Premature infants are among the smallest and most vulnerable patients cared for by the medical and nursing professions. Advances in medical technology have allowed infants to live who would not have survived as recently as 20 years ago. 

The ‘threshold of viability’ – the gestation age at which survival is possible – is moving steadily backwards with case reports of infants surviving as early as 21 weeks. However, this survival poses challenges including the provision of services for people with lifelong learning and physical disabilities. It is unclear whether technological advances can make further differences, or whether there is a barrier of immaturity that cannot be crossed.

Prematurity is a continuum. Technologies that are used for 23- and 24-week infants, who comprise 1% and 6% of all infants under 1,500g respectively (local data), also treat and support more mature premature babies. Survival rates of over 90% for very low birth weight (VLBW) infants over 1kg, 80% for infants weighing 750-1,000g and 40-50% for infants under 750 grams at birth, are considered standard. 

However, the focus is not only on survival, but also on preventing harm. These infants have not developed the lung tissue, cardiovascular control mechanisms or immune responses to survive without help. Unfortunately, much of the ICU ‘help’ we provide (eg. ventilator support) is associated with problems that can affect long-term quality of life, such as chronic lung disease and oxygen dependency.

Much of the ICU ‘help’ (eg. ventilator support) is associated with problems that can affect long-term quality of life, such as chronic lung disease and oxygen dependency(click to enlarge)

Control of gas delivery has improved

A 500g infant breathes in approximately 2.5mls of air or oxygen with every breath (the tidal volume). Larger tidal volumes result in damage to the lungs’ architecture resembling chronic lung disease of prematurity. The advent of the use of hotwire anemometry to sensitively calculate gas flow allows ventilators to control the amount of gas delivered, reducing lung disease and mortality. 

Flow sensors also allow the ventilator to determine when an infant is trying to breathe and to synchronise their efforts with the ventilator reducing pneumothorax and the duration of ventilation. The most recent technologies are potentially even more sensitive to the infants’ own breathing, and use diaphragmatic electrical activity (neuronally assisted ventilatory assistance; NAVA) to instantly detect the onset of a breath. Unlike flow sensors, this can be used even if infants are receiving non-invasive respiratory support.

Other technological advances include using different gases for ventilation. Long-term inhaled nitric oxide has been used in premature infants and may reduce pulmonary morbidity such as bronchopulmonary dysplasia (BPD), although further research is needed. 

Accurate monitoring is needed to provide precise intensive care, particularly in very preterm infants who can develop retinopathy of prematurity and blindness as result of high oxygen saturations. The newest pulse oximeters differentiate arterial and venous blood flow, allowing more precise measurement of oxygen saturation. This has made it feasible to measure both heart rate and oxygen saturation within seconds of birth. Pulse oximetry systems now exist that can automate the percentage of inspired oxygen provided to an infant, leading to tighter control of infant saturations.¹

Other novel forms of monitoring have also been studied, although for some, clinical applications are limited as yet. These include near infrared spectrometry that provides information on the oxygenation and oxygen use of tissues such as the brain. Seizures can be extremely difficult to diagnose in premature infants, because of the wide range of clinical manifestations. Modifications of established technologies such as electroencephalogram (EEG) have been developed to allow bedside monitoring of amplitude integrated EEG which can aid in the detection of seizures. 

Some of the major technological developments in neonatology have been quite ‘low-tech’. The greatest advance in the management of infants with HIE is the advent of therapeutic hypothermia, which has been shown to improve outcomes in moderately affected infants. Unfortunately, these data are not applicable to preterm infants, who do worse if allowed to get cold. It may be that some of the other interventions being studied for term hypoxic ischaemic encephalopathy (HIE), such as inhaled Xenon, may also prove useful for preterm infants.

Although the mortality rate has decreased in extremely premature infants, the same cannot be said for long-term morbidity. VLBW infants are at risk of complications including neurological (eg. HIE, periventricular leukomalacia, and intraventricular haemorrhage; IVH) and significant respiratory problems (eg. chronic lung disease and long-term oxygen dependency). 

These complications have been linked to cognitive and motor deficits, and behavioural problems. While newer technologies have impacted slightly on problems such as IVH (eg. volume ventilation), the hoped for improvements in long-term outcomes have not been seen.

While acknowledging the role of technological advances in improving the care of preterm infants, other factors have also made significant differences. Well-designed research, large epidemiological and multicentre trials, continuous benchmarking against international peers and evidence-based medicine have all made major contributions to improved outcomes. 

Low-tech developments, like our understanding of hypothermia have also been critical(click to enlarge)

Preterm infants and morbidity

VLBW infants demonstrate poorer neuromotor and cognitive outcomes compared with full-term infants, but it is important to note that the majority of VLBW infants – and at least one-third to one-half of extremely low birth weight (ELBW) infants – function within normal limits throughout childhood and adolescence. As far back as 2001, a study of near-universal provision of intensive care for infants born at or under 25 weeks gestation led to an additional 24 survivors per 100 live births, of whom seven had cerebral palsy. However, an additional 1,372 days of intensive care ventilator support were needed to achieve this result.

VLBW infants with disabilities require multidisciplinary input and have higher enrolment rates in special education programmes. Providing access to services is part of the continuum of caring for VLBW infants. Responses to people with developmental disabilities are based on a society’s approach to equality. Equality includes equality of access, participation and outcomes that influence and are influenced by political, economic, social and health policies. 

It is these policies, and the practices they engender, that shape reality for people with neurodevelopmental disabilities and their families. It is well documented that people with disabilities are disadvantaged educationally, socially and economically. Our duty of care to VLBW infants does not end on discharge from the maternity hospital, it also comprises the multidisciplinary support they need to combat any such disadvantages in the long-term. 

References

1. Claure N, Bancalari E, D’Ugard C et al. Pediatrics 2010; 127(1): e76-83