Non-invasive respiratory support of preterm neonates with respiratory distress: Continuous positive airway pressure and nasal intermittent positive pressure ventilation
Introduction
Application of intermittent positive pressure ventilation to preterm infants using an endotracheal tube began in the 1960s. High mortality rates were reported and the high rates of air leak dampened initial enthusiasm. George Gregory first described the use of continuous positive airway pressure (CPAP) in 1971 for the early treatment of respiratory distress syndrome (RDS).1 Initially this was delivered via an endotracheal tube but subsequently other, more efficient, interfaces were developed.
Attitudes to the relative merits of intubation and ventilation and non-invasive ventilation [CPAP and nasal intermittent positive pressure ventilation (NIPPV)] have evolved since Gregory's study. Advocates of non-invasive ventilation cite the reduced risk of trauma to the larynx and trachea, infection and acute and chronic lung disease with this form of support. Although there is little evidence to support these assertions, there is general acceptance of the view that endotracheal intubation when required should be as brief as possible.
Section snippets
Source material for this review
Where possible the evidence quoted in this review comes from individual randomised controlled trials (RCTs) or meta-analyses of these trials. Most meta-analyses come from systematic reviews conducted for the Cochrane Library. Results are expressed in a similar format to that used in the Library, i.e. pooled analyses are provided as typical relative risk (RR) and risk difference (RD). The number needed to treat (NNT) or harm (NNH) is the inverse of the RD. Point estimates and their 95%
How does CPAP work?
CPAP supports the breathing of premature infants in a number of ways. The upper airway of the preterm infant is very compliant and therefore prone to collapse. CPAP splints the upper airway and therefore reduces obstruction and apnoea.2 Preterm infants struggle to establish and maintain lung volumes due to surfactant deficiency, muscle hypotonia, slow clearance of lung fluid and a compliant chest wall. CPAP assists expansion of the lungs and prevents alveolar collapse. In doing so it reduces
CPAP interfaces
CPAP may be delivered through a variety of interfaces. The use of an endotracheal tube is no longer recommended because it increases the infant's work of breathing. Gregory invented a head chamber with a tight seal and a pressure release valve.1 Alternative devices included a face chamber3 and a face mask.4 These systems were hampered by difficulties achieving a good seal in order to generate adequate pressure and they fell into disuse. Interfaces using nasal prongs (nCPAP) have the advantage
Leak at the nose and mouth
The aim of nCPAP is to pressurise the infant's nasopharynx and lungs. One of the problems is that the nasal prongs rarely fit tightly into the nostrils. This means that gas can leak down the pressure gradient from inside the nose to the outside. Gas can also leak from the mouth. This leak means that the set CPAP level is rarely maintained in the pharynx.9, 21 The best way to reduce nose leak is to ensure that the prongs are of sufficient size to snugly fit the nostrils without making them
Post-extubation
Preterm infants are frequently intubated and ventilated in the days following birth. In order to minimise the risks of ventilation, most clinicians attempt to wean support and remove the endotracheal tube as soon as possible. Atelectasis and apnoea often follow extubation to air or headbox oxygen and nCPAP is used in an attempt to reduce the need to reventilate infants.
A systematic review updated in 2007 identified nine trials published between 1982 and 2005 which addressed the question of
Nasal intermittent positive pressure ventilation (NIPPV)
NIPPV is a form of respiratory support in which ventilator inflations augment nCPAP. End expiratory pressure (PEEP), peak pressure (PIP), inflation rate (IR) and time (Ti) can all be manipulated.
Terminology used to describe NIPPV is not standardised and may be confusing. Terms include synchronised nasal intermittent positive pressure ventilation (SNIPPV),42, 43 nasopharyngeal synchronised intermittent mandatory ventilation (NP-SIMV),44 nasal synchronised intermittent mandatory ventilation
Devices to generate NIPPV
Although most ventilators can be adapted to deliver non-synchronised NIPPV, with the demise of the Infant Star ventilator (Infrasonics, San Diego, CA, USA), the availability of synchronised NIPPV has decreased. The only specialised devices which attempt to provide synchronised NIPPV are the Infant Flow SiPAP and Infant Flow Advance – IFDa (Viasys Healthcare, Conshohocken, PA, USA).
Nasal interface
NIPPV may be delivered by nasal prongs, which can be short or long, single or bi-nasal or by nasal mask. In our UK
Treatment of apnoea
Two RCTs compared non-synchronised NIPPV with nCPAP for the treatment of apnoea61, 66 in premature infants. Pooled analysis showed no advantage of NIPPV over nCPAP.70
Post-extubation
Three RCTs compared SNIPPV with nCPAP following extubation.44, 68, 69 All three studies showed that more SNIPPV-treated infants remained extubated at either 48 or 72 h. Pooled analysis showed a significant reduction in extubation failure [RR 0.21 (0.10, 0.45), RD −0.32 (−0.45, −0.20), NNT 3 (2, 5)] using NIPPV.71
Initial treatment of respiratory disease
Bhandari et al.
What do we still need to learn about neonatal NIPPV?
There is strong evidence that NIPPV after extubation of very premature infants reduces the reintubation rate. The technique may be used as a primary mode of support to reduce the need for intubation and may reduce the rate of BPD. It is not clear if NIPPV has a role in treating apnoea and this requires further investigation.
We have limited understanding of how NIPPV works and there is no evidence regarding the best device, interface or settings to use, nor whether SNIPPV is advantageous when
Conclusions
Non-invasive ventilation is increasingly used both as a primary method of respiratory support for preterm infants and to facilitate early extubation if an endotracheal tube is used. Bi-nasal interfaces have the lowest resistance and are the most clinically effective. Nasal trauma and leak around the prongs are commonly seen, therefore careful selection of prong size and monitoring of position are important. CPAP is an effective alternative to endotracheal intubation when managing RDS. Some
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