Ventilation and Compliance 1 Flashcards
What is the volume of the anatomical dead space
Approx. 150 mL
What is the anatomical dead space
The volume of gas that is occupied by the conducting airways which is not available for gas exchange
What is TV
Tidal Volume
The volume of air breathed in and out of the lungs at each breath
What is ERV
Expiratory Reserve Volume
The maximum volume of air which can be expelled from the lungs at the end of a normal expiration
What is IRV
Inspiratory Reserve Volume
The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration
What is RV
Residual Volume
The volume of gas in the lungs at the end of a maximal expiration
What is VC
Vital Capacity
Vital Capacity = tidal volume + inspiratory reserve volume + expiratory reserve volume
What is TLC
Total Lung Capacity
Total Lung Capacity= vital capacity + the residual volume
What is IC
Inspiratory Capacity
Inspiratory Capacity = tidal volume + inspiratory reserve volume
What is FRC
Functional Residual Capacity
Functional Residual Capacity = expiratory reserve volume + residual volume
What is FEV1:FVC
Fraction of forced vital capacity expired in 1 second
Is pulmonary and alveolar ventilation the same
No
What is pulmonary ventilation
The total air movement into/out of lungs
What is alveolar ventilation
The fresh air getting to alveoli and therefore available for gas exchange
Is pulmonary or alveolar ventilation functionally more significant
Alveolar
Which units are used to measure pulmonary and alveolar ventilation
L/min
What is partial pressure
The pressure of a gas in a mixture of gases which is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture
What units are commonly used to express gas
mmHg or kPA
Give an example of how to calculate partial pressure
Atmospheric Pressure = 760mmHg
Pressure of air we breathe therefore = 760mmHg
21% of air we breathe = O2
Partial pressure of O2 in air we breathe = 21% x 760mmHg = 160mmHg
When is alveolar Po2 and Pco2 constant and when does it vary
Constant under normal conditions
Varies during hyper or hypo ventilation
What happens to the partial pressure during hyperventilation
Po2 rises to about 120 mmHg and Pco2 falls to about 20 mmHg
What happens to the partial pressure during hyporventilation
Po2 falls to 30 mmHg and Pco2 rises to 100 mmHg
What is surfactant
A detergent like fluid produced by type II alveolar cells
What does surfactant do
Reduce surface tension on the alveolar surface membrane so reduces the tendency for the alveoli to collapse
Where does surface tension occur
There there is an air-water interface and refers to the attraction between water molecules
State 4 properties of surfactant
1) Increases lung compliance (distensibilty)
2) Reduces lung’s tendency to recoil
3) Makes work of breathing easier
4) Is more effective in small alveoli than large alveoli
Why is surfactant more effective in small alveoli
Because surfactant molecules come closer together and are therefore more concentrated
When does surfactant production begin
About 25 weeks gestation
Complete by about 36 weeks
What stimulates surfactant production
Thyroid hormones and cortisol
At what stage of pregnancy does thyroid hormones and cortisol increase
Towards the end of the pregnancy
What do premature babies suffer from
Infant respiratory distress syndrome (IRDS).
What is compliance
The change in volume relative to the change in pressure
What does compliance represent
The stretch ability of the lungs not the elasticity
What does high compliance show
A large increase in lung volume for small decrease in ip pressure
What does low compliance show
A small increase in lung volume for large decrease in ip pressure
What is emphysema
The loss of elastic tissue, so expiration requires effort
What is fibrosis
When fibrous tissue is inert so the effort during inspiration increases
What happens to alveolar ventilation in the pressure volume curve
Declines with height from the base to apex
What happens to compliance in the pressure volume curve
Declines with height from the base to apex
Why does compliance declines with height from the base to apex in the pressure volume curve
The alveoli at the apex are more inflated at FRC
At the base the alveoli are compressed between the weight of the lung above and the diaphragm below so are more compliant on inspiration
What does a small change in intrapleural pressure cause
A larger change in volume at the base compared with the apex.
What are the two forms which lung disease can present as
Obstructive
Restrictive
What does obstructive disease cause
Obstruction of airflow, especially during expiration
Increased airway resistance
What does restrictive disease cause
Restriction of lung expansion
Loss of lung compliance
Name 2 obstructive lung disorders
Asthma
COPD
Name two types of COPD
Chronic bronchitis
Emphysema
What is chronic bronchitis
Inflammation of the bronchi
What is emphysema
Destruction of the alveoli, loss of elasticity
Name some restrictive lung disorders
Fibrosis
Infant respiratory distress syndrome
Oedema
Pneumothorax
What is a spirometry
The technique commonly used to measure lung function
How can the spirometry measurements be classed
Static or dynamic
What is a static measurement
Where the only consideration made is the volume exhaled
What is a dynamic measurement
Where the time taken to exhale a certain volume is what is being measured
What volumes can be measured directly by spirometery
Tidal Volume Expiratory reserve volume Inspiratory reserve volume Inspiratory capacity Vital capacity
What is the forced expiratory volume in 1 second in fit, healthy males
4L
What is the forced vital capacity in fit, healthy males
5L
