What do we know about chest compressions?

Current UK and European Newborn Life support guidelines2 recommend that:

• Compressions are performed in a ratio of three compressions to one ventilation breath.

• Compressions should be performed to a depth of one-third of the anteroposterior diameter of the chest.

• There should be 120 events per minute.

• Compressions should be synchronous.

Following the scoping review, the authors conclude that they did not find sufficient evidence to change any of these recommendations. They did, however, find some interesting food for thought.

This scoping review looked at a number of key questions around how to perform chest compressions in the newborn. These included a review of:

• Heart rate threshold to initiate chest compressions.

• Chest compression to ventilation ratio and synchrony.

• Chest compression technique.

• The use of supplemental oxygen during compressions.

• The use of chest compression feedback devices.

While there are no human data, some animal studies (with their inherent limitations) suggest that there is a faster return of circulation when cardiac compressions are performed with asynchronous ventilation and that providing a sustained inflation (20 s) during chest compression improved survival in piglets.

There is a suggestion from clinical trials that there may be a similar benefit in preterm infants, although the authors suggest caution in interpreting the animal studies and point out that larger-scale clinical trials are needed before making any recommendations.

While this scoping review looked at the animal evidence around compression, 15-second sustained inflation breaths for respiratory support during resuscitation have been studied previously in clinical trials. The SAIL Study5 was stopped early because of a possible increased mortality in the sustained breaths group.

In newborn infants, compromise is usually due a respiratory problem and asynchronous chest compressions may adversely affect minute ventilation. The scoping review looks at the evidence behind the recommendations to perform asynchronous compressions and ventilation. The trials they identify are mostly animal studies, with some manikin studies, highlighting the lack of good-quality human evidence when making recommendations.

The technique of chest compressions needs to balance rescuer fatigue and efficiency of compressions. The authors provide an interesting discussion about a whole variety of finger positions, but none have been shown to be superior to current recommendations. The two thumbs encircling hand technique may be preferential to two-finger chest compressions with a single rescuer.6

Mechanical cardiopulmonary resuscitation (CPR) machines have been used extensively in adult resuscitation practice, although a meta-analysis7 did not show improved outcomes in adults when compared with manual CPR. The authors highlight the lack of evidence in infants and suggest that mechanical devices should not be recommended.

The authors looked at the evidence surrounding the use of waveform end-tidal carbon dioxide (ETCO₂) monitoring during chest compressions. They reviewed animal studies that demonstrate increased survival when ETCO₂ is used to guide chest compression rate and depth.

Aside from its use to monitor chest compression effectiveness, ETCO₂ monitoring is increasingly being used in the neonatal intensive care to monitor ventilation and for the early identification of a blocked or misplaced tracheal tube. This is considered mandatory in adult and paediatric intensive care settings, and this is likely to be the case in neonatal care in the future. This is an area where further study is warranted, to identify the best way to measure carbon dioxide and the most effective way to use the data that are generated given the physiological differences between infants, children and adults.

Increasingly, technology is being used in resuscitation training, with devices to measure face mask leak and chest compression performance now being routinely used on life support courses. There are good educational reasons to provide learners with feedback about their performance, but still limited data about whether providing real-time feedback during a resuscitation improves performance and patient outcomes. Clincial trials are ongoing.

New devices to measure heart rate and the efficacy of chest compressions are under development, and this scoping review is an important reminder of the importance of high-quality research to underpin any changes to practice.

The authors highlight manikin studies that show the use of a metronome or haptic feedback can improve the consistency of chest compression rate, but there are no studies showing improvement in clinical outcomes.

Neonatal intensive care increasingly uses real-time physiological data and as technology develops, this is likely to move into resuscitation practice. This gives us an exciting opportunity to measure CPR performance and to design trials with meaningful clinical outcomes to improve the outcome for babies who require resuscitation.

The authors provide a detailed summary of the evidence around chest compressions. There are several other areas where further research is needed.

There is ongoing research into the role of laryngeal mask airway, both in maintaining an airway during neonatal resuscitation, and potentially as a means to administer surfactant. Ventilator outputs are now routinely used in managing a ventilated baby on the intensive care—the role of tidal volume and other physiological measurements during resuscitation is much debated and an area where further research is being performed.

There is a need for good-quality evidence around the role of drugs in resuscitation: in adult medicine, the role of epinephrine in out-of-hospital cardiac arrest, the Paramedic 2 trial did not show a difference in rates of favourable neurological outcomes between those given epinephrine and those given placebo.8 In neonatal practice, the use of sodium bicarbonate remains controversial and there is a lack of trial evidence to guide neonatal practice.

There have been recent changes to the recommendations about when to stop resuscitation, and the outcome of babies who had no heart rate at 10 min is currently being evaluated by the British Paediatric Surveillance Unit, which may provide useful information about the impact of this guideline change.

This scoping review highlights the challenges of producing evidence-based recommendations when there are so few high-quality neonatal resuscitation trials. There is a pressing need to continue to fund and promote research into neonatal resuscitation practice and to continue to use the ILCOR processes to review and update guidelines as new evidence becomes available.