Blood Pressure Regulating Reflexes

The infant makes its entrance into a world of gravity from the weightlessness of the womb. It has not yet had the chance to develop blood pressure regulating reflexes. Its heart pumps, but cannot increase its pumping in response to a change in posture because it has never experienced this before. If held upright, gravity would drain the infant’s blood toward its feet. That is why extreme care is taken by nurses in the delivery room to maintain the baby in a horizontal position. If, for any reason, the infant’s blood volume is reduced and its blood pressure drops, raising its head up could be disastrous. In 1996, we flew two monkeys for 12 days on a Russian spacecraft. The purpose was to study in greater detail than is possible in astronauts changes in muscles, joints, and bone. On landing in Siberia, the monkeys, who looked lively and healthy, were whisked to Moscow for evaluation by a team of doctors. The first animal was anesthetized for a whole body scan to assess its muscle and bone density status. As the doctors picked him up to turn him over, he unfortunately stopped breathing. In vain, they tried to resuscitate him, but could not.

Such A Rush

The team then noticed that the second flight monkey, seated in his chair awaiting his turn, was showing signs of distress. The animal quickly recovered and the team was able to proceed with the rest of the testing as scheduled. An independent investigation into the cause of the first animal’s death concluded that the animal’s reflexes were compromised by being in space, as well as by the anesthesia. Although doing fine while it was horizontal, the monkey was unable to respond with an appropriate increase in blood pressure and brain blood flow as it experienced the pull of gravity when it was tilted up and moved. Devastating as the loss of the animal was, it triggered new awareness among the whole medical team of the importance of maintaining astronauts in a horizontal position if emergency care were ever needed immediately after landing. An infant exposed to gravity for the first time, after immediate cord clamping when blood volume, pressure, brain blood flow, and oxygen are already low, will be extremely vulnerable to inadvertent posture change. Extreme caution in maintaining the infant in a horizontal position must be taken until its body gradually develops the reflex mechanisms it will need to live in gravity. They use a program of repetitive motor activities that emphasizes strength and there flexibility, eight hours a day, five days a week, first in the horizontal position and as soon as possible in the upright position. The children wear a safety harness at first, until they are able to stand on their own. The earlier such exposure to gravity can start, the better the outcome. All of the children benefit, but the results are best for those who start the program before they are three years old. This means they are using gravity, which is the primary stimulus for developing the sense of weight, distribution of weight during movement, and direction in propelling their weight forward.

After The Fall

Moving the legs back and forth in a walking motion could be mechanized so that even before a child would normally stand, he or she could experience motion at 1G or greater while lying down. The child’s sensitivity or threshold to gravity may also be deficient depending on how long the child has been immobile. Increasing the intensity or frequency of the gravity stimulus during such physical therapy may initially be required. Using a centrifuge or some other device to do this may one day prove to be even more beneficial. The brain is remarkably resilient and plastic. Given appropriate stimulation, involving gravity for motor coordination, it will bypass or reroute the nerve pathways to find ways of compensating for the damage suffered. The student daughter of a colleague at Stanford, whom we will call Emily, was run down by a car while trying to save her cat. The accident left her in a comatose state. Weeks later, and against all odds, Emily regained consciousness. As soon as she could sit up, the next step in her healing were daily rides on Great America’s roller coaster! Emily eventually regained some mobility and finished college. The spinal cord passes through the neck and back, is protected by bony vertebrae, and contains nerves that transport messages between the brain and the rest of the body. Consequently, forced inactivity, together with an inability to sense and use gravity in their lower body, deprives them of the stimulus provided by loading their legs, hips, and lower spine with the body’s weight.

Sitting On The Fence

Just as we’ve seen happening with astronauts, leg muscles atrophy, joints stiffen, and bones become fragile. Equally, the inability to change position without help or to accelerate by running or walking affects stamina and the ability to regulate blood pressure. Feeling faint when sitting up was once thought to be the result of nerve damage. Studies have shown that upper body exercising corrects the tendency in these patients to faint on sitting up. Furthermore, acceleration, even while sitting in a wheelchair, stimulates the gravity sensors in their inner ear. After overcoming the physical trauma of his injury, he grappled with the emotional trauma of being unable to use his legs and the challenge of figuring out how he was going to take care of himself. Craig and Andy’s passion is to encourage everyone to enjoy life through the sense of freedom that travel, adventure, and a never give up attitude make possible. Craig is still an avid skier, hitting the slopes in his specially designed equipment more than 80 days per season, and his latest sport challenge is kayaking. Individuals with these kinds of injuries who have the willpower to persevere may overcome many of these handicaps. They make the most of their upper body to stay remarkably fit. In recent decades, thousands of athletes with paralysis have raced in wheelchair marathons through the year.