Satoshi Hayamizu: Watching Over Astronaut Hoshide's Health from Earth

To be honest, it was a term I didn't know until just before I joined JAXA. "Surgeon" generally refers to a doctor in surgery, but it also has the meaning of a "military doctor." In the past, it seems the U.S. military called the military doctors who managed the health of pilots "flight surgeons."

By extension, during the space race between the U.S. and the Soviet Union, NASA expanded from aviation medicine to aerospace medicine, and the term flight surgeon is still used today to mean a specialist physician in that field.

This isn't limited to JAXA, but within the ISS program, one flight surgeon is designated from each of the five partners (JAXA, NASA, Russia, European Space Agency (ESA), and Canada) for the astronauts assigned to fly from each partner. So, in JAXA's case, I was designated as the dedicated surgeon for Mr. Hoshide, and there is also one backup dedicated flight surgeon assigned.

Currently, a total of five full-time flight surgeons are registered at JAXA.

Yes. Mr. Noguchi is still undergoing rehabilitation (as of May 26, 2021), but I am actually Mr. Hoshide's dedicated flight surgeon and also Mr. Noguchi's backup dedicated flight surgeon, so I am in charge of Mr. Noguchi's rehabilitation as well.

The work of a dedicated flight surgeon is divided into three major phases: pre-flight/launch, during flight (staying on the ISS), and return/post-flight, to manage the health of the assigned astronaut.

Astronauts move from the 1G gravity environment on Earth to the micro-G environment in the ISS. Significant physiological changes occur during that time, so as a flight surgeon, I must manage their health carefully. The same applies when returning to Earth; various symptoms can appear when re-adapting from microgravity to a 1G environment.

Therefore, in Mr. Hoshide's case, various bodily changes occur between launch and the first week or so after arriving at the ISS, so care for that is important. After launch, we conduct medical interviews about five times daily, and that was a period requiring intense concentration for health management.

The air composition inside the ISS is almost the same as on the ground, and once they adapt to that environment, we don't have to worry as much. We also manage work, including the prevention of injuries unique to the microgravity environment, as well as nutrition and exercise.

That is a very important question. Actually, there are various departments within the ISS program, and Japan manages the module called "Kibo." Naturally, some technologies related to operations cannot be shared with other countries.

However, in our medical operations department, which manages the health of astronauts, it would be a disaster if something like an infectious disease were passed among the astronauts. Therefore, it is said that we are the friendliest among the departments in the ISS program, and we place great importance on multilateral cooperation.

In a meeting held once a week, we report on the health status of the seven astronauts currently on the ISS and share information among the flight surgeons of the five partners. For example, if a JAXA astronaut develops a symptom, the relationship is close enough that we can receive advice; it is no exaggeration to say there are almost no secrets.

The ISS project began permanent astronaut residency in 2000, so nearly 20 years have passed. During that time, fortunately, there have been no medically serious situations where an astronaut became a critically ill patient.

However, of course, there is no guarantee that it won't happen in the future, so measures are firmly in place. There are two main aspects: first, we conduct evaluations during the preliminary medical examinations very strictly. If the health risk is high, flight permission might not be granted. We have a two-tier system of preventive measures: a domestic review within JAXA, followed by an international medical review among the five partners.

Second, in preparation for a real emergency, the astronauts themselves undergo training at the NASA Johnson Space Center in Houston for BLS and ACLS—cardiopulmonary resuscitation methods typically performed by doctors and co-medical staff.

That's right. Since a flight surgeon cannot go to the site and touch the patient, astronauts are trained in advance on how to accurately communicate their own health status and that of others.

In the field of technological development, redundant systems are always built so that if one thing fails, the next is ready. Similarly, in the medical procedures under the ISS program, we don't rely on chance; thorough manuals are organized in great detail, specifying "if this happens, do this."

Exactly. There are parts where I feel the preparation before launch was more difficult.

Yes. This time, Mr. Hoshide has been designated as the second JAXA astronaut to serve as ISS commander.

The rule is that the commander takes charge in an emergency. Therefore, I think he was very careful in preparing how to demonstrate teamwork on the ISS even while he was still on the ground. He always has a wonderful smile, but I think the mental burden is quite significant.

Yes. Nutritional management is, of course, important. In addition to that, mental and psychological factors—the so-called "enjoyment of eating"—are now being considered quite a bit.

Basic "standard rations" are provided by NASA. However, since JAXA astronauts are Japanese, JAXA has developed "Space Japanese Food" so they can eat at least some familiar Japanese items. Currently, there are 47 items of Space Japanese Food, so Mr. Hoshide is able to eat them on the ISS.

The dedicated flight surgeon assigned to an astronaut is essentially in the position of a family doctor. And within JAXA, there is a "Medical Operations Team" that the dedicated flight surgeon can consult with as needed. Regarding mental care, the psychiatrists and psychologists on the team are in charge. In other words, I am the point of contact for the medical operations team supporting Mr. Hoshide.

While the ISS is a symbol of world peace through international cooperation, it is also a scientific laboratory that brings together cutting-edge technology and research. Therefore, astronauts who go to the ISS perform various scientific experiments, including medical experiments.

I don't personally ask Mr. Hoshide to cooperate in my experiments, but he performs various scientific experiments. I monitor them in real-time to ensure that none of those experiments raise concerns about potential impacts on his health management.

Actually, he is the second. The person who created the opportunity for me to change jobs and become the first JAXA flight surgeon as a rehabilitation doctor was Dr. Shin Yamada, who is currently at Kyorin University. It is said that rehabilitation doctors are very well-suited to be flight surgeons. I changed jobs just after it was decided that astronaut Norishige Kanai would undergo rehabilitation in Japan for about three weeks for the first time, and I was able to participate in that.

I have seen patients with the after-effects of strokes for over 10 years in home-based medical care. Especially common in the elderly, conditions known as disuse syndrome can occur, where muscle atrophy leads to decreased strength and bone density decreases leading to osteoporosis. There are cases where people fall into a negative cycle of becoming bedridden as a result of falling and fracturing a hip, etc. By staying on the ISS for six months, astronauts experience physiological phenomena similar to this disuse syndrome. While I cannot say the causes are identical, the symptoms are very similar.

Even with muscle atrophy, we know it progresses at about 10 times the speed of an elderly person on the ground. We take a rehabilitation approach similar to that on the ground, but the decisive difference is that in the case of astronauts, it is not a disease; it is a healthy person becoming that way due to the environment.

Therefore, if they re-adapt to the ground while undergoing appropriate rehabilitation and take their time, they will almost return to their pre-launch state.

On the other hand, in many cases of post-stroke rehabilitation for the elderly, the condition is irreversible, and a complete return to the original physical state is impossible unless the after-effects are very mild.

Basically, that is the case. On the ground, a 1G load is constantly applied, so body fluids are pulled toward the legs. The phenomenon of legs swelling in the evening is because of that, but when you go to space, body fluids are redistributed evenly throughout the body. When that happens, the body adapts by losing about two liters of water to the outside to maintain the conventional balance of the whole body.

As a result, because the circulating blood volume decreases, we also know that the weight of the heart muscle decreases by about 10%. In that sense, cardiopulmonary function decreases, so endurance exercises like running are emphasized both during the flight and after the return. To return to the answer to your question, the heart muscle is a special kind of muscle, so I don't think we can say it's simply limited to skeletal muscle.

Since we know that a 15–20% decrease in muscle strength occurs over six months, exercise equipment has been developed as a countermeasure, allowing astronauts to return to Earth with the decrease limited to about 10–15%.

Rehabilitation after returning to Earth is set at 45 days by the ISS program, and muscle strength itself almost returns to normal during that time.

As for how much longer we can stay in space in the future, radiation protection will be one major key when it comes to going to the lunar surface or Mars. Although the ISS is about 400 kilometers above the Earth's surface, it is still partially protected from various types of radiation. However, once you go beyond that, the amount of radiation you are exposed to becomes very high. On the other hand, regarding muscle strength, a certain level of countermeasures is being considered.

To be honest, I didn't think so at all. But interestingly, now that I've come to JAXA, I realize there were actually various points of contact with space.

One was when I lived in Chicago for six years as a boy due to my father's work. My family went on a trip to the Kennedy Space Center, and I collected a lot of patches from Apollo and such (laughs). I even have them displayed in my room today; I was very moved at the time.

Another is that I remember well when Chiaki Mukai launched into space on the Space Shuttle when I was a student at the School of Medicine. I still see her occasionally at JAXA, and I feel there was a connection. I also had the opportunity to meet Dr. Mukai's husband, Makio Mukai, in Houston, and we had a lively conversation as senior and junior alumni.

Thirdly, as I mentioned earlier, the fact that Dr. Yamada was involved with JAXA was very significant. Dr. Yamada, who was my senior in the School of Medicine American football club and also a senior in the rehabilitation department, reached out to me and recommended becoming a flight surgeon. I really feel that one must cherish human connections. I am still a novice as a flight surgeon, but I am gradually feeling the reasons why a rehabilitation doctor is very well-suited for it.

For the 10 years before joining JAXA, I was a community family doctor, focusing on home visits at a clinic. In community medicine, teamwork with various professions such as physical therapists and care managers is very important for the work, so that experience has been very useful.

This fall, for the first time in 13 years, JAXA plans to recruit new astronauts. Since flight surgeons are involved in the selection stage before flight, I want to focus on how to build relationships of trust with the new astronauts. Currently, the Artemis program is underway at NASA, and the astronauts selected this time have the potential to be the first Japanese people to step onto the lunar surface.

However, right now, my goal is to have Mr. Hoshide return safely. After that, when I return to Japan, it will also be important to maintain my skills as a specialist in rehabilitation. Unless I can properly maintain my abilities as a clinician, I won't be able to manage the health of astronauts.