Terminology and definitions
Over the past decade the clinical definition of chronic lung disease has evolved from describing oxygen dependency at 28 days of age to oxygen dependency at 36 weeks corrected gestational age.
Chronic lung disease is the single most important factor determining length of hospital stay in babies born at less than 29 weeks. The most severely affected babies are the most premature, particularly 23-26 week gestation babies.
Risk factors for chronic lung disease
Risk factors for chronic lung disease include:
- peripartum inflammation/infection associated with preterm labour and/or clinical or subclinical chorioamnionitis
- postnatal lung injury due to volutrauma, barotrauma,oxygen toxicity, hypocarbia or infection. Visit sepsis in neonates for more information.
Clinical features of chronic lung disease
Neonatal intensive care unit (NICU) babies with chronic lung disease (actual or evolving) fall into three broad groups:
- babies receiving endotracheal mechanical ventilation (MV)
- babies receiving non-invasive respiratory support
- babies who are oxygen dependent, usually by low flow nasal prongs.
The most common clinical scenario is the 23-26 week gestation baby who, over a period of four to 10 weeks, progresses from MV, non-invasive respiratory support through to requiring supplementary oxygen. These babies are usually transferred to a special care nursery (SCN) for ongoing care.
Although some of these babies spend many weeks on non-invasive respiratory support it is common to see rapid improvement in their respiratory stability once weaned.
Respiratory stability off non-invasive respiratory support is the single most important criterion that determines suitability for transfer to a SCN. It is important to understand the NICU's experience with babies at these gestations as it has a significant impact on decision making with respect to transfer to SCNs.
Summary management of chronic lung disease in neonatal intensive care units (NICU)
Issues to note:
- Endotracheal ventilation is increasingly being replaced by non-invasive respiratory support, for even the most immature babies. Many are being managed with this from birth.
- For those who do require intubation and ventilation there is an intense focus on minimising ventilator associated lung injury from the moment a baby is placed on a ventilator.
- Oxygen damages delicate lung tissue as well as the immature retina. Pulse oximetry targets are set between 91 and 95 per cent.
- Babies who require endotracheal ventilation are aggressively weaned and extubated to non-invasive respiratory support often within two days of birth.
Drug therapy for established/evolving chronic lung disease
Issues to note regarding corticosteroid use:
- Dexamethasone is effective in achieving short-term improvement in the status of ventilator dependent babies, as well as longer term reductions in chronic lung disease.
- Typical clinical scenarios where steroids would be considered are a baby who is unable to be weaned from endotracheal MV.
- There is no place for the use of steroids in the treatment of chronic lung disease outside a Level 5 or 6 Neonatal unit.
Issues to note regarding use of diuretics:
- Diuretics may be used as an effective short-term therapy for ventilated babies.
- Typical combinations include hydrochlorothiazide +/- spironolactone.
- NaCl and KCl supplementation are commonly required.
- There is no place for long-term therapy with diuretics in SCNs.
Issues to note regarding nutrition:
- Provision of adequate calories in a nutritionally appropriate form is critical. Infants with chronic lung disease utilise 20-40 per cent more kcal than infants without chronic lung disease.
- Caloric requirements of babies with moderate to severe lung disease can be as high as 130-150 calories/kg/day.
- These babies tolerate fluid overload poorly and are modestly fluid restricted (150-160 mL/kg/day) and fed fortified breast milk or low birthweight formula.
- Growth is closely monitored and caloric intake titrated against growth.
- Babies sufficiently stable to transfer to a SCN should not require a caloric density of > 24 cal/30 mL.
- A referral to a dietician should be considered for nutritional management.
Respiratory criteria for transfer to an SCN
These criteria should be met prior to transfer:
- Absolute minimum of seven days off respiratory support including NCPAP or 'high flow' (up to 8 L/min) intranasal air/oxygen.
- Maximum of one apnoea/bradycardia that required no or minimal stimulation for recovery.
- Not receiving corticosteroids.
- Preferably the baby should not be diuretic dependent for respiratory stability.
- Consistent growth on two to three-hourly bolus feeds with a caloric density no more than 24 cal/30 mL.
- There are a small number of babies with severe but not dependent on non-invasive respiratory support chronic lung disease who are transferred to SCN units. These are a specific group of babies where the decision to transfer and the principles of ongoing medical management require an individualised management plan worked out between referring and receiving consultant medical staff, preferably in collaboration with a paediatric thoracic consultant.
- The principles of care for these babies is beyond the scope of this content.
Management in the SCN
The transition from a NICU to a SCN is a difficult time for parents as they adjust to different staff and practices. Both NICU and SCN staff should be proactive in anticipating and addressing these issues. If the referring neonatologist believes a particular approach should be considered for a particular baby, this should be discussed with the receiving paediatrician directly so that a consistent message goes to the parents.
It is strongly recommended that these babies be nursed in the SCN rather than the paediatric ward even if post term corrected age. This should reduce the risk of developing nosocomial infection particularly respiratory viral infections.
Issues to be aware of regarding nutrition for neonates with chronic lung disease in the SCN:
- Caloric requirement may be 130-150 cal/kg/day.
- Breast milk fortifier or a low birthweight formula can be continued until at least term without adverse effects if caloric supplementation is required.
- For babies on tube feeds, oral feeds should be cautiously introduced as baby develops an interest in sucking, initially one oral feed/day then two etc as the baby copes with the previous increment.
- Oxygen is the one constant in the treatment of chronic lung disease but it has been poorly studied.
- Once weaned from non-invasive respiratory support oxygen is delivered by nasal prongs using low flow (< 0.5 L/min).
- Babies with chronic lung disease have a degree of pulmonary hypertension and are therefore likely to benefit from a more generous oxygen administration regimen rather than from a restrictive policy. Some neonatal units use O2 saturation targets >95% after corrected gestation of 37 weeks. However, the corrected gestational age and the state of vascularistion of the retina need to be taken into consideration.
General considerations include the following:
- Aim to move to intermittent oximetry rather than continuous once it is clear the baby is not having apnoea or bradycardia.
- During feeding and certain parts of sleep are the times where a baby's oxygen demand is higher. Therefore if one is looking to see if a baby will manage in less oxygen, saturations should be monitored over several feed periods or for several hours during sleep.
- For babies on low-flow intranasal oxygen do not wean by more than 10 mL/24 hours.
- Blood gas monitoring is not required in stable babies.
- The indications for blood transfusion in a growing stable baby with a mild oxygen requirement have been the subject of clinical trials. It was demonstrated that there is no benefit in maintaining higher haemoglobin levels.
- This conservative approach would be especially supported if there is a good reticulocyte count.
There is no consensus on how to wean oxygen in babies with chronic lung disease:
- A prolonged period (eight to 12 hours) of saturation monitoring should be undertaken that captures extended periods of sleep and several feeds.
- These babies with chronic lung disease should not be discharged until at least 72 hours after ceasing oxygen.
Criteria for home oxygen general
- Ensure appropriate social/home environment including reasonable access to medical care.
- Baby is sucking all feeds.
- Baby is normothermic in an open cot.
- Growth is satisfactory.
- All babies discharged from neonatal units on home oxygen must have specific paediatric thoracic specialist follow-up. It is strongly recommended that paediatricians manage babies on home oxygen in collaboration with a paediatric thoracic physician.
Criteria for home oxygen - respiratory
- Babies greater than 4 weeks corrected age who are unable to be weaned from low flow intranasal oxygen.
- Baby should have passed an 'air test'. The oxygen is turned off, the nasal prongs removed and the baby monitored over 30 minutes.
- If saturations are maintained > 86 per cent for 30 minutes the test should be repeated in 48 hours. If a second test is satisfactory the baby is eligible for discharge on home oxygen on respiratory grounds. In other words the baby has demonstrated a reasonable level of respiratory reserve.
Issues to note:
- These babies require long-term follow-up throughout childhood.
- There is an increased pulmonary morbidity in the first two years of life. Parents should be counselled about this morbidity and ways to minimise it.
- Influenza vaccine is recommended for infants with ongoing cardiac, respiratory or neurological illnesses at six months of age. Recommendations are two doses, four weeks apart.
- RSV prophylaxis is not routinely recommended, there is no consensus regarding the use of Synagis (palivizumab) in Australia. The product is given IM monthly to children at high risk of RSV and has reduced the risk of hospitalisation from 10% to 5% in babies born prematurely, with chronic lung disease and with haemodynamically significant congenital heart disease.
- An additional 13-valent pneumococcal conjugate vaccine (13vPCV) is recommended at 12 months for infants with ongoing chronic lung disease requiring oxygen.
- Use of home oximeter should be considered in babies receiving O2 at home who may have failed an air test. This is assessed on individual cases and in consultation with the respiratory physician.
- Royal Prince Alfred Hospital, Sydney Chronic lung disease.
- Royal Prince Alfred Hospital, Sydney Oxygen therapy
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First published: October 2015
Last web update: February 2018
Review by: February 2018
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Page last updated: 21 Nov 2018