Respiratory System Flashcards
Carbon monoxide (CO) poisoning happens when CO binds to haemoglobin, forming __________________
carboxyhaemoglobin.
Why does CO cause a left shift in the oxygen dissociation curve?
This binding is much stronger than the binding of oxygen to haemoglobin, which reduces the availability of haemoglobin for oxygen transport. The binding of CO also causes a conformational change in the remaining sites on the haemoglobin molecule, increasing their affinity for oxygen. Therefore, in CO poisoning, there is a left shift in the oxygen dissociation curve. This means that at any given partial pressure of oxygen, haemoglobin is more saturated with oxygen. However, because CO bound to haemoglobin does not release easily into tissues, this can lead to tissue hypoxia despite normal or high levels of arterial oxygen saturation.
At the point where haemoglobin is fully saturated with oxygen, the oxygen dissociation curve _________.
flattens.
What causes a right shift in the Oxygen Dissociation curve?
The oxygen dissociation curve shifts to the right when there is an increased delivery of oxygen to tissues. This can occur due to increased carbon dioxide, exercise or increased temperature. Carbon monoxide’s binding to haemoglobin obstructs this process.
Oxygen dissociation curve Shifts to Left = Lower oxygen delivery
HbF, methaemoglobin, carboxyhaemoglobin
Low [H+] (alkali)
Low pCO2
Low 2,3-DPG
Low temperature
Oxygen dissociation curve Shifts to Right = Raised oxygen delivery
Raised [H+] (acidic)
Raised pCO2
Raised 2,3-DPG
Raised temperature
The L rule
Shifts to L → Lower oxygen delivery, caused by
Low [H+] (alkali)
Low pCO2
Low 2,3-DPG
Low temperature
CADET, face Right!
CO2, Acid, 2,3-DPG, Exercise and Temperature
How are Foetal haemoglobin’s oxygen dissociation curves different to that of adult haemoglobin?
Foetal haemoglobin’s oxygen dissociation curve lies to the left of adult haemoglobin, haemoglobin A. This allows maternal haemoglobin to preferentially offload oxygen to the foetus across the placenta, as foetal haemoglobin has a higher affinity.
The majority (roughly 60%) of CO2 is bound to haemoglobin as _______________
bicarbonate ions.
About 30% of carbon dioxide transport occurs bound to the globin portion of haemoglobin in ________________ (whilst oxygen is bound to the haem portion).
carbamino compounds
The final 10% of carbon dioxide is physically ___________ in the blood.
dissolved
Lung collapse causes the trachea to deviate _______ the affected side, is dull to percuss and has reduced breath sounds
towards
________________ should be suspected where multiple people contract pneumonia in an air conditioned space
Legionella pneumophilia
Haemophilus influenzae is one of the most common causes of lower respiratory tract infection in patients with _____
COPD.
Functional residual capacity =
Functional residual capacity = Expiratory reserve volume + Residual volume
What is FRC?
Functional residual capacity (FRC) is the volume of air in the lungs after a normal relaxed expiration, and is determined by the balance between the tendency of the lungs to recoil inwards and the chest wall to pull outwards.
the volume in the lungs at the end-expiratory position
FRC = ERV + RV
Tidal volume (TV)
volume inspired or expired with each breath at rest
500ml in males, 350ml in females
Inspiratory reserve volume (IRV) =
2-3 L
maximum volume of air that can be inspired at the end of a normal tidal inspiration
inspiratory capacity = TV + IRV
Expiratory reserve volume (ERV) =
750ml
maximum volume of air that can be expired at the end of a normal tidal expiration
significantly reduced in obesity (increased abdominal fat mass pushes up against the diaphragm, reducing the volume of air that can be expelled)
Residual volume (RV)
1.2L
volume of air remaining after maximal expiration
increases with age
RV = FRC - ERV
Vital capacity (VC)
5L
maximum volume of air that can be expired after a maximal inspiration
4,500ml in males, 3,500 mls in females
decreases with age
VC = inspiratory capacity + ERV
Total lung capacity (TLC) is the sum of the _____________
vital capacity + residual volume
_________ is the most common cause of a pleural transudate
Heart failure
