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respiratory system year 1 > ventilation and compliance > Flashcards

ventilation and compliance Flashcards

(55 cards)

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1
Q

define tidal volume

A

TV
500ml
the volume of air breathed in/out of the lungs at each breath
only uses a fraction of our lung capacity

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2
Q

define expiratory reserve volume

A

ERV
1.1L
the max vol of air which can be expelled from the lungs at the end of a normal expiration

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3
Q

define inspiratory volume

A

IRV
3L
The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration

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4
Q

define residual volume

A

RV
1.2L
the volume of gas in the lungs at the end of a normal expiration
cannot be voluntarily moved out and remains in the alveoli

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5
Q

what is the purpose of RV

A

important for gas exchange to continue at all times between breaths
helps prevent the alveoli collapsing (requires much more effort to inflate the alveoli from a collapsed state rather than a partially inflated state)

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6
Q

define vital capacity

A 
VC
4.5L
TV + IRV + ERV
max amount of air you can move on one breath 
good value to use in lung function tests
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7
Q

define total lung capacity

A

TLC

VC + RV

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8
Q

define inspiratory capacity

A

IC

TV + IRV

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9
Q

define functional residual capacity

A

FRC
ERV + RV
volume of air left in the lungs after a normal expiration

requires a greater change in pressure from FRC to reach a particular lung volume during inspiration than to maintain that volume during expiration

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10
Q

define forced expired volume in 1s

A

FEV1

4.0L in healthy, fit, young adult males

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11
Q

define fraction of forced VC expired in 1s

A

FEV1:FVC
FVC in healthy young males = 5L
FEV1/FVC = 80%
absolute values decline slightly with age

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12
Q

define anatomical dead space

A

volume of gas occupied by the conducting airways and this gas isnt available for exchange

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13
Q

what is surfactant

A

detergent like fluid secreted by type II pnuemocytes

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14
Q

what is the role of surfactant (4)

A

reduces surface tension on the alveolar surface membrane
increases lung compliance
reduces lungs tendency to recoil
makes the work of breathing easier

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15
Q

how does alveoli reduce surface tension

A

reduces the attraction between the water molecules lining the alveoli
these create inwardly directed pressure
surfactant reduces the inwardly directed pressure which reduces the tendency of the alveoli to collapse

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16
Q

where is surfactant most effective

A

in smaller alveoli

the surfactant molecules come together and are more concentrated

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17
Q

when does surfactant production begin

A

~25wks gestation and is complete ~36wkss

stimulated by thyroid hormones and cortisol

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18
Q

what is the relationship between premature babies and surfactant

A

premature babies suffer IRDS (infant respiratory distress syndrome)and are often given synthetic surfactant to help them breathe and survive

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19
Q

law of laplace

A 
P = 2T/r 
pressure = 2 x surface tension/radius
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20
Q

what is an obstructive lung disease

A

obstruction of air flow, especially on expiration

increased airway resistance

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21
Q

what is a restrictive lung disease

A

restriction of lung expansion

loss of lung compliance (lung stiffness, incomplete expansion)

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22
Q

give 2 examples of obstructive lung diseases

A

asthma

COPD

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23
Q

give 5 examples of restrictive lung diseases

Study These Flashcards
A 
fibrosis 
IRDS
oedema
pneumothorax
traumatic injury
24
Q

why is asthma an obstructive lung disease

Study These Flashcards
A

over-reaction of the bronchiole smooth muscle which restricts air movement

25
why is COPD an obstructive lung disease
- chronic bronchitis (inflammation of the bronchi) | - emphysema (destruction of alveoli, loss of elasticity)
26
why is fibrosis a restrictive lung disease
formation of XS fibrous connective tissue idiopathic or asbestosis restricts expansion of the lungs
27
why is oedema a restrictive lung disease
fluid build up around the alveoli reduces their ability to expand
28
why is pneumothorax a restrictive lung disease
lung can't expand and has collapsed | no longer associated with the chest wall
29
how can traumatic injuries restrict lung expansion
pain
30
what is a common technique used to measure lung function
spirometry
31
what are the 2 types of measurements in spirometry
static - volume exhaled | dynamic - time taken to exhale a certain volume
32
what alters normal spirometry values
height, weight, age
33
what values can spirometry measure
things you can voluntarily do yourself | TV, IRV, ERV, IC, VC
34
what happens to FEV1/FVC in obstructive lung disease
reduced e.g. 45% rate at which air is expelled is much slower FVC is reduced FRC may be increased major effect is on airways so FEV is reduced to a greater extent that FVC ratio is significantly reduced
35
what happens to FEV1/FVC in restrictive lung disease
increases e.g. 90% absolute rate of airflow is reduced total volume is reduced due to limitations on lung expansion ratio remains constant or can increase as a large proportion of volume can be exhaled in the first second
36
limitations of using FEV1/FVC
obstructive: both FEV and FVC fall but FEV more so, ratio is reduced restrictive: both FEV and FVC fall so ratio remains the same despite severe compromise of function normal ratio isnt always indicative of health
37
FEF25-75
forced expiratory flow average expired flow over the middle of an FVC correlates w/ FEV1 but changes are generally more striking normal range is greater
38
what is pulmonary ventilation
total air movement in/out of the lungs relatively insignificant in functional terms TV x breaths/min L/min
39
what is alveolar ventilation
``` FRESH AIR getting to the alveoli and therefore available for gas exchange functionally more significant (tidal dead space)/breaths/min L/min declines with height from base to apex ```
40
how efficient is normal breathing
70% 30% gets stuck in the dead space dead space has a huge impact on alveolar ventilation
41
what is the most important determinism of alveolar ventulation
depth of breathing due to the impact of dead space
42
hypoventilation
reduced alveolar ventilation | ml/min
43
hyperventilation
increased alveolar ventilation ml/min just because someone is breathing quickly doesn't mean they are hyperventilating
44
how does the pressure volume curve vary across the lungs
varies between the apex and the base at the base the given volume change is greater for a greater change in pressure a small change in intrapleural pressure brings about a larger change in volume at the base compared with the apex
45
how does compliance change across the lungs
declines with height from base to apex due to alveoli at the apex being more inflated at FRC at the base the alveoli are more compressed between the weight of the lung above and the diaphragm below and hence are more compliant on inspiration
46
Dalton's law
total pressure of a gas mixture is the sum of the pressure in the individual gases
47
define partial pressure
the pressure of a gas in a mixture of gases is equivalent to the % of that gas in the mixture multiplied by the pressure of the whole gaseous mixture partial pressure increases with increasing [gas] in the mixture
48
what are the normal partial pressures in the alveoli
100mmHg for oxygen 40mmHg for carbon dioxide these are lower than in the atmosphere as the gas mixture is diluted down (dead space, residual volume and water vapour) under normal conditions, these resting values remain fairly constant
49
what can alter alveolar PO2 and PCO2
hyper and hypoventilation
50
what changes occur during hyperventilation
PO2 rises - 120mmHg PCO2 falls - 20mmHg it is difficult to hyperventilate for a long period of time as we rely on carbon dioxide to drive the breathing cycle
51
what changes occur during hypoventilation
PO2 falls - 30mmHg PCO2 rises - 100mmHg commonly seen in pathology
52
define compliance
change in volume relative to change in pressure represents the stretchability of the lungs (how easy it is to get air in) changes in disease state/age
53
define high compliance
large increase in lung volume for a small decrease in pressure healthy lungs in some conditions lungs can be highly compliant but lose their elasticity
54
define low compliance
small increase in lung volume for a large decrease in intrapleural pressure not good, common in conditions like fibrosis
55
work of respiration
normally effort of inspiration is recovered due to elastic recoil during expiration (expiration is passive) emphysema - loss of elastic tissue means expiration requires effort fibrosis - inert fibrous tissue means effort of inspiration increases

respiratory system year 1 (25 decks)

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