Oxygen and Respiratory Failure Flashcards
What is the difference between type 1 and type 2 respiratory failure?
Type 1 - Short of oxygen
Type 2 - Short of oxygen AND too much carbon dioxide.
What problem can type 1
respiratory failure lead to?
Type 2 respiratory failure
What is hypoxaemia?
Low oxygen in the blood
What is the pathway of primary hypoxaemia in good lungs?
The Tidal volume and respiratory rate increases.
Normal pO2 levels and low pCO2 levels (good)
What is the pathway of primary hypoxaemia in bad lungs?
Low O2 and normal pCO2 (type 1 respiratory failure)
This can then lead to Low pO2 and High pCO2 (type 2 respiratory failure)
What bad thing can happen after primary hypoxaemia with good lungs?
It change into type 1 respiratory failure
What does high C02 cause in the lungs?
Acidosis
How does the body reduce acidosis?
Liver increases HCO3 to balance out pH
After the liver fixes acidosis, how can this change?
There could be an infection in which causes CO2 to be very high and so causes acidosis again.
What is more important? lack of oxygen or too much carbon dioxide?
Lack of oxygen - worry about too much CO2 later
How common is type 2 respiratory failure?
Very common
What is wrong with doctors giving patients oxygen?
They are poisoning them as the oxygen does more harm than good in certain situations.
Why is giving patients maximum oxygen bad?
This is because a patient’s oxygen saturation can can still show 100% even if their lungs have become damaged (low oxygen) - can’t see when patient is getting worse.
Why must oxygen be prescribed?
It counts as a drug and a patient will not get it if not prescribed
What is the first rule when prescribing oxygen?
Only give oxygen if the risk/benefit ratio is in the favor of oxygen.
What’s the problem with people who are sensitive to oxygen?
The CO2 levels can rise significantly when their O2 is increased. This can cause acidosis and life threatening.
What is the frequency of COPD patients retaining CO2 and are oxygen sensitive?
1 in 5
What are examples of diseases that can cause type 2 respiration?
Cystic fibrosis, kyphoscoliosis and morbid obesity.
What is V/Q mismatching?
This is when a patient has emohysema/COPD/Chronic lung disease and it leads to poor ventilation. This causes hypoxic vasoconstriction (V) and poor perfusion (Q) so V=Q. When there is oxygen it makes the perfusion good but ventilation still bad and so Q doesn’t equal V! this means alveolar pCO2 increases and it can’t be exhaled due to poor ventilation.
What is the haldane effect?
Oxygen can displace CO2 from haemoglobin
What is the Bohr effect?
High concentrations of CO2 prevent O2 binding to haemoglobin
What is the Bohr shift?
When a patient has a higher pCO2 then an increase in oxygen causes a slower increase in oxygen saturation. It also makes the limit of maximum oxygen saturation lower.
Hypoxic drive - The theory
Normal respiration driven by CO2 chemoreceptors.
Chronic hypercarbia leads to a desensitisation of these receptors. Oxygen chemoreceptors then becomes the primary drive for respiration.
What is the 3 mechanisms that cause CO2 to increases when the patient is given high inspired oxygen?
Haldane effect, Ventilation/perfusion mismatch and the removal/reduction of hypoxic drive.
What markers suggest Chronic CO2 retention?
High pCO2 and High HCO3
What can cause CO2 retention in chronically hypoxaemic patients without CO2 retention?
Too much O2 (haldane effect)
What does the Bohr effect cause in patients?
a very low SaO2 despite relatively normal pO2
What is hypocarbia?
Low carbon dioxide in the blood?
How to treat hypercarbia?
Ensure conservative oxygen management - Sa02 88%-92%.
Increase volume of air per minute - using a NIV (increases Vt)
What can severe hypoxaemia cause?
Tissue hypoxia, hyperventilation (5.3kPa), Loss of consciousness (4.3 kPa), Death (2.7 kPa)
Hypoxia is?
Lack of oxygen to tissues
Hypoxaemia is?
Lack of oxygen to tissues but doesn’t neccessarily lead to tissue hypoxia.
What is circulatory hypoxia?
When there is a problem with the circulatory system which prevents the oxygenated blood from getting to the tissues quick enough. Heart failure and obstruction of vessels can cause this.
What is the three types of anaemia?
Macrocytic anaemia - B12 and Folate deficiency.
Koilonychia - Iron deficiency anaemia (spooning of nails)
Sickle cell anaemia.
What is the CO half life in 21%, 100% AND HYPERBARIC O2?
21% of O2 - 4-6 hours
100% O2 - 80 minutes
Hyperbaric O2 - 22 minutes
What is a symptom of cyanide poisoning in an autopsy?
bright Redness of skin in some areas (causes cells to undergo anaerobic respiration and so blood stays oxygenated and bright red. This layers up where gravity flows it in autopsy) indistinguishable from carbon monoxide poisoning
What are the symptoms of carbon monoxide poisoning in autopsy?
Bright redness of skin in some areas (binds to Hb and prevents the release of oxygen from Hb and so the blood stays oxygenated and bright red. Thus layers up where gravity flows it in autopsy) indistinguishable from cyanide poisoning.
What happens when Fe2+ in haemoglobin becomes oxidised?
It becomes Fe3+ and it creates met-haemoglobin.
What is bad about met-haemoglobin?
It cannot bind to O2.
what are the causes of met-haemoglobin?
G6PD deficiency (Fava-ism)
Poopers - drug
Aromatic amines
Nitrates/nitrites
What is formed when CO binds to haemoglobin?
Carboxyhaemoglobin
What is hypoxaemic hypoxia?
Low inspired oxygen concentration - usually occurs at high altitudes
What are 6 things that cause alveolar hypo ventilation?
Opiates (drugs), laryngeal obstruction (physical obstruction), Obesity, Bronchial obstruction (chocking), anaesthesia and kyphoscoliosis.
What is impaired diffusion?
Failure of the alveolar - endothelial interface.
What causes impaired diffusion?
Interstitial thickening and vascular dysfunction
What is a good ventilation and poor perfusion called?
Lung Apex
What is poor ventilation but good perfusion called?
Lung base
What treats hypoxaemia?
Oxygen - not breathlessness
How effective is High flow/oxygen?
not very, only beneficial rarely.
What happens when acutely ill adults are treated with liberal oxygen vs conservative oxygen?
They are less likely to survive if on liberal oxygen compared to conservative oxygen - conservative oxygen is less than liberal.
What conditions should unrestricted use of oxygen be used?
Cluster headaches, carbon monoxide poisoning, pneumothorax (not treated with chest drain), and sickle cell crisis.
When should oxygen therapy stop in acutely ill adults?
96% saturation maximum
When should oxygen be stopped in patients with acute stroke or myocardial infarction?
93% oxygen saturation maximum (there is weak evidence suggesting between 90% - 92%.
What is the overall message of the oxygen powerpoints?
OXYGEN CAN DO HARM!!!
