A question that we are asked from time to time is whether a home apnea monitor should be purchased after discharge from the hospital. The typical parent is one who has experienced the ups and downs of apnea of prematurity and is faced with the disturbing notion of coming off monitors and going home. “What if he has an event at home and I don’t know”? This leads to a search on the web for home monitors which finds numerous options to choose from. This is where things get interesting from a North American perspective.
In the two centres I have worked at in Canada our answer to such a question is to save your money and not buy one. Contrast this with two families I know in the US who were sent home by the hospital with home apnea monitors. How can the advice between the two nations be so different? I suspect the great risk of a lawsuit in the US is responsible at least in part but it may have to do with risk tolerance as well.
What does the evidence say?
First off, one might surmise that the use of a home apnea monitor helps hospitals move patients to the home faster than those centres that don’t prescribe them. A 2001 Cochrane systematic review on the subject noted that this was not the case and determined that out of nearly 15000 neonates studied the greatest predictor of sending such babies home on monitors was physician preference.
In the largest home monitoring study of its kind, the Collaborative Home Infant Monitoring Evaluation (CHIME) demonstrated some very important information. First off, ex-preterm infants have events and some of them quite significant after discharge. What the study which followed discharged infants at risk of SIDS in the home environment found though was that term infants also have events although less severe. Does this mean that everyone should run out and buy such monitoring equipment though? No! The main reason was that while the study did show that events may continue after discharge, it failed to show that these events had any relation to SIDS. The apneic events noted in hospital disappeared long before the arrival of a risk for SIDS. They really are separate entities.
The other issue with such monitors pertains to false alarms which can lead to sleepless nights, anxiety in parents and eventual abandonment of such technology. This led the AAP in 2005 to declare that they did not endorse such practice. Having said that, it is clear from my own experience with two US ex-preterm infants that this practice remains alive and well.
Could this be the solution?
One of my followers sent me this tonight and I have to say at the very least I am intrigued. The device is called the Owlet and was featured in this article The Sock That Could Save Your Babies Life.
Watch the video here.
This monitor has me a little excited as it brings the home apnea monitor into the modern era with smart phone connectivity and at the same time helps the developers of this technology use data collected every two seconds to get a clearer picture on breathing patterns in infants that have been sent home. The saturation monitor in a sock is at the core of this technology which is meant to keep the probe in a relatively stable location. It brings another angle to the concept of wearable tech! What I find most interesting is the claim by the manufacturer that the device has a false alarm rate similar to that of a hospital saturation probe which would make it quite reliable.
I note though that the product has not received FDA approval yet (at least on the source I looked at) but is being worked on. The challenge though is whether this will truly make a difference. It may well have an excellent detection rate and it may in fact detect true apnea leading to bradycardia and cyanosis. What it won’t do though is change the natural history of these events once home. It may capture them very well but I suspect the four events that the mother in the video describes may have been self resolving if she hadn’t intervened. We know from the CHIME study that the events seen in the home did not lead to death from SIDS so I see no reason why these would be different.
Is it useless?
I suppose that depends on your perspective. From a data collection point, obtaining data every two seconds in a cloud based storage environment will allow this company to describe the natural history of respiratory patterns in ex-preterm infants better than I suspect has ever been done before. From a population standpoint I suppose that is something! At an individual level I suppose it depends on your strength of “needing to know”. This may well be the best monitor out there and it may one day be the most reliable. Will it save your baby’s life? I doubt it but might it give you piece of mind if it false alarms very infrequently? I think it just might but based on the low likelihood of it changing the outcome of your baby you won’t see me recommending it. If I come across one make no mistake about it, I will want to play with it myself!
Now that I have caught your attention it is only fair that I explain what I mean by such an absurd title. If you work with preterm infants, you have dealt with apnea of prematurity. If you have, then you also have had to manage such infants who seemingly are resistant to everything other than being ventilated. We have all seen them. Due to increasing events someone gives a load of methylxanthine and then starts maintenance. After a couple days a miniload is given and the dose increased with the cycle repeating itself until nCPAP or some other non-invasive modality is started. Finally, after admitting defeat due to persistent episodes of apnea and/or bradycardia, the patient is intubated. This, in the absence of some other cause for apnea such as sepsis or seizures is the methylxanthine resistant preterm infant. Seemingly no amount of treatment will amount to a reduction in events and then there is only so much that CPAP can do to help.
Other strategies have been attempted to deal with such infants but sadly none have really stood the test of time. Breathing carbon dioxide might make sense as we humans tend to breathe quickly to excrete rising CO2 but in neonates while such a response occurs it does not last and is inferior to methylxanthine therapy. Doxapram was used in the past and continues to be used in Europe but concerns over impacts on neurodevelopment have been a barrier in North America for some time. Stimulating infants through a variety of methods has been tried but the downside to using for example a vibrating mattress is that sleep could be interfered with and there are no doubt impacts to the preterm infant of having weeks of disturbed sleep states on developmental outcomes.
What if we could make our preterm infants walk?
This of course isn’t physically practical but two researchers have explored this question by using vibration at proprioceptors in the hand and foot. Such stimulation may simulate limb movement and trick the brain into thinking that the infant is walking or running. Why would we do this?. It has been known for 40 years that movement of limbs as in walking triggers a respiratory stimulatory effect by increasing breathing. This has been shown in adults but not in infants but this possibility is the basis of a study carried out in California entitled Neuromodulation of Limb Propriceptive Afferents Decreases Apnea of Prematurity and Accompanying Intermittent Hypoxia and Bradycardia. This was a small pilot study enrolling 19 patients of which 15 had analyzable data. The design was that of alternating individual preterm infants born between 23 – 35 weeks to receive either vibratory stimulation or nothing and measuring the number and extent of apnea and bradycardia over these four periods. In essence this was a proof of concept study.
The stimulation is likened to that felt when a cell phone vibrates as this was the size of device used to generate the sensation. The authors note that during the periods of stimulation the nurses noted no signs of any infant waking or seeming to be disturbed by the sensation. The results were quite interesting especially when noting that 80% of the infants were on caffeine during the time of the study so these were mostly babies already receiving some degree of stimulation
Should we run out and buy these?
The stimulation does appear to work but with any small study we need to be careful in saying with confidence that this would work in a much larger sample. Could there have been some other factor affecting the results? Absolutely but the results nonetheless do raise an eyebrow. One thing missing from the study that I hope would be done in a larger sample next time is an EEG. The authors are speculating that by placing the vibration over the hand and foot the brain is perceiving the signal as limb movement but it would have been nice to see the motor areas of the brain “lighting up” during such stimulation. As we don’t have that I am left wondering if the vibration was simply a form of mild noxious stimulus that led to these results. Of course in the end maybe it doesn’t matter if the results show improvement but an EEG could also inform us about the quality of sleep rather than relying on nursing report of how they thought the baby tolerated the stimulus. I know our nursing colleagues are phenomenal but can they really discern between quiet and active sleep cycles? Maybe some but I would guess most not. There will also be the naysayers out there that will question safety. While we may not perceive a gentle vibration as being harmful, with such a small number of patients can we say that with certainty? I am on the side of believing it is probably insignificant but then again I tend to see the world through rose coloured glasses.
Regardless of the filter through which you view this world of ours I have to say I am quite excited to see where this goes. Now we just have to figure out how to manage the “real estate” of our infant’s skin as we keep adding more and more probes that need a hand or a foot for placement!
For those of you who know me and my practice as a Neonatologist you may find the title of this piece odd. I have and will likely continue to be an advocate for the use of caffeine in premature infants. I recommend it both very early in the caseroom for those under 32 weeks to help stave off intubation and often continue caffeine until late in an infants’ stay in the NICU. Truth be told I also send children home on caffeine on occasion when all other markers needed for discharge have been met but they continue to have episodes of apnea and bradycardia that are not resolving and prolonging their stay in hospital.
In recent years I have noticed a creep of practice to begin pushing doses of caffeine base beyond the 5 mg/kg level that has been generally accepted as the upper limit of the 2.5 to 5 mg/kg range that most use in practice. The standard dosing was justified based on the CAP study by Schmidt et al indicating that it was effective in reducing the risk of bronchopulmonary dysplasia and success at earlier extubation. While there appeared to be an initial benefit to neurodevelopment favouring caffeine treatment by school age the difference disappeared. This creep effect to using higher daily maintenance dosing of 7 or 8 mg/kg/d has occurred likely for some good reasons not the least of which is a dose effect in which clinicians could see a reduction in clinical events for some patients as they increased the dose. We are no different as doctors than others in that success tends to shape our practice. Now before you accuse us of being mavericks, we did have some evidence to support the use of higher dosing beyond the 5 mg/kg dosing that had been recommended. Published in 2004, Steer and colleagues studied the effect of using a loading dose of 80 mg/kg caffeine citrate (take 50% reduction to get the base formulation we normally use) followed by 20 mg/kg maintenance dosing vs 20 mg/kg loads and 5 mg/kg maintenance in a cohort of infants < 30 weeks gestation who were having a planned extubation. The full article may be found here. The results of the study demonstrated greater success in extubation and less apnea in the group treated with the higher doses as shown here.
The results of this study certainly made some waves in the Neonatal community as can be seen by the “creep” in practice over the last number of years to increase the caffeine dose in our units to 6, 7 and sometimes 8 mg/kg of caffeine base in an effort to essentially titrate to effect especially in infants who are on CPAP. The motivation to prevent a reintubation secondary to apnea has been so compelling that the theoretical concerns over lack of long-term outcome data on high dose caffeine treatment have been largely ignored.
At this point it is important to also recognize that the way in which we use caffeine in terms of initiation of treatment has also changed. Many units have adopted the “Golden Hour” approach to neonatal resuscitation and are driven to use non-invasive means of support after encouraging results from several trials such as the Support, Boost and the more recent Canadian NIPPV trial. While not demonstrating improvements in outcomes necessarily, the fact that BPD rates are mostly unchanged means that with the use of early caffeine in the delivery room and the use of CPAP one can avoid invasive ventilation in many infants. As such, there has been a departure from the practice as described by Steer and colleagues to using caffeine to facilitate extubation to trying to prevent it in the first place.
In discussions with some of my colleagues we have expressed some reservation over the use of the higher doses of caffeine beyond 5 mg/kg and with the publication of a study this week by McPherson et al, these concerns may be quite warranted. For the complete study click here. This study of 74 preterm infants randomized them in the first 24 hours of life to either 80 mg/kg or 20 mg/kg caffeine citrate loads and then in both groups they followed these loads with 10 mg/kg per day maintenance. The primary outcome of the study was white matter structural development by MRI. Previous research by Doyle had found an improvement in this outcome with the use of standard caffeine therapy of 10 mg/kg/d so the real question here was “If a little is good, then is more better?”
Sadly the answer to the last question is a resounding NO!
None of the respiratory outcomes were any different between the standard caffeine and high dose groups but the following came out as a worrisome outcome:
Furthermore when the infants were followed up at 2 years of age a statistically significant percentage of 2 year olds previously randomized to the high dose caffeine regimen were found to be hypertonic (2.3 vs. 1.5%). Overall neurodevelopment was no different between groups but it should be pointed out that the study was not powered to detect such differences.
One question that must come up with these findings is whether or not it is plausible that a 2 day exposure to high dose caffeine followed by standard dosing for the remainder of the time could lead to cerebellar hemorrhage. I think the answer is yes given the findings from a single dose of 25 mg/kg caffeine (equivalent to 50 mg of caffeine citrate/kg as studied by Hoecker et al
As noted by the authors, this single dose was responsible for reducing cerebral blood flow velocity by about 20% from baseline. The regimen over 48 hours in the above study was to give 80 mg/kg in divided doses as a load so it is reasonable to conclude these infants would have experienced a reduction in cerebral blood flow as well, and possibly to a greater degree than the patients in the Hoecker study. Add to this that these are infants under 30 weeks of age who have a fragile arterial and venous network to begin with and it seems reasonable that a period of hypoperfusion possibly combined with hypoxemia and then reperfusion injury could account for these cerebellar bleeds.
So where does this leave us? As the authors conclude it is not wise to plan a larger study looking at the same strategy given the findings in this pilot. What remains unclear at least to me is whether 6, 7 or 8 mg/kg during the maintenance phase of treatment offers any true long-term advantage. With anything there are tradeoffs though and finding the right balance is never easy. If we use lower caffeine doses and in some patients they require intubation, is the increased risk of CLD and possible neurodevelopmental impairment from that worth the limitation of risk? After the first week of life is the risk of cerebellar hemorrhage lower as the blood vessels mature? I think so which would make the argument for using higher doses at that point but in truth we just don’t know about safety in terms of long-term outcomes. For now at least it would seem that in the absence of guidance from research all we can really say is that 2.5 to 5 mg/kg/d of caffeine base is safe but that doses higher than that need to be used with caution. It may be wise to seek informed consent for the use of higher doses in light of these findings but it is up to each unit to decide if this is justified based on your views of the data. What do you think?