Oxygen & Resp Failure & PFTs Flashcards
What is the difference between type 1 & 2 respiratory failure?
Type 1 - short of oxygen Type 2 - short of oxygen AND too much carbon dioxide
What happens in bad lungs when there is a high pCO2?
The carbon dioxide associates into acid, the kidneys produce carbonate to compensate but in the presence of a virus this process is affected and leads back to acidosis
What does it mean if someone is sensitive to oxygen?
As the pO2 increased the pCO2 rises leading to acidosis
Describe V/Q mismatching
Areas of poor ventilation have reactive vasoconstriction . When oxygen is given vasodilatation occurs leading to good perfusion but poor ventilation. Dilated vessels bring back lots of carbon dioxide but this cannot be exhaled so is shunted into the arterial system.
What is the haldane effect?
Oxygen can displace carbon dioxide from haemoglobin
What is the bohr effect?
high concentrations of carbon dioxide prevent oxygen binding to haemoglobin
Explain hypoxic drive
Carbon dioxide chemoreceptors are desensitised. Oxygen chemoreceptors become the primary drive fro respiration. Tidal volume smaller than deadspace leads to hypercarbia Hyperventilation causes low carbon dioxide but if small enough can cause high carbon dioxide
What is the treatment for hypercarbia?
Oxygen management (88-92%) Increase ventilation using a non invasive ventilator
What are they signs of hypoxaemia?
- cyanosis - dyspnoea - tachypnoea - arrhythmias
State to pO2 for each of the following scenarios; hyperventilation loss of consciousness death
less than 5.3kPa c. 4.3kPa c. 2.7kPa
Describe circulatory hypoxia
Oxygenated blood cannot get to the tissues due to the pump not working. This leads to obstruction of vessels, oedema and heart failure
Describe anaemic hypoxia
Usually due to vitamin deficiencies - B12, Folate, Iron Blood loss is also a common cause
What is toxic hypoxia?
Carbon monoxide poisoning, CO irreversibly binds to haemoglobin stopping oxygen release Cyanide inhibits ATP leading to anaerobic respiration Blood remains oxygenated so appears bright red
Name six causes of alveolar hypoventilation
- opiates
- laryngeal obstruction
- obesity
- bronchial obstruction
- anaesthesia
- kyphoscoliosis
What is meant by impaired diffusion?
Failure of the alveolar endothelial interface
Name and describe two causes of impaired diffusion
- Interstitial thickening - pulmonary fibrosis - lymphagitis - sarcoidosis 2. vascular dysfunction -pulmonary vasculitis - endothelial malignancy
Describe this graph
black - normal
blue - asthma same total volume just takes longer
red - COPD reduced total volume
How can forced expiratory volumes/flow rates be measured?
Spirometry
Name two diseases where airway closure is dependent on volume
- asthma
- chronic bronchitis
Name a disease where airway closure is dependent on pressure
emphysema
In obstructive disease what happens to the follwing
- peak flow
- FEV1
- FVC
- FEV1/FVC
- Gas transfer
- FEV1 response to beta two agonist
- reduced
- reduced
- normal
- <75%
- decreased in emphysema but normal in asthma
- >15% response in asthma but <15% response in COPD
In restrictive disease what happens to the follwing
- peak flow
- FEV1
- FVC
- FEV1/FVC
- Gas transfer
- FEV1 response to beta two agonist
- normal
- reduced
- reduced
- >75%
- Decreased
- No response
State three ways of bronchial challenge testing
- exercise
- methacholine/histamine/mannitol
- allergens/ chemicals
How can you test bronchial challenge usuing histamine/methacholine?
They are markers of airway hyper-responsiveness, you measure the concentration required to reduce FEV1 by 20%
