01/09/2005
EARLY NASAL CONTINUOUS POSITIVE AIRWAY PRESSURE AND SURFACTANT. A POTENTIAL COMBINATION THERAPY TO REDUCE BPD
Part 2. The practice.

Merran A Thomson
Department of Paediatrics and Neonatal Medicine Queen Charlotte’s and Chelsea Hospital at the Hammersmith Hospital, London - United Kingdom

This is the second part of an article discussing the role of nCPAP in the management of extremely preterm infants. The first part discussed the evidence to support the use of early nCPAP combined with surfactant in the extremely preterm infant. This part will detail the current clinical practises that have been adopted in our institution in an attempt to reduced bronchopulomonary dysplasia (BPD) in extremely preterm infants.

In the early 1990’s neonatologists had great hope that antenatal steroids combined with surfactant and either low tidal volume, low peak pressure ventilation or HFOV would not only improve the survival of extremely preterm infants but also bring about the reduction in the incidence of BPD. As evidence began to mount in the late 1990’s that a reduction in BPD was not the case we decided in our institution that we must revisit many of our standard practises in the light of evidence available. Much of this is discussed in the first part of this article. In 2000 we decided to move from a primarily ventilator dependant strategy for respiratory support to one where nCPAP was the preferred method. However we recognised that although nCPAP devices are simple, achieving success would require changes to the way many aspects of care were delivered by the multidisciplinary neonatal team. Having observed the practices in centres in Scandinavia and the USA where early nCPAP had proven successful we identified the key areas which would require a consistent guideline or approach to be followed by all senior members of the nursing and medical teams.

• nCPAP device
• surfactant use
• early management in delivery room and on admission to neonatal unit
• gentle ventilation with PEEP
• sedation
• extubation and re intubation criteria
• oxygen saturation limits
• permissive hypercapnia
• minimal handling and positioning
• reduction of infection
• early nutrition
• high quality basic nursing and medical care

In the limited space available all of the above can not be discussed in detail however this should not detract from there importance.

Choice of nCPAP device
There are many ways to deliver nCPAP; three of the most popular are the Benveniste (1) system used mainly in Scandinavia, the Infant Flow Driver™ used widely in the UK, Europe and USA, and the bubble device variation used in the USA, Australia and New Zealand and elsewhere in the world. The device used is not critical to success however there are some important points to note when choosing a device; these include variable flow (2), work of breathing (3), length and width of the prongs (4), ease of fixation, effective humidification of gases, the ability to delivery a variable pressure and the presence of safety features such as pressure monitoring with relief values and oxygen concentration monitoring.

Probably the most important factor is staff training; this is simplified if only one type of device is used within an individual neonatal unit. Staff training must pay particular attention to prong fixation, all nCPAP prongs can produce nasal trauma, this can be minimised by correct application. Lesions can be minor producing redness of the nose or severe enough to course erosion of the nasal septum which may later require corrective plastic surgery (5).

Surfactant use
We had used prophylactic Curosurf™ routinely for all babies born at less than 30 weeks gestation since 1996 and chose to continue with this policy. The evidence to support this choice is discussed in part 1. This means all extremely preterm infants are intubated within a few minutes of delivery, given a standard dose of 120mg Curosurf™ and then transported to the neonatal unit intubated. We aim to extubated as soon as possible with many placed directly on nCPAP. A single standard dose of surfactant means that the individual baby does not have to be weighed to calculate the dose nor do staff have to remember an estimated dose for each gestational age simplifying the whole process.

In addition to deciding whether to give surfactant as prophylaxis or rescue treatment one must also decide the criteria at which rescue treatment would be administered and whether this would be by the INSURE technique (intubation, surfactant, extubation) or to continue ventilation in a the conventional way. INSURE was first described in 1994 by Verder (6) and has since become a popular method to administer rescue surfactant to babies managed on nCPAP from birth. However it should be remembered that nCPAP can mask the severity of surfactant deficiency by virtue of its prime action which is to maintain the FRC. If choosing to administer surfactant as rescue treatment earlier treatment is more effective and enables INSURE to be successful (7).

In our practice the majority (85%) of extremely preterm babies require only one dose of prophylactic surfactant. Those requiring further doses often have very severe lung disease from birth; this is commonly associated with perinatal sepsis or severe hypoxia before birth due antepartum to haemorrhage etc. A number of babies who fail extubation to nCPAP will require a rescue dose of surfactant to overcome atelectasis.

Early management in delivery room including gentle ventilation with PEEP
Regular training of staff in the prevention of hypothermia, avoidance of excessive ventilation and oxygen exposure is critical to the success of early nCPAP. Placing the baby in a plastic bag immediately at delivery is an effective way to prevent heat loss while still allowing one to observe the baby fully (8,9,10). Hypothermia is a major risk factor for mortality (11), if early nCPAP is to be successful every effort must be made to optimise the baby’s condition at birth. Excessive ventilation and oxygen exposure can be avoided by using T piece positive pressure ventilation with an air-oxygen blender combined with a pulse oximeter. Our practice depends on the skill of the doctor attending the delivery; the less experienced will give face mask T piece ventilation initially moving on to intubation to give surfactant. The more experienced will intubate, give surfactant and then initiate T piece ventilation. When using T piece ventilation via an ET tube the initial peak pressure (PIP) is set at 16 cmH2O, PEEP 5 cmH2O, inspiratory time 0.5 seconds and rate at 40 breaths per minute with FiO2 0.3. PIP rate and FiO2 are adjusted to achieve chest wall minimum visible movement while keeping the oxygen saturation in the target range. The baby is transferred to the neonatal unit on these settings.

Oxygen saturation limits
Much has been written recently about the correct limits to chose and several trails are in progress to evaluate the effects of higher and lower oxygen saturation limits on mortality and morbidities such as BPD. Since 2000 our oxygen saturation limits have been set at 85-92% with a target range of 86-90%.

Extubation
We aim to extubate all extremely preterm babies as soon as possible after admission to the neonatal unit. To aid this we use the following criteria:

• The infant should be haemodynamically stable with spontaneous respiration on the ventilator.
• PIP ≤ 18 cmH2O
• FiO2 ≤ 0.3
• pH ≥ 7.20 and pCO2 ≤ 8kPa on a capillary blood gas

If these are met the baby is placed prone and extubated immediately to nCPAP pressure 6 cmH2O. If there is increased recession, tachypnoea or oxygen requirement the pressure is increased up to 8-9 cmH2O. Caffeine is administered to aid initial respiratory drive; it may also play a role in improving lung compliance (12). If a baby above 24 weeks gestational age meets extubation criteria on admission this is not delayed in order to site umbilical or percutaneous central lines; we simply site a peripheral venous line and monitor with non invasive blood pressure, pulse oximetery, transcutaneous pO2 and pCO2 monitors and capillary blood gases. For those of 24 weeks an umbilical arterial and venous catheter are sited taking care to ensure secure fixation and haemostasis so that the baby can then be nursed prone and extubated to nCPAP. If the baby’s clinical condition warrants continued ventilation then central and umbilical lines will be sited as appropriate.

Re intubation and permissive hypercapnia
Babies will remain on nCPAP as long as they have an adequate respiratory drive with a FiO2 ≤ 0.5 and pH ≥ 7.20. Hypercapnia is tolerated provided the pH is not below 7.20. The evidence to support this practice of permissive hypercapnia is limited (13) however it has been practiced in units where nCPAP is the preferred method of ventilation without reported adverse developmental out come (14). Some babies however will require re-intubation before meeting the above criteria because of poor respiratory drive often associated with increasing atelectasis; these babies present with recurrent desaturation, with or without apnoea and bradycardia which is not responsive to repositioning of the baby to open up the upper airway.

It is our experience that if re-intubation is required in the first few days of life this is almost always due to atelectasis and not infection. If the baby requires anything more then gentle ventilation: PIP ≤ 16cmH2O, PEEP 5cmH2O, and FiO2 ≤ 0.3; then a further dose of surfactant is helpful. For many extremely preterm babies INSURE is not possible as they require a few hours to recover an adequate respiratory drive however many can be extubated within 24 hours.

In our unit the primary reason for re-ventilation is failure of nCPAP presenting a poor respiratory drive, yet after the first week of life sepsis and NEC become more frequent reasons; however re-ventilation is usually required only for a very short period.

Minimal handling, positioning and airway management
The requirement for re-ventilation can be minimised by skilled nursing which is centred upon laying the baby prone or fully on the side to maximise the efficiency of diaphragmatic contraction. In addition a patent upper airway is essential to maintain an effective FRC and thereby prevent atelectasis and allow the baby to breathe without excessive work and energy expenditure. Many extremely preterm babies will have difficulty in maintaining a patent upper airway without appropriate positioning of the head, neck and jaw. This is best achieved by skilled nursing staff who can alter the baby’s position while simultaneously using a stethoscope to listen to the air entry in the chest; this should be constant through the inspiratory and expiratory cycle. This may need to be done frequently in the first few days of life however after this most babies will require less frequent attention. Some babies will lie with the mouth persistently open which results in excessive air leak and low nCPAP pressure; some advocate the use of a chin strap in this situation however we have found that the positioning of a small roll under the chin has the same effect and the advantage that it can be removed quickly and easily if required.

The upper airways also need to be kept clear of secretions to maintain patency and good nCPAP pressure. However suctioning of the nose and mouth should be preformed with caution as they are easily traumatised; the resulting bleeding and local injury can further obstruct gas flow. If effective humidification is used with the nCPAP system we have found that thick secretions are less of a problem and suction can be kept to a minimum. A point to be remembered is to check airway patency if the pCO2 becomes raised; often repositioning or clearing secretions from the upper airway will result in considerable improvement. However if a degree of upper airway obstruction has persisted for sometime the resulting loss of FRC and increasing atelectasis may be too great for the extremely preterm baby to overcome even when airway patency is restored, respiratory failure will then become severe enough to require re-ventilation. A skilled nursing team can help prevent this in many extremely preterm infants.

Nursing and medical practises must be timed to keep handling to a minimum; these infants tolerate supine lying poorly. Every effort should be made to reduce invasive procedures; this however does not mean the baby cannot have skin to skin contact with the parents providing hypothermia and air way patency are carefully monitored.

Sedation
It is not our practice to routinely sedate extremely preterm infants whom require intubation and short term ventilation. Therefore none who are intubated in the delivery room to receive prophylactic surfactant are sedated unless it becomes apparent that following admission to the neonatal unit their illness is such that early extubation to nCPAP will not be possible.

Early nutrition
When ventilated a baby uses little energy to breath, when receiving nCPAP the baby must breathe for themselves; this requires energy. Early nutrition both in the enteral and parenteral form should be commenced within 24 hours of birth to ensure sufficient energy provision. It is our practice to commence expressed breast milk (donor breast milk if necessary) and parenteral nutrition including intra-lipids from the first day of life. Enteral feeds are increased as tolerated at a rate of 10-20mls/kg/day.

Reduction of infection
Postnatally acquired sepsis is a strong predictor for the development of BPD. The extremely preterm baby with sepsis frequently requires re-ventilation. Therefore an essential part of any nCPAP programme must be continued vigilance and audit of sepsis. At the same time that we implemented the practice of using nCPAP as our preferred method of respiratory support we also introduced measures to reduce iatrogenic or postnatally acquired sepsis.

The “learning curve”
The “learning curve” can be challenging and is reliant on high quality basic nursing and medical care. Since we introduced the practice of early extubation to nCPAP following prophylactic surfactant in 2001 we have been encouraged by the reduction in ventilation we have seen. Figure 1 illustrates the overall reduction across all gestational ages. At the start we recognised we had much to learn and therefore targeted our efforts to the more mature babies of 26 – 27 weeks and above. However as our experience has grown we have been able to demonstrate a shortening of days ventilation for even the most immature babies born below 26 weeks gestation (Figure 2).

Outcomes
We recognise that data from a single unit is of limited value. We are however frequently asked; what are our longer term outcomes? We have monitored mortality data for each gestational age group and have seen no change since introducing early nCPAP, similarly there has been no change in 2 year developmental outcomes.

Summary
Hopefully these 2 articles have covered much the reader would want to know about early nCPAP. Success requires a team approach which focuses on many aspects of neonatal care. As one climbs the learning curve experience and confidence grows and one finds babies that the team thought would never breathe on nCPAP doing so.

References

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2. Courtney SE, Proy KH, Saslow JG et al. Lung recruitment and breathing pattern during variable versus continuous positive airway pressure in preterm infants: an evaluation of three devices. Pediatrics 2001;107:304-308 (Free Full Text)
   
   
3. Pandit PB, Courtney SE, Proy KH et al Work of breathing during constant and variable- flow nasal continuous positive airway pressure in preterm neonates. Pediatrics 2001;108:682-685 (Free Full Text)
   
   
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7. Verder H, Albertsen P, Ebbesen F, Greisen G, Robertson B, Bertelsen A, Agertoft L, Djernes B, Nathan E, Reinholdt J: Nasal continuous positive airway pressure and early surfactant therapy and for respiratory distress syndrome in newborns of less than 30 weeks’ gestation. Pediatrics 1999;103(2):e24 (Free Full Text)
   
   
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11. Costeloe K, Hennessy E, Gibson AT, et al. The EPICure study: outcomes to discharge from hospital for infants born at the threshold of viability. Pediatrics 2000;106:659-671 (Free Full Text)
    
    
12. Yoder B, Thomson M, Coalson J. Lung function in immature baboons with respiratory distress syndrome receiving early caffeine therapy: A pilot study. Acta Paediatr 2005;94:92-98 (PubMed)
    
    
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14. Kamper J, Feilberg Jørgensen N, Jonsbo F, Pedersen-Bjergaard L and Pryds O and the Danish ETFOL Study Group. The Danish national study in infants with extremely low gestational age and birthweight (the ETFOL study): respiratory morbidity and outcome. Acta Paediatr 2004;93:225-232 (PubMed)

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