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Resp Physiology > Lung Volumes & Capacities > Flashcards

Lung Volumes & Capacities Flashcards

1
Q

Consequence of decreased expansion of lung parenchyma

A

Decreased lung capacity

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2
Q

What do intrinsic lung diseases alter

A

Lung parenchyma

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3
Q

What do extrinsic lung diseases affect

A
  1. Pleura
  2. Chest wall
  3. Neuromuscular apparatus
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4
Q

What does tidal volume vary with

A

Exercise

Posture

Decreases with restrictive diseases

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5
Q

Inspiratory reserve vol

when is it needed

What decreases IRV

Effect of restrictive lung disease on IRV

A
  • 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
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6
Q

Expiratory Reserve Vol

Effect of RLD on ERV

A
  • Max vol of air expired after a tidal volume expiration
  • 1.1 L
  • ERV decreases with RLD
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7
Q

Functional Residual Capacity

Formula

A
  • Vol of air in lungs at the end of normal expiration
  • = 2.3L (40% total lung capacity)
  • FRC = RV + ERV
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8
Q

Consequences of increased ERV

A

Emphysema

Air trapping

Loss of elastic recoil

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9
Q

Consequnce of decreased ERV

A

Increased elastic recoil

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10
Q

Inspiratory capacity

Formula

A
  • Largest vol that can be inspired from resting end expiration
  • = 3.5 L
  • IC = TV + IRV
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11
Q

He dilution method

A

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

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12
Q

Importance of FRC

A
  1. Keeps small airways open
  2. Helps maintain blood PaO2 constant
  3. Dilution of noxious gases (lowest in newborn - prone to noxious toxins)
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13
Q

B.A.E.

3 results of an increase in FRC

A
  1. Emphysema (decreased elastic recoil)
  2. Asthma
  3. Bronchiolar obstruction (air trapping)
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14
Q

3 results of a decrease in FRC

A
  1. Pulmonary fibrosis
  2. kyphoscolosis
  3. increased movement of diaphragm (obesity, painful thoracic abdominal wound)
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15
Q

Vital capacity

formula

A

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

VC = IRV + TV + ERV

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16
Q

What is total lung capacity

A
  • = 5.8 L
  • TLC = VC + RV
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17
Q

Minute respiratory volume

Formula

Value @ rest

Value during exercise

A
  • 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
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18
Q

Forced vital capacity

What is it equal to

A

Vol of air forcefully expired in 6 s after max inspiration

= VC

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19
Q

Forced exp vol 1 second (FEV1)

What is used to characterise lung disease

A

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

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20
Q

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

A

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

21
Q

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

A

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

22
Q

O2 capacity

A

Max amt of O2 that can be bound to Hb

23
Q

How much O2 does 1g of Hb bind to

A

1.39 ml of O2

24
Q

What is normal blood Hb

Hence calculate O2 capacity

A

15g/100ml

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

25
Q

Formula for O2 saturation with Hb

A

O2 combined with Hb/O2 capacity x 100

26
Q

Saturation of arterial blood @ PO2 of 100 mmHg

A

97.5%

27
Q

Saturation of mixed venous blood @ PO2 of 40 mmHg

A

75%

not all O2 used

28
Q

What is the cut off of co-operative binding

A

50 mmHg

29
Q

3 advantages of co-operative binding

A
  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
30
Q

Hb value in:

  1. Polycythaemia
  2. Normal blood
  3. Anaemia
A
  1. 20
  2. 15
  3. 10
31
Q

Effect of pH on O2 demand conc

A

Higher pH => increased affinity (more basic)

Lower pH => decreased affinity (more acidic)

32
Q

Effect of PCO2 on O2 saturation (Bohr effect)

A

High PCO2 decreases O2 saturation

Low PCO2 increases O2 saturation

33
Q

Effect of temperature on O2 saturation

A

COLDER temps INCREASE affinity

WARMER temps DECREASE affinity

34
Q

Effect of exercise on O2 unloading

A
  • Increase in temperature
  • Increase in PCO2
  • Decrease in pH

All pormote O2 unloading due to decreased affinity for O2

35
Q

What is 2,3-DPG

With what condition is there increased 2,3-DPG

A

Glycolytic intermediate that accumulates in uniquely high levels in RBCs

Increased 2,3-DPG is linked with hypoxia

36
Q

Recently, A Cat Arrived Home Purring Constantly

7 conditions that exhibit increased 2,3-DPG

A
  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
37
Q

Tissue hypoxia

A

Abnormally low PO2 in tissues

38
Q

Hypoxic hypoxia

A

Low arterial PO2 - pulmonary diease

39
Q

Anaemic hypoxia

A

Decreased ability to carry O2 - anaemia/CO poisoning

40
Q

Circulatory/stagnant hypoxia

A

Decreased blood flow - shock, local obstruction

41
Q

Histotoxic hypoxia

A

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

42
Q

How is CO2 carried in blood (3)

CO2 and Henry’s Law

A
  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

43
Q

Where is the conversion of H2O and CO2 to H2CO3 SLOW

Where is it RAPID

A

SLOW in plasma

RAPID in RBC due to carbonic anydrase

also cerebrospinal fluid

(dissociation of H2CO3 is fast without enzyme)

44
Q

What is high in RBC (2)

Which compound can diffuse out

What compund replaces the ion diffusing out

A

[HCO3-] and [H+]

HCO3- diffuses out

H+ cannot diffuse out

Cl- diffuses in and replaces HCO3-, maintaining electroneutrality

45
Q

Which is less acidic - Hb or HbO2

therefore which one is a better acceptor of H+

A

Hb is less acidic than HbO2

therefore Hb is a better acceptor of H+

46
Q

What does O2 unloading in peripheral blood help

A

CO2 loading

47
Q

What is the Haldane effect

A

Pulmonary capillaries oxygenation helps unload CO2

48
Q

What are carbamino compounds

A

CO2 combines with terminal amino groups in blood proteins

Reduced Hb can bind more CO2 than HbO2

Resp Physiology (9 decks)

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