“No pause should be your cause,” or so French medical device manufacturer Vygon believes. In March, JEMS Editor-in-Chief A.J. Heightman and I traveled to Paris to attend a one-day emergency symposium titled, Alveolar Ventilation by Continuous Chest Compression: b-card, a new device designed for use during cardiac arrest management.
During the symposium, current cardiac arrest guidelines, the Boussignac Cardiac Arrest Resuscitation Device (b-card) and how the two are interconnected were discussed.
The b-card is available and in use in Europe and Canada; however, it’s not available or approved for sale in the United States. Vygon has applied to the Food and Drug Administration (FDA) for approval for use in the U.S.
The b-card creates a virtual valve that ensures dynamic
alveolar ventilation without the need to interrupt chest compressions.
The resuscitation symposium started with a review of the current International Liaison Council on Resuscitation (ILCOR) guidelines on cardiac arrest and a comparison of the guidelines put forth by the American Heart Association and the European Resuscitation Council.
It was emphasized during the first half of the symposium, and acknowledged by resuscitation experts present from multiple countries, that early citizen response and initiation of CPR along with high quality, consistent CPR by emergency crews are paramount to patient survival.
This was discussed and supported by observational studies which have shown that, in general, the quality of CPR is poor during out-of-hospital cardiac arrest. Additionally, multiple studies show that interruptions in chest compressions not only decrease coronary perfusion pressure1 but are also associated with decreased defibrillation success and poor outcome.2-5
Resuscitations are often hampered in Paris by the lack of early citizen response and performance of CPR prior to EMS crew arrival. This major factor has kept Paris’ ROSC level below 10%, despite an outstanding response system in place that utilizes physician-staffed ALS units operated by Service d’Aide Médicale Urgente (SAMU, translated from French as Urgent Medical Aid Service) and the predominantly BLS Paris Fire Brigade.
On the other end of the resuscitation spectrum, patients in Paris who remain in v fib and who receive extracorporeal membrane oxygenation (ECMO) bypass treatment in the field by a specialized SAMU response team are successfully resuscitated more than 30% of the time.
Paris’ medical leadership is working on ways to get citizens to perform early CPR by using software to alert citizens of the location of AEDs. If Paris ramps up its citizen involvement, it’s clear that their overall resuscitation rate could skyrocket.
Tackling Compression Interruptions
Although advanced airway devices allow for continuous chest compressions, prolonged interruptions associated with advanced airway placement may negate this benefit. One study observed that CPR was interrupted for 46.5 seconds (interquartile range [IQR] 23.5 to 73 seconds) on the first attempt at intubation and total interruptions to chest compressions due to endotracheal intubation lasted 109.5 seconds (IQR 54 to 198 seconds).6
Authors of this study also pointed out that total endotracheal intubation-associated CPR interruption time accounted for approximately one fourth of the total CPR interruptions (median 22.8%; IQR 12.6% to 36.5%; range 1.0% to 93.9%).6
Supraglottic airway devices outperformed endotracheal intubation when interruptions to chest compressions were studied using manikins. In these studies, insertion of supraglottic airway devices interrupted chest compressions on average for 8.4 to 20.0 seconds depending upon which device was being used.7,8
Questions still remain whether advanced airway management in the out-of-hospital setting improves patient survival with some studies reporting contrasting results. A nationwide registry in Japan found no survival benefit from advanced airway management compared with bag-valve mask ventilation. And, the Resuscitation Outcome Consortium (ROC) observed higher survival in patients who didn’t receive advanced airway management. However, in those patients that did undergo advanced airway management, endotracheal intubation provided for a better outcome than supraglottic airway devices.9
The second half of the resuscitation symposium focused on the b-card itself. B-card is a noninvasive ventilation system providing continuous oxygen delivery during CPR. The device ensures dynamic alveolar ventilation without the need to interrupt chest compressions.
Connected to an oxygen source delivering a flow rate of 15 L per minute, the b-card generates a virtual valve. This valve creates an initial static pressure in the airways of approximately 4 to 5 cmH2O. This acts as the “heart” of the device, optimizing the pressure created during chest compression and decompression phases of CPR. (See Figure 1.)
Each chest compression has a dual action: Helping to expel the air contained in the alveoli and simultaneously pumping blood from the chest cavity into the general circulation.
During the compression phase, the pressure within the airways is increased to 8 cmH2O. Animal and clinical studies suggest that prolonged CPR may impair lung function and promote severe atelectasis.10,11
This slight increase in pressure may protect the lower airways during CPR according to Vygon. In the decompression phase, the virtual valve creates a negative intrathoracic pressure and a pressure of -1 cmH2O in the airway, optimizing gas exchange in the alveoli. At the same time, the negative intrathoracic pressure improves venous return to the heart.
This increases the blood flow ejected from the heart during the next chest compression. So, b-card has been designed to perform the dual effect of optimizing hemodynamics and ventilation when chest compressions are being performed.
The b-card is designed with two distinctly different ends. The end that’s open to the atmosphere has a series of elevated ridges so that it can’t be easily connected to an airway circuit.
The other end of the b-card can be used with either a 15 mm or 22 mm airway connector. Because of this design, it can be used with a facemask, a supraglottic airway device, or an endotracheal tube, allowing for use by various levels of providers.
Figure 2: B-card used with a facemask (left) and supraglottic airway (right)
According to Vygon, b-card simplifies the management of cardiac arrest. As ventilation is generated by chest compression and decompression, the need for a provider ventilating the patient has been removed.
However, there’s still the need for a provider to apply a good mask seal if the b-card is used with a facemask rather than with a supraglottic airway device or endotracheal tube. The b-card is also designed to be used with both manual and mechanical CPR. Historically, most of the studies have used the Physio-Control LUCAS chest compression system with the Boussignac CPR system or the b-card.
An additional benefit of the b-card, as it’s designed, is minimal risk of gastric inflation and aspiration since it’s an open system that uses continuous oxygen insufflation. With b-card, ventilation is based on negative intrathoracic pressure unlike positive airway pressure that’s used during CPR for ventilation. The risk of aspiration during CPR is small but not insignificant and has been reported to be 0.96%.12
When the b-card was compared to standard CPR with intermittent positive pressure ventilations delivered to a cadaver by bag-valve mask, approximately 25 times more gastric insufflation was generated vs. ventilations delivered with the b-card.13
Vygon believes the b-card offers multiple benefits during the treatment of cardiac arrest and maximizes adherence to ILCOR guidelines, including:
- improved hemodynamics during CPR and continuous chest compressions;
- reduced injury to the alveoli and lungs caused by chest compressions;
- improved ventilation and oxygenation during CPR;
- reduced gastric inflation; and
- simplified management of cardiac arrest.
Does the b-card increase survival from cardiac arrest? Currently there are no published studies that used the b-card exclusively. There are, however, a few studies that have used the Boussignac CPR system manufactured by Vygon, which has the same virtual valve as the b-card.
Preliminary data from a small study conducted in the out-of-hospital setting showed an increase in ROSC rate and survival. Of the 48 patients enrolled, 38 (79%) were intubated using the Boussignac CPR system. The other 10 (21%) patients underwent standard intubation and ventilation.14
The rate of ROSC in those patients intubated with the Boussignac CPR system was 44.7% as compared to 10% in the standard interventions group. Survival to discharge was 26.3% in the Boussignac CPR system group as compared to 10% in the standard intervention group.
This small study isn’t sufficient enough to fully validate the effectiveness of the b-card, but there are ongoing studies by the Paris Fire Brigade and Marc Gillis, MD, in Belgium that will help determine the clinical benefit of the b-card.
Although approved and in use in Europe, the b-card is currently undergoing field tests and awaiting pre-market clearance submission to the FDA. Once approved, and further field studies are conducted, this device has the potential to affect the performance of CPR and, more specifically, ventilation during CPR.
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