The announcement sent shock waves through the aerospace industry. An ISS mission had to be interrupted following the deterioration of the health of a crew member. If space is a dream, it remains a hostile environment where the slightest medical glitch can become a major crisis. A look back at security protocols with the analysis of Dr. Gérald Kierzek.
How are astronauts trained in life-saving actions?
Dr Gérald Kierzek : Astronauts are not just engineers or pilots. They become real “space paramedics”. They undergo intensive training for 2 to 3 years. This includes simulations of serious emergencies such as cardiac arrest or hemorrhage management. They learn to use complex tools such as the Ultrasound-2 ultrasound system present on the ISS. Their level of autonomy is equivalent to that of an advanced paramedic. For example, they can perform minor invasive procedures, although a radio link with doctors on the ground is constantly maintained to guide them via telemedicine.
What check-up do they undergo before takeoff?
Dr Gérald Kierzek : Nothing is left to chance. Before taking off, the astronauts’ bodies are screened to limit any risk of “dormant” pathology. The assessment is ultra-complete: ECG under stress, echocardiography and hypoxia tests for the heart and lungs. We also use imaging (brain MRI, chest scanner) to track down the slightest nodule. Added to this are in-depth biological assessments (hormones, inflammatory markers), dental, psychiatric and neurocognitive evaluations. These examinations are repeated every 6 months. Then intensify 3 months before the flight, with a final “go” at D-30.
What can make an astronaut unfit to fly at the last moment?
Dr Gérald Kierzek : Even after years of preparation, the ax can fall. Mission security comes first. An astronaut is declared unfit for any cardiac (arrhythmia, stenosis), neurological (epilepsy, disabling migraines) or musculoskeletal abnormality, such as a recent herniated disc or advanced osteoporosis. The psychological level is also crucial: anxiety disorders under treatment are crippling. If the risk of serious in-flight complications exceeds 1%, the launch is postponed or the crew is changed.
What medical arsenal does the ISS have in the event of a problem?
Dr Gérald Kierzek : The ISS is not a hospital, but its “pharmacy” and its equipment are impressive for a confined environment. On board the ISS or ships like Crew Dragon, there is a kit of more than 200 medications (antibiotics, powerful intravenous painkillers, hormones). On the hardware side, there is a defibrillator, intubation and suturing equipment, as well as portable ultrasound machines powered by artificial intelligence for self-diagnosis. All constants (videos, vital parameters) are transmitted in real time to Houston or Toulouse so that experts on the ground can make a precise diagnosis.
Why decide on emergency repatriation to Earth?
Dr Gérald Kierzek : Returning to Earth is a heavy, expensive and complex decision. It is only taken if the resources on board are exceeded. We repatriate in the event of an immediate life threat: heart attack, pulmonary embolism or sepsis (generalized infection). This is also the case for the risk of permanent after-effects (stroke, complex fracture) or pain that we can no longer control. Recent repatriations in 2026 show that if the probability of death exceeds 5% or if the degradation is irreversible, the return in a Soyuz or Dragon capsule is triggered. Finally, we must understand that we cannot operate on board. Even if we sent a surgeon, weightlessness makes surgery almost impossible: fluids and organs do not behave like they do on Earth!