respiratory physiology Flashcards
(24 cards)
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
