ventilation and gas exchange Flashcards
what is the definition for minute ventilation
the volume of air expired in one minute or per minute
what is the definition for respiratory rate
the frequency of breathing per minute
what is the definition for alveolar ventilation
the volume of air reaching the respiratory zone per minute
what is the definition for respiration
the process of generating ATP either with an excess of oxygen (aerobic) or a shortfall (anaerobic)
what is the definition for anatomical dead space
the capacity of the airways incapable of undertaking gas exchange
what is the definition for alveolar dead space
capacity of the airways that should be able to undertake gas exchange but cannot (eg hypoperfused alveoli)
what is the definition for physiological dead space
equivalent to the sum of alveolar and anatomical dead space
what is the definition for hypoventilation
deficient ventilation of the lungs - unable to meet metabolic demand (increased PO2 - acidosis)
what is the definition for hyperventilation
excessive ventilation of the longs atop of metabolic demand (results in reduced PCO2 - alkalosis)
what is the definition for hyperpnoea
increased depth of breathing (to meet metabolic demand)
what is the definition for hypopnoea
decreased depth of breathing (inadequate to meet metabolic demand)
what is the definition for apnoea
cessation of breathing (no air movement)
what is the definition for dyspnoea
difficulty in breathing
what is the definition for bradypnoea
abnormally slow breathing rate
what is the definition for tachypnoea
abnormally fast breathing rate
what is the definition for orthopnoea
positional difficulty in breathing - when lying down
what is the definition for tidal volume
the amount of air that is moving in and out in a normal breath
what is the definition for inspiratory reserve volume
amount of additional air you can take in atop your tidal volume
what is the definition for expiratory volume
after a normal breath out, how much more you can breathe out
what is the definition for residual volume
volume of air you cannot get rid of
what is the definition for total lung capacity
inspiratory reserve volume + tidal volume + expiratory reserve volume + residual volume
what is the definition for vital capacity
measured
what is the definition for functional residual capacity
after a normal breath, how much air is in the lungs
what is the definition for inspiratory capacity
they didn’t really give one so?
what is the difference between volumes and capacities
volumes are discrete sections of the graph and do not overlap
capacities are the sum of 2 or more volumes
what is the definition for minute ventilation
(L/min)
gas entering and leaving the lungs
equation for minute ventilation (L/min)
tidal volume (L/breath) x breathing frequency (breaths per min) = minute ventilation
what is the definition for alveolar ventilation (L/min)
gas entering and leaving the alveoli
equation for alveolar ventilation (L/min)
(tidal volume L/breath - dead space L) x breathing freq = alveolar ventilation
what are some factors affecting lung volumes and capacities
body size - height and shape sex - males and females disease - pulmonary/neurological age - chronological, physical fitness - innate, training
what is the conducting zone
first 16 generations of bifurcations
not participating in gas exchange
typically 150 mL in adults at FRC
equivalent to anatomical dead space
what is non perfused parenchyma
alveoli without a blood supply
no gas exchange
typically 0 mL in adults
called alveolar dead space
what is the respiratory zone
7 generations of bifurcations after the 16
gas exchange does occur
air reaching here is equivalent to alveolar ventilation
how do you calculate physiological dead space
anatomical + alveolar dead space
what is a reversible procedure that can increase the amount of dead space
anaesthetic
circuit
snorkelling
what is a reversible process that can decrease the amount of dead space
tracheostomy
cricothyroctomy
what does the chest wall have a tendency to do
spring outwards
what does the lung have a tendency to do
recoil inwards
what is the neutral position of the intact chest
end tidal expiration (FRC)
the forces of the chest and the lung are in equilibrium
what is the relationship between the lung and chest at equilibrium
chest recoil = lung recoil
what happens when inspiratory muscle effort + chest recoil > lung recoil
inspiration
what happens when chest recoil < lung recoil + expiratory muscle effort
expiration
what are the lungs surrounded by
visceral pleural membrane
what is the inner surface of the chest wall covered by
parietal pleural membrane
what is the pleural cavity
the gap between pleural membranes
is a fixed volume and contains protein rich pleural fluid
what does the interpleural space contain
fluid
makes the lung and chest wall work in partnership
however things can interrupt this
what does bleeding into the interpleural space do
cause positive pressure
lung cannot expand properly
what does a puncture lead to
perforated chest wall
lose negative pressure
pneumothorax
reduce effectiveness of ventilation
which way does pressure go
high pressure to low pressure
what is negative pressure breathing
P alv is reduced below P atm
what is positive pressure breathing
P atm is increased above P alv
what are some examples of positive pressure breathing
mechanical ventilation
CPR
what is the effect of the diaphragm
pulling force in 1 direction
what is the effect of the other respiratory muscles
an upwards and outwards swinging force
What is Dalton’s law
pressure of a gas mixture is equal to the sum of the partial pressures (P) of gases in that mixture
what is Fick’s law
molecules diffuse from regions of high conc to low conc at a rate proportional to the conc gradient (P1 - P2), the exchange SA (A) and the diffusion capacity (D) of the gas and inversely proportional to the thickness of the exchange surface (T)
what is Henry’s law
at a constant temp, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid
What is Boyle’s law
at a constant temp, the volume of a gas is inversely proportional to the pressure of that gas
What is Charle’s law
at a constant pressure, the volume of a gas is proportional to the temp of that gas
what are the air percentages and partial pressures at sea level
N2 = 78.09% and 79.1 mmHg O2 = 20.95% and 21.3 Ar = 0.93% and 0.9 CO2 = 0.04% and 0.04 Ne, He, H2, Kr etc = <0.01% too small
what is the total O2 delivery at rest
16 mL.min-1
what is resting VO2 and what does this mean about reliance on dissolved O2
250 mL.min-1 so relying on dissolved O2 alone is not conducive with life
what do haemoglobin monomers consist of
a ferrous iron ion (Fe2+, haem-) at the centre of a
tetrapyrrole porphyrin ring connected to a protein chain (-globin) covalently bonded at the proximal histamine residue
how many monomers is each haemoglobin molecule made of
4
is each monomer coded for by a separate gene
yes
what are the chain structures in haemoglobin
2 alpha chains which can be accompanied by 2 beta or 2 gamma chains
to get a different haemoglobin tetramer
what are the 3 tetramers
HbA
HbA2
HbF
what do 2 alpha and 2 beta chains make
HbA
what do 2 alpha and 2 delta chains make
HbA2
what does 2 alpha and 2 gamma chains make
HbF
does haemoglobin bind reversibly or irreversibly
reversibly
what happens each time oxygen binds to haemoglobin
affinity for oxygen increases
binding site is created
what kind of a protein is Hb
allosteric protein
changes shape depending on what is bound or unbound
describe the normal oxygen dissociation curve
oxygen dissociation curve is a normal sigmoidal
left hand side = systemic
right hand side = pulmonary
what is leftwards shift
increased affinity loading decreased temp alkalosis hypocapnia decreased 2,3 DPG
what is rightwards shift
increased temp acidosis hypercapnia increased 2,3 DPG BOHR effect
what is upwards shift
polycythaemia
increased oxygen - carrying capacity
what is downwards shift
anaemia
impaired oxygen carrying capacity
what does CO do to Hb and the oxygen binding curve
increases the affinity of Hb for the oxygen it does bind but also takes binding sites away from oxygen and the oxygen is also bound more tightly
downwards and leftwards shift
decreased capacity
increased affinity
increased HbCO
what does the curve look like for foetal Hb
more left but starts at same point and ends at same point and is more r shaped
greater affinity than adult HbA to extract oxygen from mothers blood in placenta
what does the curve look like for myoglobin
starts and ends at the same place but much much more left and abrupt r shape
much much greater affinity than adult HbA to extract oxygen from circulating blood and store it
what are the steps for oxygen transport (not explained)
1) loading in lungs
2) unloading at tissues
3) loading in tissues x3
describe the STEPS for oxygen loading in lungs
1) blood returns to the lung in the pulmonary circulation
2) very saturated? unsaturated imo - each Hb has 4 binding sites
3) oxygen diffuses into blood > binds to Hb
describe the STEPS for unloading at tissues
1) coming out of left ventricle > arteries going to bronchial circulation > drains into pulmonary vein
2) oxygen moves down it’s conc gradient and supports the metabolic production of energy
how do you work out resting VO2 to be approx 250 mL.min-1
lose 5mL per dL of blood for every 100mL that passes through
cardiac output = 5L per minute
100 mL goes in 50 times so
-5 x 50 = -250 mL O2.min-1
describe the STEPS for loading at tissues
1) CO2 moves into blood
2) bind reversibly but slowly and non enzymatically with water to produce carbonic acid which dissociates into protons and bicarbonate
into red blood cells
3) carbonic anhydrase catalyses reaction 5000x quicker
4) bicarbonate moves out into blood
5) chloride exchange (negative ions enter RBC to maintain RMP)
6) water moves in RBC
7) CO2 also binds to Hb at the amine end > carbon amino haemoglobin
8) excess protons need to bind to negative anionic sites on global chains to manage pH change - enzyme function
what is CO2 flux
48 -> 52
about 80% of O2 consumption
what is pulmonary transit time
google = an indirect measure of preload and left ventricular function
there is a 3/4 of a second window for gas exchange to occur
lungs are efficient at having blood go through at the right speed and over the right amount of SA
what is a shunt
a flow of blood not doing the normal circuit
