RESP + POISONING: OXYGEN

Question 1

OXYGEN: INDICATIONS

Answer 1

• Increase tissue oxygen delivery in states of hypoxaemia
• Accelerate reabsorption of pleural gas in pneumothorax
• To reduce the half-life of carboxyhaemoglobin in CARBON MONOXIDE POISONING

Question 2

OXYGEN: MOA

Answer 2

• Abnormally low partial pressure of oxygen (Po2) in arterial blood termed HYPOXEMIA may be a consequence of a wide range of processes
• Its effect is to reduce delivery of oxygen to tissues (HYPOXIA) forcing them to use anaerobic metabolism for energy generation
• Supplemental oxygen therapy increases the p02 value in alveolar gas, driving more rapid diffusion of oxygen into blood
• Resultant increase in Pa02 increases the delivery of oxygen to the tissues which in effect BUYS TIME until the underlying disease process is corrected
• PNEUMOTHORAX = supplemental oxygen therapy has an additional benefit of reducing the fraction of nitrogen in alveolar gas
• Accelerates the diffusion of Nitrogen out of the body
• Since pleural air is composed mostly of nitrogen, this increases its rate of absorption
• CARBON MONOXIDE POISONING = oxygen competes with CO to bind to haemoglobin and thereby shortens the half life of carboxyhaemoglobin, returning Hb to a form that can again transport oxygen to tissues

Question 3

OXYGEN: ADVERSE EFFECTS

Answer 3

• Delivery device effects = discomfort of the face mask, lack of water vapour (dry throat) = can be alleviated using a DEHUMIDIFIER

Question 4

OXYGEN: WARNINGS

Answer 4

• Chronic type 2 resp failure exhibit a number of adaptive changes in response to persistent hypoxemia and hypercapnoea
• High inspired o2 concentrations = rise in the blood carbon dioxide concentration
• This can lead to respiratory acidosis, depressed consciousness and worsened tissue hypoxia
• Oxygen accelerates combustion and therefore presents a fire risk if it is bought into close proximity with a heat source or naked flame including smoking

Question 5

OXYGEN: INTERACTIONS

Answer 5

NA