Respiratory Physiology - Respiratory Volumes and Capacities

Question 1

Tidal Volume (TV)

Answer 1

air inspired/expired with normal, quiet breathing

Question 2

Inspiratory Reserve Volume (IRV):

Answer 2

air inspired beyond TV

Question 3

Expiratory Reserve Volume (ERV)

Answer 3

air expired beyond TV

Question 4

Residual Volume (RV)

Answer 4

air that remains in the lungs after ERV

Question 5

Minimal Volumes (MV)

Answer 5

small amount of air that remains in the lungs – even if the chest is opened

Question 6

Respiratory capacities

Answer 6

specific combinations of lung volumes

Question 7

Inspiratory Capacity (IC)

Answer 7

TV + IRV

Question 8

Functional Residual Capacity (FRC)

Answer 8

RV + ERV

Question 9

Vital Capacity (VC)

Answer 9

IRV + TV + ERV

Question 10

Total Lung Capacity (TLC)

Answer 10

sum of all lung volumes

Question 11

VC

Answer 11

total amount of exchangeable air in the lungs

Question 12

RV

Answer 12

total amount of non-exchangeable air

Question 13

Anatomical Dead Space

Answer 13

air that remains in the passageways and does not contribute to gas exchange; ~150mL

Question 14

Alveolar (Physiologic) Dead Space

Answer 14

air in non-functional alveoli

Question 15

Total Dead Space

Answer 15

the sum of non-useful volumes – anatomical + alveolar dead space

Question 16

Spirometer

Answer 16

Instrument used for measuring respiratory volumes and capacities
- spirometer tests help diagnose and differentiate between obstructive pulmonary diseases and restrictive disorders

Question 17

Obstructive Pulmonary Diseases

Answer 17

diseases of increased airway resistance
- TLC, FRC, RV may increase

Question 18

Restrictive Disorders

Answer 18

diseases of reduced lung capacity due to fibrosis/disease
- VC, TLC, FRC, RV may decline

Question 19

Forced Vital Capacity (FVC)

Answer 19

the amount of gas expelled when a subject takes a deep breath and then forcefully exhales as maximally and rapidly as possible

Question 20

Forced Expiratory Volume (FEV)

Answer 20

determines the amount of air expelled during specific time intervals of the FVC test

Question 21

FEV1

Answer 21

the amount of air exhaled during the 1st second – typically, about 80%

Question 22

Minute Ventilation

Answer 22

the amount of air flowing in/out of the respiratory tract in 1 minute
- provides a rough estimate of respiratory efficiency
- Normal (Resting): 500mL x 12 breaths per minute = 6L/min
- Normal (Exercising): up to 200L/min

Question 23

Alveolar Ventilation

Answer 23

amount of air flowing in/out of the alveoli per unit of time
- a more effective measurement
- AVR (mL/min) = frequency (breaths/min) x TV – dead space (mL/breath)
- Dead space is typically constant
- Rapid, shallow breathing decreases AVR

Question 24

External Respiration

Answer 24

exchange of gases in the lungs
- O2 diffuses into the blood
- CO2 diffuses out of the blood

Question 25

Internal Respiration

Answer 25

exchange of gases in the body’s tissues - O2 diffuses out of the blood - CO2 diffuses into the blood

Question 26

Dalton’s Law of Partial Pressures

Answer 26

- Attempts to explain how gas behaves when it is part of a mixture of gases - The total pressure exerted by a mixture of gases equals the sums of the pressures exerted by each gas individually - The partial pressure of each gas is proportional to its percentage in the mixture - Example: O2 makes up 21% of the atmosphere. It has a partial pressure (PO2) of 159mmHg 20.9% x 760mmHg = 159mmHg

Question 27

Henry’s Law

Answer 27

- Attempts to explain how gases move in and out of solutions - Each gas will dissolve into a liquid in proportion to its partial pressure - The greater the concentration of a particular gas, the more and the faster that gas will go into solution - The direction and amount of movement of a gas are determined by its partial pressure in the 2 phases - Additional Factors: -- Solubility - CO2 is 20x more soluble in H2O than O2 -- Temperature - as a liquid’s temperature rises, solubility decreases

Question 28

high altitude

Answer 28

At high altitude, atmospheric pressure declines, so partial pressures also decline - Ex: at 10,000 ft above sea level, the atmospheric pressure is 523mmHg – the partial pressure of Oxygen (Po2) is 110mmHg 523mmHg x 21% = 110mmHg

Question 29

low altitude

Answer 29

At low altitude, atmospheric pressure increases, so partial pressures also increase - Ex: at 99 ft below sea level, the atmospheric pressure is 3,040mmHg – the partial pressure of Oxygen (PO2) is 636 mmHg 3,040mmHg x 21% = 636mmHg

Question 30

Composition of Alveolar Gas

Answer 30

- Atmospheric air contains mostly O2 and N2 - Alveolar air contains mostly CO2 and water vapor - In the lungs, O2 is diffusing into the blood, and CO2 is diffusing out - Air is humidified by the conducting passages - With each breath, new and old alveolar gas is mixed - The partial pressures of O2 and CO2 can be altered by increasing breathing rate and depth!

Question 31

External Respiration

Answer 31

Exchange of O2 and CO2 across the respiratory membrane

Question 32

external respiration is influenced by:

Answer 32

- Thickness and surface area of the respiratory membrane - Partial pressure gradients and gas solubilities - Ventilation-perfusion coupling

Question 33

The Respiratory Membrane

Answer 33

- Typically, .5 to 1μm thick with a LARGE surface area for exchange - Membranes thicken with edema and gas exchange becomes inadequate - Surface area is reduced with emphysema, tumors, inflammation, and mucus

Question 34

Diffusion

Answer 34

driven by the partial pressure gradients of O2 and CO2

Question 35

Steep partial pressure gradient for O2 in the lungs

Answer 35

Venous Blood PO2 = 40mmHg Alveolar PO2 = 104mmHg

Question 36

oxygen is driven ______

Answer 36

into the blood - Equilibrium is achieved in .25s - a RBC typically spends .75s in a pulmonary capillary - Blood can flow 3x faster and still be well-oxygenated!

Question 37

co2 diffusion (less steep)

Answer 37

CO2 diffuses down a less steep pressure gradient Venous Blood PCO2 = 45 mmHg Alveolar PCO2 = 40 mmHg -- CO2 and O2 diffuse across in equal amounts – CO2 is much more soluble!

Question 38

Perfusion

Answer 38

amount of blood reaching the alveoli

Question 39

Ventilation

Answer 39

amount of gas reaching the alveoli -- Perfusion and ventilation must be well matched for efficient gas exchange!

Question 40

perfusion physiology

Answer 40

- Changes in PO2 control perfusion by changing arteriolar diameter - Where alveolar O2 is high, arterioles dilate to stimulate O2 pickup - Where alveolar O2 is low, arterioles constrict to divert blood elsewhere - Striving for efficient O2 pickup!

Question 41

Ventilation physiology

Answer 41

- Changes in PCO2 control ventilation by changing bronchiole diameter - Where alveolar CO2 is high, bronchioles dilate for faster CO2 removal - Where alveolar CO2 is low, bronchioles constrict Striving for efficient CO2 removal!

Question 42

Internal Respiration

Answer 42

- The exchange of O2 and CO2 between blood and body tissues - The partial pressures and diffusion gradients are reversed! - PO2 of tissues < PO2 of blood O2 is driven into the tissues - PCO2 of tissues > PCO2 of blood CO2 is driven into blood