Lecture 15 Flashcards
Lung compliance is increased in emphysema BECAUSE
chronic emphysema increases airway resistance.
B. Both statements are true but are not causally related
What can we see from a spirometry trace?
lung volumes: how much air we can get into and out of our lungs
air flow rates: how fast you can get air in and out
What are 4 volumes we can see on a spirometry trace?
- tidal volume
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
What is tidal volume?
Volume of air moved in and out during normal quiet breath
What is the normal value for tidal volume?
500mL
What is the inspiratory reserve volume?
What muscles does this involve?
Extra volume that can be inspired with maximal inhalation - external intercostal muscles.
Why do we need reserve volume?
eg. if we are exercising and we need to be able to get more O2 in and CO2 out
What is the expiratory reserve volume?
What muscles does this involve?
Extra volume that can be exhaled with maximal effort - internal intercostal and abdominal muscles.
What is the residual volume?
Volume remaining in lungs after maximal exhalation.
What are four lung capacities?
- inspiratory capacity
- vital capacity
- functional residual capacity
- total lung capacity
What is inspiratory capacity?
How can it be calculated?
This is the maximal breath in
tidal volume + inspiratory reserve volume
What is the vital capacity? How can it be calculated?
This is the maximum volume of air that you can shift in and out of the lungs
tidal volume + inspiratory reserve volume + expiratory reserve volume
What is the functional residual capacity?
How can it be calculated?
This is the remaining volume at the end of normal breath out
expiratory reserve volume + residual volume
What is the total lung capacity and how can it be calculated?
This is the total volume in the lung when they are maximally full
reserve volume + expiratory reserve volume + residual volume
Define the functional residual capacity
This is the lung volume at the end of a normal expiration when there is no inspiratory or expiratory muscle contraction
Describe the resting equilibrium position for the lungs and the thorax
This is normally large when the lungs and thorax are in their resting position. In between breaths, there is a balance between the lung trying to collapse and the chest trying to expand which means that FRC is maintained
How does the FRC change when there is a breath in?
The FRC is topped up by each breath by the smaller resting tidal volume of 500mL (2.4L + 500mL)
What is the importance of the FRC?
At all times during the breath cycle, O2 and CO2 exchange can occur between alveolar gas and pulmonary capillaries. It prevents large fluctuations in the composition of alveolar gas (ie. large fluctuations of O2 and CO2 exchange)
How does a restrictive lung disease affect the spirometry trace?
Why is this?
A restrictive lung disease such as fibrosis means that there is increased work due to a decrease in lung compliance. This means that you have to do more work to maintain inspiration and expiration. There are stiff lungs so people breathe more shallowly and rapidly. This means that all of the following decrease:
- vital capacity
- inspiratory reserve volume
- expiratory reserve volume
- residual volume
- functional residual capacity
- total lung capacity
How does an obstructive lung disease affect the spirometry trace?
Why is this?
An obstructive lung disease such as asthma or bronchitis or emphysema means that there is increased work due to an increase in the airway resistance. People have more narrow pipes and therefore they breathe more slowly and deeply.
The effect on the spirometry trace is that:
- the whole curve is shifted up
- vital capacity doesn’t change
- inspiratory reserve volume doesn’t change
- expiratory reserve volume doesn’t change
- residual volume increases
- functional residual capacity increases
- total lung capacity increases
We can use the spirometry trace to give information about air flow _______
rates
What is the forced vital capacity?
someone breathes in as much as possible and breathes out as much as possible as hard as possible
What is the forced expiratory volume?
this is the amount of forced expiration in one second
What can forced expiratory volume in one second be used for?
this is a variant of vital capacity and it is a useful diagnostic tool for the diagnosis of the lung disease - it is an indicator of airway resistance