More babies die from undiagnosed congenital heart defects than from any other abnormality. But a simple test which is safe, painless and takes only a couple of minutes could help identify these babies before they become unwell.
Current methods of detecting life-threatening heart defects include identifying the problem while the baby is still in the womb using ultrasound scans and examining newborn babies’ hearts in the first days of life. Neither of these methods is particularly effective and around a third of babies with life-threatening critical defects may leave hospital without it being picked up. These babies may become seriously unwell or even die.
Pulse oximetry has been used for many years as a non-invasive method of detecting oxygen levels in the blood. It’s used routinely in intensive care, operating theatres and emergency wards. By shining a red light through the skin, the pulse oximeter can directly measure how much oxygen there is in the blood.
Most babies with critical congenital heart defects will have slightly lower oxygen levels than normal in the first days of life. Although this may not always be detectable with the naked eye, it’s easily picked up with pulse oximetry.
This observation has led to studies investigating the possibility of using this technique as an additional screening method to identify babies with such defects before they leave hospital or become unwell.
Some of the earlier studies involved only a relatively small number of patients so it was difficult to be certain if the test was accurate enough to be used as a routine. More recently, larger projects, including the PulseOx study, which Dr Ewer led, have given greater momentum to the possibility of introducing pulse oximetry as a routine procedure.
The PulseOx study investigated over 20,000 newborn babies and found that three-quarters of babies with critical congenital heart defects could be detected by this method. When combined with existing screening methods, 92% of the defects were picked up before the babies became unwell. This meant that life-saving surgery could be performed in a timely manner with a much better chance of a good outcome.
Importantly, screening also identified other heart problems and illnesses, such as serious infections.
If the results from the study were applied to a population of 100,000 babies, an additional 35 babies with critical congenital heart defects would be picked up. And over 200 babies with other serious problems would also be identified.
But the test is not perfect. It misses some cases of critical congenital heart defects although it performs much better than existing screening methods. And when used in conjunction with current tests, it adds significant value and identifies babies who would otherwise be missed.
Dr Ewer’s team also investigated the acceptability of the test to parents and clinical staff and whether it was cost-effective. They reported that the test was readily accepted by both parents and staff and both groups felt it was important and worthwhile. It also proved to be cost-effective in the United Kingdom where the study was done.
In a recent review in The Lancet, Dr Ewer and his team analysed the results from all pulse oximetry studies (almost 230,000 babies) and concluded that there’s now compelling evidence that it’s sufficiently accurate to use as part of routine screening.
A number of hospitals in Australia and the UK are already using pulse oximetry screening, although it’s not routine. But introduction has been slowed down by concerns that screening may result in increased requirements to transfer babies with a positive screen to children’s hospitals for further tests.
These fears have been allayed by early data from hospitals that are screening, which found a high level of accuracy with very few false alarms. Consensus guidelines for hospitals in Australia are currently being developed.
Dr Ewer has discussed his study with the United States national screening committee and the technique has now been adopted there with various states in the process of introducing it. He has also been in discussion with the United Kingdom national screening committee and they’re considering the information with a view to making a decision in the near future.
The introduction of pulse oximetry screening as a routine is feasible and likely to save the lives of many babies.