Why is hyperbaric medical device?
A hyperbaric chamber is a pressure chamber that increases air pressure. Higher pressures proportionally increase the amount of gas, especially oxygen dissolved in the body.
Hyperbaric chambers modulate both nitrogen and oxygen dissolved in the body.
Hyperbaric chambers were originally used to enable divers to slowly release nitrogen absorbed by body tissues during stays in high pressure nitrogen-rich environments . Slow decompression enables divers to slowly release dissolved nitrogen to avoid or treat the bends.
During nitrogen decompression, divers noted that extra oxygen helped healing and recovery from incidental conditions and injuries.
Oxygen Partial Pressure
NITROX, an air mixture that uses extra oxygen to displace nitrogen, enables divers to dive deeper and longer without decompression.
Diving combines the exercise of swimming, elevated oxygen pressure from compression from water depth often with oxygen boosted by breathing NITROX. This process increases oxygen partial pressure in the body several times above normal.
It has a long history of safety. Divers have long observed that diving with NITROX often creates surprising health benefits from dramatically increased oxygen partial pressure in the body for short periods.
The diving community first recognized health effects of stand-alone use of hyperbaric chambers to increase body oxygen levels. This prompted adoption of stand-alone use of hyperbaric chambers as a medical therapy.
The effects of NITROX diving and hyperbaric therapy are similar because both processes temporarily increase the amount of oxygen dissolved in tissue, one uses exercise under variable respiratory conditions while the other requires occupancy in a chamber of compressed gas.
Diving remains a sport, form of exercise, while hyperbaric treatment is a medical therapy.
Hyperbaric chambers are pressure capsules
The existence and acceptance of NITROX as a breathing mixture illustrates that oxygen partial pressure does not constitute the basis for regulation of hyperbaric chambers as a medical device.
The main reason for regulation of hyperbaric devices appears to be that their standalone use is intended as a treatment for 14 accepted conditions.
Excerpted from: Mayo Clinic Hyperbaric oxygen therapy is used to treat several medical conditions. And medical institutions use it in different ways. Your doctor may suggest hyperbaric oxygen therapy if you have one of the following conditions:
- Anemia, severe
- Brain abscess
- Bubbles of air in your blood vessels (arterial gas embolism)
- Burn
- Decompression sickness
- Carbon monoxide poisoning
- Crushing injury
- Deafness, sudden
- Gangrene
- Infection of skin or bone that causes tissue death
- Nonhealing wounds, such as a diabetic foot ulcer
- Radiation injury
- Skin graft or skin flap at risk of tissue death
- Vision loss, sudden and painless
Pressure Chamber Effects & Risks:
Hyperbaric chambers were adopted for health support.
Most risks from Hyperbaric chambers stem from mechanical pressure effects on the body.
The human body is mostly water except for the inner ear and the lungs are air chambers. Gas in these compartments expands and contracts as pressure changes.
When pressure changes, air must enter or escape to adjust.
Too rapid air pressure change cause injury as these compartments under or over-inflate.
When air pressure changes, more rapidly than these compartments adjust, injury occurs.
These effects are well known. Diver’s know not to ascend while holding breath, to avoid lung injury, or descend too rapidly to avoid ear injury.
Ear injury may occur when external air pressure drops more quickly than air can escape. Similarly, holding the breath during rapid depressurization, like when a scuba diver ascends from depth, can also occur with a rapid hyperbaric depressurization while holding the breath.
Holding your breath while resulting in Rapid air pressure changes may cause injury.
Pressure Swing Equalization on the ears
When you gain altitude, your ears pop because the air inside your inner ear expands and must escape to avoid overpressure in the inner ear compartment.
When you lose altitude, the air inside your inner ear compartment shrinks, so our body must open the eustachian tube add more to refill the chamber.
If your body cannot equalize pressure as fast as the pressure changes, discomfort and injury may occur.
During normal operation hyperbaric chamber pressure changes slowly to allow the occupant to equalize air pressure in the ears. This can cause discomfort or injury if it happens too fast.
Risk of Ear Injury for different types of chambers
One reason that hyperbaric treatment is a medical treatment because the rate of pressure change must be regulated to avoid injury and discomfort.
The rate of pressure change must be managed during both pressurization and depressurization for the safety and comfort of the occupant.
Medical and military hyperbaric chambers use heavy-duty materials to minimize the risk of injury from rapid depressurization from material failure high pressures over 2 atmospheres. A depressurization failure could cause a significant injury.
Portable flexible chambers, made of fabric and plastic, are limited to low pressure, 1.4 Atmospheres, because a loss of .4 atmospheres is only likely to result in discomfort and mild injury.
Captivity and Claustrophobia
Physical use of a hyperbaric chamber has both discomfort and risk:
- Pressure increases temperature and may be uncomfortable for users intolerant of heat;
- Movement is restricted due to small size;
- Suffocation may occur in a power failure for users unable to self escape;
- Use is tedious. Dwell times tend to be long 1 – 2 hours per treatment, with many treatments required;
- Panic is possible for users subject to claustrophobia.
This combination of factors contribute to the reasons why hyperbaric is a medically regulated treatment and requires medical supervision.
Blood Gas Effects
Blood gasses control respiration.
We inhale when Carbon Dioxide accumulates in the blood as Carbonic Acid. Inhale creates a vacuum in the lungs which draws Carbon Dioxide through the alveolar membrane to neutralize carbonic acid.
Exhale pressurizes the air in the lungs, 21% oxygen, to force oxygen through the alveolar membrane to oxygenate Red Blood Cells and blood plasma.
Carbon Dioxide as carbonic acid is the primary trigger for respiration, and oxygen depletion is a secondary respiratory trigger.
Concern for dysfunction in respiratory drive resulting from unanticipated deviations in blood gas concentrations while in a captive pressurized environment creates an element of risk for patients with respiratory disorders resulting in various contraindications for hyperbaric therapy.
Oxygen Toxicity Effects
Oxygen toxicity has been documented to occur very high oxygen partial pressure environments and for infants. There are three different oxygen toxicity effects affecting different organs:
Data Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4925834/
| Pressure | PO2 | Duration | |
| Central Nervous System | 3 ATM | 100% | >6 minutes |
| Lung | 1 ATM | 50% | Over 10 hours |
| Ocular (eye) | 1 ATM | >60% (infants) |
The conditions for oxygen toxicity generally do not occur in hyperbaric chambers except possibly with infants. Normal administration limits keep oxygen exposure within well established safe limits.
Summary
Hyperbaric therapy is regulated as a medical treatment because of four user risk elements:
- Ear injury to the user from rapid pressure swings;
- Anxiety or panic from claustrophobia during confined captivity;
- Risk of suffocation from airflow loss during power failure when a user cannot self-escape;
- Oxygen Toxicity is only possible with 4x hyperbaric chambers or with infants;
- Secondary contraindications from respiratory system dysfunction or drugs that increase oxidative stress, certain antibiotics and chemotherapeutic agents.
All of these factors combine to create a small user risk. This risk is mitigated by distributing hyperbaric therapy and therapy devices by prescription.
Hyperbaric chambers have a many year history of safety with very few reported adverse events or effects, and many reported benefits.