For as long as I can remember I was taught that there is a desperate need to intubate babies with congenital diaphragmatic hernia right after birth and place an NG to suction. The goal of this manouver was to minimize the amount of swallowed air into the GI tract and thereby give our best chance at ventilation. If there was a dogma in Neonatology this had to be one right near the top. In fact, attending the delivery of a baby with a known CDH has been ike watching a well trained SWAT team in action with everyone committed to their roles and importantly getting that ETT in as fast as possible being the first goal. Once the tube is in though we often have the problem of having a vigorous term infant who needs a fair bit of sedation to keep the tube in. Moreover, they don’t want to be intubated so keeping them settled may require significant doses of opiates and or benzodiazepines which in turn may wreak havoc with their hemodynamics and require pressor support. Not a great start to life.
There is a subset of patients with CDH who are said to have “mild CDH” Their characteristics are that they have an isolated leftsided CDH with an observed-to-expected lung to-head ratio (O/E LHR) greater than or equal to 50%, and intraabdominal liver position. The survival for this group exceeds 95%.
Researchers from the Netherlands published last year Routine Intubation in Newborns With Congenital Diaphragmatic Hernia. In the paper they make the argument that there could be another way to handle such babies whcih they call the spontaneous breathing approach or SBA. Basically, a team approach with perinatology is used to identify these lower risk fetuses with CDH and then at birth the following approach is used as per the paper.
“The newborn is positioned on the resuscitation table and a Replogle tube (10F catheter) is inserted for continuous stomach decompression. In the case of planned SBA, the infant is supported with oxygen if necessary (Neopuff infant T-piece resuscitator; Fisher & Paykel Healthcare, Ltd, Auckland, New Zealand), aiming for preductal saturations .85%.4 Continuous positive airway pressure isallowed. The infant is intubated if insufflation breaths or ventilation are needed because positive pressure ventilation via mask increases the air in the digestive tract, subsequently compressing the lungs, resulting in hypoxia and PH.”
They Tried it Out
Armed with this approach the authors performed a retrospective study to determine whether the approach above is a reasonable one to take based on their own experience. Looking at the figure below over about a 5 year period they had 71 patients with CDH. Eighteen met their criteria for low risk and 15 of those had a planned SBA. Of the 15, SBA was successful (meaning they did not require intubation prior to surgery) in 6 or 40% while the other 60% did not tolerate the approach.
Looking at characteristics of those who were successful vs not was presented in table 1 below. There were no baseline characteristics that stood out to indicate higher or lower likelihood of success but it is clear that not having success has an impact. Those who did not tolerate the SBA had longer durations of ventilation and length of stay. This is an association but I would imagine the increased durations have more to do with the fact that the infants were sicker than expected rather than anything else.
What Can We Say About It?
I think there are a number of interesting aspects to this approach. The first is that the old dogma of saying that all these infants need to be intubated to prevent intestinal distension is incorrect. Secondly, the use of CPAP as long as there was gastric suction did not impact these infants to any signicant degree. The survival of this group regardless of tolerance or failure of the SBA was 100% and only one patient needed iNO therapy with an LHR of 57%. Of course the numbers here are small so I am not suggesting for a moment that this clearly is the way to go. It does provide strong support though for a prospective trial that I understand is in the works. In the meantime what do we do with the babies that are to come? For the most part I think units need to decide as a group what approach they are willing to take with these low risk patients. It will cause great confusion for staff if one week a baby is put on CPAP and the next with a similar risk profile a baby is urgently intubated. Lastly let me say that I love that something I was taught 25 years ago to ALWAYS do is now being questioned. What’s next?
Who doesn’t love a good match up?! Supporting neonates in need of resuscitation after delivery has been the subject of many studies over the years. The movement has certainly been to non-invasive support with CPAP or NIPPV but some babies need some degree of support with PPV after delivery when they simply won’t breathe. Prior to intubation the rise of the t-piece resuscitator has meant that practitioners can set a PIP and PEEP and with only a finger press to deliver a tidal volume at set pressure and with the finger released provide CPAP through the same device. The only problem potentially with use of these devices is the imposed work of breathing (iWOB) which has been measured in other studies. Any device I have used has provided ventilation through a mask so imagine my surprise to come across a new device called rPAP using prongs from the original infant flow design. From the manufacturers website the company claims that their design used with either a mask or nasal prongs reduces iWOB by 92% compared to other comparable machines! Imagine my greater surprise to see a head to head RCT comparing this new device to standard t-piece resuscitators with a mask.
The intervention was completed with one of three outcomes were met.
Stable and breathing on method of support after a minimum of 10 minutes of support.
At 30 minutes when respiratory support could continue as decided by the clinician without crossover allowed.
Looking at the appendices for the trial it appears that one could use either device to administer PPV or CPAP but the point of the trial was that the devices would be used to support the infants until one of the three above criteria were met. If the claims about reduced iWOB were true compared to other devices in use then one might expect to see a difference in the primary outcome of incidence of intubation or death within 30 minutes of birth.
In total there were 250 infants recruited with 127 assigned to the rPAP and the other 123 to t-piece resuscitation. The mean GA in the trial was 24.8 weeks and the baseline characteristics between groups were similar although the group randomized to the rPAP has more c-sections and more general anesthetic exposure compared to the t-piece group. Lastly, humidification of gases during resuscitation was similar between the two groups.
How Did They Compare?
It just might be that the claims of decreased iWOB might have merit. In Figure 2 below the Kaplan-Meier curves show a difference favouring the rPAP device when looking at the primary outcome. This difference was significant with 41 of 124 infants (33.1%) in the rPAP group and in 55 of 122 infants (45.1%) in the T-piece group having the primary outcome of intubation or death within the first 30 minutes of life. Moreover when looking at the adjusted odds ratio it was still significant at 0.53; 95% CI, 0.30-0.94. The incidence of intubation and death in the first 72 hours although trending towards favouring the new system did not reach statistical significance.
Finally, none of the secondary outcomes reached statistical significance which included such things as death in the delivery room, use of surfactant, or PPV in the DR.
Does it make sense?
If you had asked me to tell you prior to the study whether resuscitation with nasal prongs vs a mask would be different I would have said a mask would be better due to less leak. Turns out based on this data that I would be wrong in that guess. A look at the website though for the rPAP device indicates that it can be used with a mask or nasal prongs. It would have been nice in the study presented here to have used a mask as a third arm with the rPAP device as it leaves me wondering a bit whether it was the interface that mattered more than the type of driver used? Maybe I am wrong and by using prongs it allows the infant to have less iWOB than with a mask over the mouth and nose? Could it be that it has more to do with that that the type of driver whether it is a traditional t-piece resuscitator or the new rPAP device? Regardless, I have a suspicion that these results will resonate with people. A posting of the abstract alone has garnered a lot of attention on twitter this week so clearly this is of interest.
I don’t think there is much fault to find in this study other than my question of why they didn’t choose to have a head to head comparison with masks as well but perhaps that is for another study. I imagine we will see this approach adopted in many centres around the world as they replace their traditional t-piece resuscitators in need of replacement. I also suspect there will be many that will want a larger study before adopting this strategy to look more closely with come faith in the results at secondary outcomes in particular having to do with safety.
One thing is for certain. There will be more studies to come!
Here in Winnipeg we don’t use t-piece resuscitators for any resuscitation. I did use them in my past position in Edmonton and I came to appreciate them for their ease of use. For the majority of infants, setting a PIP and a PEEP and then using your finger to occlude and release offers a relatively simple and less difficult approach to ventilation than using a self inflating or jackson-rees bag. I say the majority of infants, as most infants are not born from 22-32 weeks but the lion’s share are born at gestations older than that. The larger more mature infants have lungs that are much more forgiving to excessive ventilation. For the smallest of infants though questions have remained for some time around the volumes delivered to the fragile lung when a fixed pressure is used in the presence of moment to moment changes in compliance.
Measuring Tidal Volume in Intubated At Risk Infants
Vaidya R et al published Tidal volume measurements in the delivery room in preterm infants requiring positive pressure ventilation via endotracheal tube feasibility study in Journal of Perinatology. The prospective observational study looked at 10 infants born at < 32 weeks with a mean GA of 23.9(±1.5) weeks and mean BW 618.5(±155)g. A mean of 17.8 minutes of recordings were examined using the setup below and in total looked at 8175 individual breaths. All patients in the study were intubated with non-cuffed ETT but by only including intubated infants in the delivery room the issue of mask leak was avoided. As in many units the target Vt was 4-6 mL/kg. It wasn’t specified what criteria they use for setting initial pressures but the included patients had a mean PIP of 24.4±5 and PEEP of 5.9 ±2.4. Importantly, those providing ventilation with the t-piece resuscitator were blinded to the data on tidal volume measurements.
How Good Were They At Meeting Their Goal?
It turns out that they weren’t that great (I am not faulting them by the way) as it is a challenge to try and adjust pressures based on chest rise. We are not good at it at all. As shown in the figure below there was a wide range of volumes administered. In fact here is the breakdown. The goal Vt between 4-6 was only 25% of the time. In other words you are dealing with either a risk of atelectotrauma or volutrauma 75% of the time. It is worth noting that the neonatal flow sensor has a dead space of 1 mL. If that is the case and the infants on average were about 600g that is almost 2 mL/kg in non-ventilated space that this volume is going into. It doesn’t change the numbers that much if you factor that in but it does mean that some infants who were getting a measured 3 mL/kg were actually seeing under 2 mL/kg of lung ventilation. On the other hand those getting 7 mL/kg were actually seeing under 6 mL/kg so were in target. Bottom line though is that when using fixed pressure settings in the presence of changing compliance even if one is adjusting pressure in real time it is difficult to maintain stable volumes in target range. The authors also demonstrate in another graph that even in individual patients there is fluctuation as well.
Call to Action
I think this study is actually quite useful in confirming what I imagine many have always suspected. We just aren’t that great at assessing tidal volume when we watch the chest rise. As many have noted, the first 6 breaths at least in an animal model can damage the lungs. Imagine what excessive or low volumes can do to the lung over 18 minutes?!
What this study does is demonstrate especially in the smallest and most vulnerable infants that if ventilation is needed one should put the infant onto a volume guaranteed mode of ventilation ASAP. Ventilators should be in the resuscitation area as we have in our hospital and not have to be brought in should the baby be intubated. Hand bagging even with a t-piece resuscitator should be kept to a minimum. At risk is the development of BPD and knowing that even in experienced hands we just aren’t that good at delivering tidal volumes in a target range we need to strive to minimize the time that we expose our infants to such modalities. Ventilation isn’t always avoidable but when needed my advice is to control volume and allow pressures to fluctuate as resistance and compliance change. Especially after administration of surfactant the pulmonary mechanics are changing constantly and no matter how good you are you just won’t be able to keep pace. Let the ventilator do it!