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eBMS2031 > RESPIRATORY SYSTEM > Flashcards

RESPIRATORY SYSTEM Flashcards

1
Q

Within the intrapleural space, the pressure is…

A

negative

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2
Q

Outline the mechanics of inspiration

A

Diaphragm and intercostal muscles contract

chest moves out and upwards

volume of thoracic cavity and lungs increases, intrapulmonary pressure decreases

gas moves from atmosphere into lungs

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3
Q

Outline the mechanics of expiration

A

pressure inside lungs = Patm, muscles relax

volume of chest decreases, intrapulmonary pressure increases

air moves out of lungs

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4
Q

What is spirometry

A

measures patients volume of air they can inspire and expire.

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5
Q

How does a spirometer work

A

Patient breaths into mouthpiece connected to computer which records volume and flow rate changes

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6
Q

What are

TV

VC

A

TV (or VT) is tidal volume, the normal amount of air inhaled or exhaled in a
normal breath

VC is the vital capacity, the volume of air inhaled when a maximum breathe is taken, reflects compliance of chest and lungs

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7
Q

Is VC the same in all people

A

no as it is related to the size of the thorax

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8
Q

What is RV

A

residual volume, the volume left in the lungs are exhalation

Cannot be measured by spirometry alone

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9
Q

How does lung parenchymal tissue effect compliance

A

Collagen fibrils in parenchyma stretch and thus the alveoli expand.

more collagen = less compliance

more fibroblasts in interstitium = thickened area = harder to stretch = less compliance

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10
Q

What are the factors effecting compliance

A

compliance of lung parenchymal tissue

surface tension in the alveoli

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11
Q

How does surface tension of the alveoli affect compliance

A

Less pressure is required to fill fluid filled sacs.

Surface tension accounts for 2/3s of lung compliance and elastic forces only 1/3

Surface tension overcome by surfactant

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12
Q

What is the composition of the surfactant in the alveoli

A

mixture of phospholipids, proteins & Ca++

reduces surface tension by 7- 40%

Secreted by type II alveolar cells

production starts at 6-7th month of gestation

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13
Q

What is poiseiulles law

A

resistance = (constant x length) / (radius^4)

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14
Q

How does airway radius and length affect airflow

A

As a decrease in radius would increase resistance, this would decrease flow

As an decrease in length would decrease resistance, this would increase flow

poiseiulles law

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15
Q

basic calculation of flow

A

change in pressure / resistance

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16
Q

What is bronchomotor tone

A

the tone of smooth muscle around the bronchi and bronchioles maintained by vagal efferent nerves

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17
Q

How does spirometry measure air flow rate

A

patient is asked to do their maximum inspiration and exhalation as fast as they can

FVC and FEV1 calculated

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18
Q

What are

FVC

FEV1

A

FVC is forced vital capacity, the total air capacity of lungs, volume of exhaled air when inhalation and exhalation is forceful

FEV1 is the forced expiratory volume after 1 second, the amount of air expired forcefully after 1 second

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19
Q

What % FEV1/FVC symbolises a healthy respiratory system

A

> 75%

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20
Q

How would a COPD of obstructive defect affect % FEV1/FVC

A

Collapsed or narrowed airways

slower air flow therefore smaller FEV1 and normal FVC

= decreased %

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21
Q

How would a restrictive defect affect % FEV1/FVC

A

Decrease in both FEV1 and FVC

= normal %

thus, not an issue with airways and flow but a problem with lung compliance and inspiring volume

22
Q

What is ficks law

A

Diffusion = (A/T) x D x (P1 -P2)

A = area of lungs available for diffusion

T = thickness of alveoli membrane

D = diffusion constant, solubility of gas

P1 - P2 = partial pressure gases on either side of membrane

Other factor: matching of ventilation and perfusion

23
Q

What are the values of the pressure gradient of oxygen at the membrane

A

100mmHg to 40

oxygen travels into blood

24
Q

What are the values of the pressure gradient of carbon dioxide at the membrane

A

40mmHg to 46

carbon dioxide travels out of blood

25
Q

what is barometric pressure

A

another name of atmospheric pressure

26
Q

What is daltons law

A

partial pressure is proportional to % of the gas in the mixture

27
Q

What is henrys law

A

amount of gas in solution depends on atmospheric pressure

partial pressure in solution will reflect partial pressure in air by diffusion

28
Q

What factors of the alveolar membrane affect diffusion

A

Thickness

Area

29
Q

Explain how thickness affects diffusion at the alveolar membrane

A

thin membranes = small distance for gas to travel = more efficient exchange to RBCs

Fibrosis and edema will increase thickness of membrane and therefore reduce diffusion

30
Q

Explain how area affects diffusion at the alveolar membrane

A

More area = more diffusion

31
Q

Explain how emphysema affects area of alveoli

A

reduces area available for diffusion

alveoli collapse and are non-functional

32
Q

How do we measure gas diffusion

A

we use an oximeter which calculates %Hb bound to oxygen

Also could do a DLCO or TLCO test

33
Q

What %Hb should be bound to oxygen for a healthy individual

A

90%

34
Q

Explain how a DLCO/TLCO test works

A

diffusion/transfer in lungs CO

Patient breaths in small amount of CO and He from a small bag and the amount taken up is measured

35
Q

Why do we use CO and He in a DLCO test

A

CO: easily diffuses, not normally present in plasma therefore good for measurement

He: does not cross alveolar membrane, remains in lungs so used to measure lung volume

36
Q

What is ventilation perfusion matching

A

measures the amount of ventilation compared to the blood available to take on the new oxygen

37
Q

What values of V/Q ratio represent

A

= 0.8: normal

< 0.8: shunting - reduced ventilation

> 0.8: dead space - reduced perfusion

38
Q

What is a V/Q lung scan

A

patient breathes in radioactive isotope and blood injected with tracer

ventilation part looks at if it reaches all parts of the lung

perfusion part looks at how well blood circulates within the lungs

39
Q

What local mechanism can have effects on V/Q ratio

A

If pressure of oxygen is low in specific alveoli capillaries, the blood flow is directed to better alveoli

If pressure of CO2 increases, this causes bronchodilation

40
Q

At 100mmHg, how much oxygen does a litre of blood contain

A

200 ml

41
Q

what are the 2 ways oxygen can be transported

A

dissolved in plasma and erythrocyte cytoplasm

reversibly bound to Hb

42
Q

What is the ICU point

A

point of Hb-O2 dissociation curve that is considered the lowest acceptable pO2 in an ICU patient

this is usually a pO2 of 60mmHg and %Hb saturation of about 90%

43
Q

What is the Bohr effect and what factors cause it

A

shifting of the curve to the right (less oxygen bound, offloaded more easily)

decrease pH (more acidic)

increased pCO2

increased temperature

increased 2,3-DPG (product of metabolism by RBC)

These all happen in exercise, meaning more O2 will be offloaded into the muscles where it is needed

44
Q

What are the 3 ways CO2 can be transported

A

dissolved in blood (7%)

bound to Hb (23%)

dissolved as HCO3 (70%)

45
Q

Discuss CO2 transformation to HCO3

A

HCO3 produced in RBC

Moves out of RBC while Cl moves in to maintain electroneutrality (chloride shift)

When leaving the body, these reactions reverse

46
Q

What are the 2 ways ventilation is controlled

A

neural control by the brain (automatic rhythm and modulation)

chemical control by O2 and CO2 and chemoreceptors (modulation of rhythm)

47
Q

Outline neural control of ventilation

A

Peripheral chemoreceptors, lung and chest mechano- and irritant- receptors, muscle and joints input to:

vagus and glossopharyngeal nerves which input to:

respiratory centre in medulla

48
Q

Outline the respiratory centres role in ventilation

A

VRG sets up breathing rate pattern and DRG modulates it.

49
Q

How does the VRG set up breathing pattern

A

Pre-Botzinger complex in VRG sends signals to diaphragm and intercostal muscles for inspiration.

The apneustic centre stimulates the ramping up of the PB complex

The pneumotaxic centre shuts off signal

50
Q

Outline chemical control of ventilation

A

central receptors in medulla monitor and are activated by CO2 via H+. Increased H+ increases respiration

peripheral receptors in carotid bodies and aortic arch monitors and are activated by O2, CO2 and H+. afferents project to DRG. Decreased pO2, increased H+ and pCO2 increase respiration.

51
Q

How do peripheral and central chemoreceptors differ

A

arterial pCO2 causes steeper gradient of increased ventilation compared to plasma H+.

But, central are responsible for 80% of response but are slower to act. peripheral act faster but only result in 20% of response.

eBMS2031 (6 decks)

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