RGI 4 Barotrauma

Section 1: Gauge Pressure Effect & SCUBA Apparatus

Definition of Barotrauma

  • Barotrauma: Injury caused by abnormal air pressure changes.

  • Commonly associated with scuba diving but can happen with any sudden pressure change.

    • Cerebral Embolism Pnemothorax Mediatinal Emphysima ( are all examples of barotrauma)

Pressure Changes in Diving

  • Total Pressure Increase: Total pressure increases by 1 atmosphere for every 10 meters of depth (h).

  • Equation: Ptotal = Patm + (rgh)

  • SCUBA Apparatus Functionality: SCUBA equipment delivers air at ambient pressure, which includes both atmospheric and gauge pressure.

Section 2: Decompression Sickness (DCS)

Understanding DCS

  • DCS, often referred to as "The Bends," occurs when gas solubility in tissues increases with partial pressure of gases such as oxygen (O2) and nitrogen (N2) during a dive. ( dalton’s law of partial pressures)

  • It isn’t problematic at depth, but during ascent, reduced pressure causes gas to come out of solution, forming bubbles in the body if ascent is too rapid.

  • Henry's Law: States that gas solubility in a liquid is proportional to the partial pressure of that gas above it.

Ascent and DCS Risk

  • If diver ascends slowly (10m/min), excess micro-bubbles can be expelled during normal respiration.

  • Rapid ascent doesn’t allow enough time for gas expulsion which leads to bubble formation in joints, muscles, and bloodstream, causing spasms.

  • The body cant get rid of N2

  • Symptoms: Joint pain and neurological symptoms due to gas bubbles.

    • This is not always immediate and can take up to 24 hours. (esp bone marrow)

  • The reason why its called the bends is because they go into fetal position (hence they bend)

  • Treatment: Administer oxygen and transport to the nearest recompression chamber; hyperbaric treatment is essential.

Extra info

Commercial divers often use Heloix or Tri-Mix gases where the N2 has either been diluted or replaces by helium or argon.

Section 3: DCS in Non-Aquatic Situations

Risks Beyond Diving

  • DCS can occur from sudden loss of cabin pressure in aircraft, requiring precautions for divers.

    • the need of gas masks to avoid DCS as well as hypoxia

  • History: First documented DCS cases occurred in caisson construction; the first fatality recorded in 1872 during work on the Brooklyn Bridge.

  • Space Diving Risk: DCS is also a concern during spacewalks, where pressure must be managed carefully. ( must decompress slowly over 2 hour beforehand.

Section 4: Oxygen Toxicity & Nitrogen Narcosis

Oxygen Toxicity and Management

  • Oxygen Toxicity: Occurs at pO2 greater than 1.6 atm, leading to severe convulsions underwater.

    • 6m for pure PO2

    • 66m for air-mix

  • Mix Recommendations: Divers use Heliox or Tri-Mix to dilute or replace nitrogen (N2) to prevent narcotic effects.

Understanding Nitrogen Narcosis

  • Narcosis Effects: At depths exceeding 25 meters, and when pN2 is greater than 3.2, nitrogen becomes intoxicating, impairing decision-making capabilities.

  • 1 unit of alcohol for each 10m of depth

  • results is loss of motor function and deterioration in decision making.

  • Ascending gradually helps alleviate symptoms.

Section 5: Boyle's Law in Diving

Application and Consequences

  • Boyle's Law: PV = constant; pressure volume relationships become critical in diving settings, especially with air spaces in the body.

  • Diving Effects: Inexperienced divers face squeeze sensations during descent; Valsalva Maneuver helps equalize pressure in the ears.(= squeeze on the ears pain or perforated ear drums= why you should never dive with an upper respiratory tract infection.)

  • Equalized pressure is important in face masks in order not to suffer Mask Squeeze. this is why divers dont wear. masks since you need space for the front of your eyes.

  • Risks of Holding Breath: During an unexpected ascent, holding one's breath can lead to pulmonary injuries like air embolism. Due to the over expansion of the lungs. or a pneumothorax

  • Arterial Gas Embolism an ischeamic damage due to gass in the blood

  • Bullous emphysema a permenant mechanical deformation of the aveoli caused by the expansion beyond its elastic limit. This can occur even if alveoli dont rupture.

  • Mediastinal emphysema is when air leasks through the alveoli into the mediatinum NOT pleural space.

Section 6: Shallow Water Blackout

Mechanisms and Risks

  • Occurrence Triggers: Shallow water blackout happens during breath-holding activities, often influenced by twin factors of too low CO2 levels due to hyperventilation before diving.

  • Start the dive with 0.25 atm

  • normal is 0.21 atm

  • Consciousness Loss: Loss of consciousness can occur rapidly if pO2 falls below safe levels which is 0.1 atm.

Pre-Dive Preparation

  • Proper oxygen and CO2 levels maintenance among divers is crucial to avoid critical injuries related to over-hyperventilation.