Ventilation & Compliance Flashcards
What is tidal volume? (Vt)
The volume of air inspired or expired on each normal breath
ERV stands for…
Expiratory reserve volume
What is the ERV?
Max. volume of air which can be expelled from lungs
Inspiratory reserve volume is?
The max. volume of air which can be drawn into the lungs at the end of normal inspiration
What is residual volume?
Volume of air in the lungs that cannot be expired
What is anatomical dead space?
Volume of gas occupied by the conducting airways which is not available for exchange
How is vital capacity (VC) calculated?
TV + IRV + ERV
How is total lung capacity calculated?
VC + The residual volume
How is inspiratory capacity calculated?
Tidal volume + inspiratory reserve volume
What is FRC
Functional residual capacity
How is FRC calculated?
Expiratoy reserve volume + residual volume.
What is FEV 1?
Forced expiratory volume in 1 second
What is FEV1:FVC?
Fraction of Forced Vital Capacity expired in 1 second
Pulmonary ventilation is?
Total movement of air into and out of lungs
Alveolar ventilation is?
The volume of fresh air getting to alveoli and therefore available for gas exchange
What is pulmonary and alveolar ventilation measured in?
L/min
Which one is functionally more significant out of the two?
Alveolar
What is the volume of anatomical dead space?
150ml
What is Tidal Volume (TV) in a normal adult?
500ml
What happens to respiratory rate in hypo-ventilation?
It increases
What happens to the total pulmonary ventilation in hypo-ventilation?
Stays normal
Tidal volume is increased in BLANK and decreased in BLANK
Increased in hyperventilation and decreased in hypoventilation
Air to alveoli volume is decreased in BLANK and increased in BLANK
Decreased in hypoventilation and increased in hyperventilation
Alevolar ventilation is …
Decreased in hypoventilation and increased in hyperventilation
Partial pressure definition?
Pressure of gas in mixture = % of gas x pressure of whole gaseous mix
Partial pressure increases with increasing?
Conc. of gas mixture
Partial pressure units?
mmHg/kPa
During hyperventilation, partial pressure of oxygen is
Increased
During hyperventilation, partial pressure of carbon dioxide is
Decreased
During hypoventilation, partial pressure of oxygen is
Decreased
During hypoventilation, partial pressure of CO2 is
Increased
When alveolar ventilation is increased partial pressure of CO2?
Is decreased
What alveolar cell secretes surfactant?
Type 2
What type of alveolar cell is thin for gas exchange?
Type 1
What happens if surfactant is removed?
The inwardly directed pressure in alveoli would cause them to collapse, surfactant stops this
How does surfactant do this, what are its functions?
Reduces the surface tension stopping alveoli collapsing
Reduced work of breathing
Increases lung compliance
Where is surfactant more effective? Small or large alveoli? Why?
Small as surfactant molecules come cloder together in smaller alveoli and are more concentrated
What is surfactant classed as?
Detergent
When does surface tension occur?
When there is a water to air interface
Surface tension refers to the attraction between…
Water molecules
What is the Law of LaPlace?
Equation for calculating surface tention
What is the surface tension equation?
P = (2T/ r)
P is inwardly directed pressure
T is surface tension
r is radius
When does surfactant production start and when is it complete?
~25 weeks gestation
complete by ~36 weeks gestation
What stimulates surfactant production?
Thyroid hormones and cortisol which increases towards end of a pregnancy
What happens to a premature baby?
Suffers infant respiratory distress syndrome (IRDS) due to insufficient surfactant levels
What is compliance and what does it represent?
Change in volume relative to change in pressure
Represents the strechability not the elasticity
What does a high and low compliance mean respectively?
Large increase in lung volume for a small change in intrapleural pressure
Small change in lung volume for a large decrease in intrapleural pressure
Does compliance give information about the expiratory phase?
No, just inspiration
What is a healthy compliance?
High compliance
What level of compliance would be seen in cystic fibrosis?
Low compliance
In cystic fibrosis, lung expansion/inspiration is made more difficult due to?
The increased laying down of fibrous tissue
What does emphysema cause?
Loss of elastic tissue meaning expiration needs effort
In the early inspiratory phase, what two things need to be overcome?
Surface tension
Elastic recoil of lungs
The rapid movement of air out of the lungs after the early phase of expiration is due to?
Compression of airways
As the volume of the thoracic cavity decreases, the resistance of the airways…
Increases
Is a larger or smaller pressure needed to overcome the resistance as the volume of the thoracic cavity decreases?
Larger
The effort of inspiration is normally recovered as…
Elastic recoil during expiration
Is expiration active or passive in a healthy individual?
Passive
Compliance and alveolar resistance decrease with height from….
Base to the apex
Why does compliance and alveolar resistance decrease with height from the base to the apex?
Alveoli at the apex being more inflated at FRC.
Alveolar ventilation declines with height from the…
Base to the apex
At the base of the lung, alveoli are compressed between..
The weight of the lung above and the diaphragm below
At the base of the lung, are alveoli more compliant on expiration or inspiration?
Inspiration due to the compression
At the base of the lung, what change in volume is brought about by a small change in intrapleural pressure compared with at the apex?
A larger change in volume aka Higher compliance
What is an obstructive disease?
Obstruction of air flow, especially on expiration
What is a restrictive disease?
Restriction of lung expansion
Which one causes increased airway resistance, obstructive or restrictive?
Obstructive
Give examples of an obstructive lung disorder…
Asthma
COPD
Chronic Bronchitis
Emphysema
What does COPD stand for?
Chronic obstructive pulmonary disease
What is chronic bronchitis?
Inflammation of the bronchi
What is emphysema?
Destruction of the alveoli, loss of elasticity
Is loss of lung compliance seen in obstructive or restrictive lung disorders?
Restrictive
What does loss of lung compliance cause?
Lung stiffness and incomplete expansion
Examples of restrictive diseases?
Fibrosis
Infant respiratory distress syndrome
Oedema
Pneumothorax
What is fibrosis? What is the cause?
formation or development of excess fibrous connective tissue
Cause is idiopathic, asbestos known to cause it
What is infact respiratory distress syndrome caused by?
Premature babies/ insufficient surfactant production
What does spirometry measure?
Lung function
What is a static reading?
Where the only consideration made is the volume exhaled
What is a dynamic reading?
Where the time taken to exhale a certain volume is what is being measured
What is the FEV1 (forced expiratory volume) and FVC (Forced vital capacity) in a healthy males?
FEV1 is 4L
FVC is 5l
Makes the FEV1/FVC 80%
What effect is there on FEV, FVC and FEV1/FVC ratio in obstructive lung disorders, e.g. COPD?
FEV - greatly decreased
FVC - decreased FEV1/FVC ratio -decreased
What effect is there on FEV, FVC and FEV1/FVC ratio in restrictive lung disorders e.g. pulmonary fibrosis?
FEV - decreased
FVC - decreased FEV1/FVC ratio - remains constant or increases
Why is FVC reduced in restrictive diseases
Total volume is reduced due to limitations to lung expansion
Is a normal FEV1/FVC ratio be indicative of health? Why?
No, as in Obstructive it reduced but in restrictive it stays constant or increases despite severe compromise of function
The forced expiratory flow (FEF 25-75) is the…
Average expired flow over the middle of an FVC (middle 50% or expiration)
What does the FEF correlate with?
FEV1, but changes are more striking, meaning lung disease can be caught earlier, however FEF has a wider normal range
