Unit 4: Respiratory, Cardiovascular, Cell Physiology

Question 1

Define gas volume: STPD

Answer 1

STPD: Standard Temperature, Pressure and Dry Gas (no water vapor)

(0° C [273K]; 760 mm Hg; 0 mm Hg)

Question 2

Define gas volume: BTPS

Answer 2

BTPS: Body Temperature, Pressure and Saturated (i.e. water vapor)

(37°C [310K]; 760 mmHg; 47 mmHg)

Question 3

Define gas volume: ATPS

Answer 3

ATPS: Ambient Temperature, Pressure and Saturated (i.e. water vapor)

(25° C [298K]; 760 mmHg; 24 mmHg)

Question 4

How do you convert between STPD, ATPS, or BTPS (or any other) gas volumes?

Answer 4

Use ideal gas law relationship:

PV=nrT

P₁V₁/T₁ = P₂V₂/T₂

Question 5

State equation to calculate V_L from spirometry data

Answer 5

V_L = 1.07V_sp

Volume of the lung is 1.07 times the measured volume from the spirometer. Interpretation: volume of the lung is a 7% greater than that measured by spirometer (a small but clinically significant difference);

Question 6

Calculate or state:

• Dry Inspired P_O2
• P_TRO2 (inspired)
• P_AO2
• P_aO2
• P_vO2

Answer 6

Question 7

Calculate or state:

• P_ACO2
• P_vCO2
• P_aCO2
• Dry Inspired CO2

Answer 7

Note: we inspire a neglible amount of CO2

Question 8

Modes of breathing:

Eupnea

Hyperpnea

Tachypnea

Answer 8

Eupnea: Normal quiet breathing; active inspiration and passive expiration

(Eu= good or well; -pnea=to breathe)

Hyperpnea: Active breathing during exercise; deeper and faster breathing than normal due to increased tidal volume and frequency (i.e. increased ventilation); active inspiration and expiration;

(Hyper= above, excessive; -pnea= to breathe)

Tachypnea: Rapid (but not necessarily deeper) breathing; often occurs during anxiety;

(tachy = swift or fast; -pnea=to breathe)

Question 9

Modes of breathing:

Hypoventilation

Hyperventilation

Related term: Hypercapnea

Answer 9

Hypoventilation: a RR insufficient to achieve normal oxygenation of the tissues; slow breathing rate causes hypoxia and hypercapnea (retention of CO2 in blood–> acidemia);

(Hypo = under, beneath; ventilation= supply of air/O2)

Hyperventilation: a RR that is faster than required for normal oxygenation of tissues; fast breathing rates causes increased “blowing off” of CO2–> alkalemia;

(Hyper = over, above; ventilation= supply of air/O2)

Hypercapnea: the accumulation of CO2 in blood (acidifies blood);

Question 10

Muscles of Respiration:

• List the muscles of inspiration (MOI)
• indicate primary muscle and mechanism of action
• indicate additional muscles, their action and conditions under which they are active

Answer 10

Primary muscle respiration: diaphragm; contracts down and increases volume of intrapleural space and decreases pressure; active inspiration;

External intercostals: active during exercise; push ribs down, increasing anterior-posterior diameter of ribcage;

Accessory muscles: sternocleidomastoid (SCM), face, neck muscles; exercise/active inspiration conditions.

Question 11

Muscles of Respiration:

• List muscles of expiration (MOE)
• indicate primary muscle of experation
• indicate accessory muscles and conditions under which they are active

Answer 11

Primary muscle of expiration: NONE;

expiration is a passive process only during normal breathing;

Accessory muscles include internal intercostals which are active during exercise or active breathing conditions.

Question 12

List the 2 major function of the respiratory system

Answer 12

• Deliver O2 to body tissues
• Remove CO2 from body tissues (metabolism waste)

Question 13

State equation for total ventilation (V_E)

give the normal value

State equation for alveolar ventilation (V_A)

give the normal value

Answer 13

V_E = V_T x f = V_A + V_D

Total ventilation = alveolar ventilation + dead space ventilation; aka “minute ventilation”

normal V_T = Volume_alv+ Volume_ds = 500 mL;

normal f= 15 breaths/min

normal V_E = 7.5 L/min

V_A= V_T x f = V_E - V_D

Alveolar ventilation = Alveolar (tidal) volume x frequency of breaths (aka respiratory rate (RR))

alveolar tidal volume = 350 mL

normal V_A = 5250 mL

dead space volume = 150 mL;

normal V_D = 150*15= 2250 mL

(cross check: V_E-V_D= 7500-2250=5250 mL=V_A)

Question 14

List and describe the 4 lung volumes

Answer 14

1. Tidal volume (VT): amount of air entering or leaving the lung in 1 breath (respiratory cycle). Normal VT = 500 mL
2. Inspiratory Reserve Volume (IRV): Additional amount of air (volume) that can be inspired above normal VT (end-tidal position). IRV allows you to reach upper limit of Total Lung Capacity.
3. Expiratory Reserve Volume (ERV): Additional volume that can be expired after passive expiration (end-tidal position); ERV allows you to reach the lower limit of Total Lung Capacity;
4. Residual Voume (RV): Amount (volume) of air that cannot be exhaled; it remains in the lung after maximal forced expiration; RV is the lowest limit of Total Lung Capacity;

Question 15

List and describe the 4 lung capacities

give equations where applicable

Answer 15

1. Vital Capacity (VC): Maximal volume of air that can be expired forcibly after a maximal inspiration; “forced vital capacity.” VC = IRV+ V_T + ERV = TLC-RV; (think: big bad wolf huffing and puffing to blow the house down!)
2. Inspiratory Capacity (IC): Maximal volume of air that can be inspired from FRC (resting equilibrium position); IC = IRV + V_T = TLC- FRC
3. Functional Residual Capacity (FRC): The volume of air remaining in lungs at end of a normal expiration with all muscles relaxed; Equilibrium position of the lung; FRC = ERV + RV = TLC - IC. measured by N2 washout, body plethysmograph or He dilution methods (NOT spirometry). Normal value = 2700 mL;
4. Total Lung Capacity (TLC): Maximal volume of air the lungs can contain; Normal value = 6-7 L; TLC = VC + RV = IRV + V_T+ ERV+ RV

Question 16

Describe the effect of compliance on FRC of lung

Answer 16

Compliance = delta V/delta P_Lung

Recall: C œ V œ 1/elasticity (recoil pressure)

so C inversely proportional to 1/recoil (elasticity)

If C increases: recoil decreased; so lung does NOT return to normal FRC–it is hyperinflated (Increased FRC). Example: Emphysema

If C decreases: recoil increased; so lung assumes smaller than normal FRC (Decreased FRC); it is a stiffer lung and as a result there is limited inflation during inspiration (i.e. restricted); Example: interstitial fibrosis

Notes:

delta P (transmural across lung) = P_C + P_L

PC = Ppl - Patm

PL= Palv-Ppl

Question 17

State the Alveolar Gas Equation for CO2

-using the equation show how V_A determines P_ACO2

Note: V_A (V dot A) refers to alveolar ventilation

Answer 17

P_ACO2 = Vdot CO2 x P_T/V_A

PACO2 is inversely proportional to V_A

If increase V_A (hyperventilation), then P_ACO2 decreases giving rise to hypocapnea and hyperoxia (tissues)

If decrease V_A (hypoventilation), then P_ACO2 increases giving rise to hypercapnea and hypoxia (tissue)

Question 18

State the Alveolar Gas Equation for O2

-using the equation show how it is the basis for administration of oxygen therapy

Answer 18

P_AO2 = P_IO2 - (Vdot O2 x P_T)/V_A = P_IO2 - P_ACO2 /R

We can increase oxygenation (PAO2) by directly increasing the inspired O2 (oxygen therapy)

Note: R = Vdot CO2/ Vdot O2; (R=0.8)

(CO2 production/O2 consumption)

Question 19

How is ventilation measured clinically?

Describe it graphically

State the equation for volume of the lung derived from spirometry measurements

Answer 19

Ventilation is measured using spirometry; graphically it is measure of tidal waves (volume) over time; Slope of a volume-time curve gives flow (Q) (aka ventilation);

V_Lung = 1.07(V_sp)

Question 20

Compare and contrast:

Conducting Zone (CZ) & Respiratory Zone (RZ):

• functions
• anatomical differences
• ventilation and perfusion
• gas exchange
• immunological defenses

Answer 20

CZ: Ventilation +; Perfusion –; large airways; brings air into lungs; anatomic dead space (150 mL); Ø capillaries –> NO GAS EXCHANGE; Ciliated (mucociliary elevator defense).

RZ: Ventilation +; Perfusion +; bronchioles/small airways and alveoli; participate in gas exchange; many capillaries; produce surfactant (Type 2 alveolar cells); No cilia; macrophages for defense;

Question 21

State the equation:

fraction (F_x) of a dry gas

State the equation:

Partial pressure (P_i) of a dry gas

State the equation:

Partial pressure of an inspired (wet) gas

Answer 21

Fx = n_i /n_t = P_i /P_t

mols of n_i gas/ total mols (n_t) of all gases

P_i = F_i (P_t)

fraction of gas * total pressure all gases

P_I gas = F_i (P_t-P_H20)

fraction of gas * total pressure-water pressure

Question 22

State the fraction (%) of listed dry gases in ambient air

N₂

O₂

CO2

Argon

State the pressure of water vapor (BTPS)

Answer 22

P_H2O = 47 mm Hg

Question 23

State the Ideal Gas Law (IGL)

List its variations and proportional relationships

State the equation to calculation [concentration] of a gas in solution (Henry’s law)

indicate solubility coefficient for CO2

Answer 23

IGL: PV = nRT

Variations: P₁V₁/T₁ = P₂V₂/T₂

P = nRT/V

Pressure inversely proportional to volume

Pressure and volume proportional to temperature

[concentration_gas] = solubility coefficient * P_i

Concentration of gas in solution is proportional to partial pressure of gas (at constant temperature)

solubility coefficient (CO2)= .03

Note: partial pressure of a gas in liquid phase does NOT contribute to pressure of the liquid.

Question 24

Trace the pulmonary circulation circuit:

start at RV and ending with aorta/systemic circulation

Describe Bronchial flow (aka shunt flow) in terms:

• relation to CO
• ventilation/perfusion
• pathway of circuit

Answer 24

RV–> Pulmonary Artery (deoxygenated blood) –> Lung (gas exchange)–> Pulmonary Vein (oxygenated blood)–> LA–> LV–>Aorta/systemic circulation

Bronchial circulation (normal “shunt” flow): 1% CO that perfuses the lung conducting airways; airways perfused+; ventilated -; bypasses gas exchange

Bronchial artery–>Conducting airways–>Pulmonary vein–> LA

Question 25

# Define: Alveolar dead space Trapped Volume

Answer 25

Alveolar dead space: Alveoli that are ventilation + but perfusion - (no capillary perfusion); ventilated but not perfused alveolus; Trapped volume: Alveoli that are ventilation -- but perfusion +; perfused alveolus but no ventilation; the capillary blood is "trapped."