Capnography or colorimetric detection of CO2 in the delivery suite.  What to choose?

Capnography or colorimetric detection of CO2 in the delivery suite. What to choose?

For almost a decade now confirmation of intubation is to be done using detection of exhaled CO2. The 7th Edition of NRP has the following to say about confirmation of ETT placement “The primary methods of confirming endotracheal tube placement within the trachea are detecting exhaled CO2 and a rapidly rising heart rate.” They further acknowledge that there are two options for determining the presence of CO2 “There are 2 types of CO2 detectors available. Colorimetric devices change color in the presence of CO2. These are the most commonly used devices in the delivery room. Capnographs are electronic monitors that display the CO2 concentration with each breath.” The NRP program stops short of recommending one versus the other. I don’t have access to the costs of the colorimetric detectors but I would imagine they are MUCH cheaper than the equipment and sensors required to perform capnography using the NM3 monitor as an example. The real question though is if capnography is truly better and might change practice and create a safer resuscitation, is it the way to go?

Fast but not fast enough?

So we have a direct comparison to look at. Hunt KA st al published Detection of exhaled carbon dioxide following intubation during resuscitation at delivery this month. They started from the standpoint of knowing from the manufacturer of the Pedicap that it takes a partial pressure of CO2 of 4 mm Hg to begin seeing a colour change from purple to yellow but only when the CO2 reaches 15 mm Hg do you see a consistent colour change with that device. The capnograph from the NM3 monitor on the other hand is quantitative so is able to accurately display when those two thresholds are reached. This allowed the group to compare how long it took to see the first colour change compared to any detection of CO2 and then at the 4 and 15 mm Hg levels to see which is the quicker method of detection. It is an interesting question as what would happen if you were in a resuscitation and the person intubates and swears that they are in but there is no colour change for 5, 10 or 15 seconds or longer? At what point do you pull the ETT? Compare that with a quantitative method in which there is CO2 present but it is lower than 4. Would you leave the tube in and use more pressure (either PIP/PEEP or both?)? Before looking at the results, it will not shock you that ANY CO2 should be detected faster than two thresholds but does it make a difference to your resuscitation?

The Head to Head Comparison

The study was done retrospectively for 64 infants with a confirmed intubation using the NM3 monitor and capnography.  Notably the centre did not use a colorimetric detector as a comparison group but rather relied on the manufacturers data indicating the 4 and 15 mm Hg thresholds for colour changes.  The mean age of patients intubated was 27 weeks with a range of 23 – 34 weeks.  The results I believe show something quite interesting and informative.

Median time secs (range)
Earliest CO2 detection 3.7 (0 – 44s)
4 mm Hg 5.3 (0 – 727)
15 mm Hg 8.1 (0 – 727)

I wouldn’t worry too much about a difference of 1.6 seconds to start getting a colour change but it is the range that has me a little worried.  The vast majority of the patients demonstrated a level of 4 or 15 mm Hg within 50 seconds although many were found to take 25-50 seconds.  When compared to a highest level of 44 seconds in the first detection of CO2 group it leads one to scratch their head.  How many times have you been in a resuscitation and with no CO2 change you keep the ETT in past 25 seconds?  Looking closer at the patients, there were 12 patients that took more than 30 seconds to reach a threshold of 4 mm Hg.  All but one of the patients had a heart rate in between 60-85.  Additionally there was an inverse relationship found between gestational age and time to detection.  In other words, the smallest of the babies in the study took the longest to establish the threshold of 4 and 15 mm Hg.

Putting it into context?

What this study tells me is that the most fragile of infants may take the longest time to register a colour change using the colorimetric devices.  It may well be that these infants take longer to open up their pulmonary vasculature and deliver CO2 to the alveoli.  As well these same infants may take longer to open the lung and exhale the CO2.  I suppose I worry that when a resuscitation is not going well and an infant at 25 weeks is bradycardic and being given PPV through an ETT without colour change, are they really not intubated?  In our own centre we use capnometry in these infants (looks for a wave form of CO2) which may be the best option if you are looking to avoid purchasing equipment for quantitative CO2 measurements.  I do worry though that in places where the colorimetric devices are used for all there will be patients who are extubated due to the thought that they in fact have an esophageal intubation when the truth is they just need time to get the CO2 high enough to register a change in colour.

Anyways, this is food for thought and a chance to look at your own practice and see if it is in need of a tweak…

Can’t intubate to give surfactant? Maybe try this!

Can’t intubate to give surfactant? Maybe try this!

Intubation is not an easy skill to maintain with the declining opportunities that exist as we move more and more to supporting neonates with CPAP.  In the tertiary centres this is true and even more so in rural centres or non academic sites where the number of deliveries are lower and the number of infants born before 37 weeks gestational age even smaller.  If you are a practitioner working in such a centre you may relate to the following scenario.  A woman comes in unexpectedly at 33 weeks gestational age and is in active labour.  She is assessed and found to be 8 cm and is too far along to transport.  The provider calls for support but there will be an estimated two hours for a team to arrive to retrieve the infant who is about to be born.  The baby is born 30 minutes later and develops significant respiratory distress.  There is a t-piece resuscitator available but despite application the baby needs 40% oxygen and continues to work hard to breathe.  A call is made to the transport team who asks if you can intubate and give surfactant.  Your reply is that you haven’t intubated in quite some time and aren’t sure if you can do it.  It is in this scenario that the following strategy might be helpful.

Surfactant Administration Through and Laryngeal Mask Airway (LMA)

Use of an LMA has been taught for years in NRP now as a good choice to support ventilation when one can’t intubate.  The device is easy enough to insert and given that it has a central lumen through which gases are exchanged it provides a means by which surfactant could be instilled through a catheter placed down the lumen of the device.  Roberts KD et al published an interesting unmasked but randomized study on this topic Laryngeal Mask Airway for Surfactant Administration in Neonates: A Randomized, Controlled Trial. Due to size limitations (ELBWs are too small to use this in using LMA devices) the eligible infants included those from 28 0/7 to 35 6/7 weeks and ≥1250 g.  The infants needed to all be on CPAP +6 first and then fell into one of two treatment groups based on the following inclusion criteria: age ≤36 hours,
(FiO2) 0.30-0.40 for ≥30 minutes (target SpO2 88% and 92%), and chest radiograph and clinical presentation consistent with RDS.
Exclusion criteria included prior mechanical ventilation or surfactant administration, major congenital anomalies, abnormality of the airway, respiratory distress because of an etiology other than RDS, or an Apgar score <5 at 5 minutes of age.

Procedure & Primary Outcome

After the LMA was placed a y-connector was attached to the proximal end.  On one side a CO2 detector was placed and then a bag valve mask in order to provide manual breaths and confirm placement over the airway.  The other port was used to advance a catheter and administer curosurf in 2 mL aliquots.  Prior to and then at the conclusion of the procedure the stomach contents were aspirated and the amount of surfactant determined to provide an estimate of how much surfactant was delivered to the lungs.  The primary outcome was treatment failure necessitating intubation and mechanical ventilation in the first 7 days of life.  Treatment failure was defined upfront and required 2 of the following: (1) FiO2 >0.40 for >30
minutes (to maintain SpO2 between 88% and 92%), (2) PCO2 >65 mmHg on arterial or capillary blood gas or >70 on venous blood gas, or (3) pH <7.22 or 1 of the following: (1)  recurrent or severe apnea, (2) hemodynamic instability requiring pressors, (3) repeat surfactant dose, or (4) deemed necessary by medical provider.

Did it work?

It actually did. Of the 103 patients enrolled (50 LMA and 53 control) 38% required intubation in the LMA group vs 64% in the control arm.  The authors did not reach their desired enrollment based on their power calculation but that is ok given that they found a difference.  What is really interesting is that they found a difference in the clinical end point despite many infants clearly not receiving a full dose of surfactant as measured by gastric aspirate. Roughly 25% of the infants were found to have not received any surfactant, 20% had >50% of the dose in the stomach and the other 50+% had < 10% of the dose in the stomach meaning that the majority was in fact deposited in the lungs.  I suppose it shouldn’t come as a surprise that among the secondary outcomes the duration length of mechanical ventilation did not differ between two groups which I presume occurred due to the babies needing intubation being similar.  If you needed it you needed it so to speak. Further evidence though of the effectiveness of the therapy was that the average FiO2 30 minutes after being treated was significantly lower in the group with the LMA treatment 27 vs 35%.  What would have been interesting to see is if you excluded the patients who received little or no surfactant, how did the ones treated with intratracheal deposition of the dose fare?  One nice thing to see though was the lack of harm as evidenced by no increased rate of pneumothorax, prolonged ventilation or higher oxygen.

Should we do this routinely?

There was a 26% reduction in intubations in te LMA group which if we take this as the absolute risk reduction means that for every 4 patients treated with an LMA surfactant approach, one patient will avoid intubation.  That is pretty darn good!  If we also take into account that in the real world, if we thought that little of the surfactant entered the lung we would reapply the mask and try the treatment again.  Even if we didn’t do it right away we might do it hours later.

In a tertiary care centre, this approach may not be needed as a primary method.  If you fail to intubate though for surfactant this might well be a safe approach to try while waiting for a more definitive airway.  Importantly this won’t help you below 28 weeks or 1250g as the LMA is too small but with smaller LMAs might this be possible.  Stay tuned as I suspect this is not the last we will hear of this strategy!

Resuscitating before 22 weeks. It’s happening.

Resuscitating before 22 weeks. It’s happening.

Given that today is world prematurity day  it seems fitting to talk about prematurity at the absolute extreme of it.

It has been some time since as a regional program we came to accept that we would offer resuscitation to preterm infants born as early as 23 weeks gestational age.  This is perhaps a little later in the game that other centers but it took time to digest the idea that the rate of intact survival was high enough to warrant a trial of resuscitation.  This of course is not a unilateral decision but rather a decision arrived at after consultation with the family and interprofessional team.  To be sure it is not an easy one.  Other centers have argued that resuscitation should be offered to those infants as young as 22 weeks gestational age and data now exists due to enough centres doing so to provide families with some guidance as to expected survival rates and importantly the likelihood of disability. This topic has been covered previously in /2015/09/25/winnipeg-hospital-about-to-start-resuscitating-infants-at-23-weeks/. Why cover this topic again?  Well an article on CNN might have something to do with it.

Resuscitating Below 22 weeks

This week as I was perusing the news I came across a rather shocking article on CNN. Born before 22 weeks, ‘most premature’ baby is now thrivingThe article tells the tale of a baby delivered at 21 weeks and 4 days that now as a three year old is reaching appropriate milestones without any significant impairments.  It is a story that is filled with inspiration and so I am not mistaken I am delighted for this child and their family that this outcome has occurred.  When the lay press latches onto stories like this there is no doubt a great deal of sensationalism to them and in turn that gathers a lot of attention.  This in turn is a great thing for media.

A Few Caveats Though

With the exception of pregnancies conceived through IVF the best dating we have is only good to about +/- 5 days when an early first trimester ultrasound is performed or the date of the last menstrual period is fairly certain.  A baby though who is born at 21 weeks + 4 days may in fact be 22 +3 days or even more depending on when the dating was done (second trimester worse).  Let’s not take away though from the outcome being this good even at 22 weeks.  That is a pretty perfect outcome for this family but the point is that this baby may in fact be older than 21 weeks.

Secondly, there are millions of babies born each year in North America.  Some of these infants are born at 22 weeks.  How do they fare overall?  From the paper by Rysavy et al from 2015 the results are as follows.

If you look at the overall rate of survival it is on an average of 5.1%.  If you take a look though at those infants in whom resuscitation is provided that number increases to a mean of 23%.  Intact survival is 9% overall.  The odds aren’t great but they are there and I suspect the infant in the article is one of those babies.  Flipping the argument though to the glass is half empty, 91% of infants born at 22 weeks by best estimate who are offered resuscitation will have a moderate or severe disability or die. I am not saying what one should do in this situation but depending on how a family processes the data they will either see the 110 chance of intact survival as a good thing or a 9/10 chance of death or disability as a very bad thing.  What a family chooses though is anyone’s best guess.

Should we resuscitate below 22 weeks if the family wishes?

I guess in the end this really depends on a couple things.  First off, how certain are the dates?  If there is any degree of uncertainty then perhaps the answer is yes.  If the dates are firm then I at least believe there is a barrier at which futility is reached.  Perhaps this isn’t at 21 weeks as some patients may indeed be older but think about what you would offer if a family presented at 20 weeks and wanted everything done.  What if it were 19 weeks?  I suspect the point of futility for all lies somewhere between 19-21 weeks.

As I prepare to attend the annual meeting in Ottawa tomorrow for the Fetus and Newborn Committee I think it is prudent to point out just how difficult all of this is.  The current statement on Counselling and management for anticipated extremely preterm birth I think hits on many of these issues.  The statement is the product on not only the think tank that exists on this committee but was the product of a national consultation.  I know I may be biased since I sit on the committee but I do believe it really hits the mark.

Should we be thinking about resuscitating at 21 weeks?  For me the answer is one clouded by a whole host of variables and not one that can be easily answered here.  What I do think though is that the answer in the future may be a yes provided such infants can be put onto an artificial placenta.  Even getting a few more weeks of growth before aerating those lungs is necessary may make all the difference.  The NICUs of tomorrow certainly may look quite different than they do now.

Can a chest x-ray predict the future?

Can a chest x-ray predict the future?

If you work in Neonatology then chances are you have ordered or assisted with obtaining many chest x-rays in your time.  If you look at home many chest x-rays some of our patients get, especially the ones who are with us the longest it can be in the hundreds. I am happy to say the tide though is changing as we move more and more to using other imaging modalities such as ultrasound to replace some instances in which we would have ordered a chest x-ray.  This has been covered before on this site a few times; see Point of Care Ultrasound in the NICU, Reducing Radiation Exposure in Neonates: Replacing Radiographs With Bedside Ultrasound. and Point of Care Ultrasound: Changing Practice For The Better in NICU.This post though is about something altogether different.

If you do a test then know what you will do with the result before you order it.

If there is one thing I tend to harp on with students it is to think about every test you do before you order it.  If the result is positive how will this help you and if negative what does it tell you as well.  In essence the question is how will this change your current management. If you really can’t think of a good answer to that question then perhaps you should spare the infant the poke or radiation exposure depending on what is being investigated.  When it comes to the baby born before 30 weeks these infants are the ones with the highest risk of developing chronic lung disease.  So many x-rays are done through their course in hospital but usually in response to an event such as an increase in oxygen requirements or a new tube with a position that needs to be identified.  This is all reactionary but what if you could do one x-ray and take action based on the result in a prospective fashion?

What an x-ray at 7 days may tell you

How many times have you caught yourself looking at an x-ray and saying out loud “looks like evolving chronic lung disease”.  It turns out that Kim et al in their publication Interstitial pneumonia pattern on day 7 chest radiograph predicts bronchopulmonary dysplasia in preterm infants.believe that we can maybe do something proactively with such information.

In this study they looked retrospectively at 336 preterm infants weighing less than 1500g and less than 32 weeks at birth.  Armed with the knowledge that many infants who have an early abnormal x-ray early in life who go on to develop BPD, this group decided to test the hypothesis that an x-ray demonstrating a pneumonia like pattern at day 7 of life predicts development of BPD.  The patterns they were looking at are demonstrated in this figure from the paper.  Essentially what the authors noted was that having the worst pattern of the lot predicted the development of later BPD.  The odds ratio was 4.0 with a confidence interval of 1.1 – 14.4 for this marker of BPD.  Moreover, birthweight below 1000g, gestational age < 28 weeks and need for invasive ventilation at 7 days were also linked to the development of the interstitial pneumonia pattern.

What do we do with such information?

I suppose the paper tells us something that we have really already known for awhile.  Bad lungs early on predict bad lungs at a later date and in particular at 36 weeks giving a diagnosis of BPD.  What this study adds if anything is that one can tell quite early whether they are destined to develop this condition or not.  The issue then is what to do with such information.  The authors suggest that by knowing the x-ray findings this early we can do something about it to perhaps modify the course.  What exactly is that though?  I guess it is possible that we can use steroids postnatally in this cohort and target such infants as this. I am not sure how far ahead this would get us though as if I had to guess I would say that these are the same infants that more often than not are current recipients of dexamethasone.

Would another dose of surfactant help?  The evidence for late surfactant isn’t so hot itself so that isn’t likely to offer much in the way of benefit either.

In the end the truth is I am not sure if knowing concretely that a patient will develop BPD really offers much in the way of options to modify the outcome at this point.  Having said that the future may well bring the use of stem cells for the treatment of BPD and that is where I think such information might truly be helpful.  Perhaps a screening x-ray at 7 days might help us choose in the future which babies should receive stem cell therapy (should it be proven to work) and which should not.  I am proud to say I had a chance to work with a pioneer in this field of research who may one day cure BPD.  Dr. Thebaud has written many papers of the subject and if you are looking for recent review here is one Stem cell biology and regenerative medicine for neonatal lung diseases.Do I think that this one paper is going to help us eradicate BPD?  I do not but one day this strategy in combination with work such as Dr. Thebaud is doing may lead us to talk about BPD at some point using phrases like “remember when we used to see bad BPD”.  One can only hope.

 

Is our approach to ventilation really harming babies?

Is our approach to ventilation really harming babies?

A grenade was thrown this week with the publication of the Australian experience comparing three epochs of 1991-92, 1997 and 2005 in terms of long term respiratory outcomes. The paper was published in the prestigious New England Journal of Medicine; Ventilation in Extremely Preterm Infants and Respiratory Function at 8 Years. This journal alone gives “street cred” to any publication and it didn’t take long for other news agencies to notice such as Med Page Today. The claim of the paper is that the modern cohort has fared worse in the long run. This has got to be alarming for anyone reading this! As the authors point out, over the years that are being compared rates of antenatal steroid use increased, surfactant was introduced and its use became more widespread and a trend to using non-invasive ventilation began. All of these things have been associated with better short term outcomes. Another trend was declining use of post-natal steroids after 2001 when alarms were raised about the potential harm of administering such treatments.

Where then does this leave us?

I suppose the first thing to do is to look at the study and see if they were on the mark. To evaluate lung function the study looked at markers of obstructive lung disease at 8 years of age in survivors from these time periods. All babies recruited were born between 22-27 completed weeks so were clearly at risk of long term injury. Measurements included FEV1, FVC, FVC:FEV1 and FEF 25-75%. Of the babies measured the only two significant findings were in the FEV1 and ratio of FEV1:FVC. The former showed a drop off comparing 1997 to 2005 while the latter was worse in 2005 than both epochs.

Variable 1991-92 1997 2005
%predicted value N=183 N=112 N=123
FEV1 87.9+/-13.4 92.0+/-15.7 85.4+/-14.4
FEV1:FVC 98.3+/-10 96.8+/-10.1 93.4+/-9.2

This should indeed cause alarm. Babies born in a later period when we thought that we were doing the right things fared worse. The authors wonder if perhaps a strategy of using more CPAP may be a possible issue. Could the avoidance of intubation and dependence on CPAP for longer periods actually contribute to injury in some way? An alternative explanation might be that the use of continuous oximetry is to blame. Might the use of nasal cannulae with temporary rises in O2 expose the infant to oxygen toxicity?

There may be a problem here though

Despite everyone’s best efforts survival and/or BPD as an outcome has not changed much over the years. That might be due to a shift from more children dying to more children living with BPD. Certainly in our own centre we have seen changes in BPD at 36 weeks over time and I suspect other centres have as well. With concerted efforts many centres report better survival of the smallest infants and with that they may survive with BPD. The other significant factor here is after the extreme fear of the early 2000s, use of postnatal steroids fell off substantially. This study was no different in that comparing the epochs, postnatal glucocorticoid use fell from 40 and 46% to 23%. One can’t ignore the possibility that the sickest of the infants in the 2005 cohort would have spent much more time on the ventilator that their earlier counterparts and this could have an impact on the long term lung function.

Another question that I don’t think was answered in the paper is the distribution of babies at each gestational age. Although all babies were born between 22-27 weeks gestational age, do we know if there was a skewing of babies who survived to more of the earlier gestations as more survived? We know that in the survivors the GA was not different so that is reassuring but did the sickest possible die more frequently leaving healthier kids in the early cohorts?

This bigger issue interestingly is not mentioned in the paper. Looking at the original cohorts there were 438 in the first two year cohort of which 203 died yielding a survival of 54% while in 1997 survival increased to 70% and in 2005 it was 65%. I can’t help but wonder if the drop in survival may have reflected a few more babies at less than 24 weeks being born and in addition the holding of post natal steroids leading to a few more deaths. Either way, there are enough questions about the cohorts not really being the same that I think we have to take the conclusions of this paper with a grain of salt.

It is a sensational suggestion and one that I think may garner some press indeed. I for one believe strongly though as I see our rates of BPD falling with the strategies we are using that when my patients return at 8 years for a visit they will be better off due to the strategies we are using in the current era. Having said that we do have so much more to learn and I look forward to better outcomes with time!