5.3 - Lung Compliance and Elastance Flashcards
Define lung compliance
change in lung volume produced by a change in pressure
TRUE OR FALSE:
The lower the lung compliance, the harder it is to expand the lungs (inhalation)
TRUE
People with low lung compliance breath ____ and _______
shallowly and rapidly
What are restrictive lung diseases?
pathological conditions that affect lung compliance
List some restrictive lung diseases
fibrotic lung disease
New-Born Respiratory Distress Syndrome (NRDS)
What causes fibrotic lung disease?
chronic inhalation of asbestos, silicon, coal, dust
What is the effect of fibrotic lung disease?
build up of scar tissue in lungs: lowers compliance, makes it harder to breathe
Where does the majority of the resistance to stretch come from within the lungs?
from surface tension within the lungs
What causes the NRDS?
inadequate surfactant production
TRUE OR FALSE:
surfactant synthesis becomes adequate at 12 weeks of gestation
FALSE
at 34 weeks of gestation
Define lung elastance
the speed at which the lungs return to resting volume after being stretched
What happens when lung elastance is low?
expiration must be active as lungs will not return to resting volume passively
What happens during emphysema?
- elastin fibres in lung are destroyed
- lung have high compliance and low elastance
- breathing in is easy, breathing out is hard and forced
What is primarily determined by airway diameter?
airway resistance
What increases the resistance of the airways?
mucus accumulation from allergies/infections
What are factors that affect bronchiole diameter?
nervous system, hormones, paracrines
What are some things that can cause bronchiodilation and bronchioconstriction?
bronchiodilation: CO2
bronchioconstriction: histamine, severe allergic reaction
Bronchioconstriction is primarily controlled by _____
parasympathetic neurons, no significant sympathetic innervation
hormonal control of bronchioles is done primarily by _____ to cause ____
circulating epinephrine via adrenal medulla acting on b2 receptors in smooth muscle of bronchioles to cause bronchiodilation
What does pulmonary function assess?
the amount of air someone can move during quiet breating and maximal breathing effort
What is a spirometer? What can be diagnosed using it?
instrument used to measure movement of air during breathing
asthma, emphysema, chronic bronchitis
List and define the 4 lung volumes that can be measured as air moves during breathing
tidal volume (TV) - volume of air moved in single/normal inspiration or expiration
Inspiratory Reserve Volume (IRV)
- MAXIMUM of air that can be inspired above VT
Expiratory Reserve Volume (ERV)
- MAX air that can be expired after normal expiration
Residual Volume (RV) - ammount of air left after maximal expiration
The sum of 2 or more lung volumes is called a capacity. List and define the 2 capacities:
vital capacity: VC
- maximum amount of air that can be voluntarily moved in or out of the lungs
VC = IRV + ERV + IRV
Total Lung Capacity (TLC)
- TLC = vital capacity + RV
How is the minute volume calculated?
MV (ml/min) = VT (mL/breath) X respiratory rate (breaths/min)
What is the anatomical dead space in the airways?
- no gas exchange
- trachea, brochi, bronchioles
How is alveolar volume calculated?
alveolar volume = VT - dead space
What is the effectiveness of ventilation determined by?
rate and depth of breathing
What is alveolar ventilation?
the amount of air reaching the alveoli per minute
TRUE OR FALSE:
Alveolar ventilation is a more accurate indicator of the efficiency of ventilation
TRUE
How is alveolar ventilation calculated?
alveolar ventilation = alveolar volume X ventilation rate
How is the efficiency of gas exchange maximized?
the body attempts to match the airflow to alveolar blood flow
How does decrease in tissue PO2 result in vasoconstriction of the arteriole?
depends on local control exerted by O2 levels in the interstitial fluid around arteriole surrounding alveoli
- ventilation of alveoli in an area of lung decreases, tissue O2 also decreases, blood diverted away from this area
