Respiratory 2 Flashcards
Which 3 things affect alveolar gas exchange
O2 reached to the alveoli
Diffusion pathway
Perfusion
What affects o2 reaching alveoli for exchange
Composition of air
Alveoli/pulmonary ventilation
Which 4 things affect alveolar ventilation (how much o2)
Lung compliance
Rate and depth of breaths
Airway resistance
Alveolar surface tension
Flow rate is pressure/ resistance , which factors affect resistance
Length of path
Viscosity of gas
Diameter of airway
Which kind of flow and resistance is at the upper respiratory tract/ down trachea
Turbulent flow
Which kind of flow is at the lower respiratory tract from the bronchioles down
Laminar flow
Which area is resistance highest and why
Bronchi
Smallest area
Trachea is wider and bronchioles have a large cross sectional area for lower resistance
Which 3 events can cause resistance
Mucus
Inflammation
Tumour
What causes smooth muscle bronchoconstriction in bronchioles
Parasympathetic ach binding to M3
Why is there surface tension in alveoli which affects their ventilation and therefore exchange
Liquid inside which h20 can form cohesive H bonds
The gases are non polar so can’t form bonds
Creates surface tension at gas water boundary
When is surface tension highest
In expiration where diameter is lowest
What does surface tension cause
Obstruction to alveolar inflation
Which substance do type 2 cells need to produce to reduce surface tension in small alveoli (they have largest ST)
Surfactant
What does surfactant do
Reduces tension by disrupting H2O bonds
Allows alveolar inflation
What is RDS produced by which means alveoli can’t inflate
Late production / lack of surfactant
Can’t inflate due to high ST
What does lung compliance affecting ventilation and therefore exchange mean
Ability of lungs to stretch
What allows lung compliance
Increase in surfactant to cause inflation of alveoli
Swelling of elastic tissue around lungs
Ability of chest wall to move up in inspiration
What is lung compliance triggered by
Increase in pressure from the air in atmosphere ie in inspiration
What is the max amount of lung compliance called
Vital capacity
What limits lung compliance
Elastic recoil
What happens to lung compliance in emphysema
Large compliance even at a lower atmospheric pressure
due to lack of elastic recoil
Why does fibrosis cause lack of compliance
They have lack of elastic tissue to stretch the lungs
This is replaced with scar tissue
Affects compliance / has a lower vital capacity
What is the rate and depth of breathing affecting ventilation measured by
Spirometer
What is tidal volume
Volume of air in and out in a normal breath
What is expiratory reserve volume
Amount of extra air which can be breathed out along with every normal breath (tidal volume)
What is Inspiratory reserve volume
Extra amount of air breathed in alongside the normal breath (tidal volume)
What is the air called left inside the lungs after even expiratory reserve volume
Residual volume
How do you work out vital capacity of the lungs (max air in and out)
Tidal volume + ERV + IRV
How do you work out total lung capacity
Residual volume + erv + irv + tidal volume
What is forced vital capacity and what other measure does it use
Measure of Total amount of air expired after a forced breath over time
Uses the FEV (forced expiratory volume)
What does FEV1 mean
Forced expiratory volume in 1 second
Which types of lung disease have lower FVC
Restrictive lung disease
Their vital capacity is lower due to low compliance (lack of elastic)
Why would the FEV in 1 second be slower in those with obstructive lung diseases like asthma
They have an obstruction to expiration and so the expiration rate is slower (FEV)
What is anatomic dead space
Volume of air in conducting airways which isn’t used for exchange
What is physiologic dead space
Vol of air in airways and also alveolar space which isn’t used for exchange
Why is conducting airways volume (anatomic dead space) not always used for exchange
Because it is expired via the tidal volume expiration
Only some inspired air reaches alveoli
How do you work out pulmonary ventilation
Ventilation rate(eg 12 breaths) x tidal volume (500ml)
Why is alveolar ventilation a better measure
It accounts for dead space volume
How do you work out alveolar ventilation rate
Ventilation rate x (tidal volume - dead space vol)
