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Respiratory Physiology Flashcards

1
Q

What are the functions of the respiratory system

A

Gas exchanged
Acid base balance
Protect from infection
Communication

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2
Q

What happens in systemic circulation

A

02 rich blood from L side of heart to tissue

CO2 rich blood from tissue taken to R side

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3
Q

What happens in pulmonary circulation

A

C02 rich blood from R rich goes to lungs for gas exchange

Returns O2 rich blood to L side

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4
Q

What is the pulmonary circulation compared to systemic

A

High flow but low pressure as 5l takes same time as it does to go through systemic

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5
Q

How does actual lung tissue get its blood supply

A

From systemic

Part of bronchial circulation

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6
Q

What is the conducting zone of the respiratory system

A

Trachea
Primary bronchi
Bronchioles
Resistance decreases as go down as less molecules and more anatomical dead space

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7
Q

What is the respiratory zone / exchange

A

Alveoli surrounded by pulmonary capillaries

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8
Q

What makes alveoli good for gas exchange

A

Single layer of epithelium

Elastic fibres that stretch when you breath in creating a recoil

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9
Q

What are type 1 alveoli for

A

Gas exchange

Simple sqaumous

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10
Q

What are type 2 alveoli for

A

Producing surfactant - decreased tension, prevent collapse and increase compliance

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11
Q

What are the lungs enveloped in

A

Visceral (outer surface of lungs) and parietal (inner surface of ribs) pleura

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12
Q

What is the space between lungs and thoracic wall called

A

Pleural space

Filled with pleural fluid (30ml) which creates a seal holding lungs to thoracic wall to move with breathing

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13
Q

What content state are the lungs in

A

Wanting to recoil due to inspiration
Elastic recoil pushes chest out when inspire
Creates a negative pressure in the pleural cavity

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14
Q

What are muscles of inspiration

A

Diaphragm = most important
External intercostal

Accessory
Scalene
SCM

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15
Q

What are muscles of expiration

A

Passive at rest
Internal intercostal
Abdominal

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16
Q

What is Boyle’s law

A

Pressure is inversely proportional to volume

As pressure increases volume decreases

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17
Q

What happens in inspiration

A

Diaphragm contracts pushes abdominal cavity down
External intercostal and scalene pull ribs out
Leads to increase in volume of thoracic cavity
Intrapleural pressure decreases
Alveolar pressure becomes < than atmosphere and air drawn in

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18
Q

What happens in passive expiration

A

Muscles relax
Elastic recoil of stretched lungs allow them to recoil back to original volume
Decreased volume so increased P and air drawn out

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19
Q

What happens in forced expiration

A

Contraction of abdominal muscles push thoracic cavity up
Internal intercostal pull ribs in
Alveolar pressure increases pushing air out
Reduces duration of breathing cycle

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20
Q

What happens in forced inspiration

A

Similar to normal
Requires accessory muscles
SCM, scalene, pec majro and minor, lattismus dorsi, serratura anterior

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21
Q

What is the alveolar pressure

A

Pressure inside thoracic cavity

Equal to atmosphere

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22
Q

What is intrapleural pressure

A

Pressur inside pleural cavity

Always -ve due to state of wanting to recoil

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23
Q

What is transpulmonary pressure

A 
Difference between alveolar and intrapleural
Always +ve
Opposes elastic recoil
Dpeendent on volume of lung
Larger lung = larger pressure
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24
Q

What happens between breaths at the end of an unforced expiration

A

No air I flowing
Lungs stretched and attempting to recoil
Chest wall attempting to move out
Creates sub atmospheric intrapleural pressure
Transpulmonary pressure opposes this recoil

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25
What part of brains is involved in subconscious ventilation
Pons | Medulla
26
What nerves
``` Phrenic = diaphragm Intercostal = external intercostal ```
27
What part of medulla set breathing pattern
DRG - control muscles of inspiration through phrenic and intercostal, receive sensory from vagus VRG - control muscles of larynx / pharynx PRG - receive sensory info from DRG, speak with higher brain to initiate and terminate inspiration
28
How do you change respiratory drive
``` Emotion via limbic Voluntary Mechano-sensory Swalloing inhibits Drugs Chemical composition detected by chemoreceptors ```
29
What is the primary stimulus for changes in ventilation
CO2 Detected by central chemoreceptors in medulla More sensitive to small changes in PCo2
30
How do central chemoreceptors work
Detect changes in H+ in CSF which are related to CO2
31
What happens when there is an increase in CO2
Rate and depth of breathing increases to remove CO2
32
Where are peripheral receptors located
Carotid and aortic bodies
33
What do peripheral receptors detect
Change in arterial Po2 NOT CONTENT | Relatively insensitive and require a significant fall in Po2 or rise in H
34
Can you override peripheral
``` No Effects are instantaneous Increased RR and TV Blood flow directed to kidney and brain INceased CO ```
35
When are peripheral chemoreceptor important
If chronic elevation of PCO2 Central response is blunted Patients go into hypoxic drive and rely on peripheral receptors to detect O2 falling
36
Why do you have to be careful in patients who rely on peripheral
Careful when giving O2 to patients with chronic lung disease e.g. COPD They will have elevated PCO2 Rely only on O2 levels for their breathing
37
What does hypoventilation cause
Increased CO2 Blood = acidic COPD / neuro / chest wall
38
What does hyperventilation cause
Decreased CO2 and alkaline blood Decreases free Ca = paraesthesia / cramps Anxiety / HF / PE
39
What drugs affect ventilation
Opiods / barbiturates = depress Anasthetic = increase RR but decrease TV NO = blunts peripheral chemo so if chronic lung = no way to control ventilation
40
What happens at altitude
Peripheral detect fall in O2 = hyperventilation Resulting hypocapnia and alkalosis stop any increase in RR due to central chemoreceptors After a few days kidney works to remove alkalosis so peripheral takes over again Rise in DPG Polycythaemia - physiological as erythropoietin produced from kidney but can cause hypervisocotyi
41
If an anaemic patient has o2 content 1/2 normal what happens to RR + depth
No change Receptors respond to partial pressure Amount of O2 in plasma is normal but just decreased RBC to hold O2 so content reduced Haem saturation will be the same
42
What is more uncomfortable 1- a high PCo2 and low Po2 2- a low o2 and no CO2
1 | PACO2 increased and impairs the gradient so will stay in blood
43
What is the pressure of O2 and CO2 in artery PA
``` O2 = 100 CO2 = 40 ```
44
What is the pressure of O2 and CO2 in alveoli Pa
``` O2 = 100 CO2 = 40 ```
45
What is the pressure of O2 and CO2 in venous Pv
``` O2 = 40 CO2 = 46 ```
46
What is the difference between partial pressure and o2 content
``` Content = all 02 in solution Partial = solubility ```
47
How does gas exchange work
Gas moves across permeable membrane down pressure gradient until equilibrium reached
48
What is the rate of diffusion affected by
``` Directly proportional to gradient Solubility - more soluble = faster SA - larger = faster (alveoli destroyed in emphysema so decreased SA) Distance - smaller = faster Molecular weight - smaller = faster ```
49
What diffuses faster CO2 or O2
CO2 | Although O2 is smaller but CO2 is much more soluble
50
Once O2 is in the blood what happens
Binds to haemoglobin = oxyhaemoglobin Only 3ml O2 dissolves per L plasma so Hg greater increases capacity of O2 Hg = high affinity for O2 so will pull until saturated
51
Does exercise affect gas exchange
No as only takes 0.25s
52
What type of molecules does haemoglobin bind
``` 92% = HbA (2 alpha and 2 beta) 8%. = HbF (gamma chains replace beta) ```
53
What determines degree of saturation
Partial pressure of O2
54
When does partial pressure of O2 begin to affect saturation
Almost 100% saturated at normal PaO2 100mHg 90% if PaO2 60 When PaO2 = 40 very difficult to saturate Hg and deliver O2 to cell
55
If two individuals with partial pressure of 100 and 80 who has most O2
No diff in saturation | Individual with most haemoglobin
56
``` What are variables in oxyhemoglobin dissociation curve Acidic PCO2 Hyperventilation Asthma Temp DPG ```
More acidic = more Co2 and less O2 and curve shifts to right (less saturated) Increase pCo2 = shifts to R Voluntary hyperventilation = shifts to the L Asthma = shifts to R as constricted so decreased ventilation Temp = shifts to R as want oxygen available for exercise DPG added = shifts to R as produced when No o2 so want o2 to be available
57
What type of haem molecules have highest affinity for oxygen
Myoglobin - as muscles need most Fetal - 2nd most as want to extract from maternal vblood HbA has least affinity
58
Can you have a low partial pressure and normal O2 content
No Partial pressure is what pushes O2 onto haemoglobin If o2 content low but partial pressure normal then haemoglobin would still be saturated
59
What happens in anaemia
Partial pressure is normal O2 content reduced as not enough RBC to carry O2 Ventilatory drive is normal as PaO2 is normal
60
What happens in CO poisoning
CO binds to haemoglobin | Affinity much greater than O2 and dissociates more slowly
61
What are the symptoms of CO poisoning
``` Hypoxia Anaemia Headache Cherry red skin Nausea RR unaffected as PCo2 is normal ```
62
How is Co2 transported in the blood
Only 7% dissolves in plasma 93% diffuse into RBC Converted to H2CO3 with H20 -> HCO3 + H Products removed to keep reaction going
63
What enzyme catalyses
Carbonic anhydrase
64
What are products exchanged for
HCO3 for Cl = chloride shift H binds to deoxyhaemoglobin to bufer If CO2 increases not enough Hg = acidosis
65
How does CO2 go back to alveoli
``` Pco2 alveoli < venous blood CO2 diffuses out of RBC Disturbes Co2-HCO3 H leaves Hg CL shift reverses Co2 diffuses into alveoli ```
66
What needs to be matched adequately
Ventilation Perfusion Usually both 5l/ minute Ideally ratio would be 1
67
What affects ventilation / perfusion
Disruption of blood flow - influenced by Pa (hydrostatic) and PA (alveolar) Resistance
68
What happens as you move from the apex to base of the lung
Ventilation and perfusion rise Perfusion increases at a greater rate Pleural pressure greater at base = more compliant and greater ventilation Hydrostatic pressure is decreased at apex = decreased blood flow and perfusion
69
What happens at the base of the lung
``` Blood flow high as Pa is higher Pa > PA Low resistance Blood flow > ventilation V/Q = 0.8 ```
70
What happens at the apex of the lung
``` Blood flow low as Pa < PA Alveoli compressed and more compliant Higher resistance Ventilation > blood flow V/Q = 3.3 ```
71
What happens when perfusion > ventilation | V/Q <1
Po2 falls in the alveoli and Pco2 will rise Less O2 in alveoli than is being pulled out Decrease in partial pressure of O2 Increase in partial pressure CO2 Lose gradient so can't get ri dog CO2 in blood Shunt form as blood goes from R-L without getting O2
72
What could cause V/Q <1
``` Low O2 in air Poor alveolar ventilation as decreased compliance Increased resistance Drug overdose COPD / asthma / pneumonia / IRDS ```
73
What happens to deal with this
Hyperventilation Blood vessels in lung constrict Mild bronchial relaxation Causes hypoxia as reduced ventilation, CO2 can still get out as rest of lung takes over so no hypercapnia = type 1
74
What happens when ventilation > perfusion | V/Q >1
Increase in alveolar O2
75
What causes V/Q >1
Blood clot / PE
76
What happens to deal with this
Pulmonary vasodilatation to well perfused areas so V/Q in this is <1 Bronchial constriction if decrease in PCo2
77
What is type 1 respiratory failure
PaO2 <8kPa PaCO2 normal or low Problem is with diffusion or exchange so cannot oxygenate haemoglobin Unaffected part of lung will keep CO2 out
78
What is type 2 respiratory failure
PaCO2 >6.5kPA Respiratory mechanism fails Not usually primary
79
What is hypoxia
Insufficient O2 supply
80
What is hyperaemia
O2 arterial supply low
81
What causes hypoxaemia in type 1
V/Q mismatch = most common and responds well to increase FIO2 Shunt = no ventilation so respond poorly to FIo2 Alveolar hypoventilation due to reduced res drive - will respond to increase in FIo2 Diffusion impairment if loss of alveoli

Respiratory (14 decks)

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