Nasal High Frequency Oscillatory Ventilation For Preventing Intubation

Nasal High Frequency Oscillatory Ventilation For Preventing Intubation

I have reviewed many articles on this site in the last few years. My favourite pieces are ones in which I know the authors and I have to say my ultimate favourite is when I know the authors as colleagues. Such is the case this time around and it pertains to a topic that is not without controversy. Nasal High Frequency Oscillatory Ventilation or NHFOV for short is a form of non-invasive ventilation that claims to be able to prevent reintubation whether used prophylactically (extubation directly to NHFOV) or as a rescue (failing CPAP so use NHFOV instead of intubation). I have written about the topic before in the piece Can Nasal High Frequency Ventilation Prevent Reintubations? but this time around the publication we are looking at is from my own centre!

Retrospective Experience

One of our former fellows who then worked with us for a period of time Dr. Yaser Ali decided to review our experience with NHFOV in the paper Noninvasive High-Frequency Oscillatory Ventilation: A Retrospective Chart Review. Not only is one of our fellows behind this paper but an additional former fellow and current employee Dr. Ebtihal Ali and two of my wonderful colleagues Dr. Molly Seshia and Dr. Ruben Alvaro who both taught be a few things about this chosen career of mine.

The study involved our experience with using this technique (Draeger VN500 providing HFOV through first a RAM cannulae and then later with the FlexiTrunk Midline Interface (FlexiTrunk Midline Interface, Fisher & Paykel Healthcare) either using a prophylactic or rescue approach. The settings were standardized in both approaches as follows.


• Frequency of 6 to 8 Hz.
• Mean airway pressure (MAP)2 cmH2Oabove the MAP of invasive ventilation (whether conventional or high-frequency
• Amplitude to achieve adequate chest oscillation while at rest.


• Frequency of 6 to 8 Hz.
• MAP 1 to 2 cm H2O higher than positive end expiratory pressure (PEEP) on CPAP or biphasic CPAP.
• Amplitude to achieve adequate chest oscillation while at rest.

All in all there were 32 occasions for 27 patients in which prophylaxis was used in 10 and rescue in 22. In the rescue group 77% of the time transfer onto NHFOV was done due to apneic events. The study was retrospective and lacked a control group as such so when it comes to the prophylactic approach it is impossible to know how many of these babies would have done fine with CPAP or Biphasic CPAP. Having said that, in that arm the intervention was successful in keeping babies extubated for at least 72 hours in 6/10. Since I really don’t know if those same babies would have done just as well with CPAP I will stop the discussion about them now.

The Rescue Group

These infants were on a fair bit of support though prior to going on to HFNOV with a mean SD
CPAP of 7.9 cm H2O; while for the biphasic CPAP, the levels were 10.2 cm H2O and 7.7 cm H2O. In the rescue group 73% of the infants did not get intubated.

Let’s Process This For A Minute

I think most of you would agree that an infant on CPAP of +8 or NIPPV who is having repetitive apnea or significant desaturations would inevitably be intubated. In three quarters of these patients they were not but I can assure you they would have been if we had not implemented this treatment. When you look at the whole cohort including prophylactic and rescue you can see that the only real difference in the babies were that the ones who were on lower MAP before going onto NHFOV were more likely to fail.

Interestingly, looking at the effect on apnea frequency there was a very significant reduction in events with NHFOV while FiO2 trended lower (possibly due to the higher MAP that is typically used by 1-2 cm H2O) and pCO2 remained the same.

If pCO2 is no different how does this treatment work if the results are to be believed? Although high frequency ventilation is known for working well to clear CO2 I don’t think when given via this nasal interface it does much in that regard. It may be that the oscillations mostly die out in the nasopharynx. I have often wondered though if the agitation and higher mean airway pressures are responsible compared to straight CPAP or biphasic CPAP alone. There is something going on though as it is hard to argue with the results in our centre that in those who would have been otherwise intubated they avoided this outcome. You could argue I suppose since the study was not blinded that we were willing to ride it out if we believe that NHFOV is superior and will save the day but the information in Table 3 suggests that the babies on this modality truly had a reduction in apnea and I suspect had the sample size been larger we would have seen a reduction that was significant in FiO2.

My thoughts on this therefore is that while I can’t profess that a prophylactic approach after extubation would be any better than going straight to CPAP, I do wonder if NHFOV is something that we should have in our toolkits to deal with the baby who seems to need reintubation due to rising FiO2 and/or apnea frequency. What may need to be looked at prospectively though is a comparison between higher pressures using CPAP and NHFOV. If you were to use CPAP pressures of +10, +11 or +12 and reach equivalent pressures to NHFOV would these advantages disappear?

Can Nasal High Frequency Ventilation Prevent Reintubations?

Can Nasal High Frequency Ventilation Prevent Reintubations?

A patient has been extubated to CPAP and is failing with increasing oxygen requirements or increasing apnea and bradycardia. In most cases an infant would be reintubated but is there another way? While CPAP has been around for some time to support our infants after extubation, a new method using high frequency nasal ventilation has arrived and just doesn’t want to go away.  Depending on your viewpoint, maybe it should or maybe it is worth a closer look.  I have written about the modality before in High Frequency Nasal Ventilation: What Are We Waiting For?  While it remains a promising technology questions still remain as to whether it actually delivers as promised.

Better CO2 elimination?

For those who have used a high frequency oscillator, you would know that it does a marvelous job of removing CO2 from the lungs.  If it does so well when using an endotracheal tube, why wouldn’t it do just as good a job when used in a non-invasive way?   That is the hypothesis that a group of German Neonatologists put forth in their paper this month entitled Non-invasive high-frequency oscillatory ventilation in preterm infants: a randomised controlled crossover trial.  In this relatively small study of 26 preterm infants who were all less than 32 weeks at delivery, babies following extubation or less invasive surfactant application were randomized to either receive nHFOV then CPAP for four hours each or the reverse order for the same duration.  The primary outcome here was reduction in pCO2 with the goal of seeking a difference of 5% or more in favour of nHFOV.  Based on their power calculation they thought they would need 24 infants total and therefore exceeded that number in their enrollment.

The babies in both arms were a bit different which may have confounded the results.  The group randomized to CPAP first were larger (mean BW 1083 vs 814g), and there was a much greater proportion of males in the CPAP group.  As well, the group randomized first to CPAP had higher baseline O2 saturation of 95% compared to 92% in the nHFOV group.  Lastly and perhaps most importantly, there was a much higher rate of capillary blood sampling instead of arterial in the CPAP first group (38% vs 15%).  In all cases the numbers are small but when looking for such a small difference in pCO2 and the above mentioned factors tipping the scales one way or the other in terms of illness severity and accuracy of measurement it does give one reason to pause when looking at the results.

The Results

No difference was found in the mean pCO2 from the two groups.  As expected, pCO2 obtained from capillary blood gases nearly met significance for being higher than arterial samples (50 vs 47; p=0.052).  A similar rate of babies had to drop out of the study (3 on the nCPAP first and 2 on the nHFOV side).

In the end should we really be surprised by the results?  I do believe that in the right baby who is about to fail nCPAP a trial of nHFOV may indeed work.  By what means I really don’t understand.  Is it the fact that the mean airway pressure is generally set higher than on nCPAP in some studies?  Could it be the oscillatory vibration being a kind of noxious stimulus that prevents apneic events through irritation of the infant?

While traditional invasive HFOV does a marvelous job of clearing out CO2 I have to wonder how the presence of secretions and a nasopharynx that the oscillatory wave has to avoid (almost like a magic wave that takes a 90 degree turn and then moves down the airway) allows much of any of the wave to reach the distal alveoli.  It would be similar to what we know of inhaled steroids being deposited 90 or so percent in the oral cavity and pharynx.  There is just a lot of “stuff” in the way from the nostril to the alveolus.

This leads me to my conclusion that if it is pCO2 you are trying to lower, I wouldn’t expect any miracles with nHFOV.  Is it totally useless? I don’t think so but for now as a respiratory modality I think for the time being it will continue to be “looking for a place to happen”