Respiratory Physiology Flashcards
what supplies bronchial circulation?
the bronchial arteries arising from the systematic circulation
what does the pulmonary circulation consist of?
the left and right pulmonary arteries originating from the right ventricle which carries the entire cardiac output supplying a dense capillary network which surrounds the alveoli. oxygenated blood then returns to the left atrium via the pulmonary vein. high flow low pressure system.
what is systolic pressure?
the maximum arterial pressure
what is the…
> PAO2
> PACO2
> 100mmHg
>40mmHg
what is the…
> PaO2
> PaCO2
> 100mmHg
> 40mmHg
what is the…
> PvO2
> PvCO2
> 40mmHg
> 46mmHg
what factors affect the diffusion of the rate of diffusion across a membrane?
> directly proportional to partial pressure gradient
directly proportional to gas solubility
directly proportional to surface area
inversely proportional to thickness of the membrane
diffusion distance
how does emphysema reduce diffusion of gas between the blood and alveoli?
it destructs the alveoli reducing the surface area impairing ventilation
how does fibrotic lung disease reduce gas exchange?
the fibrous tissue pushes the capillaries and type 1 cells apart increasing the diffusion distance
how does a pulmonary oedema reduce gas exchange?
fluid build up between the alveoli and capillary increasing diffusion distance
how does asthma reduce gas exchange?
increased airway resistance decreases ventilation so the is a low PO2
Is blood flow higher at the base of the lung or the apex?
the base as arterial pressure exceeds alveolar pressure therefore vascular resistance is low. at the apex of the lung blood flow is low as arterial pressure is less than alveolar pressure.
what happens if ventilation is lower than perfusion (or blood Flow)?
blood is effectively shunted from the right side of the heart to the left without being properly oxygenated. there is dilation of oxygenated blood from better ventilated areas.
what is the local control mechanism to keep ventilation and perfusion matched?
the increase in PACO2 causes mild bronchial dilation.
hypoxia in tissue around under ventilated alveoli causes constriction of the pulmonary blood vessels (while systematic vessels dilate) diverting the blood to better ventilated areas.
when does alveolar dead space occur?
if ventilation > blood flow as the alveoli are ventilated but not perfused, this is the opposite to shunt.
what is anatomical dead space?
this is the air in the conduction zone of the respiratory tract that is unable to participate in gas exchange
what does haemoglobin increase the red blood cells carrying capacity to?
200ml/L
how is the arterial partial pressure of O2 determined?
O2 solubility and the partial pressure of oxygen in gaseous phase driving O2 into solution
describe the different types of haemoglobin
HbA
HbA2 beta chains replaced with sigma chains
HbF beta chains replaced by gamma
glycosylated Hb
how long does saturation of haemoglobin with oxygen take?
0.25 secs
what decreases the affinity of haemoglobin for oxygen?
> decrease in pH
> increase in temperature, PCO2
what affect does 2,3-diphosphoglycerate (2,3-DPG) have on haemoglobin?
it decreases it affinity for oxygen
in what situation is 2,3-DPG useful to the body?
this increases in situations associated with inadequate oxygen supply; heart disease, lung disease, living in high altitude. it helps maintain oxygen release to the tissues.
do foetal haemoglobin and myoglobin have a higher or lower affinity for oxygen than HbA?
a higher affinity which is necessary for extracting o2 from the maternal arterial blood.
what is the structural difference between HbF and HbA?
in foetal haemoglobin the beta chain is replaced by gamma. beta has a higher affinity for oxygen.
what is anaemia?
any condition where oxygen carrying capacity of the blood is compromised (iron deficiency, haemorrhage, vit.B12 deficiency)
in anaemic patients is Po2 higher or lower?
It remains the same as partial pressure simply refers to the o2 in the blood not the o2 bound to haemoglobin
describe the affects of CO binding to haemoglobin
since CO has an affinity for HbA that is 250 times higher than oxygen so it binds readily and dissociated very slowly.
symptoms: hypoxia, anaemia, nausea, headaches, cherry red skin and mucous membranes.
describe hypoxic hypoxia
this is a reduction in o2 diffusion at the lungs due to PO2atoms or tissue pathology
describe anaemic hypoxia
reduction in o2 carrying capacity of blood due to anaemia
describe ischaemic hypoxia
heart disease results in inefficient pumping of blood around the body/lungs
what is histotoxic hypoxia?
when poisoning prevents cells utilising oxygen delivered to them (carbon monoxide or cyanide)
describe metabolic hypoxia?
when oxygen delivered to the tissues does not meet the increased demand of oxygen by the cells
