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
What is the effect of an obstructive lung disease on the FEV1/FVC?
What is the ratio for these individuals and what does this indicate?
FEV1 decreases a lot and FVC and decreases so FEV1/FVC also decreases
There is a ratio of less than 70% which indicates increased airway resistance
What is the FEV1/FVC?
This is the ratio showing how much we can force out in one second out of the total amount we can force out
What is the FEV1/FVC for a normal individual? What does this mean?
80%
this means that 80% is expiration in 1 second
What is the effect of a restrictive lung disease on the FEV1/FVC?
What is the ratio for these individuals and what does this indicate?
FVC decreases but the ratio doesn’t change
this is because there is no change to airway resistance, there is only a change in the stiffness of the lungs - it is harder to expand but they shrink back to their original position quickly
FEV1/FVC ratio does not decrease below 70% in restrictive lung disease BECAUSE restrictive lung disease does not affect the airway resistance
A. Both statements (the one before and the one after “BECAUSE”) are true, and are causally related (the fact presented in the first statement is a result of the fact presented in the second statement).
Define ventilation
this is the process by which air moves in and out of the lungs
Is ventilation the same as respiration?
No, ventilation is only one process of respiration but the processes are interdependent because ventilation determines respiration and vice versa
What does . mean?
V
volume and time ventilation
ie volume per minute
What does VD mean?
dead space volume
What does .
VD mean?
dead space ventilation (per minute)
What does .
VA mean?
alveolar ventilation (per minute)
What does F mean? eg. FA O2?
this is the fraction concentration of gas
eg. fraction of O2 in alveolar air
What does P mean? eg. PaO2?
PA O2?
Partial pressure of a gas
eg. PaO2 = partial Pressure of O2 in arterial blood
PA O2 = partial Pressure of O2 in Alveoli
What is Dalton’s Law of partial pressure?
In a gas mixture (air), each gas exerts its own individual pressure, called a partial pressure (P), in direct proportion to its fractional concentration in the mixture.
What is the equation for partial pressure?
Partial Pressure = fraction of individual gas x total gas pressure
What are the fractions of O2, CO2 and N2 in the atmosphere?
FIO2= 0.2093 FICO2 = 0.0003 FIN2 = 0.7904
What is the total gas pressure?
this is the barometric pressure (normally 760 mmHg but this can change eg. going up a mountain)
Calculate the partial pressure of O2 in the summit of Mt Everest is PB.= 253 mmHg
PO2 =FIO2 XPB
= 0.2093 X 253
= 53 mmHg
As the air moves down the respiratory tract, it gets _________ by _________ ________
warmed
water vapour
What is the effect of water vapour warming the air on the partial pressure at the trachea?
Give an example calculation
You have to minus the water vapour pressure at body temperature (47mmHg) off the barometric pressure when doing calculations:
PiO2=FIO2 X (PB-47)=0.2093X (760-47)=150mmHg
What does the respiratory quotient show?
What is. it dependent on?
the amount of CO2 produced in relation to the amount of O2 consumed by metabolism and is dependent on calorie intake
What is the equation for the respiratory quotient?
What do these mean?
.
VCO2/.
VO2
.
VCO2 = amount of CO2 excreted/produced
.
VO2 = amount of O2 taken upWhat is the equation for total ventilation and what does this show?
This is the amount of air we breathe in and out: frequency (f) x tidal
What is the normal breathing frequency?
10/12 breathes a minutes
Aish takes 12 breaths per minute and each breath has a volume of 5̇ 00 mls What’s her .
VE ?
12/min x 500 mL
6000mL/min = 6 L/min
Why can .
VE change?
- to match metabolic demands (involuntarily eg. exercise)
- voluntary (changing breathing behaviour)
Some of the inhaled air never gets to the alveoli so cannot undergo gas exchange. This is known as ________ _________
dead space
What are the two types of dead space?
- anatomical dead space
- physiological dead space
What is anatomical dead space?
Dead space of the Conducting airways
including mouth, trachea) Ventilated but no respiration (no gas exchange
What is physiological dead space?
dead space of the respiratory area (gas exchange). Some alveoli are not involves in gas exchange so they are unused
Dead space is approximately how much?
How does this get distributed?
150mL
145mL in anatomical dead space
5mL of functional dead space
Ventilation =
tidal volume x breathing frequency
dead space ventilation =
dead space volume x breathing frequency
alveolar ventilation =
alveolar volume x breathing frequency
Alveolar ventilation =
ventilation - dead space
What are conditions that can be seen from dead space?
pulmonary fibrosis:
- this increases dead space by transforming respiratory tissue in fibrotic tissue (increased physiological dead space)
pulmonary hypertension: this increases dead space by impairing pulmonary perfusion ie. there is no exchange as no blood flows there
