Lung Physiology 1

Question 1

what is dead space in alveolar ventilation? what is the anatomic, alveolar and physiological dead space?

Answer 1

volume of air not contributing to ventilation,

In anatomic its 150 mls (in bronchi and trachea)
in alveolar its 25 mls (air in alveoli with no blood supply)
Physiological dead space is 175 mls

Question 2

static lung

Answer 2

resting (unstressed) volume pulled back by elastic properties of chest wall and lung

Question 3

Types of nerves that inervate the lungs?

Answer 3

sensory (sensory receptors assess flow and stretch, C fibres, afferents via vagus nerve)
autonomic sympathetic and parasympathetic

Question 4

ventilation vs perfusion

Answer 4

bulk flow of air in the airways
adequate pulmonary blood supply

Question 5

pressure profiles of RA, RV, PA, LA, LV, Aorta?

Answer 5

Pressure profiles;
RA 5 mmHg
RV 25/0
Pulmonary Artery 25/8
LA 5
LV 120/0
Aorta 120/80

Question 6

how many capliaries per alveolus?

Answer 6

1000, by 25percent way throiugh erythrocyte has picked up oxygen and haemoglobin is saturated

Question 7

What does perfusion of capillaries depend on?

Answer 7

Perfusion of capillaries also depends on;
Pulmonary artery pressure
Pulmonary venous pressure
Alveolar pressure

Question 8

Matching vetilation and perfusion: how do systemic vessels react to oxygen vs CO2?
how do pulmonary vessels react to oxygen vs CO2?

Answer 8

Systemic vessels deliver oxygen to hypoxic tissues: Hypoxia/acidosis/CO2 are vasodilators
Oxygen is a vasoconstrictor

Pulmonary vessels pick up oxygen from oxygenated lung: Oxygen is a vasodilator
Hypoxia/acidosis/CO2 are vasoconstrictors
(hypoxic pulmonary vasoconstriction)- mechanism to divert blood away from areas of lung that cannot oxygenate

Question 9

What does PACO2 mean? What does PaCO2 mean?

Answer 9

Alveolar CO2, arterial CO2

Question 10

what does PiO2 mean?
What does FiO2 mean?

Answer 10

pressure of inspired air, fraction of inspired air

Question 11

what does V’A and V’CO2 mean?

Answer 11

alveolar ventilation and CO2 production

Question 12

What is the formula for PaCO2? normal range for it?
relationship betwreen the two?

Answer 12

PaCO2 = KV’CO2/V’A
4-6 Kpa

arteriorly pressure of CO2 is inversly proportional to alveolar vetilation

Question 13

Three ways of CO2 elimination?

Answer 13

bound to haemoglobin
dissolved in plams
as carbonic acid

Question 14

physiological causes of high CO2?

Answer 14

alveolar ventilation is reduced:
1. reduce minute ventilation
2. increase dead space ventilation by rapid shallow breathing
3. increase dead space by ventilation/perfusion mismatching
OR
4. increased CO2 production

Question 15

Formula for PAO2? pressure of alveolar oxygen

Answer 15

PiO2 – PaCO2/R

R= repiratory quotient which is always assumed 0.8 (carb is 1, fat is 0.7)

Question 16

Causes of low PaO2?

Answer 16

Alveolar hypoventilation
Reduced PiO2
Ventilation/perfusion mismatching (V/Q)
Diffusion abnormality

Question 17

what may cause a right curve shift?

Answer 17

increased acidity
increased 2,3-DPG

Question 18

Alveolar arterial O2 difference?

Answer 18

PAO2 – PaO2 = (approx) 1KPa

Question 19

Normal arterial blood gases values: PaO2, PaCO2, pH, HCO3

Answer 19

PaO2 11-13 KPa
PaCO2 4.7-6.0 KPa
pH 7.35-7.45
HCO3- 22 - 26 mEq/L

Question 20

Acid base control in blood- normal pH and H+ concentration?

Answer 20

pH normally 7.40 (7.36-7.44)
H+ concentration 40nmol/l [34-44 nmol/l]

Question 21

How is pH of blood controlled?

Answer 21

Blood and tissue buffers important
Carbonic acid / bicarbonate buffer in particular

CO2 under predominant respiratory control (rapid)
HCO3- under predominant renal control (less rapid)

The respiratory system is able to compensate for increased carbonic acid production,
but elimination of fixed acids requires a functioning renal system

Question 22

Carbonic acid equilibrium equation?

Answer 22

Carbonic acid equilibrium
CO2 + H2O = H2CO3 = H+ + HCO3

Carbonic anhydrase

Question 23

What is the Hendersons-Hasselbalch equation?

Answer 23

pH=6.1 + log10[[HCO3-]/[0.03*PCO2]]

6.1- is base level, rest depends upon HCO3 and CO2 levels

Question 24

Discuss the 4 main acid base disorders:

Answer 24

respiratory acidosis- increased PaCO2, decreased pH, mild increased HCO3-

Respiratory alkalosis; decreased PaCO2, increased pH, mild decreased HCO3-

Metabolic acidosis; reduced bicarbonate and decreased pH

Metabolic alkalosis; increased bicarbonate and increased pH