Oxygen Therapy Indications and Hazards

Question 1

Does oxygen require a prescription?

Answer 1

Yes, it is considered a drug and must be given with just cause, properly, and safely.

Question 2

What does oxygen bind to in the blood?

Answer 2

Hemoglobin.

Question 3

What molecule is used to generate ATP?

Answer 3

Oxygen

Question 4

What role does oxygen play in angiogenesis?

Answer 4

Hypoxia promotes angiogenesis (generation of new blood vessels).

Question 5

What does it mean when we say oxygen is a vasoactive substance?

Answer 5

It has a strong effect on the actions of vessels, causing both vasodilation and vasoconstriction depending on site and concentration.

Question 6

How does oxygen affect immune function?

Answer 6

Suppresses anaerobic bacteria, supports proper function of WBCs.

Question 7

What are the indications for oxygen therapy?

Answer 7

Hypoxia and hypoxemia.

Question 8

What is the difference between hypoxemia and hypoxia?

Answer 8

Hypoxemia is too little oxygen in the blood, hypoxia is inadequate oxygen for cellular metabolism.

Question 9

What are some causes of hypoxemia?

Answer 9

Decreased alveolar oxygen tension, increased altitude, inadequate ventilation, or a ventilation to perfusion mismatch caused by shunting or deadspace

Question 10

What does it mean to shunt?

Answer 10

When we have blood but there is no air, for example a collapsed lung.

Question 11

What is deadspace?

Answer 11

When there is air but there is no blood to pick up the oxygen, for example if the capillaries are constricted or occluded such as a pulmonary embolism.

Question 12

What are the three physiological responses to hypoxemia.

Answer 12

Increase in minute ventilation, increase in cardiac output, and increase red blood cell production.

Question 13

Define polycythemia.

Answer 13

A type of blood cancer caused by chronic hypoxemia where the bone marrow produces too many RBCs.

Question 14

What are some signs and symptoms of hypoxemia?

Answer 14

Cyanosis, arrythmias, confusion or disorentation, polycythemia, lethargy.

Question 15

What is the typical hemoglobin level?

Answer 15

Males typically have higher than females, but generally 120-160.

Question 16

Why is hypoxia so dangerous?

Answer 16

It activates anaerobic metabolism which produces a toxic metabolite called lactate that can kill cells.

Question 17

What are the four types of hypoxia?

Answer 17

Hypoxic (not enough oxygen), anemic (not enough carriers in blood), circulatory (blood is prevented from moving around), histotoxic (there is a poisoning the prevents the tissues from utilizing the oxygen, for example cyanide or end-stage septicemia).

Question 18

What are some causes of hypoxic hypoxia?

Answer 18

Depressed respiratory drive, suffocation, etc.

Question 19

What are some causes of anemic hypoxia?

Answer 19

Dyshemoglobin like carbon monoxide poisoning (binds to hemoglobin preferentially over oxygen).

Question 20

What are some causes of circulatory hypoxia?

Answer 20

Cardiac arrest or ischemic stroke.

Question 21

What are some causes of histotoxic hypoxia?

Answer 21

Cyanide poisoning or end-stage septicemia.

Question 22

What are some contraindications of oxygen therapy?

Answer 22

Drugs that increase sensitivity to oxygen and oxygen free-radicals (bleomycin), known paraquat (herbicide) poisoning, and demonstrated oxygen sensitivity in end-stage COPD.

Question 23

Why is too much oxygen bad?

Answer 23

It releases oxygen free-radicals which cause oxidative damage to organs and tissues.

Question 24

What are some symptoms of oxygen toxicity?

Answer 24

Mucosal inflammation and cilia inactivation, red blood cell destruction (hemolysis), nitrogen washout atelectasis.

Question 25

How much oxygen is too much?

Answer 25

375 mmHg (~0.5 FiO2 for roughly 14 hours)

Question 26

When do CNS vs pulmonary effects occur with oxygen toxicity?

Answer 26

CNS effects will not occur until there are hyperbaric pressures (positive pressure ventilation) but pulmonary effects can occur at clinical PO2 levels.

Question 27

Explain how oxygen toxicity occurs.

Answer 27

High PO2 damages capillary endothelium which causes interstitial edema and alveolar capillary (AC) membrane thickening; type 1 cells are destroyed and type 2 cells proliferate triggering the inflamax response and causing alveolar fluid buildup. Shunting occurs and hypoxemia results; hyaline membranes form at alveolar level which is proteinaceous eosinophilic (basic) material composed of cellular debris and condensed plasma proteins. Pulmonary fibrosis and pulmonary hypertension develop.

Question 28

What is the inflamax response?

Answer 28

Normally antioxidants and other enzymes get rid of other free radicals but during the inflamax response neutrophils and macrophages flood the tissue leading to more free radicals.

Question 29

What is absorption/nitrogen atelactesis (washout)?

Answer 29

When there is high levels of oxygen in the lungs (meaning less room for other gases) the oxygen diffuses into the vessels and leaves empty space in the lungs that causes the lung to collapse.