patient s mouth where it is intermittently captured to take a few assisted breaths from the ventilator and subsequently released. An advantage is to clear the face from a face-attached interface. Thus the patient needing assistance night and day may use a combination of interfaces. Ventilator and Mode for Noninvasive Positive Pressure Ventilation Ventilators use one of two basic methods volume-preset and pressure-preset 10 . With volume-preset the ventilator always delivers the tidal volume which is set by the clinician regardless of the patient s pulmonary system mechanics compliance resistance and active inspiration . However leaks at the skin-mask interface or through the mouth when using a nasal mask reduce the volume received by the patient. Conversely with pressure-preset changes in pulmonary mechanics directly influence the flow and the delivered tidal volume lower or higher since the ventilator delivers the set pressure all along inspiration. Then leaks augment the flow and tend to maintain the tidal volume 19 20 . It is important to understand that NIPPV is dominated both by rapid variations of nonintentional leaks and of the geometry and the resistance of the upper airway 21 . Obviously leaks and airway resistance partly interact. Facing these continuous changes the respective advantages and drawbacks of volume-
