respiratory physiology

Question 1

what is gas exchange

Answer 1

exchange of O2 and CO2
occurs via diffusion
each gas follows its concen gradient

Question 2

what is the difference between diffusion and perfusion

Answer 2

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

Question 3

where are the two sites of gas exchange and what happens

Answer 3

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

Question 4

what are the different lung volumes

Answer 4

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

Question 5

what is minute ventilation (VE)

Answer 5

breathing frequency (fb) x tidal volume (VT)
~6000 mL/min
- not all reaches the alveoli

Question 6

what is alveolar ventilation

Answer 6

fb x alveolar volume
- alveolar volume = VT - dead space

Question 7

what is dead space in the lungs

Answer 7

portion of each breath that fills the mouth, nasal passage, pharynx, and larynx

Question 8

how much volume is alveolar ventilation

Answer 8

4200 mL/min

Question 9

what is partial pressure

Answer 9

fraction of total air that contains the gas x total pressure

Question 10

what is the total air pressure and partial pressure of oxygen at sea level

Answer 10

760 mmHg

O2 = 159 mmHg

Question 11

when does fraction of gases in air change

Answer 11

never
- stays the same regardless of partial pressure changes

Question 12

how does PO2 change from the atmosphere to the cells

Answer 12

atmosphere = 159 mmHg
trachea = 149 mmHg
alveolar = 103 mmHg
arterial air = 100 mmHg
mean capillary = 40 mmHg
mitochondria = 2-3 mmHg

Question 13

why is PO2 lower in trachea

Answer 13

air is humidified
- volume of air includes gas and water

Question 14

why is PO2 lower in the alveoli

Answer 14

CO2 continually enters the alveoli from blood
higher % of CO2 and lower % of O2

Question 15

why is PO2 in arterial air slightly lower than in the alveoli

Answer 15

Shunting blood
- not all capillaries touch the alveoli (can bypass)
Some poorly ventilated alveoli
- not all have perfect diffusion levels (function decreases)

Question 16

why is PO2 lower in mean capillaries

Answer 16

includes a mix of arterial and venous blood

Question 17

how do atmospheric, tracheal, alveolar, and arterial PO2 change during exercise

Answer 17

DON’T CHANGE
- increased ventilation offsets increased oxygen uptake

Question 18

how does venous PO2 change during exercise

Answer 18

DECREASES
~15 mmHg with intense exercise
- more O2 taken up by muscles

Question 19

how does venous PCO2 change during exercise

Answer 19

INCREASES
~60 mmHg with intense exercise
- more CO2 is produced by muscles

Question 20

what are the approx concentrations of gases in whole air

Answer 20

nitrogen = 79%
oxygen = 21%
CO2 = 0.03%

Question 21

how is oxygen transported in the blood

Answer 21

1. dissolved in the fluid of blood (4%)
   - very little due to poor solubility
2. bound to hemoglobin (96%)
   - each hemoglobin can bind 4 O2 molecules (4 heme units that can carry 1 O2)

Question 22

which sex has greater Hb mass, males or females

Answer 22

males have significantly greater Hb mass than females

Question 23

what does O2 carrying capacity depend on

Answer 23

hemoglobin concen
- amount of hemoglobin in blood

oxygen capacity of hemoglobin (1.34 mL O2/g)
- multiply with hemoglobin concen to find capacity

Question 24

what does arterial oxygen content (amount of O2 in blood) depend on

Answer 24

hemoglobin concen

saturation of hemoglobin with oxygen
- much higher affinity to CO2 and CO to hemoglobin compared to O2

PO2 of blood