18 Pulmonary Gases And Equations

Front 1

Oxygen pathway

Back 1

1) ventilation
- active
- variables = rate V
2) Diffusion
- passive diffusion
- variables = SA, distance
3) Circulation
- active
- rate V
4) Diffusion
- passive diffusion
- SA, distance

-in series, any one can be rate limiting for O2 uptake
- each has variables that ↑ O2 transfer

Front 2

O2 uptake

Back 2

- mitochondria 80% resting O2 uptake (high affinity)
- non MT pathways (synthesis of NE, Dopamine, Serotonin) hepatic cell function --> other 20% more sensitive to hypoxia

Front 3

BMR

Back 3

- basal metabolic rate or resting O2 consumption
- 250 ml O2 per minute in 70 kg adult

Front 4

Critical PO2

Back 4

- diffusion from blood to tissues last step
- PO2 in cap. ↓, rate of diffusion limits and tissue will infarct (die)
- brain and heart have highest critical PO2

Front 5

CO2 production

Back 5

- same as O2 consumption (pure carbo diet)
- ratio of CO2 production to O2 consumption --> respiratory quotient in tissues, respiratory exchange ration (R) in lungs
- R = V(flow)CO2/ V(flow)O2

Front 6

Steady state

Back 6

- R = RQ
- gas exchange is matched in tissues and lungs
-non steady state: crying, breath holding
Fats metabolized: RQ=.7 (fasting metabolism)
Proteins RQ= .8

Front 7

Respiratory gases

Back 7

- alveolar ventilation and fraction of ispired O2 --> amt of O2 delivered to alveoli
- PAO2 + PAN2 + PACO2 + PAH2O= PB

Front 8

PIO2

Back 8

- inspired oxygen pressure, dependent on O2 inaled in air and PB
- PIO2 = (PB-PH2O)(FIO2)
-PH2O water vapor pressure (temp) 47 mm hg at 37c
FIO2 - .21
PB = 760

Front 9

Alveolar gas equation PO2

Back 9

- calculate efficiency of gas exchange by comparing arterial and alveolar values
- need PaO2
- water vapor added to inspired air reduced PIO2
- CO2 from pulmonary cap into alveoli reduces PIO2
- PIO@ = (Pb-Ph20) x FO2
- PaO2 = PIO2 - PACO2
if R<1
PaO2= PIO2 - (PACO2/R)
R = tissue< 1 (CO2 being removed is greater than O2 being added)
(RQ lungs)

Front 10

Alveolar-arterial PO2 difference

Back 10

- PaO2 5-20 mmHg > PAO2
- increases with incraseing fraction of PIO2 (upper flat portion of oxyHg dissociation flat)
-PAO2 falls with age, Pa02 constant
- PACO2 doesn't change with age, meduallary brain stem control

Front 11

Alveolar CO2

Back 11

- only source is from tissues
- increased alveolar ventilation dilutes PCO2
- PACO2 = V(flow)CO2/VA(flow) x 863
863 = gas constant

Front 12

hyperventilation

Back 12

- excess of what's needed to maintain normal PACO2
-