Lung Volumes & Capacities

Question 1

Consequence of decreased expansion of lung parenchyma

Answer 1

Decreased lung capacity

Question 2

What do intrinsic lung diseases alter

Answer 2

Lung parenchyma

Question 3

What do extrinsic lung diseases affect

Answer 3

1. Pleura
2. Chest wall
3. Neuromuscular apparatus

Question 4

What does tidal volume vary with

Answer 4

Exercise

Posture

Decreases with restrictive diseases

Question 5

Inspiratory reserve vol

when is it needed

What decreases IRV

Effect of restrictive lung disease on IRV

Answer 5

• Max vol of air inspired above tidal vol inspiration
• = 3 L
• Reservoir for when increased ventilation is required
• Increased air intake during exercise
• Increased tidal volume DECREASES IRV
• IRV decreases with restrictive lung disease

Question 6

Expiratory Reserve Vol

Effect of RLD on ERV

Answer 6

• Max vol of air expired after a tidal volume expiration
• 1.1 L
• ERV decreases with RLD

Question 7

Functional Residual Capacity

Formula

Answer 7

• Vol of air in lungs at the end of normal expiration
• = 2.3L (40% total lung capacity)
• FRC = RV + ERV

Question 8

Consequences of increased ERV

Answer 8

Emphysema

Air trapping

Loss of elastic recoil

Question 9

Consequnce of decreased ERV

Answer 9

Increased elastic recoil

Question 10

Inspiratory capacity

Formula

Answer 10

• Largest vol that can be inspired from resting end expiration
• = 3.5 L
• IC = TV + IRV

Question 11

He dilution method

Answer 11

Amount before equilibration = C1 x V1 = amount after

C2 x (V1 + V2)

V2 = V1 (C1 - C2)/C2 = FRC

https://en.wikipedia.org/wiki/Helium_dilution_techniquee

Question 12

Importance of FRC

Answer 12

1. Keeps small airways open
2. Helps maintain blood PaO2 constant
3. Dilution of noxious gases (lowest in newborn - prone to noxious toxins)

Question 13

B.A.E.

3 results of an increase in FRC

Answer 13

1. Emphysema (decreased elastic recoil)
2. Asthma
3. Bronchiolar obstruction (air trapping)

Question 14

3 results of a decrease in FRC

Answer 14

1. Pulmonary fibrosis
2. kyphoscolosis
3. increased movement of diaphragm (obesity, painful thoracic abdominal wound)

Question 15

Vital capacity

formula

Answer 15

Vol change that occurs between maximal inspiration and maximal expiration (4.8 L)

VC = IRV + TV + ERV

Question 16

What is total lung capacity

Answer 16

• = 5.8 L
• TLC = VC + RV

Question 17

Minute respiratory volume

Formula

Value @ rest

Value during exercise

Answer 17

• Volume of air moved into or out of the lung in 1 min
• TV x resp rate
• REST - 500 ml (12 breaths/min) = 6L/min
• EXERCISE - 3-4 L (30 breaths/min) = 90-120L/min

Question 18

Forced vital capacity

What is it equal to

Answer 18

Vol of air forcefully expired in 6 s after max inspiration

= VC

Question 19

Forced exp vol 1 second (FEV1)

What is used to characterise lung disease

Answer 19

Total volume of air that can be exhaled forcefully in 1s from TLC (L)

Majority can be exhaled < 3s in normal people

=> 75-80% of VC in 1st second

FEV1/FVC is used to characterise lung disease

Question 20

Apart from being bound to Hb, how is O2 carried in blood

Answer 20

Dissolved

Obey’s Henry’s Law

Amount dissolved is proportional to the partial P ONLY

1 mmHg PO2 => 0.003 ml O2 dissolves in 100 ml blood

Question 21

Amt of O2 needed to be delivered to tissues vs how much is actually delivered (by dissolution)

Answer 21

15 ml delivered, but resting O2 consumption = 250 ml/min

Question 22

O2 capacity

Answer 22

Max amt of O2 that can be bound to Hb

Question 23

How much O2 does 1g of Hb bind to

Answer 23

1.39 ml of O2

Question 24

What is normal blood Hb

Hence calculate O2 capacity

Answer 24

15g/100ml

=> 15 x 1.39 = 20.8 ml/100ml = O2 CAPACITY

Question 25

Formula for O2 saturation with Hb

Answer 25

O2 combined with Hb/O2 capacity x 100

Question 26

Saturation of arterial blood @ PO2 of 100 mmHg

Answer 26

97.5%

Question 27

Saturation of mixed venous blood @ PO2 of 40 mmHg

Answer 27

75% not all O2 used

Question 28

What is the cut off of co-operative binding

Answer 28

50 mmHg

Question 29

3 advantages of co-operative binding

Answer 29

1. Flat upper portion - alveolar PO2 can drop significantly with little effect on the carriage of O2 2. As RBC takes up O2 along the capillary, a large partial pressure difference for O2 between alveolar gas and capillary blood exists even when most O2 has been transferred 3. Steep lower portion =\> that tissues can withdraw large amts of O2 from blood for small drop in tissue capillary

Question 30

Hb value in: 1. Polycythaemia 2. Normal blood 3. Anaemia

Answer 30

1. 20 2. 15 3. 10

Question 31

Effect of pH on O2 demand conc

Answer 31

Higher pH =\> increased affinity (more basic) Lower pH =\> decreased affinity (more acidic)

Question 32

Effect of PCO2 on O2 saturation (Bohr effect)

Answer 32

High PCO2 decreases O2 saturation Low PCO2 increases O2 saturation

Question 33

Effect of temperature on O2 saturation

Answer 33

COLDER temps INCREASE affinity WARMER temps DECREASE affinity

Question 34

Effect of exercise on O2 unloading

Answer 34

* Increase in temperature * Increase in PCO2 * Decrease in pH All pormote O2 unloading due to decreased affinity for O2

Question 35

What is 2,3-DPG With what condition is there increased 2,3-DPG

Answer 35

Glycolytic intermediate that accumulates in uniquely high levels in RBCs Increased 2,3-DPG is linked with hypoxia

Question 36

# Recently, A Cat Arrived Home Purring Constantly 7 conditions that exhibit increased 2,3-DPG

Answer 36

1. Acclimatisation to high altitudes 2. Chronic lung disease - emphysema 3. Anemia 4. Hyperthyroidism 5. Right to left shunt 6. Congenital heart disease 7. Pulmonary vascular disease

Question 37

Tissue hypoxia

Answer 37

Abnormally low PO2 in tissues

Question 38

Hypoxic hypoxia

Answer 38

Low arterial PO2 - pulmonary diease

Question 39

Anaemic hypoxia

Answer 39

Decreased ability to carry O2 - anaemia/CO poisoning

Question 40

Circulatory/stagnant hypoxia

Answer 40

Decreased blood flow - shock, local obstruction

Question 41

Histotoxic hypoxia

Answer 41

Toxic substance stops tissue using available O2 (cyanide) inhibits Ox Phos =\> inability to generate ATP - energy needed by cancer cells because they're growing so fast - therefore cyanide is a drug used for cancer treatment

Question 42

How is CO2 carried in blood (3) CO2 and Henry's Law

Answer 42

1. Dissolved in plasma - 7% 2. Bicarbonate - 70% 3. Carbamino compounds - 23% CO2 (like O2) obeys Henry's law - however CO2 is 20x more soluble than O2 Conc is directly proportional to PCO2

Question 43

Where is the conversion of H2O and CO2 to H2CO3 SLOW Where is it RAPID

Answer 43

SLOW in plasma RAPID in RBC due to carbonic anydrase also cerebrospinal fluid (dissociation of H2CO3 is fast without enzyme)

Question 44

What is high in RBC (2) Which compound can diffuse out What compund replaces the ion diffusing out

Answer 44

[HCO3-] and [H+] HCO3- diffuses out H+ cannot diffuse out Cl- diffuses in and replaces HCO3-, maintaining electroneutrality

Question 45

Which is less acidic - Hb or HbO2 therefore which one is a better acceptor of H+

Answer 45

Hb is less acidic than HbO2 therefore Hb is a better acceptor of H+

Question 46

What does O2 unloading in peripheral blood help

Answer 46

CO2 loading

Question 47

What is the Haldane effect

Answer 47

Pulmonary capillaries oxygenation helps unload CO2

Question 48

What are carbamino compounds

Answer 48

CO2 combines with terminal amino groups in blood proteins Reduced Hb can bind more CO2 than HbO2