The lungs of a preterm infant are so fragile that over time pressure limited time cycled ventilation has given way to volume guaranteed (VG) or at least measured breaths. It really hasn’t been that long that this has been in vogue. As a fellow I moved from one program that only used VG modes to another program where VG may as well have been a four letter word. With time and some good research it has become evident that minimizing excessive tidal volumes by controlling the volume provided with each breath is the way to go in the NICU and was the subject of a Cochrane review entitled Volume-targeted versus pressure-limited ventilation in neonates. In case you missed it, the highlights are that neonates ventilated with volume instead of pressure limits had reduced rates of:
death or BPD
pneumothoraces
hypocarbia
severe cranial ultrasound pathologies
duration of ventilation
These are all outcomes that matter greatly but the question is would starting this approach earlier make an even bigger difference?
Volume Ventilation In The Delivery Room
I was taught a long time ago that overdistending the lungs of an ELBW in the first few breaths can make the difference between a baby who extubates quickly and one who goes onto have terribly scarred lungs and a reliance on ventilation for a protracted period of time. How do we ventilate the newborn though? Some use a self inflating bag, others an anaesthesia bag and still others a t-piece resuscitator. In each case one either attempts to deliver a PIP using the sensitivity of their hand or sets a pressure as with a t-piece resuscitator and hopes that the delivered volume gets into the lungs. The question though is how much are we giving when we do that?
High or Low – Does it make a difference to rates of IVH?
One of my favourite groups in Edmonton recently published the following paper; Impact of delivered tidal volume on the occurrence of intraventricular haemorrhage in preterm infants during positive pressure ventilation in the delivery room. This prospective study used a t-piece resuscitator with a flow sensor attached that was able to calculate the volume of each breath delivered over 120 seconds to babies born at < 29 weeks who required support for that duration. In each case the pressure was set at 24 for PIP and +6 for PEEP. The question on the authors’ minds was that all other things being equal (baseline characteristics of the two groups were the same) would 41 infants given a mean volume < 6 ml/kg have less IVH compared to the larger group of 124 with a mean Vt of > 6 ml/kg. Before getting into the results, the median numbers for each group were 5.3 and 8.7 mL/kg respectively for the low and high groups. The higher group having a median quite different from the mean suggests the distribution of values was skewed to the left meaning a greater number of babies were ventilated with lower values but that some ones with higher values dragged the median up.
Results
IVH | < 6 mL/kg | > 6 ml/kg | p |
1 | 5% | 48% | |
2 | 2% | 13% | |
3 | 0 | 5% | |
4 | 5% | 35% | |
Grade 3 or 4 | 6% | 27% | 0.01 |
All grades | 12% | 51% | 0.008 |
Let’s be fair though and acknowledge that much can happen from the time a patient leaves the delivery room until the time of their head ultrasounds. The authors did a reasonable job though of accounting for these things by looking at such variables as NIRS cerebral oxygenation readings, blood pressures, rates of prophylactic indomethacin use all of which might be expected to influence rates of IVH and none were different. The message regardless from this study is that excessive tidal volume delivered after delivery is likely harmful. The problem now is what to do about it?
The Quandary
Unless I am mistaken, there isn’t a volume regulated bag-mask device that we can turn to for control of delivered tidal volume. Given that all the babies were treated the same with the same pressures I have to believe that the babies with stiffer lungs responded less in terms of lung expansion so in essence the worse the baby, the better they did in the long run at least from the IVH standpoint. The babies with the more compliant lungs may have suffered from being “too good”. Getting a good seal and providing good breathes with a BVM takes a lot of skill and practice. This is why the t-piece resuscitator grew in popularity so quickly. If you can turn a couple of dials and place it over the mouth and nose of a baby you can ventilate a newborn. The challenge though is that there is no feedback. How much volume are you giving when you start with the same settings for everyone? What may seem easy is actually quite complicated in terms of knowing what we are truly delivering to the patient. I would put to you that someone far smarter than I needs to develop a commercially available BVM device with real-time feedback on delivered volume rather than pressure. Being able to adjust our pressure settings whether they be manual or set on a device is needed and fast!
Perhaps someone reading this might whisper in the ear of an engineer somewhere and figure out how to do this in a device that is low enough cost for everyday use.
Rule of thumb is watch the chest movement with every breath. Careful not to get too much of a chest rise. A minimal chest rise is usually sufficient to provide Co2 exchange and increase saturation provided you use peep and make every breath count. New professionals get too excited and overlook their bagging pressures. Every breath has to be minimal, it only takes one breath to over stretch those Alveoli.
Thats right the wsy I did it good to hear it
Agreed
Something similar to this?
Solevåg AL, Haemmerle E, van Os S, A Novel Prototype Neonatal Resuscitator That Controls Tidal Volume and Ventilation Rate: A Comparative Study of MaskVentilation in a Newborn Manikin (2016)
I have seen similar devices at conferences, but these all rely on the user reducing the pressure and Ti to reduce to TV.
Though looks a little bulky to be using on a small baby and interestingly after the comment above, the practitioners in the study did not get to see any chest rise in the mannequin so did not get that piece of clinical feedback.
I do agree the first breath making all the deference, a great neonatologist tuaght me this many years ago at the center.
It would be very nice ( optimal) to use the VG strategy right away in the delivery room ( where indicted ).
So far T price serving the purpose much batter thean other bagging tool but it will be great to a tool where we aware how much volume wil deliver till that time our vigilant ( obsessive behavior with our self and junior staff ) will hopefully limits a possible damage .
I believe the biggest challenge is the variable leak that occurs with a mask. Masimo has a small capnography device called the EMMA that has a Neo-Ped adaptor with less than 1 ml of dead space and low resistance.
I wonder if they could measure flow to determine a volume? The engineers always like challenges and are very receptive to clinician feedback and product enhancement suggestions.
The other problem I see at reususcitations is hyperventilation by the person bagging. Even with appropriate volumes, the babe gets breatstacked unintentionally due to the anxiety of the person bagging.
Becky
Becky
To avoid unintensionally hyperinflation just Debriefing the team and simulation can solve this issue
Follow the NRP song for ventilation the one who take caring of the Air way must sing it loudly
Breath 2 3 Breath 2 3 Breath 2 3
Breath insspiration
2 3 expiration
Jess soto
We are adusting the flow to 10 L/m
If T piece is not available we are using the Ambubags with manometer to know how much pressure we are giving initially up to 25 green zone
To achieve a good chest rise we are following ventilation corrective steps MRSOPA
IF there is no chest rise
Tthank you.
I beleive that all physicians taking care of newborns in D.R should always keep in mind that gentle non invasive ventilation is so far.more safe and promising than other methods of ventilation in more than 90 percent of cases