Respiratory support

Published on 03/06/2015 by admin

Filed under Neonatal - Perinatal Medicine

Last modified 03/06/2015

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CHAPTER 4 Respiratory support

Respiratory distress

Respiratory distress, and the need for respiratory support, is one of the most common problems seen in neonatal units. Respiratory distress is characterised by one or more of the following:

The most common cause is hyaline membrane disease (HMD), also known as infant respiratory distress syndrome. The most important cause is infection (see pages 10712).

Other causes soon after birth include: retained fetal lung fluid (also known as transient tachypnoea of the newborn or ‘wet lung’); meconium aspiration syndrome; other aspiration syndromes (blood or liquor); air leak (pneumothorax or pulmonary interstitial emphysema); pulmonary hypoplasia (usually due to a space-occupying lesion in the chest, such as in congenital diaphragmatic hernia, or oligohydramnios); pleural fluid; and airway obstruction.

Other late-onset causes include: infection (viral or bacterial); chronic lung disease; chylothorax; and heart failure secondary to a left-to-right shunt.

The general principles of management include:

Continuous positive airway pressure (CPAP)

CPAP is a method of respiratory support used in the care of preterm and term infants. Indications for CPAP include:

Delivery methods vary according to institution, and include single prong (long or short), bi-nasal prongs (long or short), or mask.

The aim of CPAP is to hold the alveoli and airways open and prevent them collapsing during expiration. It therefore protects functional residual capacity, allowing the lungs to operate at maximal efficiency (by optimising their position on the pressure–volume curve). CPAP also stabilises the ribcage, reduces chest wall distortion during inspiration, and increases the efficiency of the diaphragm. It also regulates the respiratory rate (because of stimulation of the Hering–Breuer reflex) and results in increased inspiratory time and tidal volume. When given via the nose (nasal CPAP or NCPAP) it dilates the upper airway, which may explain its benefit in mixed or obstructive apnoea.

The benefits of CPAP include: a reduction in the need for intermittent positive-pressure ventilation (IPPV); decreased rate and severity of apnoea; increased chance of successful extubation; and decreased respiratory acidosis and oxygen requirements post-extubation.

The risks of CPAP include a potential for an increased incidence of intraventricular haemorrhage, nasal trauma and pneumothorax, as well as increased nursing care and the cost of consumables.

Starting CPAP: try a starting CPAP of 7 cmH2O (range 5–10). This may be decreased or increased depending on the level of oxygenation and severity of apnoea.

Surfactant

Surfactant administration

It is not clear which is the best method of giving surfactant; there are variations in the methods of administration between and within different neonatal units. Administration of the total surfactant dose into four equally divided aliquots is the method recommended by the manufacturer of Survanta. Some administer it as a slow instillation via an endotracheal tube (ETT) over 5–10 minutes. However, animal studies have shown that a more rapid single bolus gives more uniform pulmonary distribution and dispersion of surfactant.

Assisted ventilation

The decision to ventilate a baby with respiratory distress needs to be taken in discussion with the relevant consultant. Generally accepted criteria are: