The pure oxygen allows the atrial oxygenvto remain saturated at high altitudes

1. Drowsiness
2. Mental and muscle fatigue
3. Headache
4. Nausea
5. Euphoria
6. Decreased judgement, memory and motor skills
7. Muscle twitching and seizures
8. Coma and death (above 23,000 feet)

High Altitude→ ↓P_atm, ↓Alveolar PO₂

Ventilation: ↑V_A

Arterial Blood: ↓P_aO2, ↑pH(respitory alkalosis)

Pulmonary Blood Flow(restrict in hypoxia): ↑Pulmonary resistance, ↑Pulmonary artery pressure, Hypertrophy of right ventricle.

Oxygen Hb Curve: ↑2,3-DPG(shifts to right), ↑P₅₀, ↓Affinity for O₂

1. Increased pulmonary ventilation:

2. Increased RBC and Hb concentration:

3. Increased Diffusing capacity of O₂ through pulmonary membrane:

-increased surface area, lung volume, arterial pressure.

4. Increased capillarity: systematic capillaries

5. Changes at cellular level: Increased mitochondria and oxidative enzymes to use oxygen more effectively.

1. Increased chest size compared to body size → high ratio of ventilation capacity to body mass.
2. Increased right side of the heart → high pulmonary arterial pressure → expanded pulmonary capillary system
3. Better delivery of Oxygen by the blood to tissues

Effects:

1. High Hematocrit

2. Increased pulmonary arterial pressure

3. Enlarged right side of the heart.

4. Decreased peripheral arterial pressure

5. Congestive heart failure

6. Death unless moved to lower altitude.

Causes:

1. High Hematocrit→ increased blood viscosity→ decreased tissue blood flow→ decreased Oxygen delivery to the tissues.

2. Lung hypoxia→ constriction of pulmonary capillaries→ increased pulmonary arterial pressure→ right side heart failure.

3. Alveolar arterial spasm due to hypoxia→ increased pulmonary blood flow shunt.

Treatment: move person to lower altitude

From few hrs to 2 days after ascending to high altitude.

Effects:

1. Acute cerebral edema: Hypoxia→ dilation of cerebral blood vessels→ increased capillaries filtration→ edema

2. Acute pulmonary edema: pulmonary hypertentsion→ pulmonary engorgement→ edema

The volume of the lung is inversely proportional to the pressure.

Effects:

-Start at 120ft deep and get worse with depth.

-Initial euphoric feeling

-Decreased strength

-Unconsciousness(narcotic)

Mechanism:

Nitrogen dissolves in fatty substances of neural membrane→ alter ionic conductance through the membrane→ reduces neural excitability

• Nausea, muscle twitching, dizziness, disturbances of vision, irritability and disorientation
• Oxygen free radicals formation→ damage the cell membrane and metabolic system.
• Seizures followed by coma (PO₂=3040mmHg for 30 min)

• Lung airway congestion
• Pulmonary edema
• Atelectasis

CO₂ toxicity at the high sea depth(when diving gear does not work properly)

Depressed respitory center→ respitory acidosis, lethargy, narcosis

• The amount of Nitrogen that dissolves in the body increases with depth.
• Under high pressure the Nitrogen remains fluid.  When pressure is suddenly increased, like when a diver comes up too fast, the Nitrogen turns to gas an forms bubbles.
• These bubbles can plug vessels anywhere in the body.

(85-90%): Pain in joints and muscles of the legs and arms.

(5-10%): Nervous system symptoms such as dizziness, paralysis, collapse, and unconsciousness.

(2%):"The chokes", massive number of bubbles plug lung capillaries→ shortness of breath, pulmonary edema and occcasionally death.

Helium is usually used in the gas mixture:

-has 1/5 narcotic effect of nitrogen

-only 1/2 the volume of helium dissolves in body tissue so it has no problem diffusing out.

-Has low density→ reduces work of breathing

Low O₂ concentration is used in the gas mixture to prevent oxygen toxicity.

O₂ is administered to the patient at high pressure (2-3 atmospheric pressure) through a mack or intra-tracheal tube.

Most beneficial in treatment of Gas Gangrene because it is an anerobic bacteria.