Lecture 2 - How Do Lungs Work Flashcards
What is the average perfusion at rest?
5 litres per minute
What is the perfect gas exchange?
When blood flow matches the ventilation
What is mixed venous blood?
Low levels of oxygen but high levels of co2
What is a VQ scan?
Ventialition perfusion scan
Describe “Not pure atmosphere”
It’s between the air that is left in the alveoli and in the atmosphere
What is the ideal ratio for real life gas exchange?
1
Is ventilation even or uneven in real life gas exchange?
Uneven
Is perfusion even or uneven in real life gas exchange?
Uneven
What happens to ventilation and perfusion in lung disease?
Unevenness increases
How much blood is at the top of the lungs compared to the bottom?
There is less blood at the top then at the bottom
Is pathology homogenous?
No it’s patchy
What does disease look like in abnormal lungs?
Looks really patchy, some areas of the lungs will have the disease and some areas wont
What are the consequences of gravity?
Ventilation perfusion ratio will change
What is reverse barotrauma?
When high pressure goes back into your lungs
What happens as the alveoli gets bigger?
The stretchability changes
Define compliance
The more compliance something is the easier it is to expand
Describe larger alveoli in terms of lung compliance
Larger alveoli has elastin properties and so are harder to expand, they also tend to be stiffer and expand a bit less during breathing
What is the relationship between lung volume and recoil pressure?
Curved linear relationship
What’s the difference between the upper parts of the lungs and the lower parts of the lung in regards to ventilation?
Upper parts of the lung aren’t as well ventilated as the lower parts of the lungs
What is the oxygen dissociation curve?
An integrated system that involves the circulation and the components of blood
What does haemoglobin do in the blood?
Takes up oxygen and remains well saturated even at a very low oxygen tension
What units is oxygen tension measured in?
Kpa
What units is oxygen content measured in?
MmHg
What does the blood system help?
Compensate for small inequalities for ventilation and perfusion
What happens to respiratory when in hypoventilation?
Respiratory rate has decreased
What happens if you have problems with diffusion of alveoli?
End up with lower levels of oxygen in the blood
What is ventilation - perfusion mismatching?
The optimal ratio of 1 becomes out of sink and therefore you are no longer taking up the maximum amount of oxygen
What happens if a component in ventialition or circulation goes wrong?
The relationship of VQ becomes dysregulated and can lead to hypoxemia
What is normalcy?
Arterial blood oxygen becomes matched with the level of the oxygen within the alveoli
Describe perfect gas exchange
An airway open to the outside atmosphere,
Oxygen comes down into the alveolus and there is mixed venous blood bathing the alveoli,
Allows oxygen to diffuse into the oxygenated blood,
CO2 diffuses out of the blood and is removed from the alveoli through mechanisms
Describe reduced ventilation
Means that is no longer the normalicy - not enough oxygen getting bound to the alveoli and oxygen will decrease
What happens to the blood due to hypoventilation?
Gradual build up of co2 in the blood
What happens if the membrane becomes thickened?
It increases the distance for gases to travel and as a result oxygen is not getting into the blood where it is needed
What does thickening do?
Decreases the amount of diffusion and decreases oxygen
What is hypoxemia due to?
Due to hyperventilation perfusion mismatch
What can broncheoscatsis cause?
Narrowing of the airways
What is flow proportional to?
The radius of the tubes to the power of 4
What does change in blood gases mean?
Changes in flow proximity
What is a common disease due to hypoventilation?
Neuromuscular disease
What are examples of alveolar hypoventilation?
COPD and severe asthma
What is the carbon monoxide diffusing capacity (DLCO) also known as?
CO transfer factor (TLCO)
What are some factors affecting DLCO?
Distribution of inspired gas, thickness of alveolar capillary membrane, function of pulmonary capillaries and haemoglobin contraction
What is the transit factor of someone who has a one lung transplant and someone who has a two lung transplant?
It’s higher in two lung transport than one
What is KCO?
The rate of uptake of CO per litre of effective alveolar volume
DLCO =
KCO x Va
What does reporting both DLCO and KCO improve?
Specificity
What is an example of DLCO reducing?
After removal of lung tissue
