You will encounter various terms, some associated with specific medical conditions, but others related to HBOT. To gain a depth of understanding about this therapy, included are definitions and explanations to provide a working knowledge of the language when hyperbaric oxygen is discussed.. This is an easy to read glossary graciously prepared by Dr. Paul Harch and is printed in his book, The Oxygen Revolution. When the pronoun “I” appears, it is Dr. Harch.
ACUTE: This refers to an injury at the onset of a disease or condition that has just happened; in medicine it implies the immediate time at which an injury or accident occurs, essentially, a fresh injury or sudden change in condition. It also includes the period after the injury during the first few days. Subacute refers to the period of time after an injury or event between the first few days or so and the chronic period. Of course, a large overlay and gray zone exists between the subacute and chronic periods.
AT DEPTH: This refers to being in the chamber under pressure, usually at the final treatment pressure. When we pressurize the chamber we go from surrounding ambient pressure (one atmosphere absolute if we are at sea level) to the treatment pressure. When patients are under pressure greater than atmospheric pressure they are said to be in the chamber “at depth.”
ATMOSPHERES OR PRESSURE: The earth’s atmosphere consists of nothing more than “air” that is about 21 percent oxygen, 79 percent nitrogen, and a tiny percentage of other gases such as carbon dioxide. Despite the seeming “nothingness” of air, it has weight. That weight of all of the air from the surface to the edges of the earth’s stratosphere is measured at the earth’s surface as atmospheric pressure. It is about 14.7 pounds per square inch (psi), or about one third of the pressure in a typical car tire. This 14.7 psi is called one atmosphere absolute.
Imagine digging a hole in the earth, and as we descend deeper we have an increasing amount and density of air from the top of the hole (which includes all of the air above it to the stratosphere), at surface level, to the bottom. This increased amount of air in the hole exerts greater pressure as we descend deeper into the hole. Similarly, when we dive under water, rather than the weight of air, the weight of the water exerts pressure and is added to the weight of the air on top of the water extending to the stratosphere. Every 33 feet of seawater below the surface is equivalent to another atmosphere of pressure or equivalent to the entire weight of the atmosphere of air extending up to the stratosphere.
With HBOT for acute conditions we usually treat at the equivalent pressure of 33 to 66 feet of seawater of pure oxygen. For chronic neurological conditions it is usually less, the equivalent of 16.5 feet of seawater or less. (Remember, in both cases we add to the weight of air, or one atmosphere at sea level, to each of these pressures).
CHRONIC: This term implies the passage of time. In medicine we say a condition or situation is chronic when it has reached a clinical plateau and is no longer changing. In neurology this typically refers to at least six months to one year after an event. We now know that improvements from rehabilitation of an injury can have a much longer time course, but are still in the chronic phase.
DIVE: A slang term for a hyperbaric treatment, it has its roots in diving medicine. When receiving a hyperbaric treatment, you’re subjected to increased pressure and you breathe air or oxygen at increased pressure. It is identical to taking a SCUBA dive, meaning that in both cases you breathe air or oxygen under pressure. The only difference in HBOT is the lack of water to cause the increased pressure. Instead of having to descend underwater, we increase pressure with an air compressor or oxygen tank that forces increased air or oxygen into the hyperbaric chamber. Essentially, it is a “dry” dive.
DOSE: Since HBOT is a drug, doctors use the term dose to describe the amount of the drug delivered to the patient. In the case of HBOT, we believe it is the increased amount of oxygen. As with all drugs, we can think of the dose in terms of the childhood story of the three bears: a mama bear dose, a papa bear dose, and a baby bear dose that’s just right. We’re trying to find the baby bear dose that’s right for any given patient and his or her disease.
In HBOT, the right dose is a combination of the pressure of increased oxygen, duration of each exposure, frequency of treatments, and the total number of treatments delivered at the particular time in the course of the patient’s disease. The tricky part of HBOT dosing is that no one has the ability to discern the ideal dose for each patient and the condition. Instead, we use approximations based on experience, research, and medical reports. Further compounding the problem is the fact that we don’t know the minimum amount of increased oxygen it takes to get the job done.
The early HOBT pioneer, Dr.. Orval Cunningham, found that the small amount of increased oxygen that could be obtained by pressurizing air to 1.3 times sea level atmospheric pressure and beyond (just 30 percent additional oxygen) was enough to save the lives of patients dying of the flu. This is the same amount of additional oxygen used inn some portable air chambers to treat children with cerebral palsy. So it appears that even small increases in oxygen can have beneficial effects. This means that the dose of oxygen necessary to ameliorate a patient’s condition can range from the slight increases used by Cunningham, up to the six atmospheres of 100 percent oxygen used by my partner for cardiac resuscitation-and every combination of pressure and percentage of oxygen in between.
EVIDENCE-BASED MEDICINE: For many in the medical field, evidence-based medicine includes only those treatments that have been shown to be effective through a narrow lens, especially double-blind studies. Lack of those studies (which may be completely impractical and not particularly wise in many cases) sometimes leads to dismissing some of the most effective therapies, including HBOT. However, a better definition of evidence-based medicine is more inclusive. The best statement I know comes from researcher David Sackett. He defines evidence-based medicine as: “The conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients. The practice of evidence-based medicine means integrating individual clinical expertise with the best available external clinical evidence from systematic research.” More recently this has been described as the “integration of best research evidence with clinical expertise and patient values.”
HERNIATION: Disks are the rubber-like cushions that sit between each vertebra in our spine. They absorb shock and help our spine bend. Each disk is similar to round pieces of gum that have a soft center. The outer rim of the disk is firm and tough and the inner core is softer material. When someone herniates a disk, the soft center portion ruptures through the tough outer “tire” and presses on the spinal cord or nerves, causing extreme pain.
HYPOXIA: This term refers to a decreased level of oxygen relative to a certain norm. Commonly, the normal level of oxygen is the amount in air at sea level, which is about 160 mm mercury pressure, or 21 percent of atmospheric pressure at sea level. In normal, healthy people this translates to a level in the blood of about 90 mm mercury pressure. While there is a range of normal for oxygen levels in the blood at sea level, any measurement considerably less than these numbers is considered hypoxia. At altitude, however, the atmosphere is less than 21 percent and blood levels are less than 90 mm mercury pressure. The atmosphere and people are hypoxic relative to sea level, but because human beings can adapt to altitude, we can tolerate the hypoxia. In order to cause a hypoxic insult, a significant reduction in oxygen must exist, and, of course, a much less reduction in oxygen level at altitude than at sea level.
HBOT ATTENDANT OR INSIDE OBSERVERS: These individuals accompany patients inside multiplace chambers. They can be hyperbaric technicians or more highly trained or skilled medical personnel. At our center, often, this is the parent of the child.
HBOT TECHNICIANS: In the context of HBOT, these individuals are trained to operate hyperbaric chambers. They can have a variety of different basic degrees, but most are EMT’s (emergency medical technicians) who traditionally staff ambulances.
INSULT: Used in a generic fashion, it describes injury processes that affect the brain. We use it to refer to anything that has a negative impact on the brain, such as a traumatic blow or force, a loss or decrease of oxygen, a loss or decrease of blood flow, a toxin, a toxic drug, and so forth.
PRESCRIPTION: The actual order given by your hyperbaric physician for HBOT, for example, 1.5 ATA/60 minutes, twice/day, five days/week consecutively, for 4 weeks; total number of treatments = 40.
SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY (SPECT): It is essentially CT or CAT scanning applied to nuclear medicine. The patient consumes a small dose of a radioactive drug that takes up in the brain and emits a type of x-ray that is captured by SPECT. It measures brain blood flow, which is linked to brain metabolism, which determines brain function.
SHAKEN BABY SYNDROME: An insult to an infant caused by violent shaking sometimes resulting in death or leaving the infant in a vegetative state. HBOT is the only known therapy that can improve the infant’s condition in about 75% of the cases.
SURFACE AIR: This term refers to the ambient room air that is present at the “surface,” which in HBOT is the room where the hyperbaric chamber is sitting. Surface air is not all the same, however. If you are at an altitude of 5,000 feet, the surface air is not the same as surface air at sea level; at altitude there is quite a bit less oxygen. So, pressurizing someone with surface air in Denver is not the same as pressurizing someone with surface air at sea level; you get different doses of oxygen.
TREATMENT BLOCKS: In hyperbaric medicine, you will hear treatments spoken in “blocks.” They are a concentrated number of treatments needed to effect change in an acute or chronic condition. In acute conditions, we inhibit the acute inflammatory and destructive processes that cause much of the long-term damage. In this acute stage, we have found that we need only a few treatments delivered early on to quench the inflammatory process.
However, once the chronic pathology is established we are then treating a different clinical situation; we are trying to grow new tissue, among other things. This process requires many more treatment, which are usually delivered in blocks of 40. This number can taper as we deliver more treatments, and in some cases, patients have more than one block of treatment.
Treatments generally last one to two hours and blocks of treatments are administered over successive days. Ideally, no more than a day or two should elapse between treatments. Depending on the dose of HBOT and the severity or acuity of the illness, treatments can be delivered repetitively up to four or more times per day or for prolonged periods of time (6, 12, 24 hours or more).
Glossary Courtesy of Dr. Paul Harch