respiration - lecture 2 Flashcards
what is spirometry
measuring lung volumes
what is total lung capacity
very deep breath
around 7l
total amount of air in lungs
what is vital capacity
diff between tlc and residual volume
what is tidal volume
breathing at rest ~1L in/out
what is functional residual capacity
around 3L left in lungs
during quiet breathing = do not breathe out all the air
what is residual volume
breathe out at max effort
expire air, still some left in lungs tho
if make too much effort = lungs collapse, need some air always to keep open
describe spirometer
upside down cannister floating above water
nose clip
breathe into cannister so pen goes upwards
what cant you measure with spirometer
what you breathe in = pen goes ip
cannot measure tlc and cannot measure functional residual capacity
what is inspiratory reserve vol
tidal volume to total
what is expiratory reserve volume
functional residual capacity to residual vol
what is vital capacity
functional to total
describe measurement of frc - helium dilution - gen
dissolved in air that subject breathes in
measures functional residual capacity
describe measurement of frc - helium dilution - experiment
breathe through spirometer with dissolved helium - concentration c1 known
also know volume
breath out to frc and then open valve and takes a few. breaths and equilibrates helium between canister and lungs
have new concentration and helium less concentrated = diluted in lungs
total vol = at beginning + frc
describe measurement of frc - helium dilution - math
c1 x v1 = c2 x (v1 + frc)
so
frc = (c1 x v1 / c2) -v1
what is minute ventilation
amount of air inspired or expired over one minute = VE
VE = VT x f
VT = tidal vol and f = number of breaths per min
(dot above VE = per min)
what is anatomical dead space
not all the air inhaled into the lungs reaches the gas exchange area
some of air remains in conducting airways = anatomical dead space
describe volumes of air
tidal = 450ml
dead space = 150ml ish - wasted in terms of gas exchange
around 450ml useful inside alveolar region
how to know how much anatomical dead space is
around 150ml in adult
hard to measure but close approx = subjects weight in pounds
describe volumes - formulas
healthy adult male VT=500ml and f=12 breaths/min
so VE = 6000ml/min = 6L/min
anatomical dead space = 150ml
alveolar ventilation = VA = (500-150ml) x 12/min = 4200ml/min = 4.2L/min
what is alveolar dead space
under some pathological conditions
certain amount of inspired air reaches respiratory zone but does not take part in gas exchange
can be due to decrease blood supply or no blood supply at alls
describe alveoli during alveolar dead space
ventilated region not perfused=wasted air
occluded blood vessel by blood clots = little blood flow
so no gas exchange since no blood flow
describe pressure formulas
P = total pressure
Px = partial pressure of gas x
Fx = fractional concentration in dry gas
Px = P (Fx)
what is physiological dead space
VD = (alveolar + anatomical) dead space
usually equal but sometimes under pathological conditions alveolar greater
describe pressure formulas - ex
Barometric P = 760mmHg
FO2 = 21% *
FCO2 = 0.03% *
(percent of O2 in air ~2% - fractional concentration)
Px = (P-47mmHg)Fx (in a gas with a water vapor pressure of 47mmHg)
PO2 = (760mmHg – 47mmHg)(21/100) = 150mmHg
PCO2 = (760mmHg – 47mmHg)(0.03/100) = 0.2mmHg
(must subtract 47 bc of water vapour pressure)
describe fractional concentrations
generally given as the fraction of dry gas volume that is occupied by the gas in question. Because of that convention, barometric pressure has to be corrected for the contribution from water vapor
describe partial pressures of air vs alveoli
air po2 = 160mmhg, pco2=0.3mmhg
alveoli po2 = 105mmhg, pco2 = 40 mmhg
avg values = as inspire, fresh air mixes with old air and diffuses and co2 diffuses into alveoli
describe partial pressures of left heart
in pulmonary veins - po2 = 100mmhg, pco2 = 40mmhg
in systemic arteries = po2 = 100mmhg, pco2=40mmhg
describe partial pressures of tissue capillaries
o2 diffused into cells and co2 into capillaries
in cells p02<40mmhg (mitochondrial po2 <5mmhg), pco2 > 46mmhg
describe partial pressures of right heart
systemic veins po2=40mmhg, pco2=46mmhg
pulmonary arteries - po2 = 40mmhg, pco2 = 46mmhg
describe the components important for partial pressures
pressure gradient
other components important like solubility in blood co2 diffuses better - more soluble
describe normal alveolar ventilation
alveolar ventilation keeps p arterial co2 at a constant level of 40mmhg
arterial co2 keeps ventilation proper
in systemic blood
what is A and what is a
A = alveolar
a = arterial
see ventilation increase and decrease as measure of arterial co2
describe alveolar hyperventilation
ventilation exceeds needs of body
more o2 supplied and more co2 removed than metabolism needs
describe alveolar hyperventilation - pressures
p alv o2 and p arterial o2 rise
palv co2 and p arterial co2 decrease
describe alveolar hyperventilation - metabolism
all with respect to metabolism so not during exercise (which increases metabolism and ventilation)
there are limits to increase in p arterial o2
describe alveolar hyperventilation - how to fix
in paper bag = arterial co2 goes down and in brain = artery constricts= leads to fainting but bag build co2 and then you breath in and reestablish co2 levels
describe alveolar hypoventilation
decrease in alveolar ventilation below metabolic requirements
less o2 supplied and less co2 removed than metabolism requires
describe alveolar hypoventilation - pressures
palv o2 and parter o2 decrease
palv co2 and parter co2 rise
describe alveolar hypoventilation - disorders
chronic obstructive lung disease
damage to respiratory muscles
rib cage injuries
cns depression
pneumothorax
drugs
describe pressures when breathe air with low po2
alveolar po2 decreases
no change in alveolar pco2
describe pressures when increase alv ventilation and unchanged metabolism
palv o2 increases
palv co2 decreases
describe pressures when decrease alv vent and unchanged metabolism
palv o2 decreases
palv co2 increases
describe pressures when unchange alv vent and increase metabolism
palv o2 decreases
palv co2 increases
describe pressures when unchange alv vent and decrease metabolism
palv o2 increases
palv co2 decreases
describe pressures when proportional increases in metabolism and alv vent
no change in palv co2 or o2
describe diffusion rate
transfer of gasses across alveolar capillary membrane = by passive diffusion
diffusion v efficient in lungs bc of huge surface area and v thin membrane
what is diffusion governed by
ficks law
describe diffusion rate - mayth
proportional to surface area (50-100m^2)
proportional to partial pressure gradient
inversely proportional to thickness (~0.2mm)
describe diffusion pathway
o2 flows from alveolus through fluid layer inside alveolus and surfactant through alveolar epithelium and bm through interstitial space then capillary bm then capillary endothelium then plasma and rbc
co2 = opp dir - passive
gasses must be liquid soluble and plasma - also has to be soluble in liquid
gas dissolved = proportional to partial pressure
what is henrys law
to diffuse through a liquid, a gas must be soluble in the liquid. The amount of gas dissolved is proportional to its partial pressure
more diffusion = more pressure
what diffuses faster
co2 diffused 20 times faster than o2 bc co2 is more soluble in water
describe time required for equilibrium between alveolar air and capillary blood
same for 2 gases
pco2 between 2 sides of alveolar capillary membrane is 10 times smaller than for po2
describe transit time
~0.75s in capillary
po2 = 105mmhg
describe transit time - po2
as flow in through pulmonary cap = po2 increases v fast
~0.35s = o2 saturated
describe transit time - pco2
same thing = ~0.25 sec - decrease co2 to same level of lungs = desaturate
describe transit time - athlete
increase blood flow - goes faster
transit time ~0.3s
still enough time to be saturated
describe transit time - edema
fluid in interstitial alveolar cap membrane = thicken so takes longer
can still have enough time but if exercise = wont saturate and desaturated = diffusion problem
