Question

A scuba diver who has the bends is treated by being placed in a chamber that has a high pressure of air. The air pressure in the chamber is lowered gradually. How does this treatment help the diver?

Short answer

This treatment helps the diver by recreating a slow and controlled ascent from the pressures experienced during a deep dive. When a diver is placed in a chamber with high air pressure, the dangerous gas bubbles in the body are forced to re-dissolve back into the blood. As the pressure is then gradually lowered within the controlled environment of the chamber, this nitrogen has the chance to be gradually expelled from the body in a safe manner, thus eliminating the symptoms and potential dangers of the bends, or decompression sickness.

Step-by-step solution

Understanding 'The Bends' condition

The bends or decompression sickness occurs when a diver ascends too quickly from a deep dive. It is the result of inert gases (mostly nitrogen), which were dissolved in the body tissues under high pressure during the dive, coming out of solution into bubbles as the pressure decreases too rapidly with the ascent. These bubbles can cause joint pain, paralysis or even death, in severe cases.

Understanding the treatment procedure

The diver is placed in a hyperbaric chamber where the air pressure is increased. This pressure forces the nitrogen bubbles in the tissues to re-dissolve back into the blood. In a controlled environment within the chamber, the pressure is then gradually lowered. This controlled pressure reduction allows the nitrogen to be gradually expelled from the body in a safe manner, usually through respiration.

Making the connection

The gradual reduction of pressure in the treatment chamber is crucial in allowing the body to safely get rid of the excess dissolved gases. If the pressure is lowered too quickly, it will simulate a rapid ascent and cause the gases to form bubbles in the body tissues. So, this gradual reduction of pressure mimics a slow and controlled ascent from a dive, which is how divers can naturally avoid decompression sickness.

Key concepts

Hyperbaric Chamber Therapy

Hyperbaric chamber therapy is a critical treatment for decompression sickness, often referred to as 'the bends,' a risk associated with scuba diving. When a diver is subjected to this treatment, they are placed in a specialized chamber where air pressure can be carefully manipulated. Initially, the pressure inside the chamber is increased to a level higher than atmospheric pressure, which has a compressing effect on the nitrogen gas bubbles that have formed in the diver's body. This increased pressure helps to reduce the size of the bubbles and encourages them to dissolve back into the body's tissues.

The real benefit of the hyperbaric chamber comes from the controlled gradual decrease in pressure. Similar to how a diver would make a slow ascent to the water's surface, the pressure within the chamber is slowly reduced. This methodical decompression allows nitrogen to be expelled from the body at a rate that doesn't cause harm, typically via the lungs as the diver breathes. This treatment can be lengthy but is essential in ensuring the diver's safety and recovery.

Scuba Diving Physiology

Understanding the physiology of scuba diving is crucial to protecting diver health. When a diver descends into the depths of the ocean, the pressure on their body increases significantly. Under these conditions, gases like nitrogen, which are breathed in from the scuba gear, dissolve into the diver's blood and tissues due to the elevated pressure. This is a result of Henry's Law, which states that the amount of gas that can dissolve in a liquid at a given temperature is proportional to the pressure of the gas above the liquid.

The body can handle increased amounts of dissolved gases while under pressure, but issues arise during ascent. If a diver ascends too quickly, the rapid decrease in pressure can lead to the formation of nitrogen gas bubbles within the body, which is the central issue in decompression sickness. These nitrogen bubbles can disrupt normal circulation and pose serious threats to health. Therefore, a careful balance must be maintained during the descent and ascent to control the gas pressures within the body.

Nitrogen Gas Bubbles

The formation of nitrogen gas bubbles in the tissues is the primary problem in decompression sickness. These bubbles occur because as a diver ascends and the surrounding pressure decreases, gases that were once dissolved in the diver's bodily fluids begin to come out of solution, forming bubbles. This can happen within any part of the body, including joints, the spinal cord, and even around the brain.

These nitrogen bubbles can cause a range of symptoms, from the mild, such as pain in the joints ('the bends'), to severe neurological and cardiovascular complications. The key to treating these symptoms is to manage the size and formation of these nitrogen bubbles. Effective treatment involves minimizing bubble formation by ensuring a slow ascent rate and utilizing hyperbaric oxygen therapy post-dive if symptoms present, aiming to dissolve these bubbles back into the body's tissues.

Controlled Pressure Reduction

Controlled pressure reduction is the cornerstone of safely treating decompression sickness through hyperbaric oxygen therapy. Just as a diver must ascend slowly to prevent rapid changes in pressure, which can lead to bubble formation, the hyperbaric chamber must decrease pressure at a rate that allows the body to safely offload the excess dissolved nitrogen.

Controlled pressure reduction follows a decompression schedule, which is a calculated gradual reduction in pressure that matches the body's ability to eliminate inert gases without bubble formation. Divers can use decompression tables or dive computers to guide their ascent in a similar gradual manner in the open water. In a hyperbaric chamber, this process is carefully monitored and adjusted by medical professionals to ensure the optimal rate of decompression for an individual's specific physiology, thus preventing the exacerbation of decompression sickness symptoms.