Fig. 95.1
Nasal pillows or plugs
Fig. 95.2
Nasal mask on an infant
Fig. 95.3
Nasal mask on a boy with Prader Willi syndrome
Fig. 95.4
Nasobuccal mask on a boy with Treacher Collins syndrome
Fig. 95.5
Full face mask
Fig. 95.6
Oral mask on a child with severe obstructive sleep apnea and total obstruction of the nasal airways
Fig. 95.7
Mouthpieces for mouthpiece ventilation
Fig. 95.8
Helmet on an infant in the pediatric intensive care unit
Fig. 95.9
Infant nasal cannula
Nasal pillows or plugs (which occlude the outer part of the nostrils),
Nasal masks, which cover the nose
Nasobuccal masks, which cover the nose and the mouth
Full face masks, which cover the mouth, the nose, and the eyes
Mouthpieces or oral masks
And the helmet, which covers the entire head.
Nasal pillows or plugs are minimal-contact interfaces that are available for patients weighing more than 30 kg, but small sizes can be used in children of 6–8 years (Fig. 95.1). They have the major advantage of exerting no pressure contact on the child’s face. The acceptance of these interfaces is generally excellent in school-aged children in whom they are proposed as first-line interfaces for NPPV [18]. Because of the minimal dead space, the patient may sometimes have the impression that the level of positive pressure is higher with nasal pillows than with another interface. The headgear may be a limitation in these interfaces that have been mainly developed for adults.
Nasal masks are the most commonly used interfaces, with numerous different models being available (Figs. 95.2 and 95.3). Models differ with regard to the presence or not of a forehead support, internal flap, and type of fixation. These masks are the only industrially available interfaces for preschool children and, more recently, infants and neonates (weight >3–3.5 kg) (Fig. 95.2). In young children, nasal masks are preferred to larger masks because they have less static dead space, are less claustrophobic, and allow communication and expectoration more easily than nasobuccal or full face masks. Nasal masks also allow the use of a pacifier in infants, which may contribute to a better acceptance of NPPV and the reduction of mouth leaks (Fig. 95.2). New models integrating thin internal flaps that inflate with the airway pressure are associated with a better skin tolerance because of a reduction in the pressure forces.
Nasobuccal masks cover the nose and the mouth and are indicated in case of mouth breathing during sleep (Fig. 95.4). These interfaces are larger, have a greater dead space, and are heavier than nasal masks. Some have a forehead support. These interfaces are contraindicated in case of esogastric reflux and when the child is not able to remove the interface by himself because of the potential risk of inhalation.
Full face masks cover the mouth, the nose, and the eyes (Fig. 95.5). They are used as last-choice masks, in case of intolerance or non-acceptance of all the other interfaces. They may cause claustrophobia and, as with the nasobuccal masks, are not recommended in case of reflux.
Mouthpiece and oral masks allow ventilation through the mouth (Figs. 95.6 and 95.7). Mouthpieces are generally used on demand during daytime in patients with neuromuscular disease as a daytime extension of nocturnal ventilation with another interface [19, 20]. They have been exceptionally used in children with total nasal obstruction and severe obstructive sleep apnea syndrome (OSAS) [21].
The helmet is a commonly used interface in the PICU (Fig. 95.8). This interface is composed of a plastic transparent bag that covers the entire head of the patient and that is sealed around the neck by a hermetic collar. Two ports act as an inlet (upper) and outlet (lower) of the gas flows. This interface can be used for continuous positive airway pressure (CPAP) or bilevel ventilation. Its use has been evaluated during acute exacerbations of neuromuscular disease in children in the PICU [22, 23]. The helmet has proved to be an efficient alternative to a nasal or a face mask but its large dead space and the risk of asphyxia in case of power failure or other technical problems restricts its use to the PICU. Also, the quality of the ventilatory support may be less optimal with this interface compared with a nasobuccal mask or a tracheal cannula [24]. In premature infants or neonates, nasal cannula or nasal masks can be used to deliver oxygen, CPAP, or humidified high-flow oxygen, which creates a low CPAP level, in the neonatal ICU (Fig. 95.9).
Interfaces can be vented or non-vented, that is, with or without intentional leaks. The choice of non-vented interfaces is more limited than that of vented interfaces. Vented interfaces need a minimal positive end-expiratory pressure, which is generally 4 cmH2O. In adult patients, the importance of manufacturer intentional leaks on the mask may influence the quality of NPPV. Indeed, a first bench study showed that the type of interface and importance of leaks did not influence trigger performances [25]. However, the ability to achieve and maintain inspiratory positive airway pressure was significantly decreased with all ventilators and in all simulated lung conditions when intentional leaks increased (especially when leaks > 40 l/min). Another study showed that the importance of manufacturer intentional leaks on the mask was able to modify patient-ventilator synchronization, ventilator performance, and risk of rebreathing [26]. Such studies have not been performed in children. However, a systematic clinical evaluation of every mask change is recommended, checking and eventually adjusting the inspiratory trigger sensitivity and pressurization, and checking the absence of rebreathing [27].
For all types of interfaces, the headgear is of crucial importance. Indeed, the face and skull of children requiring ventilatory support differ from healthy children [18]. An inappropriate headgear may compromise the use of a well-adapted interface in children. The most important qualities of a headgear are the appropriate size, stability, and the ease with which it can be put on and removed.
95.3 Side Effects and Monitoring of the Interface
The interface represents a crucial determinant of the success of NPPV. The patient will be unable to tolerate and accept NPPV in case of facial discomfort, skin injury, or significant unintentional leaks. The evaluation of the short- and long-term tolerance of the nasal mask is thus an essential component of NPPV [28] (Figs. 95.10, 95.11 and 95.12).
Fig. 95.10
Skin injury caused by a nasal mask
Fig. 95.11
Maxilla retrusion in a boy ventilated since 3 years for severe laryngomalacia
Interfaces for NPPV need to be adapted to the facial anatomy and physiognomy of children. In the chronic setting, a growing number of young patients are treated with NPPV. These patients represent a heterogeneous group, not only with regard to the underlying disease, but also with regard to age, weight, and maxillofacial physiognomy [15, 18, 29–31]. Numerous children have genetic diseases associated with facial deformities, such as, for example, Treacher Collins syndrome, Goldenhar syndrome, Pierre Robin syndrome, achondroplasia, or osteogenesis imperfecta. Individually adapted interfaces are thus mandatory for these patients. In our experience, children with OSAS resulting from maxillofacial deformity represented the group that needed the greatest number of mask changes [18].
The soft tissue beneath the skin is thinner in children compared with adults. Children are thus at greater risk of skin injury during NPPV than adults (Fig. 95.10). Skin injury occurs as a consequence of pressure sores, which are defined as a lesion on any skin surface that occurs as a result of pressure. The principal causative factor is the application of localized pressure to an area of skin not adapted to the magnitude and duration of such external forces. Tissue damage will occur if both a critical pressure threshold and a critical time are exceeded. Because young children may need NPPV during extended periods including nocturnal sleep and daytime naps, they are at increased risk of skin injury [28]. The effect of repetitive loading on skin and bone tissue is also of major importance, which is the case during NPPV. The anatomy of the facial bones and the proportions between the facial elements differ in children compared with adults. The anatomy of the maxillofacial structures changes continuously during growth, which is particularly rapid during the two first years of life. Facial growth occurs predominantly in an anterior and sagittal axis in children. NPPV hinders this normal facial growth and may cause facial deformity (Figs. 95.11 and 95.12). Indeed, NPPV is always used during sleep, which can represent the major part of the day in young infants. In these young patients, there is thus a potential risk of facial flattening and maxilla retrusion, caused by the pressure applied by the mask on growing facial structures. Facial flattening and maxilla retrusion are commonly observed in children receiving long-term NPPV by means of nasal or nasobuccal masks, which justifies a systematic evaluation and follow-up by a pediatric maxillofacial surgeon before and during NPPV [28]. When possible, alternative use of different interfaces to vary the pressure forces may reduce these side effects.
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