respiratory physiology Flashcards
what is gas exchange
exchange of O2 and CO2
occurs via diffusion
each gas follows its concen gradient
what is the difference between diffusion and perfusion
diffusion = travelling from one area to another (lungs to capillary to muscle cell)
perfusion = gases moving through the vascular system ***no change in environment - no exchange
where are the two sites of gas exchange and what happens
lungs to blood:
uptake = O2 moved from environment to the mito (facilitates fat and glucose oxidation)
blood to tissue:
removal = CO2 moved from the mito to the environment
what are the different lung volumes
Inspiratory reserve volume (IRV):
- maximal inspiration at the end of tidal volume
Tidal volume (VT) (~0.5L at rest, higher during exercise)
- volume inspired or expired per breath
Expiratory reserve volume (ERV)
- maximal expiration at the end of tidal volume
Residual lung volume
~1L never leaves the lung - otherwise they collapse
what is minute ventilation (VE)
breathing frequency (fb) x tidal volume (VT)
~6000 mL/min
- not all reaches the alveoli
what is alveolar ventilation
fb x alveolar volume
- alveolar volume = VT - dead space
what is dead space in the lungs
portion of each breath that fills the mouth, nasal passage, pharynx, and larynx
how much volume is alveolar ventilation
4200 mL/min
what is partial pressure
fraction of total air that contains the gas x total pressure
what is the total air pressure and partial pressure of oxygen at sea level
760 mmHg
O2 = 159 mmHg
when does fraction of gases in air change
never
- stays the same regardless of partial pressure changes
how does PO2 change from the atmosphere to the cells
atmosphere = 159 mmHg
trachea = 149 mmHg
alveolar = 103 mmHg
arterial air = 100 mmHg
mean capillary = 40 mmHg
mitochondria = 2-3 mmHg
why is PO2 lower in trachea
air is humidified
- volume of air includes gas and water
why is PO2 lower in the alveoli
CO2 continually enters the alveoli from blood
higher % of CO2 and lower % of O2
why is PO2 in arterial air slightly lower than in the alveoli
Shunting blood
- not all capillaries touch the alveoli (can bypass)
Some poorly ventilated alveoli
- not all have perfect diffusion levels (function decreases)
why is PO2 lower in mean capillaries
includes a mix of arterial and venous blood
how do atmospheric, tracheal, alveolar, and arterial PO2 change during exercise
DON’T CHANGE
- increased ventilation offsets increased oxygen uptake
how does venous PO2 change during exercise
DECREASES
~15 mmHg with intense exercise
- more O2 taken up by muscles
how does venous PCO2 change during exercise
INCREASES
~60 mmHg with intense exercise
- more CO2 is produced by muscles
what are the approx concentrations of gases in whole air
nitrogen = 79%
oxygen = 21%
CO2 = 0.03%
how is oxygen transported in the blood
- dissolved in the fluid of blood (4%)
- very little due to poor solubility - bound to hemoglobin (96%)
- each hemoglobin can bind 4 O2 molecules (4 heme units that can carry 1 O2)
which sex has greater Hb mass, males or females
males have significantly greater Hb mass than females
what does O2 carrying capacity depend on
hemoglobin concen
- amount of hemoglobin in blood
oxygen capacity of hemoglobin (1.34 mL O2/g)
- multiply with hemoglobin concen to find capacity
what does arterial oxygen content (amount of O2 in blood) depend on
hemoglobin concen
saturation of hemoglobin with oxygen
- much higher affinity to CO2 and CO to hemoglobin compared to O2
PO2 of blood
