Scuba Diving - Section 3

- In basic terms, describe the respiratory process and give an example of how gas could enter the bloodstream.

 When you breathe, the gas you take in is rich in oxygen.

The blood entering the pulmonary capillary bed has been transported from other parts of the body. By then, that blood is low in oxygen and high in carbon dioxide.

The oxygen you just inhaled will move from the inside the alveoli passing through the tissue layers into the pulmonary capillaries and the bloodstream. The carbon dioxide is then transferred from the blood into the alveoli to be expelled when you exhale. This movement of gas from an area of higher concentration to an area of lower concentration is called diffusion. The oxygen and carbon dioxide are constantly diffusing in opposite directions.

- List four possible lung overexpansion injuries, identify the most serious of these injuries and describe the cause,

symptoms, treatment, and prevention for each.

• Arterial Gas Embolism (AGE) is one of the most serious diving injuries. It occurs when an untrained diver holds his breath and ascends. Symptoms include  unconsciousness, which often occurs before the diver reaches the surface or within four to six minutes after surfacing. Its treatment is, 
  
  
• In Pneumothorax, the second most serious lung overexpansion injury, air escapes from the lungs and moves between the covering of the lungs and the rib cage. Symptoms are essentially the same as mediastinal emphysema. However, breathing difficulties may be more pronounced, particularly if both lungs are collapsed. Its treatment is,
  
  
• In Subcutaneous Emphysema, the air escapes from the lungs into the area of the heart  and moves up along the windpipe  into the region around the collarbone and the neck. Symptoms include swelling in the neck area with crepitation (a crackling sensation upon touching the swollen area), voice changes as a result of the swelling and possible breathing difficulties. Its treatment is,
  
  
• In Mediastinal Emphysema, air escapes from the lungs into the area of the heart (mediastinum) and presses on the heart and surrounding blood vessels. Symptoms include chest pain, breathing difficulties, weakness, collapse due to pressure on the heart and large blood vessels plus cyanosis (blueness) of the lips and nail beds because of circulatory difficulties. Its treatment is, 

All these overexpansion injuries can be prevented by:

1) Breathing continuously throughout the dive and never holding your breath

2) Not diving with respiratory congestion, and having a chest x-ray if you have had serious lung problems to determine your fitness to dive.

3) Not smoking, which has been linked to lung disease and cause alveoli to lose their elasticity

4) Using the right equipment and keep it in top condition

5) Take your time, and never ascend faster than 9 meters per minute. Always look up to ensure your airway stays open. 

- Define the term partial pressure.

The pressure that would be exerted by one of the gases in a mixture if it occupied the same volume on its own.

- List the percentages of nitrogen and oxygen in gas and calculate the partial pressure…