Cardiac Arrest in Space: Automatic Chest Compressions Superior in Microgravity CPR, reveals research
New research has found a more effective way to conduct cardiopulmonary resuscitation (CPR) in microgravity,* which causes the weightlessness astronauts experience in space.
The study found that a type of automatic chest compression, carried out by a standard mechanical piston device, reached the depth needed to be effective, while the current CPR methods recommended for space travel are undereffective regarding this depth criteria.
Treating cardiac arrest during spaceflight is challenging because both the rescuer and the patient are floating due to microgravity. The current NASA emergency protocol for the International Space Station recommends the hand-stand method of CPR, where the rescuer performs a handstand on the patient’s chest with their legs pressing on the side of the spaceship to create the pressure needed for chest compressions.
“We tested different ways of giving chest compressions aboard a ‘flying laboratory’ which recreated the microgravity conditions that astronauts experience in space. Use of a particular type of automatic chest compression device was the only method that gave the depth that is recommended by international resuscitation guidelines to keep blood flowing to the brain in a real life cardiac arrest. We hope that our findings will be incorporated into the next guidelines (1) for treating cardiac arrest in space,” Explained Nathan Reynette from the Cardiology Department at Université de Lorraine – CHRU de Nancy.
The research was conducted in a ‘flying laboratory’ onboard a modified civil aircraft, the only one of its kind in Europe, called the A310 Air Zero G at the Centre National d'Etudes Spatiales, the French space agency. Freefalling phases of parabolic flight were used to accurately recreate microgravity for 22 seconds during each parabola, with around 30 parabolas per single fight. The experiments were conducted over three flights. Chest compression depths and rates were monitored by a high fidelity CPR training manikin.
Earth-based chest compressions during CPR are based on the rescuer’s weight, which does not exist in microgravity. As a result, over the last 30 years, researchers have searched for alternative methods, such as the Handstand method, Reverse Bear Hug method and the Evetts Russomano method. Until now, despite numerous trials, none of the proposed methods were shown to reach the depth standards needed for effective chest compressions.
Three types of automatic chest compression devices were tested. Automatic chest compression devices are routinely used on Earth by doctors in restricted environments such as emergency helicopter, or where prolonged CPR needs to be carried out over a longer period of time, such as refractory cardiac arrest which can last for more than 40 minutes. This type of CPR is not considered to be superior to manual CPR in normal conditions but has been proven to be effective when chest compressions are challenging.
Three types of automatic chest compression devices were tested; a standard mechanical piston device, a compression band device, and a small-sized piston device. Best practice guidance, such as advice given by the European Resuscitation Council (2), suggests that to be effective chest compressions must reach a depth of between 50 to 60mm.
Of the three automatic chest compression devices tested, the standard mechanical piston device had the highest median compression depth. The median compression depth of the standard mechanical piston device was 53.0mm, which was considerably more than the other two automatic chest compression devices, that both had median depths of 29mm, and the manual handstand method of CPR which achieved a depth of 34.5mm.
Reflecting on whether future space missions will take automatic chest compression devices in their emergency medical kit, Mr Reynette said, “It will be up to every space agency whether they want to include automatic chest compression devices in their emergency medical kit. We know they have other considerations beyond effectiveness, such as weight and space constraints.
“While cardiac arrest is a high danger event, that could even terminate a space mission, it is a relatively low risk for now. Most astronauts are young, healthy and physically fit individuals who have intensive medical monitoring, including scanning for chronic heart disease, before going into space. Nevertheless, longer lasting space missions in future and space tourism could increase the risks of a medical emergency occurring.” He continued.
The research project was a collaboration between clinicians from the CHU de Nancy, medical researchers from University of Lorraine and University of Paris, engineers from the Laboratoire Georges Charpak of the Ecole Nationale des Arts et Metiers Paris Tech and from the Centre National d'Etudes Spatiales, the French space agency and Novespace.
“This research highlights once again the usefulness of automated chest compression devices to perform CPR in challenging environments. Space medicine often provides transferable lessons for emergency procedures in isolated environments on Earth, where space and clinical experience are also limited. Further research could explore whether automated chest compression devices could prove useful to carry out CPR in environments such as submarines and artic bases.” Mr Reynette concluded.
