If you are reading this and have a baby in the NICU with respiratory distress syndrome (RDS) otherwise known as hyaline membrane disease you might be surprised to know that it is because of the same condition that modern NICUs exist. The newspaper clipping from above sparked a multibillion dollar expansion of research to find a cure for the condition that took the life of President Kennedy’s preterm infant Patrick Bouvier Kennedy. He died of complications of RDS as there was nothing other than oxygen to treat him with. After his death the President committeed dollars to research to find a treatment and from that came surfactant and modern ventilators to support these little ones.
What is surfactant and what is it’s relationship to RDS?
When you take a breath (all of us including you reading this) oxygen travels down your windpipe (trachea) down into your lung and goes left and right down what are called your mainstem bronchi and then travels to the deep parts of the lung eventually finding its way to your tiny air sacs called alveoli (there are millions of them). Each alveolus has a substance in it called surfactant which helps to reduce the surface tension in the sac allowing it to open to receive oxygen and then shrink to get rid of carbon dioxide that the blood stream brings to these sacs to eliminate. Preterm infants don’t have enough surfactant and therefore the tension is high and the sacs are hard to open and easily collapse. Think of surface tension like blowing up those latex balloons as a child. Very hard to get them started but once those little balloons open a little it is much easier! The x-ray above shows you what the lungs of a newborn with RDS look like. They are described as having a “ground glass” appearance which if you recall is the white glass that you write on using a grease pencil when you are using a microscope slide. Remember that?
Before your infant was born you may have received two needles in your buttocks. These needles contain steroid that helps your unborn baby make surfactant so that when they are born they have a better chance of breathing on their own.
Things we can do after birth
Even with steroids the lungs may be “sticky” after birth and difficult to open. The way this will look to you is that when your baby takes a breath since it is so difficult the skin in between the ribs may seem to suck in. That is because the lungs are working so hard to take breath in that the negative pressure is seen on the chest. If your baby is doing that we can start them on something called CPAP which is a machine that uses a mask covering the nose and blows air into the chest. This air is under pressure and helps get oxygen into the lungs and gives them the assist they need to overcome the resistance to opening.
Some babies need more than this though and will need surfactant put into the lungs. The way this is done is typically by one of two ways. One option is to put a plastic tube in between the vocal cords and then squirt in surfactant (we get it from cow’s or pigs) and then typically the tube is withdrawn (you may hear people call it the INSURE technique – INtubate, SURfactant, Extubate). For some babies who still need oxygen after the tube is put in they may need to remain on the ventilator to help them breathe for awhile. The other technique is the LISA (Less Invasive Surfactant Administration). This is a newer way of giving surfactant and typically involves putting a baby on CPAP and then looking at the vocal cords and putting a thin catheter in between them. Surfactant is then squirted into the trachea and the catheter taken out. The difference between the two methods is that in the LISA method your baby is breathing on their own throughout the procedure while receiving CPAP.
Even if no surfactant is given the good news is that while RDS typically worsens over the first 2-3 days, by day 3-4 your baby will start to make their own surfactant. When that happens they will start to feel better and breathe easier. Come to think of it you will too.
On occasion two articles will be published in short succession and have discrepant findings. This appears to be one of those times. Hishikawa K in Japan published a paper in September entitled Pulmonary air leak associated with CPAP at term birth resuscitation while Calebi MY from Turkey published Impact of Prophylactic Continuous Positive Airway Pressure on Transient Tachypnea of the Newborn and Neonatal Intensive Care Admission in Newborns Delivered by Elective Cesarean Section in August of this year.
The findings as we will discuss were quite discrepant which on the surface leaves the practitioner in a quandry. How do I best treat my patients? The key difference between the two studies was the finding of an increased rate of pneumothorax in the study by Hishikawa when CPAP was used in term infants with respiratory distress after delivery. Curiously prophylactic CPAP of +5 was used in both studies but the populations under study were quite different. The study by Calebi targeted infants between 34 0/7 weeks and 38/6/7 weeks vs term infants in the study from the Japanese group.
Another important difference is the utilization of CPAP which in the study by Calebi involved prophylactic administration within twenty minutes of birth and in the Japanese cohort the indication was the development of symptoms. Thinking about this for a moment, these two groups are actually quite different. A newborn with TTN has an increased amount of interstitial fluid that has not made it’s way to the hilum for reabsorption in the lymphatic system. The lungs of these infants are heavier with fluid than comparable infants without such pathology and therefore are also less compliant. Non compliant lungs are prone to microatelectasis as the infants progressively experience alveolar collapse. The longer the clinician waits to start supportive CPAP the more the lungs collapse and greater negative pressure is required to open these closing alveoli. Furthermore if there is fluid in the airway itself there is the potential for a ball valve mechanism to come into effect whereby air is able to pass through the dilated airways during inspiration but on expiration the collapse leads to air trapping. Such trapping places the infant at risk for air leak. CPAP is used to establish an adequate functional residual capacity (FRC) as indicated in this picture. Failure to do so results in atelectasis.
The Japanese study examines the impact of CPAP after a change in guidelines in 2010 suggesting that CPAP should be utilized in the delivery suite for those infants with ongoing respiratory distress. The study by Calebi really examines a different patient group being those who are near term patients with TTN who have early CPAP implemented. The early administration of CPAP may be the technique that prevents alveolar collapse as mentioned above and avoids the requirement by the infant to generate such high negative pressure with its inherent risk of air leak.
Is All CPAP The Same?
Another important distinction between the two papers is the way in which CPAP was administered. The Japanese utilized a flow inflating bag with a pressure valve and manometer while the study by Calebi employed a T-piece resuscitator. When it comes to maintaining CPAP there is no question having used both devices that I find the T-piece resuscitator much easier to use and over longer periods the reliability of the pressure delivered by the T-piece would be superior to that with the flow inflating bag. The Neopuff T-Piece Resuscitator possesses a pressure relief valve which could help during an instance when the patient is crying or breath holding. The constant flow without a relief valve could lead to airleak which is precisely the situation that may occur during the use of a flow inflating bag.
Yes there was over a three fold increase in airleak at near term gestational age in the Japanese cohort but this was not seen at all in the Turkish study in which CPAP was implemented early. So the message here is that if you start CPAP early enough you can prevent airleaks from occurring. This in and of itself is worth implementing.
Can CPAP Reduce Hospital Admission to NICU?
There is more to the story however. The Turkish group demonstrated a significant difference in admission rates to the NICU as shown in the following figure. The results here although just achieving significance should not be minimized. Avoiding progressive atelectasis decreases admission rates. The conclusion here is that there is little benefit in adopting a wait and see approach to those kids born by elective c-section. While it is true that you may be treating a significant number of healthy patients between 34 0/7 – 38 6/7 weeks with CPAP it is for a brief period and makes a significant difference in frequency of admission.
We live in an era of bed shortages and I would argue that anything we can do to reduce admissions and moreover keep babies with their parents is worth exploring. From my perspective treating these kids with the appropriate CPAP device for twenty minutes after birth is well worth it. Perhaps your unit should consider the same.