A number of conditions interfere with normal regulation of breathing by the brain and the CNS. Respiration is initiated in the pre-Bötzinger complex in the pons and medulla oblongata in the brainstem and further regulated by the carotid and aortic bodies. These areas submit electrical pulses to the diaphragm through the phrenic and thoracic nerves in the spinal column. Conditions associated with the spinal column or head, such as trauma, tumors, or malformations (e.g., an Arnold-Chiari malformation), can interfere with respiratory drive, respiratory rhythm, or respiratory regulation. The hypoxic response is primarily driven by the carotid bodies, whereas the response to carbon dioxide (CO₂) is primarily driven by brainstem structures. These combined abnormalities result in susceptibility to CSA and/or hypoventilation and a need for the child to be treated with positive pressure or volume ventilation in order
to regulate the respiratory rate and/or tidal volume. If a child requires only nocturnal support, then noninvasive ventilation (NIV) is the optimal treatment. On the basis of modern technology, NIV is predominately positive pressure ventilation. If the individual requires assistance during wake and sleep and has a chronic condition, then invasive ventilation should be considered. Depending on the severity of the lack of respiratory drive, invasive ventilation can be pressure or volume ventilation.

Structural abnormalities in the airway can interfere with optimal gas exchange by predisposing to narrowing or collapse of the airway. Obstruction to airflow can occur at any point along the airway from the nares to the alveoli. Examples of the physical obstruction in the upper airway include adenoid and/or tonsil hypertrophy, choanal atresia/stenosis, a cleft palate, or an enlarged tongue (macroglossia). These may be identified on physical examination or through more invasive testing procedures including nasendoscopy. Children at risk for upper airway obstruction may also be assessed using the Mallampati classification (1). Other causes of structural narrowing include micrognathia, a congenitally narrow airway, or childhood obesity whereby increased adipose tissue surrounds the muscular soft tissue of the upper airway. The primary example of a congenital floppy airway is laryngomalacia in infants, usually presenting soon after birth.

Surgical interventions can often alleviate these problems, but CPAP may be required for stabilization or long-term therapy when surgery is either contraindicated or not curative. The most easily corrected cause of obstruction is adenotonsillar enlargement, but other commonly performed surgical procedures include mandibular distraction and supraglottoplasty.

Gas exchange abnormalities can also be caused by structural abnormalities in the lower airway such as restrictive lung disease and/or chest wall abnormalities (i.e., kyphoscoliosis, cystic fibrosis, and bronchiectasis). It is important to note that morbidly obese children (particularly adolescents) may be at an increased risk of nocturnal hypoventilation because of the excessive adipose tissue deposited on the truck and abdomen restricting pulmonary function. If hypoventilation is present, treatment with NIV (with or without oxygen therapy) should be considered. It is common for children with lung disease (i.e., neonatal lung disease and cystic fibrosis) to be treated with supplemental oxygen, but in some cases, CPAP or NIV is also required because of associated conditions such as OSA or airway malacia.

Gas exchange is also influenced by the effectiveness of respiratory muscle function. Many congenital myopathies are associated with progressive muscle weakness; the classic example is Duchenne muscular dystrophy. Mild loss of muscle tone can also affect the upper airway and predispose to upper airway obstruction, and treatment with CPAP therapy may be sufficient in these cases.

More severe loss of muscle power, such as in spinal muscular atrophy or at the later stages of Duchenne
muscular dystrophy, requires ventilation because of loss of diaphragmatic and/or intercostal muscles, with additional compromise in sleep due to loss of respiratory accessory muscle activity.

The use of CPAP or NIV for patients with congenital heart disease (CHD) is often for the management of respiratory issues occurring secondary to the underlying cardiac condition. CHD can affect the respiratory system by causing obstructive and/or diffusion defects.

Direct anatomic compression of the airway can occur in association with cardiac abnormalities, secondary to the enlargement of cardiac structures or abnormal vascular structures (such as vascular rings). As an example, tetralogy of Fallot is associated with the narrowing of the pulmonary artery as well as ventricular septal defect, and leads to the deviation of the aorta to the right and thickening of the right ventricle. This in turn can lead to pulmonary artery dilation, bronchial or tracheal compression, and atelectasis, resulting in respiratory distress (2).

In terms of diffusion defects, ventricular or atrial septal defects can result in increased pulmonary blood flow because of left to right shunts (3). The increase in pulmonary blood flow can result in loss of elasticity in pulmonary vessels and increase the resistance in the pulmonary bed (4), thus impacting on gas exchange.

The use of CPAP or NIV should be aimed at relieving airway compression, increasing lung volume, equalizing transalveolar pressures (in addition to cardiac medications), and expanding surface area available for gas exchange to occur in the pulmonary bed (5).

The data presented here regarding the commencement of CPAP in children are derived largely from clinical practice and experience. An intervention that can be specific for children includes behavioral strategies to assist with compliance. If hospital or home nursing resources are available, another strategy can be CPAP acclimatization in the presence of medical and nursing care. This provides family support, aids with adherence, and optimizes CPAP pressure. Otherwise, many of the other steps for commencing CPAP therapy follow adult practice (27). A few published studies address the issues surrounding CPAP initiation and adherence for children, and there has been limited formal evaluation of the acceptance by pediatric patients of different devices (28). However, what is known is that with proper training good adherence can be achieved in children (29, 30) and that it can be maintained with careful follow-up.

The strategies to commencing CPAP vary according to the age and development of the child. For infants (less than ˜6 months old), the therapy can generally begin immediately, with no need for prior behavioral programs. Instead, intervention strategies and education should be primarily geared toward the parents/primary caregiver because of their primary role in achieving adherence with therapy. The adaptation process for CPAP is approximately 3 to 7 days; however, in some cases, infants take to the therapy almost immediately.

For older children, success in implementing CPAP therapy is improved if it is commenced in a graduated manner. To maximize adherence, the children must first become adapted to the nasal mask. This takes approximately a week and is done in the home environment. Role-playing with the child (e.g., acting as an elephant, “Buzz Lightyear,” or an astronaut) assists with this. Allowing the child to wear the mask for 10 to 15 minutes when awake minimizes the “scare factor.” Once the mask is accepted, the child is admitted to hospital and a CPAP pressure is introduced. Others report successful introduction of CPAP in an immediate manner, with or without the addition of behavioral intervention programs (31).

In adolescents, in general the process is the same as for adult patients. Reports now suggest that adults utilizing CPAP also benefit from access to a multidisciplinary approach to aid adherence with therapy (32). Practice guidelines derived from evidence in the literature suggest that once a diagnostic study has demonstrated the presence of OSA, the patient is fitted with the mask interface, and the process is explained to the patient. A trial of CPAP can be undertaken with the patient awake and participating. An overnight sleep study for pressure titration can be undertaken almost immediately. Pressures are adjusted during the study and the patient is discharged the next day on the pressure setting deemed optimal on the basis of a single night of determination. Although this may be appropriate for the older adolescent, a hospital admission to commence therapy may still be appropriate for younger or developmentally delayed teenagers.

In all age categories, CPAP therapy is commenced on a low pressure (e.g., 5 cm H₂O) to allow the child to get used to the sensation of the therapy and therefore maximize the likelihood of adherence. The first stage is to achieve overnight adherence with low-pressure therapy. A clinical review permits appropriate pressure changes to follow, for example, in the presence of ongoing snoring, pressures need to be increased. It is also important to note, depending on the age and complexity of a child’s condition, that commencing CPAP at home with the assistance of a community nurse may also help the child and parents adjust to using CPAP as part of their bedtime routine.

Once the patient has adapted to the use of the pressure support, a full CPAP titration polysomnogram is undertaken in the sleep center. It is recommended that
titration studies follow the American Academy of Sleep Medicine (AASM) guidelines (34). In general, pressure titration studies commence with minimal positive pressure (e.g., 4 cm H₂O) and do not exceed 15 cm H₂O for children less than 12 years old. The priorities for pressure adjustment are to eliminate discrete obstructive respiratory events, eliminate signs of increased work of breathing, and eliminate signs of airflow limitation.

Discrete obstructive events and labored breathing on the polysomnogram are seen as a loss of nasal airflow and increased respiratory effort with, or without, oxygen desaturations and/or arousals. The general practice is to increase the CPAP in 1 cm H₂O increments if at least one obstructive apnea or two hypopneas are seen in children aged 12 or less or at least two apneas or three hypopneas are present in children greater than age 12. Each pressure change should be separated by at least 5 minutes of recording.

Once discrete obstructive events are eliminated, the next step is to put an end to nasal airflow limitation, residual snoring, and respiratory effort-related arousals (RERAs). The CPAP for children aged less than 12 years is to be increased if there are at least three RERAs or 1 minute of loud or unambiguous snoring. The CPAP is to be titrated higher for children 12 years or older who experience at least five RERAs or 3 minutes of loud or unambiguous snoring. CPAP is increased in approximately 1 cm H₂O increments until this is achieved.

Once optimal pressure is achieved, there should be no snoring or stridor, and there should be normal nasal airflow and respiratory effort, stable oxygenation without intermittent desaturations, and normal CO₂. Allowing 30 to 60 minutes before additional incremental increases in CPAP will provide sufficient time for the patient to blow off any excess CO₂ and allow adequate sleep for analysis by the assessing physician. To allow the sleep physician to assess and confirm the optimal pressure, an ideal study includes pressure adjustments to a level slightly above the optimal CPAP. Acute signs that the CPAP has been increased too high include increased frequency of arousals, recurrence of the use of accessory muscles, fall in baseline oxygenation and CO₂ retention, and the occurrence of central (rather than obstructive) respiratory events (9). AASM standards indicate that an optimal CPAP is achieved when the respiratory disturbance index (RDI) is less than five events per hour for at least 15 minutes, SpO₂ is above 90%, and a rapid eye movement (REM) period in the supine position is recorded (34). The titration is considered good when the RDI remains greater than 10 events per hour and SpO₂ is above 90%. The titration may be adequate if the RDI has been reduced by 75% from diagnosis or titration was not assessed during supine REM sleep. AASM standards indicate that a titration is unacceptable when any of the above-mentioned criteria remain unmet.