Physiology 2 - Respiratory mechanisms Flashcards
2 major inspiratory muscles
1) diaphragm
2) external intercostal muscles
3 accessory muscles of inspiration
1) sternacleidomastoid
2) scalenus
3) pectoral
2 muscles of active expiration
1) abdominal muscles
2) internal intercostal muscles
tidal volume
volume of air entering of leaving lungs during a single breath
inspiratory reserve volume
extra volume of air that can be maximally inspired over and above the typical resting tidal volume
expiratory reserve volume
extra volume of air that can be actively expired by maximal contraction beyond normal volume of air after resting tidal volume
residual volume
minimum volume of air remaining in lungs even after maximum expiration
functional residual capacity
volume of air in lungs at end of passive expiration
vital capacity
maximum volume of air that can be moved out during a single breath following a maximal inspiration
total lung capacity
Total volume of air that the lungs can hold
inspiratory capacity
maximum volume of air that can be inspired at the end of a normal quiet expiration
can residual volume be measured by spirometry?
residual volume CANNOT be measured by this piece of apparatus
whats the effects on residual volume when the elastic recoil of the lungs is lost
residual volume increases/worsens
what is forced vital capacity (FVC)
maximum volume that can be forcibly expelled from lungs following maximum inspiration
what is FEV1
forced expiratory volume in one second
what is FEV1/FVC ratio
the proportion of forced vital capacity that can be expired in the first second
what is the primary determinant of airway resistance?
radius of the conducting airway
name 5 factors that affect airway resistance
1) lung volume
2) bronchial smooth muscle tone
3) type of airflow
4) gas density & viscosity
5) dynamic airway collapse
what would you need to do to lung volume to decrease airway resistance?
BACKGROUD
- bronchi are supported by lung tissue
- increasing volume of lung tissue, decreases resistance as the diameter is increased
what type of bronchial smooth muscle causes contraction and what causes dilation and thus which causes more & less resistance?
PARAsympathetic = bronchoCONSTRICTION, most resistance
Sympathetic = bronchoDILATION, increasing airway diameter, decreased resistance
what type of airflow causes less resistance and what causes the most?
1) laminar flow causes less = air molecules move parallel down bronchi
2) bronchi causes more = air molecule move in a disordered fashion
describe what effect to gas density & viscosity increases resistance?
increasing gas density & viscosity increases resistance
what is dynamic airway compression?
the rising pleural pressure during active expiration which compresses the alveoli & airway
explain the effect dynamic airway compression has on normal healthy people.
- it causes no problems
- increased airway resistance causes an increase in airway pressure upstream
- helping open the airways by increasing the driving pressure between the alveolus & airway
explain the effect of dynamic airway compression if there is an airway OBSTRUCTION.
- if there is an obstruction, the driving pressure between alveolus & airway is lost
- causing a fall in airway pressure along the airway downstream resulting in airway compression by rising pleural pressure during active expiration
what effect does disease have on airways?
diseased airways are more likely to COLLAPSE
what is pulmonary compliance
measure of the effort that has to go into stretching or distending the lungs/chest walls
what 2 factors affect pulmonary compliance
1) elasticity
2) surface tension
if the lungs are less compliant, what does that mean in terms of work required?
more work is required to produce a degree of inflation
5 things that decrease pulmonary compliance?
1) pulmonary fibrosis
2) pulmonary oedema
3) collapsed lung
4) pneumonia
5) absence of surfactant
2 factors which increase pulmonary compliance
1) elastic recoil of lung is lost (easier to inflate)
2) increases with age
what disease is associated with increased compliance
EMPHYSEMA
- elastic tissue is lost, so patients have no problem inhaling and inflating the lugs but more effort is needed to exhale. leading to hyperinflation.
what does work of breathing refer to?
amount of effort needed to expand the lungs
what is work of breathing
amount of effort needed to expand the lungs
3 factors which increase work of breathing in people with lung diseases
1) lung volumes
- low lung volumes, the airways marrows & therefore increase resistance
2) airway obstruction
- increase airway resistance
- increasing work of breathing
3) restrictive chest wall or lung disease (e.g. obesity)
- increase the effort required to stretch the chest wall & thus increase the work of breathing
give 4 scenarios where work of breathing is increased
1) pulmonary compliance is decreased
2) airway resistance increased
3) elastic recoil decreased
4) need for increased ventilation
