I think the literature is clear, if you need surfactant, the earlier you get it the better. If you don’t need surfactant you are better off never being intubated. So how do we decide? Current management protocols usually put babies on CPAP if possible at first, then watch to see if the O2 requirements go up, and then intubate when it seems inevitable that the baby will benefit from surfactant, often this is at 30%, or 40% (as in the Vermont DR management trial), or 50% (such as in the SUPPORT trial), or 60% (as in the COIN trial). This variability is evidence that we are not really sure when we should intervene.
What would help would be a simple test, minimally invasive which could predict, shortly after birth, whether a baby is producing enough of their own surfactant to avoid intubation. here have been a few attempts to do this, and measuring some aspect of surfactant production on the gastric aspirate is promising.
Why gastric aspirate? Mostly because it is easily available without intubation. Fetuses swallow what is in the pharynx, a mixture of fetal lung fluid and amniotic fluid. Remember that amniotic fluid in late gestation is a mixture of fetal urine and fetal lung fluid, FLF is a product of the cells lining the future air sacs, which is produced under the influence of an alveolar cell chloride pump. So FLF has a much higher Cl than amniotic fluid. Anyway, if the fetus is producing a lot of surfactant there will be lamellar bodies and surfactant in the stomach of the newly delivered infant.
If you put some gastric aspirate in a blood counter, the lamellar bodies will be counted as platelets, so you can get a quick answer with equipement that your hospital already has.
This newly published study marks I think a potentially important advance. Henrik Verder and his associates, in Denmark and Sweden, have performed an RCT of a diagnostic test: which in itself is fairly innovative. They have tested whether gastric aspiration for testing whether there are enough lamellar bodies allows more selective treatment of the preterm infant, and whether their clinical outcomes would be better as a result.
The authors randomized about 400 preterms less than 30 weeks gestation to one of two groups. Everyone was on CPAP and had a gastric aspirate analyzed before 1.5 h of age, and then they either were intubated for surfactant if the lamellar body count was less than 8000 per microliter after centrifugation, or they were intubated when their a/APO2 was <0.36 (based on transcutaneous gas values). The primary outcome variable of the study was not affected, that is the proportion of infants who needed to be intubated in the first 5 days of life.
But the babies treated according to the lamellar body count got their surfactant significantly earlier, at 3 hours rather than 5 hours for the controls. And they were off supplemental oxygen earlier, which was significant for the more mature babies 26 to 29 weeks, 2 days of O2 on average compared to 9 days.
I think that we do not to be a little careful, as the primary outcome was not affected (and there was some difference in the numbers of very immature babies in the two groups), but I don’t think the lack of effect on proportion intubated is too surprising, the test was previously shown to predict who will get RDS, so the equal numbers treated are just confirmation that the test does predict which babies will get RDS. Treating them earlier in several previous studies makes a difference to lung injury, with differences of only 1 hour in the OSIRIS study leading to improved outcomes.
There were quite a few babies that they were unable to get enough aspirate to do the testing, so that will be one limitation, but this looks simple (and cheap!) if you can persuade your lab to do the test.