Respiratory Physiology - Respiratory Volumes and Capacities Flashcards

1
Q

Tidal Volume (TV)

A

air inspired/expired with normal, quiet breathing

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2
Q

Inspiratory Reserve Volume (IRV):

A

air inspired beyond TV

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3
Q

Expiratory Reserve Volume (ERV)

A

air expired beyond TV

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4
Q

Residual Volume (RV)

A

air that remains in the lungs after ERV

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5
Q

Minimal Volumes (MV)

A

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

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6
Q

Respiratory capacities

A

specific combinations of lung volumes

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7
Q

Inspiratory Capacity (IC)

A

TV + IRV

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8
Q

Functional Residual Capacity (FRC)

A

RV + ERV

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9
Q

Vital Capacity (VC)

A

IRV + TV + ERV

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10
Q

Total Lung Capacity (TLC)

A

sum of all lung volumes

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11
Q

VC

A

total amount of exchangeable air in the lungs

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12
Q

RV

A

total amount of non-exchangeable air

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13
Q

Anatomical Dead Space

A

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

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14
Q

Alveolar (Physiologic) Dead Space

A

air in non-functional alveoli

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15
Q

Total Dead Space

A

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

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16
Q

Spirometer

A

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

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17
Q

Obstructive Pulmonary Diseases

A

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

18
Q

Restrictive Disorders

A

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

19
Q

Forced Vital Capacity (FVC)

A

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

20
Q

Forced Expiratory Volume (FEV)

A

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

21
Q

FEV1

A

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

22
Q

Minute Ventilation

A

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

23
Q

Alveolar Ventilation

A

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

24
Q

External Respiration

A

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

25
Q

Internal Respiration

A

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

26
Q

Dalton’s Law of Partial Pressures

A
  • 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
27
Q

Henry’s Law

A
  • 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
28
Q

high altitude

A

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

29
Q

low altitude

A

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

30
Q

Composition of Alveolar Gas

A
  • 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!
31
Q

External Respiration

A

Exchange of O2 and CO2 across the respiratory membrane

32
Q

external respiration is influenced by:

A
  • Thickness and surface area of the respiratory membrane
  • Partial pressure gradients and gas solubilities
  • Ventilation-perfusion coupling
33
Q

The Respiratory Membrane

A
  • 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
34
Q

Diffusion

A

driven by the partial pressure gradients of O2 and CO2

35
Q

Steep partial pressure gradient for O2 in the lungs

A

Venous Blood PO2 = 40mmHg
Alveolar PO2 = 104mmHg

36
Q

oxygen is driven ______

A

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!

37
Q

co2 diffusion (less steep)

A

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!

38
Q

Perfusion

A

amount of blood reaching the alveoli

39
Q

Ventilation

A

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

40
Q

perfusion physiology

A
  • 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!
41
Q

Ventilation physiology

A
  • 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!
42
Q

Internal Respiration

A
  • 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