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Respiratory System > Session 5 > Flashcards

Session 5 Flashcards

1
Q

Define hypoxia.

A

Deficiency in the amount of oxygen reaching tissues.

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2
Q

Define hypocapnia.

A

Reduced carbon dioxide levels in the blood.

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3
Q

Define hypercapnia.

A

Increased carbon dioxide levels in the blood.

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4
Q

Define hyperventilation.

A

Increase in ventilation without a change in metabolism.

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5
Q

Define hypoventilation.

A

Decrease in ventilation without a change in metabolism.

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6
Q

What does hyperventilation cause?

A

Increase in pO2 and decrease in pCO2.

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7
Q

What does hypoventilation cause?

A

Decrease in pO2 and increase in pCO2.

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8
Q

What happens if pO2 rises without a change in pCO2?

A

pO2 is corrected physiologically which results in a reduction of pCO2, causing hypocapnia.

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9
Q

What is the normal range of values for blood pH?

A

7.35-7.45.

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10
Q

Briefly, what happens if blood pH becomes too low?

A

Enzymes begin to denature.

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11
Q

briefly, what happens if blood pH becomes too high?

A

Free calcium concentration drops causing tetany.

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12
Q

Describe the effect of hypoventilation on plasma pH.

A

Causes increased pCO2; hypercapnia causes reduced plasma pH; respiratory acidosis sets in.

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13
Q

Describe the effect of hyperventilation on plasma pH.

A

Causes decreased pCO2; hypocapnia causes increased plasma pH; respiratory alkalosis.

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14
Q

How are respiratory driven changes in plasma pH compensated?

A

By changing plasma bicarb concentration via the kidneys.

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15
Q

What causes metabolic acidosis?

A

Tissues produce more acid due to increased activity; acid reacts with bicarb in the plasma; [bicarb] decreases so pH falls; metabolic acidosis sets in.

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16
Q

How is metabolic acidosis compensated?

A

By increasing ventilation to reduce pCO2.

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17
Q

What innate barrier can cause metabolic alkalosis?

A

Vomiting as it causes increased plasma [bicarb].

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18
Q

How can metabolic alkalosis be compensated?

A

By decreasing ventilation.

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19
Q

Where are the sensors for respiratory control and what do they detect?

A

Pulmonary receptors detect stretch; joint and muscle receptors detect stretch and tension; central chemoreceptors in the brain medulla detect [H]; peripheral chemoreceptors in the carotid and aortic bodies detect [O2], [CO2] and [H].

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20
Q

Where is the control centre for respiration?

A

In the medulla of the brain.

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21
Q

What can the respiratory control centre affect to allow respiratory control?

A

Diaphragm; external intercostals and accessory muscles for inspiration; internal intercostals and abdominal muscles for expiration.

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22
Q

Which of the chemoreceptors involved i respiratory control are most sensitive to pCO2 changes?

A

Central chemoreceptors in the brain medulla.

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23
Q

Describe briefly how central chemoreceptors work.

A

Located in the brain ECF; respond to changes in CSF pH; CSF pH is controlled by the choroid plexus cells.

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24
Q

How is CSF pH determined?

A

By the ratio of [bicarb] to pCO2; CSF [bicarb] is fixed in the short term as it can’t penetrate the BBB; persisting changes in pH are corrected by the choroid plexus cells which change [bicarb].

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25
Q

Describe how increased plasma pCO2 is detected by central chemoreceptors.

A

Increased plasma pCO2 drives CO2 across the BBB into the CSF; CSF [bicarb] is initially constant so CSF pH falls; chemoreceptors detect the decrease in pH.

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26
Q

What is the function of the choroid plexus?

A

Determines what pCO2 is associated with normal CSF pH so sets the control system to a particular pCO2.

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27
Q

Define hypoxaemic hypoxia.

A

Poor oxygenation in the lungs causing a low pO2 and low O2 sats.

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28
Q

Define anaemic hypoxia.

A

Hypoxia caused by insufficient Hb to carry O2.

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29
Q

What commonly causes anaemic hypoxia?

A

Anaemia or carbon monoxide poisoning.

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30
Q

Define stagnant hypoxia.

A

Hypoxia due to poor perfusion of tissues; may be local or global.

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31
Q

What are common causes of stagnant hypoxia?

A

Shock, peripheral vascular disease, etc.

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32
Q

Define cytotoxic hypoxia.

A

Hypoxia due to tissues being unable to utilise oxygen despite adequate oxygen delivery.

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33
Q

What is the normal range of blood oxygen saturation?

A

94-98%.

34
Q

Below what oxygen saturation is tissue damage likely to occur?

A

Below 90%.

35
Q

Define type 1 respiratory failure.

A

Low arterial pO2 and oxygen saturations but normal or low pCO2.

36
Q

Define type 2 respiratory failure

A

Low arterial pO2 and oxygen saturations with elevated pCO2.

37
Q

What is the underlying mechanism behind type 2 respiratory failure?

A

Failure of ventilation causing insufficient air to be moved in and out of the lungs.

38
Q

What is the underlying mechanism behind type 1 respiratory failure?

A

Either poor diffusion across the alveolar membrane or ventilation-perfusion mismatching.

39
Q

Give some common causes of type 2 respiratory failure.

A

Head injury, trauma, myasthenia gravis, flail rib segment, pneumothorax, PE, upper airway obstruction, severe acute asthma.

40
Q

Give some common causes of chronic type 2 respiratory failure.

A

Myopathy, MND, kyphoscoliosis, lung fibrosis, late stage COPD.

41
Q

What diffusion defects can cause respiratory failure?

A

Lung fibrosis, emphysema, etc.

42
Q

Why does diffusion impairment usually cause type 1 respiratory failure?

A

Oxygen diffusion rate is less than CO2; O2 diffusion is impaired more easily; disease will affect oxygen but not CO2.

43
Q

Why may pCO2 be lowered in type 2 respiratory failure?

A

Hypoxia stimulates peripheral chemoreceptors to increase ventilation so more CO2 will be removed and pCO2 falls.

44
Q

What happens when ventilation perfusion ratio falls below 1?

A

pO2 falls and pCO2 rises; causes type 1 respiratory failure.

45
Q

What causes V/Q mismatching?

A

Reduced ventilation to part of the lungs; reduced perfusion to part of the lungs.

46
Q

How is respiratory failure managed?

A

Cause is treated. Oxygen therapy to improve hypoxia in type 1; type 2 may need ventilation due to hypercapnia.

47
Q

How does hypoxia typically present?

A

Exercise intolerance; tachypnoea (seen as breathlessness); confusion (cerebral hypoxia); cyanosis.

48
Q

What are the effects of chronic hypoxia?

A

Increased oxygen delivery: elevated Hb levels; increased 2-3-BPG levels. Hypoxic vasoconstriction of pulmonary arterioles causing: pulmonary hypertension; right heart failure; cor pulmonale.

49
Q

What usually causes chronic hypercapnia?

A

COPD.

50
Q

How is an increase in Hb levels brought about?

A

Kidneys increase erythropoietin secretion to stimulate erythropoiesis in bones, more RBCs are made so more Hb.

51
Q

Which microbes are commensal in the upper respiratory tract?

A

Viridans streptococci, Neisseria spp., anaerobes, Candida sp.

52
Q

What mechanisms does the respiratory tract have to defend against infection?

A

Muco-ciliary clearance; coughing; sneezing; respiratory mucosal immune system.

53
Q

What usually causes upper respiratory tract infections?

A

Viruses such as rhinovirus or coronavirus, influenza, etc. May also be due to bacteria.

54
Q

Give some examples of URT infections.

A

Rhinitis, pharyngitis, laryngitis, sinusitis, otitis media.

55
Q

Give some examples of LRT infections.

A

Bronchitis, bronchiolitis, bronchiectasis, pneumonia, empyema, lung abcess.

56
Q

What is bronchitis?

A

Inflammation of the medium sized airways (bronchi).

57
Q

What are the common symptoms of acute bronchitis?

A

Cough, fever, more sputum, SOB.

58
Q

What typically causes acute bronchitis?

A

Strep. pneumoniae, H. influenzae, M. catarrhalis.

59
Q

How is acute bronchitis usually treated?

A

Chest physio and antibiotics.

60
Q

What is pneumonia?

A

Inflammation of the lung alveoli due to infection.

61
Q

How do pneumonia sufferers usually present?

A

Fever, cough, pleuritic chest pain, SOB, yellow sputum, malaise, nausea, vomiting.

62
Q

How is pneumonia classified?

A

By clinical setting where it was acquired; presentation (acute/chronic); organism(bacterial, fungal, etc.); lung pathology (lobar, broncho-, interstitial, etc.).

63
Q

What is pneumonitis?

A

Inflammation of the lung alveoli. May be with or without infection.

64
Q

How may pneumonia appear histologically?

A

Fibrin rich exudate, neutrophil infiltration and macrophage infiltration in the affected tissues.

65
Q

What are the risk factors for pneumonia?

A

Pre-existing lung disease, immunocompromisation, travel history, exposure to animals, ventilation.

66
Q

What organisms usually cause community-acquired pneumonia?

A

Strep. pneumoniae, H. influenzae, M. catarrhalis, Staph. aureus, K. pneumoniae. Mainly first 2.

67
Q

What may be found on examination of pneumonia sufferers?

A

Pyrexia, tachycardia, tachypnoea, cyanosis, dullness of percussion, bronchial breathing, auscultative crackles.

68
Q

What investigations should be performed for pneumonia patients?

A

FBC, U&E, CRP, ABG, CXR, sputum sample, blood cultures, BAL fluid sample, nose and throat swabs.

69
Q

How is pneumonia managed?

A

Do CURB-65 score, if 2 ?admit, if 2-5 manage as severe.

70
Q

What factors are taken into account in a CURB-65 score?

A

Confusion, urea conc, resp rate, blood pressure, age (over 65).

71
Q

What is the empiric therapy for CAP pneumonia?

A

Amoxicillin/doxycycline/erythromycin/clarithromycin if mild to moderate illness. Co-amoxiclav and clarithromycin/doxycycline if moderate to severe illness.

72
Q

What complications may result from bacterial pneumonia?

A

Lung abscess, bronchiectasis, empyema.

73
Q

How is Strep. pneumoniae pneumonia treated?

A

Penicillin or amoxicillin.

74
Q

What samples are usually taken in hospital acquired pneumonia and why?

A

Bronchial lavage fluid samples so URT and LRT bacteria can be distinguished.

75
Q

How is hospital acquired pneumonia typically treated?

A

Co-amoxiclav as first line, if fails or in ITU use tazobactam/pipperacilin/meropenem.

76
Q

What is aspiration pneumonia?

A

Pneumonia caused by aspiration of exogenous material or endogenous secretions into the RT.

77
Q

Who is at increased risk of aspiration pneumonia?

A

Patients with neurological dysphagia, epilepsy, alcoholics, drowning victims, nursing home residents, drug overdose patients.

78
Q

How is aspiration pneumonia treated?

A

Co-amoxiclav.

79
Q

What causes aspiration pneumonia?

A

Viridans streptococci and anaerobes in a mixed infection.

80
Q

How is pneumonia prevented?

A

Immunization wit flu vaccine/pneumococcal vaccine, chemoprophylaxis for at risk groups, smoking advice.

Respiratory System (9 decks)

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