RCM Week 2 (COPD)

Question 1

What are the 2 types of chemoreceptors

Answer 1

Central chemoreceptors: (CCRs) found on the medulla- sensitive to changes in [H+] and pCO2

Peripheral chemoreceptors (PCRs) found within the aortic arch and carotid arteries - sensitive to changes in arterial pO2 and pH

Question 2

Describe the structure of the central chemoreceptor

Answer 2

Blood vessel is surrounded by BBB (blood brain barrier) which is impermeable to H+ and HCO3- but permeable to CO2
- increase in pCO2 causes CO2 to diffuse out of the blood vessel
H+ ions are formed from the reaction

• increase in [H+] in the ECF and CSF is detected by CCRs and leads to hyperventilation
• hyperventilation decreases pCO2 in the blood and CSF
• decrease in pCO2 = hypoventilation

Question 3

Describe the structure of peripheral chemoreceptors

Answer 3

Found within the aortic arch and carotid arteries

• decreased arterial O2- hyperventilation (stimulated when arterial pO2 falls below 13.3 kPa)
• increased pCO2- not as important as the CCR response
• fall in pH- detected by carotid and not aortic bodies

Question 4

What is respiratory acidosis (due to hypoventilation)

Answer 4

Increase in CO2 which will then have an effect on the pCO2 in arterial blood
- leads to an increase in [H+] and then an acidic environment

This is responded to by the kidneys that excrete excess [H+] in the urine but also increase bicarbonate which acts as a buffer to correct imbalance

Question 5

What is metabolic acidosis

Answer 5

A decrease in the ability of the kidneys to excrete H+ and reabsorb HCO3 (due to uncontrolled diabetes)
So an increase in H+, decrease in pH
This is resolved by hyperventilating to try and decrease the levels of CO2

Question 6

What is metabolic alkalosis

Answer 6

Caused by vomiting or ingesting a base

- increase in bicarbonate ions, decrease in [H+] and increase in pH

Question 7

What is the difference in terms of sensitivity of central chemoreceptors and peripheral chemoreceptors

Answer 7

Central chemoreceptors- are most sensitive to pCO2 changes- levels held to within 0.3 kPa

Peripheral chemoreceptors will detect rapid changes in pCO2 but are comparatively insensitive - levels held to within 1.3 kPa

Question 8

What detects pO2 and why is it important

Answer 8

Peripheral chemoreceptors detect changes in pO2
PO2 levels have a wider control margin but PCRs are stimulated when pO2 levels drop below 13.3 kPa

PO2 levels are controlled to avoid hypoxia

Question 9

What is the purpose of neural regulation of ventilation

Answer 9

Sets the rhythm and pattern of ventilation

Controls the respiratory muscles

Question 10

What is the purpose of chemical regulation of ventilation

Answer 10

Detects central and peripheral arterial pCO2 and pH and peripheral pO2

Question 11

Why is neural regulation faster than chemical regulation

Answer 11

Neural control is dependent on fast acting impulses to and from the CNS.
Chemical control responds to changes in partial pressure of CO2 / O2

Question 12

What is respiratory depression

Answer 12

The rate and / or depth of respiration is insufficient to maintain adequate gas exchange in the lungs
Occurs as a result of effects on the medullary and pons respiratory centres

Some drug side effects eg benzodiazepines, opioids can cause respiratory depression - can be reversed by analeptics eg doxapram hydrochloride

Question 13

What is the role of the dorsal respiratory group (DRG)

Answer 13

Fibres from DRG innervated the diaphragm and external intercostal muscles.

• diaphragm contraction and thoracic cavity expansion causes inspiration
• DRG neurons switch on for 2 seconds and switch off for 3 seconds causing a rhythmic pattern

Question 14

What is the role of the ventral respiratory group (VRG)

Answer 14

Fibres from VRG innervated the abdominal muscles and internal intercostal muscles
- activity enhanced during forced expiration

Question 15

What is the role of the pneumotaxic centre

Answer 15

Transmits signals to the DRG

• role is to limit inspiration
• ‘fine tunes’ breathing - sends inhibitory impulses to the DRG
• limits the period of inspiration to 2 seconds
• prevents over inflation of the lungs

Question 16

What is the role of the apneustic centre

Answer 16

Responsible for prolonged inspiration gasps (apneusis)

• prolongs DRG stimulation
• not clear on involvement in normal human respiration
• apneusis observed in severe brain injury

Question 17

What is the role of the vagus nerve

Answer 17

Sends afferent information from the lungs to the DRG

- role is to prevent over inflation of the lungs by switching off inspiration

Question 18

Summary of the functions of the different elements of the respiratory control system

Answer 18

DRG- inspiration
VRG- forced expiration
Pneumotaxic centre- switch off inspiration
Apneustic centre- prolongs DRG stimulation (inspiration)
Vagus nerve - switch off inspiration

Question 19

What is the role of the cerebral cortex

Answer 19

Stimulates motor neurons of the inspiratory muscles
Bypasses the medullary centres when consciously controlling breathing eg breath holding or changing the depth of breathing

Question 20

What is the role of the hypothalamus

Answer 20

Strong emotions, pain and changes in temperature can alter respiration rate and rhythm
- apnoea : suspension of breathing - can be induced by a germ pain or a decrease in temperature

Tachypnoea: rapid breathing- can be induced by excitation or an increase in temperature

Question 21

What are stretch receptors

Answer 21

Located in smooth muscle of trachea and bronchi

Sensitive to lung expansion

Question 22

What are respiratory reflexes

Answer 22

Juxtapulmonary aka J or C fibre receptors

• lie in alveolar wall between the epithelium and endothelium - close to the pulmonary capillaries
• stimulated by congestion, oedema, histamine
• activation results in apnoea or rapid shallow breathing, bronchoconstirction and mucus secretion

Question 23

What are irritant receptors

Answer 23

Located between epithelial cells

• sensitive to irritant gases, smoke and dust
• activation results in rapid shallow breathing cough, bronchoconstriction, mucus secretion and augmented breaths (gasps)

Question 24

What does stimulation of different respiratory receptors affect

Answer 24

Stimulation of receptors in the bronchioles- airways constrict (asthma)

Stimulation of receptors in the trachea and bronchi - coughing

Stimulation of receptors in the nasal cavity - sneezing

Question 25

What happens during exercise

Answer 25

Increase in pulmonary ventilation rate At rest = 6 l/min During exercise can reach 120 l/min

Question 26

How do you calculate pulmonary ventilation rate

Answer 26

Freq / resp rate x tidal volume

Question 27

What happens in initial stage o exercise ( rapid increase in ventilation )

Answer 27

Attributed to motor centre activity and afferent impulses from proprioceptors of the limbs, joints and muscles Neural control- activates the respiratory centres in the brain

Question 28

What adaptations happen during exercise

Answer 28

- increased blood flow to muscles, increased cardiac output, increased oxygen consumption - decreased pH and increased temp, unloading O2 from blood into muscle

Question 29

Effects of altitude on the body

Answer 29

- hypoxia - reduction in barometric pressure - loss of appetite - changes in mental performance - insomnia

Question 30

Role of peripheral chemoreceptors

Answer 30

Detect acute hypoxia and then try to increase breathing As ventilation increases, PaCO2 falls and cerebrospinal fluid becomes alkaline and system is trapped : Breathe more = die from alkalosis Don’t breathe more = die from hypoxia

Question 31

Adaptations to high altitude

Answer 31

Mild hypoxia = decreased PO2, increased ventilation, decreased PCO2 Decreased PCO2= increased CSF pH (alkaline), increased HCO3- Choroid plexus cells export HCO3- from CSF to correct pH Hypoxic drive is reinstated and ventilation increases further Breathing is controlled around lower PCO2, increased ventilation from hypoxic drive (over a couple of hours) Over a couple of days the alkalinity of blood is corrected by excretion of HCO3- in urine

Question 32

Adaptations to high altitude (chronic exposure)

Answer 32

Oxygen carrying capacity of blood is increased with adaptations like 2,3 DPG and polycythaemia Cardiac output is increased and directed to vital organs Systemic acid-base imbalance is corrected

Question 33

Describe the increase in pressure when scuba diving

Answer 33

Scuba diving increase in pressure At 33 feet (10.1 metres) pressure is exerted by weight from the atmosphere above sea level as well as pressure from the weight of the water so at 33 feet = 2 atm pressure = 200kPa (sea level- 101 kPa)

Question 34

Effects of diving exposure on the body

Answer 34

Gases physiologic at sea level can be harmful at depth Oxygen partial pressure increases at depth- breathing air at a depth of 40m is equivalent to breathing 100% oxygen at seal level (hyperoxia) Nitrogen is insoluble at sea level but soluble at depth - nitrogen narcosis or rupture of the deep during descent - decompression sickness during ascent (excruciating pain)

Question 35

Summary of lung function at depth

Answer 35

Increase in FVC- does the repeated exposure to breathing ‘dense’ gas lead to the training effect on the respiratory muscles - loss of lung function : is this due to continued exposure to increased levels of oxygen and nitrogen leading to hyperoxia and decompression stress Effects on susceptible individuals eg asthma: inconclusive findings with some reporting significant deterioration in spirometry measurements and others reporting no differences

Question 36

What are the causes of breathlessness

Answer 36

Respiratory: - asthma: reversible - COPD - pneumonia - COVID 19 - lung cancer - interstitial lung disease Cardiovascular: - heart failure: pulmonary oedema - pulmonary embolism - AF Others: - functional breathlessness eg due to obesity - anaemia : need for a full blood count

Question 37

What is the significance of different colours of sputum

Answer 37

Colour signifies WBC Green shows an abundance of neutrophils Patient knows what is normal for them eg if they have chronic lung disease and so should monitor any changes but ensure they are not constantly taking antibiotics as green sputum can be normal

Question 38

Causes of a cough

Answer 38

- coryza- a cold - acute bronchitis - tracheitis - a dry rasping and painful cough which is often associated with a viral infection - pneumonia - COPD - asthma : wheezing and breathlessness, often a nocturnal cough (particularly in a child) - drug induced eg ACE inhibitors

Question 39

Any other conditions that have similar symptoms to COPD that would also be considered when diagnosing

Answer 39

Chronic lung disease Heart failure Asthma Fibrosis

Question 40

How relevant is age to making a diagnosis of COPD

Answer 40

Be aware of COPD in patients over the age of 40 presenting with a relevant trigger eg smoking, occupational

Question 41

What is the difference between bronchiectasis and COPD

Answer 41

Bronchiectasis is a pathological situation that develops when the bronchi become like pockets in the lung - less functioning - cilia are damaged so sputum collects in pores in the lungs - higher chance of it becoming infected so patients have to be taught different ways to expel sputum eg going for a walk, postural drainage

Question 42

Alerting symptoms for COPD

Answer 42

- cough >3 weeks - a history of smoking associated with haemoptysis (coughing up blood) - a change in ‘smokers cough’ is a serious alerting symptom

Question 43

Describe the types of wheezes that may be shown on examination

Answer 43

Polyphonic - multiple frequency of sounds - affects the bronchi of all different calibres and can be heard throughout the lung Monophonic - one frequency, one tone - due to a narrowing of one specific bronchi can be due to a foreign body or a cancer

Question 44

What are normal O2 sats for a patient with COPD

Answer 44

Lower than 92% may be considered for oxygen therapy as long as they have stopped smoking

Question 45

For measurements of FVC and FEV1 at what point would you consider the % of the predicted value to be low

Answer 45

In COPD, peak flow is often low but stable unlike asthma where it fluctuates Usually FEV1 below 80%, below 50% is severe and below 30% is very severe

Question 46

Why may a patient have stained fingers

Answer 46

Nicotine staining - smoker

Question 47

What is the difference between emphysema and chronic bronchitis

Answer 47

Emphysema is alveolar destruction- not directly detected on any lung function or chest X-ray it is detected on a CT scan Bronchitis is a physiological diagnosis by nature of productive sputum for more than 3 months in 2 consecutive years - history based diagnosis

Question 48

Causes of COPD in patients that haven’t smoked

Answer 48

Household air pollution- particularly in low income countries where they cook over an open fire Occupation- more exposure to gases/ pollution Air pollution

Question 49

What is eGFR

Answer 49

Estimated glomerular filtration rate | The best test to measure level of kidney function and determine stage of kidney disease

Question 50

What vaccinations would be recommended for a patient with COPD

Answer 50

Influenza on an annual basis One off pneumococcal Covid vaccine when offered

Question 51

Are mucolytics given to every patient with COPD

Answer 51

Are of value to some patients with COPD: the ones that produce thick and tenacious phlegm (sticky, having to pull out) Mucolytics make this more liquidy

Question 52

Is there evidence that e cigarettes can be harmful towards patients

Answer 52

Full of chemicals, not clean, fresh air Likely in the majority to be better than cigarettes in terms of carcinogens Should not be encouraged but could be used to help someone quit smoking - cuts down nicotine and tobacco - would still be encouraged to come off e cigarettes as can cause lung reaction, still contain nicotine and contain chemicals that we don’t know much about

Question 53

What are the cardiovascular adaptations to exercise

Answer 53

Myocardial contractile force Cardiac acceleration Peripheral vasoconstriction Activation of sympathetic nervous system

Question 54

Why do skeletal muscle contract

Answer 54

Compresses blood vessels Blood is translocated from peripheral vessels into heart and lungs Increased cardiac output

Question 55

What happens in acute exposure of inadequate delivery of oxygen to body tissues

Answer 55

Acute hypoxia is detected by peripheral chemoreceptors which try to increase breathing As ventilation increase, PaCO2 falls and cerebrospinal fluid (CSF) becomes alkaline System is trapped because breathe more = die from alkalosis, don’t breathe more = die from hypoxia

Question 56

What happens in chronic exposure to inadequate delivery of oxygen to body tissues

Answer 56

Mild hypoxia Choroid plexus cells export HCO3- from CSF as a pH correction mechanism Hypoxia drive is reinstated and ventilation increases further Hours P breathing is controlled around lower PCO2, ventilation from hypoxic drive Days P alkalinity of blood is corrected by excretion of HCO3- in urine.

Question 57

What is boyles law

Answer 57

P u 1/V Pressure is inversely proportional to volume at a constant temperature

Question 58

What happens in terms or respiration on descent

Answer 58

Body and equipment occupy a smaller volume (compress) Compress air in lungs, gut, sinuses and middle ear Valsalva manoeuvre

Question 59

What happens in terms of respiration on ascent

Answer 59

Body an equipment occupy a larger volume (expand) Expand air in lungs, gut, sinuses and middle ear Release air from buoyancy control device

Question 60

Respiratory consequences of diving - nitrogen

Answer 60

Air = 79% N2 which is poorly soluble at sea level pressure Increased pressure in diving causes more N2 to dissolve in the body Descent: N2 dissolves in Body Nitrogen narcosis Euphoria, drowsiness, weakness, clumsiness, unconsciousness Ascent: already dissolves N2 comes out of solution and forms N2 gas bubbles Decompression sickness Excruciating pain, fatigue

Question 61

Consequences of space flight

Answer 61

Weightlessness is characterised by zero gravity Puffy face and bird legs Acute: motion sickness with nausea and vomiting Chronic: - in blood volume, - in cardiac output, - in red blood cell mass, - in muscle strength Loss of Ca2+ and PO43- from bones

Question 62

What happens on return to earth after space flight

Answer 62

Orthostatic hypotension - cardiovascular system not used to responding to gravity hence dizziness, fainting etc may be experienced Due to the fact that baroreceptor reflexes (maintains blood pressure) are down-regulated due to lack of use in space

Question 63

What are the steps of cheyne- stokes | Occurs in individuals with CNS diseases, head trauma, intracranial pressure, heart failure

Answer 63

1) Over breathing = removal of excess CO2 from pulmonary blood and increased O2 2) takes several seconds for message on change in pulmonary blood to get to the brain and inhibit excess ventilation 3) person is overventilated for the extra few seconds 4) overventilated blood eventually gets to the respiratory centres causing their depression 5) opposite cycle commences resulting in CO2 increase and O2 decrease

Question 64

What is respiratory depression

Answer 64

The rate and / or depth of respiration is insufficient to maintain adequate gas exchange in the lungs - occurs as a result of the effects on the medullary and pons respiratory centres - some drug side effects can cause respiratory depression eg benzodiazepines, opiods) - respiratory depression reversed by analeptics eg doxapram hydrochloride

Question 65

What is the dorsal respiratory group

Answer 65

Fibres from DRG innervate the diaphragm and external intercostal muscles Diaphragm contraction and thoracic cavity expansion causes inspiration DRG neurons switch on for 2s and switch off for 3s causing a rhythmic pattern

Question 66

What is the ventral respiratory group

Answer 66

Fibres from VRG innervate the abdominal muscles and internal intercostal muscles Activity enhanced during forced expiration

Question 67

What is the pneumotaxic center of the respiratory control system

Answer 67

``` Transmits signals to the DRG Role is to limit inspiration Fine tunes breathing - sends inhibitory impulses to the DRG Limit the period of inspiration to 2s Prevents over inflation of the lungs ```

Question 68

What is the apneustic centre of the respiratory control system

Answer 68

Responsible for prolonged inspiratory gasps (apneusis) Prolongs DRG stimulation Not clear on involvement in normal human respiration Apneusis observed in severe brain injury

Question 69

What is the role of the cerebral cortex

Answer 69

- stimulates motor neurons of the inspiratory muscles - bypasses the medullary centres when consciously controlling breathing eg breath holding - limited ability to breath hold- respiratory centres automatically reinitiate breathing when O2 conc in the blood reach critical levels - drowning victims eventually reinstate breathing with the result of water in the lungs

Question 70

What is the role of the hypothalamus

Answer 70

Strong emotions, pain and changes in temperature can alter the respiration rate and rhythm - apnoea (suspension of breathing) can be induced by anger, pain, or decrease in temperature - tachypnoea (rapid breathing) can be induced by excitation, or increase in temperature

Question 71

What are stretch receptors

Answer 71

Located in smooth muscle of trachea and bronchi Sensitive to lung expansion Prevent over inflating of the lungs

Question 72

What are irritant receptors

Answer 72

Located between epithelial cells Sensitive to irritant gases, smoke and dust Activation results in rapid shallow breathing, cough, bronchoconstriction, mucus secretion, augmented breaths

Question 73

What factors influence the rate and depth of breathing

Answer 73

- pulmonary (and non pulmonary) irritant reflexes are stimulated by activation of receptors that repsond to irritants in the lungs eg accumulated mucus, inhaled smoke, dust, lint or noxious fumes - irritant receptors send signals to the respiratory centres via afferent fibres of the vagus nerve - stimulation of receptors in the bronchioles - airways constrict (asthma) - stimulation of receptors in the trachea and bronchi - coughing - stimulation of receptors in the nasal cavity - sneezing

Question 74

What do you need to include when counselling a patient for a drug

Answer 74

``` What the medicine is for When to take How to take Dose Frequency Key side effects What to do if miss a dose How long for treatment ```