Respiratory Physilogy Block 1(Handout 3, Alv Venti)

Front 1

what gas mixtures make up the air inside a room

Back 1

Nitrogen (79%)
O2 (21)

Front 2

what gas mixture makes up the air inside our airways

Back 2

N2, O2, and Vapro pressure

Front 3

if we breathe in 3600 ml of air, how do we determine the amount of air in the alveoli (vol inside the alveoli)

Back 3

the volumes inside the alveoli depends on the gases that are exchanged, only gases exchanged are O2 and Co2, N2 is ignored, the amount of O2 figured out by following:
3600X.21 (since O2 makes up 21%)= 756, we extract 250 ml so total amount of O2 in the alveolus is 756-250= 506ml
N2 is 3600X.79= 2844ml
Co2 is based on what's put inside the blood, w/c= 200ml
if add all of these up we get total amount of Air inside the alveolus= 2844+506+200= 3550
To figure out the mole fractions (F)we use these #'s divided by 3550 e.g
FO2= 556/3550= .142
FN2=2844/3550=.80
FCo2=200/3550=.06
TO CALCULATE THE PARTIAL PRESSURES OF ALL OF THESE GASES WE USE:
PP=FXTotal Pressure
PO2= .14X713= 102
PCo2= .80X713=571,
we ignore the vapor pressure for simplicity

Front 4

when measuring alveolar ventilation where does the gas comes from?

Back 4

2 places
1 dead space called VD
2 alveoli called VA,

Front 5

what does total ventilation or expired vol equal

Back 5

Vexpired= Vd+Va

Front 6

what is the key thing to remember w/Va and Vd

Back 6

since gase exchange only takes place in the alveoli, the dead space doesn't contribute much

Front 7

how is ventilation measured

Back 7

by getting a patient to slowly exhale, remembering that first burst of air expelled is from dead space, once the exhalation continues, it comes form the alveolus and that's what measured

Front 8

why is amount of gas breathed out smaller than amount breathed in

Back 8

b/c it depends in O2 breathed in. when we breathe in O2, it goes to Co2, 1 O2 yields 1 Co2, but some of the O2 also combines w/H to make H2O, so we breathe more O2 and it is divided into 2 places and we only exhale Co2, w/c is less O2 then we take in

Front 9

what is total/tidal minute ventilation

Back 9

it Vt= Vd+Va, it is usually measured by taking into account the frequency (F) of breaths/minute, so its actually:
VtF=VdF+VaF,
it is always denoted w/a dot

Front 10

what does total minute ventilation tell us

Back 10

it tells us the fraction of ventilation that goes to the dead space and the amount that goes the actual exchange area or alveolus

Front 11

what is Alveolar Gas eq 1

Back 11

PaCo2~ VCo2/Va

Front 12

according to the alveolar gas eq 1, what does the PaCo2 depend on

Back 12

it is dependent on Vol of Co2 (directly) and amount of ventilation (inversely)

Front 13

what happen to PaCo2 when
hyperventilate
Hypoventilate

Back 13

PaCo2 decreases
PaCo2 Increase,
assuming that vol of Co2 stays constant

Front 14

what is alveolar gas equation 2

Back 14

PAO2= PIo2-PaCO2/r
r=0.8
PIo2= pressure of O2 inhlaed

Front 15

what is the purpose of this eqution

Back 15

this equation is there to assess the lung function in a patient

Front 16

what are the dead spaces

Back 16

2 types
1)anatomical(large airways, not measured)
2)physiological(measured), this is usually strongly elevated in pulmonary embolus

Front 17

where are physiological dead spaces elevated

Back 17

anywhere there is high V?Q ratio or anywhere a tube is inserted in series w/a patients airways