Lung Volumes, flow and ventilation: Lecture 7 Flashcards
What is restrictive disease?
- they have a stiff or scarred lung
- they have smaller/restrictive lung capacity
- THIS LIMITS THE LUNGS VOLUME
What are the 2 causes of a restrictive disease?
- pulmonary fibrosis (thickening of elastic tissue)
- neuromuscular disorder
how do we measure lung volume and capacities?
we look at the change in air volume that is displaced by inspiration and expiration
- via spirometer
True or False
The change in volume is a function of time, in reference to flow
True
What is Tidal Volume? (Vt)
the volume of air entering or leaving the lungs during one breath
- average value under resting conditions
What is Inspiratory reserve volume? (IRV)
EXTRA volume that can be maximally inspired over the above typical resting tidal volume
What is Inspiratory capacity? (IC)
Max volume that can be inspired
- starting from the end of a normal expiration
(IC = IRV + VT)
What is Expiratory reserve volume? (ERV)
Max volume that can be actively expired starting from the end of a typical resting tidal volume
How do we measure ventilation?
via a spirometer
True or False
Do taller people have bigger lungs?
True
Will we always have a residual volume?
yes, if we have healthy lungs
What is the functional capacity that we have control over? aka doing a big breath in or out
Vital capacity
What are examples of neuromuscular disorders?
- polio
- amyotrophic lateral sclerosis (ALS)
- muscular dystrophy
What does a spirogram do?
tracks the change in volume
True or False
There is 21% oxygen
True
What is Residual Volume?
the volume of air remaining in the lungs after a maximal expiration
True or False
Residual lung volume is about 1/4 of your total lung capacity give or take
True
What is Function residual capacity? (FRC)
the volume of air in the lungs at the end of a normal passive expiration
(FRC = ERV +RV)
What is Vital capacity? (VC)
max volume of air that can be moved out during a one-breath after a maximum inspiration
(VC = IRV + VT + ERV)
What is Total lung capacity?
max volume of air that the lungs can hold
(TLC= VC +RV)
True or False
The TLC, VC and RV are typically fixed numbers
True
From a respiratory mechanics point of view, what does the FRC represent?
natural relaxation volume of the respiratory system
- volume where there is a balance between the outwards chest wall forces and the inwards elastic recoil forces of the lung
The FRC is what two volumes put together?
Expiratory reserve volume ERV + Residual volume RV
What will the FRC plus the total lung capacity be?
Inspiratory capacity IC
True or False
If the FRC goes up in a clinical disease the IC will go down
True
When can our FRC change?
- when exercising
- if we have asthma
What are the 2 force maneuvers?
- Forced expiratory volume in one second (FEV1)
- Forced vital capacity (FVC)
What is FEV1?
the volume of air expired during the 1st second of a maximal expiratory effort from TLC
- how much air did you move out with the volume of air you expired in one second
What is FVC?
- similar to VC
- measured during max expiratory effort starting from TLC
What is the ratio for forced manurers?
FEV1/FVC ratio
How much air can we forcefully expire in the 1st second. (HEALTHY LUNG)
70%-80%, 0.7-0.8
In a flow-volume loop/curve, where volume is on the x-axis, as we go left on the axis what happens to the lung volume?
increasing lung volume up to total lung capacity
In a flow-volume loop/curve, where volume is on the x-axis, as we go to the right on the axis what happens to the lung volume?
represents an empty lung going towards residual volume
What is negaitve vs positive flow
negative flow represents inspiration and positive flow represents expiration
What is happening at the peak expiratory flow?
recoil pressure is huge, and we use expiratory muscles to breathe out
What are the 3 factors/point that are affects with COPD (obstruction)?
- They are able to inflate their lungs
- Trouble with expiring
- due to narrowing airways
- loss or elastic recoil
- highly compliant lungs - Flow limitation on expiring results in a lower FEV1/FVC ratio
What is the typical FEV1/FVC ratio for a highly compliant lung?
less than 0.7
What are the 2 factors/point that are affects with ILD (restrictive)?
- Cannot inflate sufficiently
- poor lung compliance
- stiff lungs
- Low FEV1 due to a low FVC - Flow will either mimic a normal lung or be higher
What is the typical FEV1/FVC ratio for a poorly compliant lung?
more than 0.7, sever restrictions can increase to over 0.8
What is ventilation?
the movement of air in and out of the alveoli
How is ventilation expressed?
per minute aka as a rate
What is the equation for ventilation?
tidal volume (ml/breath) x respiratory rate (breaths/min)
What is the ventilation rate if you are holding your breath and there is no air moving in or out?
zero ventilatory rate
What is the size of our typical breath?
500 ml
What are the 2 types of tubes used for ventilation?
- Dead space
- Alveolar ventilation
What percentage of gas that we breathe in will not reach the gas exchange zones?
30%
What percentage of gas that we breathe in will be considered alveolar ventilation?
70%
What is Ve?
the total volume of expired ventilation
Why do we care more about expired rather than rate than inspired when talking about ventilation?
Expired will have a higher CO2 value
What would the equation for ventilation look like when we account for dead space?
Va = (Vt-Vd) x f
How do we know if alveolar ventilation is sufficient?
- if we look at our arterial O2 content
(96-100% Hb saturated)
What do we monitor to know if we are breathing enough?
Alveolar CO2 (36-40 mmHg)
What is the alveolar ventilation equation?
PaCO2 = (VCO2/Va) x K (constant)
If our Va goes down, what happens to our PaCO2?
goes up
If our Va goes up, what happens to our PaCO2?
goes down
