**2.3 Use of CPAP in neonates**

CPAP is commonly used in neonates with the following conditions:

### 1.RDS

Prophylactic CPAP i.e. CPAP started immediately after delivery in preterm or low birth weight infant or within the first 15 min of life (before the onset of respiratory disease) has been shown to reduce the incidence of BPD (bronchopulmonary disease), the combined outcome of death or BPD, and the need for mechanical ventilation [20, 21].

In preterm or low birth weight infants with established respiratory distress, CPAP reduces the incidence of respiratory failure, the use of mechanical ventilation and mortality however there is an increased rate of pneumothorax compared to spontaneous breathing with supplemental oxygen [3].

## 2.Post extubation

NCPAP can also be used as "step-down" therapy to provide respiratory support following extubation after mechanical ventilation. These infants have a less likelihood of developing respiratory failure and having the need for reintubation and mechanical ventilation. The reason for this may be due to the fact that CPAP maintains lung volumes, causes airflow stimulation of the nasal passage and upper airway and by reducing apnoea in the preterm infant [22, 23].

## 3.Apnoea

CPAP decreases both obstructive and a combination of obstructive and central apnoea and prevents hypoxia. Central apnoea by itself is not affected by CPAP. Miller postulated that CPAP reduces upper airway obstruction by splinting the pharyngeal airway [24].

### **2.4 CPAP apparatus**

CPAP has two main components: a device to generate pressure and a patient interface used to deliver pressure.

CPAP devices include:

Variable flow devices ie devices that generate CPAP by a jet of blended air delivered by the Infant Flow Driver. This system requires air flows in excess of 8 L/min in order to generate positive end expiratory pressures of 5 cm H2O.

Constant or continuous flow examples of which are bubble CPAP and ventilator CPAP.

With bubble CPAP the PEEP is maintained by immersing the distal end of the expiratory tubing in water. The pressures are determined by the depth of the tubing in the water. For example 5 cm below the surface equals to 5 cm H2O blended humidified gas oxygen or air is delivered by nasal prongs or nasal masks and as air flows out of the infant via the expiratory tubing it gives its characteristic bubbling [1, 3, 25]. Bubble CPAP is inexpensive and is easy to adapt for newborns [3]; however, if the interface is not well adapted or if there is leakage through the nose or mouth, the PEEP is not guaranteed.

Studies have shown that there is little difference in terms of respiratory rate, heart rate, blood pressure or comfort scores between the use of continuous flow CPAP and variable flow CPAP [8, 26–31].

Many neonatal units use CPAP pressures delivered between 5 and 6 cm H2O. Some units use starting pressures of 8 cm H2O. Elgellab noted that CPAP pressures of 8 cm H2O improved the thoraco-abdominal synchrony, lowered the respiratory rate and increased the tidal volume of preterm infants with respiratory failure [18].

For preterm infants with poorly compliant lungs, higher CPAP pressures 32 (e.g. 8 cm H2O may be needed 3 as the first line of support immediately after birth or at the start of the respiratory distress with escalation to intubation and mechanical ventilation if CPAP fails.

#### **2.5 CPAP delivery**

The most common interfaces for CPAP delivery include:

Short binasal prongs that fits directly into the nostrils or nasal mask. Other interfaces used included single nasal prongs and nasopharyngeal prongs which uses a nasopharyngeal tube (NGT) in which the tip of the tube sits in the nasopharynx thereby bypassing the nasal cavity [32, 33].

Short binasal prongs when compared to single nasal prongs and nasopharyngeal prongs showed that there was a decrease in the babies oxygen requirement and respiratory rate thereby reducing the need for reintubation [23, 34, 35]. Endotracheal tubes are still used to deliver CPAP when the infants have facial anomalies such as bilateral cleft lip and or palate [2].

The problem with binasal prongs however is that it must be fitted snugly which can lead to injury to the nares and nasal septum [35, 36].

With the nasal mask, this is placed over the babies nose and mouth forming a good seal.

When compared to binasal prongs, nasal masks decreased the incidence of moderate-to-severe BPD and the need for surfactant. However there were no differences in mortality or other morbidities [7, 30].

CPAP failure i.e. babies requiring mechanical ventilation while on CPAP is defined when one or more of the following conditions arise: persistent or frequent apnoeic episodes, PaCO2 of ≥60 mm Hg (8.3 kPa), FiO2 of ≥0.6 to maintain acceptable oxygen saturation. 14% to as high as 40% of infants with respiratory distress who have initially been started on CPAP may need to be intubated and ventilated. CPAP failure was associated with an increased rate of pneumothorax, death, bronchopulmonary dysplasia (BPD) and other morbidities compared with those managed on CPAP alone [37–39].

#### **2.6 Contraindications in the use of CPAP in babies**

This includes upper airway abnormalities such as choanal atresia, cleft palate and trachea oeophageal fistula.

Babies in shock i.e. cardiovascular instability.

Frequent apnoeic episodes with bradycardia and desaturations.

Respiratory failure PCO2 of >60 mmHg FiO2 > 0.6 to maintain an acceptable O2 saturation.

Congenital diaphragmatic hernia as the gastric distension caused by CPAP can result in further compromise of the organs in the chest.

Complications that can occur with CPAP giving rise to inefficient delivery include [40]


#### **2.7 CPAP and surfactant**

Studies have shown that in babies with moderate to severe respiratory distress syndrome the combination of nasal continuous positive airway pressure (nCPAP) and a single dose of surfactant reduces the need for intubation and mechanical ventilation [36].

Methods of delivering surfactant to an infant on CPAP include:

INSURE method (INtubation-SURfactant-Extubation), Surfactant administration via thin catheter and Nebulized surfactant [41].

The INSURE method (INtubation-SURfactant-Extubation) is done by intubating the infant, administrating surfactant via the endotracheal tube followed by a short period of mechanical ventilation, extubation and then onto CPAP. This is done at the onset of RDS [42] Stevens suggest that in spontaneously breathing preterm infants with RDS the INSURE method of surfactant administration followed by early extubation to NCPAP is preferable to traditional intubation and surfactant treatment and keeping the baby on the ventilator. INSURE reduces the need for mechanical ventilation. Its also reduces the incidence of pneumothorax and BPD.

Surfactant administration via thin catheter (S-TC) encompasses any method in which a thin catheter, narrower than a standard endotracheal tube (ETT), is passed through the vocal cords to allow surfactant instillation. The most commonly used methods are [43].

A flexible thin catheter and Magill's forceps (Cologne method), as described by Kribs and colleagues [33], flexible thin feeding tube without Magill's forceps (take care method), as described by Kanmaz and colleagues, semi-rigid thin catheter (Hobart method), as described by Dargaville and colleagues [30]; and modifications of the above methods.

Differences of the various methods may be encountered in (1) the pre-medication used, (2) the means of laryngoscopy used, including videolaryngoscopy, (3) the type of catheter, (4) the method used to guide the catheter through the vocal cords, (5) the approach to surfactant delivery (bolus versus infusion, rapid versus slow), (6) the surfactant preparation, (7) the surfactant dose, and (8) the approach to respiratory management before, during, and after the technique, including the type of non-invasive respiratory support used. It is expected that infants are spontaneously breathing, and therefore positive-pressure inflations are not required for surfactant dispersal. Unlike an ETT, a thin catheter is unsuitable for delivery of positive-pressure inflations.

Several different acronyms may be used for the above methods, including:


Abdel-Latif et al. concluded in his Cochrane review that surfactant therapy via thin catheter (S-TC) compared to surfactant via endotracheal tube (ETT) reduced the incidence of the combined outcome of death or bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age (PMA) [31].

#### **2.8 Nebulised surfactant**

This method is carried out when Aerosolised surfactant is given to the neonate via a customised vibrating membrane nebuliser positioned between the mask and the bubble nCPAP circuit. Minocchieri et al. showed that nebulised surfactant administered in the first 4h of life to very and moderately preterm infants with mild RDS may benefit these babies [44]. These findings require confirmation in a adequately powered randomised controlled trial evaluating the benefits of nebulised surfactant in infants with mild to moderate respiratory distress [44].

## **3. Conclusion**

In conclusion CPAP is a safe and effective method of noninvasive ventilation in the preterm infant with RDS and it reduces the need for assisted ventilation by almost half, and substantially reduced the use of surfactant. CPAP is a simple and inexpensive form of treatment to implement and hence has implications for use in low- and middle-income countries (LMIC).
