The research has shown that one of the causes of autism is the continuous period of ischemia and insufficient oxygen supply to the brain starting from infancy, leading to developmental disorders in relevant areas of the brain, particularly the blood vessels.
There are two theoretical ways to increase oxygen supply. One is to increase the oxygen concentration in the blood. The other is vascular regeneration or dilation to increase (or restore) cerebral blood circulation. From this, two parallel clinical treatment methods have been developed, namely hyperbaric oxygen therapy and vascular dilation surgery. The latter is more difficult, while the former is clearly more practical.
1) Hyperbaric oxygen therapy can rapidly improve hypoxia in the body and promote brain tissue growth and development. Since the brain development is incomplete before the age of 7-8, hyperbaric oxygen therapy can promote the development of nerve cells and repair damaged tissues, thereby facilitating the recovery of brain function.
2) Hyperbaric oxygen therapy can inhibit the growth and reproduction of anaerobic bacteria. Some bacteria in the intestines are anaerobic, and children with autism often have imbalanced gut bacteria, functional disorders, constipation, and limited toxin excretion. Hyperbaric oxygen therapy can promote gastrointestinal motility and have a certain therapeutic effect on gut dysbiosis.
3) Hyperbaric oxygen therapy can promote the body's metabolism and enhance immunity. If autism is related to excessive heavy metals in the body, the dietary structure should not be significantly different from that of normal children, and the intake should be similar. The problem lies in the metabolic disorders of heavy metals, and substance metabolism requires the involvement of enzymes and oxygen. Therefore, hyperbaric oxygen therapy can accelerate substance metabolism and promote the elimination of heavy metals.
Increasing communication abilities with the environment, greater activity, commitment and concentration, reducing frustration and fear, improving visual contact, enhancing language comprehension, absorption of new concepts and vocabulary, significantly increasing appetite, and improving bowel function.
The brain is undoubtedly the most active organ in the human body and consumes the most oxygen. It can be said that even when the rest of the body rests or significantly reduces activity, the brain remains actively functioning, for example, processing significant information from the previous day through dreaming to facilitate future survival. However, most dreams are not consciously perceived by people. The brain accounts for only 2% to 3% of body weight, but in a quiet state, it requires over 20% of the cardiac output, indicating that brain tissue has a rich blood supply and occupies a priority position. Consequently, if there is a lack of oxygen, the consequences can be severe. Experiments have shown that if blood flow is completely blocked for 6 seconds, it can damage neuronal metabolism, and if it is blocked for 10-15 seconds, the oxygen reserve in the brain is exhausted, causing loss of consciousness, and if oxygen deprivation lasts for two minutes, brain electrical activity ceases completely. When brain electrical activity ceases, it leads to the cessation of heartbeat, breathing, and blood flow. Even if oxygen is supplied again, it is already too late, and the body will irreversibly progress towards death (although cardiac pacing and artificial respiration can be performed). In warm conditions, after 5 minutes of ischemia, cellular energy ATP is exhausted, and energy metabolism stops; even if oxygen is subsequently supplied, brain cells have already suffered irreversible damage.
Analysis of Physical Parameters: Normal cerebral blood flow should be 0.5 milliliters per minute per gram of brain tissue. When this index drops below 0.1 milliliters per minute, it is referred to as "anoxic state," where brain cells undergo irreversible necrosis (neurons are non-regenerative). Even if oxygen supply is restored at this stage, it can only lead to brain death or a vegetative state.
When blood flow is between 0.1 and 0.2 milliliters per minute, it is called "hypoxic state." Brain cell function and electrical activity cease, but the cells can survive, maintaining the structural integrity of the brain. The area in a hypoxic state is called the "penumbral zone," which can be sustained for a long time, possibly even a lifetime. However, brain cells in this region cannot persist indefinitely; if blood flow remains low, they will enter a dormant state and gradually undergo chronic necrosis.
Blood enters the brain through the arteries, branching into various blood vessels until reaching capillaries that supply different regions of the brain. Contrary to common belief, capillaries do not cover all brain cells. In reality, two capillaries (in the gray matter of a normal brain) are spaced approximately 60 micrometers apart. Therefore, the cells located between them and the blood vessels are about 30 micrometers apart and cannot directly receive the required oxygen molecules. However, oxygen molecules leaving the capillaries have a physical diffusing mechanism (also known as diffusion function). At a normal atmospheric pressure, the effective diffusion radius of oxygen molecules in brain tissue is about 30 micrometers, precisely enough to satisfy metabolic needs in these "remote areas." Similarly, metabolic waste products (such as carbon dioxide) are carried away by hemoglobin through diffusion to the capillary region. However, this is an ideal scenario. If, for some reason, capillaries are underdeveloped, sparse, too small, or if there are structural barriers in brain tissue (hindering diffusion), it may lead to suboptimal oxygen delivery, resulting in some remote brain cells experiencing insufficient oxygen supply. This may lead to the formation of a long-term hypoxic penumbral zone, affecting brain development and physiological functions, and potentially leading to an autism-like state.
The Ischemic Autism Hypothesis proposes that autism spectrum disorder (ASD) children experience prolonged and chronic hypoxia from early infancy due to unknown reasons (such as certain genes not expressing or delayed expression), resulting in developmental disorders in specific brain regions (especially blood vessels). In some cases, medical examinations have indeed confirmed partial vascular blockages or atrophy in the brain. The vascular atrophy leads to incomplete brain development and impaired neuronal growth from a young age. Some regions of the brain are in the "dark zone" or "grey area." Early vascular expansion to increase blood circulation can partially reverse this condition and improve or even cure ASD in affected children.
The most optimal approach to such conditions is undoubtedly to promptly improve oxygen supply, allowing brain cells in the penumbral zone to recover, resume development, and regain functionality, thereby reversing brain damage and its after-effects.
There are theoretically two ways to increase oxygen supply. One is to elevate blood oxygen concentration, and the other is to regenerate or expand blood vessels to increase (or restore) cerebral blood flow. This has led to the development of two parallel clinical treatments (two branches of the hyperoxia theory): hyperbaric oxygen therapy and vascular dilation procedures. The latter is more difficult, while the former is evidently more practical.
This typical "curable theory" suggests that since autism is caused by developmental deficiencies, stimulating brain growth may catch up postnatally. Even if complete transformation in outcomes is not possible, improving the functional state during treatment is still worth pursuing.
We are well aware that a normal human body can survive in an atmosphere with 20% oxygen pressure, resulting in a blood oxygen concentration of 4.4 ml/L. The blood oxygen concentration (PaO2) is the product of the gas pressure and the oxygen partial pressure, and the physical dissolved oxygen content in the blood is directly proportional to it. For example, when comparing breathing pure oxygen (100%) at 2 atmospheres absolute (ATA) to breathing air (20%) at 1 ATA, the PaO2 and the physical dissolved oxygen in the blood increase by a factor of 100%/20% x 2ATA/1ATA = 10 times. Hence, increasing the chamber pressure has the same effect as increasing the oxygen partial pressure, both of which effectively enhance the therapeutic effects. For instance, using air at 1.3 ATA is equivalent to breathing air with 26% oxygen content at 1 ATA. Some soft hyperbaric chambers leverage this principle by solely increasing the chamber pressure (usually around 1.3-1.5 ATA) instead of raising the oxygen purity, thereby reducing technical complexity and potential risks.
Under a pressure of 3 atmospheres absolute, the dissolved oxygen in the blood can reach 15 times the normal amount, equivalent to 66 ml/L. At this high pressure, oxygen molecules can even dissolve into the bloodstream without the need for hemoglobin transport, diffusing directly to body cells to sustain life. Therefore, it provides an irreplaceable rescue effect for conditions like severe anemia (lack of red blood cells), carbon monoxide poisoning, or cyanide poisoning. Although this procedure carries certain risks (fire hazard), it can temporarily overcome blood-related issues. As hyperbaric oxygen increases blood oxygen concentration, it effectively extends the diffusion radius of oxygen, mitigating the problem of insufficient oxygen supply.