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Breathlessness Flashcards

1
Q

Hypoxaemia (hypoxic hypoxia):

A
  • Abnormally low arterial partial pressure of oxygen (PaO2)
  • Associated with clinical signs of central cyanosis
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2
Q

Hypoxia:

A
  • Low tissue partial pressure of oxygen. Either due to a reduced O2 supply or inability to utilise it
  • Hypoxaemia is one, but not the only, cause of hypoxia
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3
Q

Alveolar-arterial (Aa) difference:

A

Aa difference = PAO2 - PaO2
- PA02: calculated using the alveolar gas equation
- PaO2 is measured via blood gas analysis

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4
Q

How to find PAO2 and PaO2:

A
  • PA02: calculated using the alveolar gas equation
  • PaO2 is measured via blood gas analysis
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5
Q

Aa difference: healthy ranges
- Healthy subjects
- Elderly

A
  • 2 KPa
  • 5 KPa
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6
Q

Causes of tissue hypoxia: Hypoxaemia

A
  • Hypoxaemia leads to a decrease in total oxygen content by lowering oxygen saturation (SaO2) and partial pressure of arterial oxygen (PaO2)
  • Total content (C) = (O2 binding capacity X SaO2) + (PaO2X solubility)
  • Rate of O2 delivery = Cardiac output (Q) X O2 content (C)
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7
Q

Causes of tissue hypoxia: stagnant hypoxia

A
  • Cardiac output is insufficient due to cardiac failure at normal filling pressures
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8
Q

Causes of tissue hypoxia: Anaemic hypoxia (2)

A
  • Rate of O2 delivery is reduced by a decrease in O2 content, this is due to a reduction in oxygen binding capacity
  • This reduced O2 binding capacity is caused by a reduction in viable RBCs
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9
Q

Causes of tissue hypoxia: histotoxic hypoxia
- Explanation (2)
- Cause

A
  • Rate of O2 delivery is normal but the tissues are unable to utilise the O2
  • Causes elevated CvO2 and a low arteriovenous difference in blood O2 content
  • Classic cause is cyanide poisoning (also smoke inhalation)
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10
Q

Alveolar ventilation equation:

A
  • PACO2 = PaCO2 § Rate of CO2 production by metabolism / Rate of CO2 removal by AV
  • PACO2 is directly proportionate to CO2 production rate and inversely proportionate to Rate of CO2 removal by AV
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11
Q

Type 2 respiratory failure:

A
  • “Pump failure”: CO2 production rate remains constant, hypoventilation causes hypercapnia (+PaCO2)
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12
Q

Clinical features of type 2 respiratory failure: (4)

A
  • vary according to underlying cause
  • Headache (cerebral vasodilation)
  • Flapping tremor of wrist
  • Bounding pulse
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13
Q

Type 1 respiratory failure:

A
  • When the respiratory system is unable to supply the body with an adequate amount of oxygen
    (lower PaO2)
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14
Q

Heart failure definition: (2)

A
  • An inability of the heart to maintain an adequate perfusion of the tissues (cardiac output) at a normal filling pressure
  • It is not a diagnosis but a syndrome of signs and symptoms caused by a variety of pathological conditions
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15
Q

Pathophysiology of Chronic Left-sided Heart Failure:
- Systolic dysfunction (emptying): (2)

A
  • Impaired emptying due to reduced contractility and/or increased afterload
  • End-systolic volume is increased due to the reduction in stroke volume and ejection fraction
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16
Q

Impaired contractility causes: (3)

A
  • MI or ischaemia
  • Dilated cardiomyopathy
  • Chronic “volume overload” e.g. mitral or aortic regurgitation
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17
Q

Excessive afterload cause: (3)

A
  • Aortic stenosis: narrowing of the aortic valve outlet
  • May result in a slow rising pulse and an ejection systolic murmur in aortic area
  • Systemic hypertension (+TPR)
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18
Q

Physiology of chronic left-sided heart failure:
- Diastolic dysfunction:

A
  • Increased stiffness of the ventricle impairs filling during diastole
  • Fibrosis and hypertrophy of ventricular wall or pericardium constriction
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19
Q

Right-sided heart failure:
- Definition
- Causes

A
  • Right ventricle fails if the afterload is too high
  • Secondary to LVF (commonest), Cor pulmonale, Acute PE, pulmonary stenosis
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20
Q

Cor pulmonale:
- Definition
- Symptoms (6)

A
  • RHF due to hypoxic lung disease (COPD)
  • Central cyanosis, raised JVP, pitting oedema, hepatomegaly, Parasternal heave (RVH), tricuspid regurgitation
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21
Q

Compensatory mechanisms for CHF:
- Increased renal salt …..

A
  • Increased renal salt and water retention leading to
    increased filling pressures (↑JVP) and (hopefully!)
    stroke volume by Frank-Starling mechanism
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22
Q

Compensatory mechanisms for CHF:
- Baroreceptor …..

A
  • Baroreceptor reflex increases sympathetic tone
    increasing heart rate and contractility and producing
    increased peripheral vasoconstriction with a relative
    diversion to the coronary and cerebral circulations
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23
Q

Compensatory mechanisms in CHF:
- Heart

A
  • Ventricular hypertrophy (LVH) and remodelling
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24
Q

What causes the increase in filling pressure?: (3)

A
  • Renin-angiotensin-aldosterone system
    The release of renin is stimulated by
    (1) Reduced renal artery pressure secondary to the fall in cardiac
    output
    (2) Increased renal sympathetic tone (due to baroreceptor reflex)
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25
Detrimental effects of increased filling pressures (4)
* A dilated heart is less efficient at contracting (Law of Laplace) * Widening of the atrioventricular valve orifices leads to regurgitation of blood through the valves * Increased filling pressure of the left ventricle leads to pulmonary oedema and breathlessness * Increased filling pressure of right ventricle leads to peripheral pitting oedema
26
Increased sympathetic tone: friend or foe?
- Probably beneficial in mild failure but in more severe cases the effects can be detrimental
27
Increased sympathetic tone: detrimental effects (3)
1. Venoconstriction raises the filling pressure 2. Vasoconstriction leads to increase in afterload and hence myocardial oxygen consumption 3. Uncoupling and down regulation of beta 1 receptors reduces the positive inotropic effects of sympathetic stimulation
28
Signalling molecules increased in plasma in HF: (3)
- ADH: Promotes water retention by kidney. - Endothelin: Potent vasoconstrictor (future therapeutic target?) - BNP: B-type natriuretic peptide produced by failing myocardium Plasma levels correlate with degree of severity, used as a biomarker
29
Ventricular hypertrophy and remodelling: (2)
- Chronic elevations in wall stress and neuro-humoral factors lead to remodelling - The associated decrease in compliance leads to increased diastolic filling pressures
30
How does cardiac failure produce oedema?: (3)
- Increased venous filling pressure increases capillary pressure - Salt & water retention reduces conc. of proteins in plasma and decreases colloid osmotic pressure in plasma - This increases production of tissue fluid by capillaries by ultrafiltration
31
Heart failure signs: dysponea and orthopnoea
- Dysponea: Abnormal feeling of need to breath due to pulmonary venous congestion - Othopnoea: Breathlessness upon laying flat due to redistribution of blood from lower limbs
32
Heart failure signs: PND and fatigue
- PND: Paroxysmal nocturnal dysponea, wakes patient from sleep. Gradual reabsorption of peripheral oedema fluid when laying flat - Fatigue: reduced perfusion of skeletal muscle
33
Signs of acute LVF: (4)
- Tachypnoea: Due to stimulation of J receptors - Cold hands: Due to increased sympathetic tone - Tachycardia: Due to increased sympathetic tone - Crackles or wheeze: Due to pulmonary oedema
34
Breathlessness investigations: Lungs - Full Blood Count Result Possible diagnosis
- Raised WCC - Possible infection
35
Breathlessness investigations: Lungs - BNP Result Possible diagnosis
- >400pg/mL - Heart failure if over, if under then rule out
36
Breathlessness investigations: Lungs - U & E Result Possible diagnosis
- Increased urea and creatinine - Acute kidney injury which can cause breathlessness via several mechanisms
37
Breathlessness investigations: Lungs - D-dimer Result Possible diagnosis
- Positive - DVT/PE, if negative then rule out
38
Breathlessness investigations: Lungs - ABG Result Possible diagnosis
- Respiratory acidosis/alkalosis - Many, including COPD, severe asthma, panic attack
39
Breathlessness investigations: Lungs - CRP Result Possible diagnosis
- Raised - inflammation, non-specific infection, blood cultures needed
40
Breathlessness investigations: circulation - FBC Result Possible diagnosis
- Decrease in Hb - Anaemia, further tests needed to distinguish the type
41
Breathlessness investigations: circulation - Troponin Result Possible diagnosis
- Positive - Myocardial damage
42
Breathlessness investigations: circulation - Carboxyhaemoglobin Result Possible diagnosis
- Raised - CO poisoning
43
Breathlessness investigations: circulation - Methaemoglobin Result Possible diagnosis
- Raised - Congenital, drugs
44
Breathlessness investigations: circulation - LFTs Result Possible diagnosis
- Deranged - Several
45
Lung cancer causes: (3)
- Smoking 72% - Workplace exposure 13% - Air pollution 8%
46
Lung cancer subtypes: 1. 2. (3)
1. Small cell (15-20%) 2. Non-small cell (80-85%) - Adenocarcinoma - Squamous cell - Large cell
47
Lung cancer: symptoms - Usual - Red flags (3)
- Usually no signs or symptoms in early stages - Persistent cough/chest infection/breathlessness/tiredness - Coughing up blood - Loss of appetite/unexplained weight loss
48
Lung cancer: metastatic tumour effects (4)
- Cervical or supraclavicular lymphadenopathy - Palpable liver edge - Bone pain or pathological fracture - Persistent vomiting, seizures, focal neurology, headaches, confusion
49
lung cancer screening: low dose CT scan - Detection - Shift? - Mortality
- Increases lung cancer detection - With stage shift towards treatable disease - Reduction in lung cancer mortality
50
Upper respiratory tract infections: - Symptoms (4) - Complications - Signs (3)
- Pain, fever, headache, stridor - Quinsy (peri-tonsillar abscess) - Raised temperature, erythema, exudate
51
Lower respiratory tract: - Symptoms (5) - Complications (2) - Signs (5)
- Cough, wheeze, sputum, production, pleuritic chest pain - Empyema, pulmonary cavity - Raised RR and intercostal , muscle movement, wheeze, dull percussion, bronchial breathing
52
Pneumonia and LRTI: - Detection - Difference
- Pneumonia = consolidative change on radiology - LRTI = no consolidative change on CXR - Any pathogen can cause either, all about radiological change - LRTI and pneumonia are a spectrum of disease
53
Streptococcus pneumoniae (pneumococcus): - Prevalence - Structure/variation
- 50-60% community-acquired pneumonia - Gram positive coccus, surrounded by polysaccharide capsule, over 90 serotypes
54
Streptococcus pneumoniae (pneumococcus) - Variation - Infections (7)
- Over 90 serotypes, - Can cause multitude of infections (LRTI/pneumonia, empyema, meningitis, infective endocarditis, abscesses, otis media and externa)
55
Legionella pneumophila: - Description - Incubation - Transmission (4)
- Atypical pneumonia - 2-10 days - Spread by breathing contaminated aerosolised water or soil: AC units, hotels/conferences, care homes, water sprinklers
56
Legionella pneumophila: - Outbreak definition - Symptoms
- 2+ cases where onset is closely linked in time and in space - Hyponatraemia and liver dysfunction
57
Pneymocytsis pneumonia (PCP): - Cause - Effects - Diagnosis
- Caused by fungus - Associated with immunosuppression, high risk of pneumothorax - Diagnosis by PCR on sputum (beta glucan usually posistive)
58
Tuberculosis (TB): - Transmission - Culture - Relevance
- Transmission by droplets - Very difficult to culture in the lab - Notifiable disease of public health importance
59
TB: active infection risk factors (5)
- Young children - Immunocompromised hosts - Prison contact - Recent contact with TB - Country of high incidence
60
TB: latent infection risk factors (4)
- Exposure at some time - Evidence of scars on CXR - Immune response to TB (memory T-cell recognition of TB) - Risk of reactivation in later life
61
TB signs and symptoms: P C L Chest H
Pale Cachexic Lymphadenopathy Chest: dullness to percussion, bronchial breathing, clear - High temperature
62
Is TB vaccine-preventable:
- BCG recommended at birth in areas with high incidence - Protects children from severe forms of TB (TB meningitis)
63
stenotic valve:
- Blood flows backwards through the valve (turbulent flow)
64
Bacteraemia: (3)
- Presence of bacteria in the blood - Detected by blood cultures - Assessment of significance
65
Infective Endocarditis (IE): definition - definition - Clinical presentation - Diagnosis requirements
- Bacterial (or fungal) infection of a heart valve or area of endocardium - Either acute or sub-acute - Constellations of clinical signs and investigations required to make diagnosis
66
IE: Epidemiology - Prevalence - Mortality - Infecting organisms / pre-disposing factors
- <10 per 100,000 population per year - 20% - Have changed over time, rheumatic fever was a risk factor pre-antibiotic era (75%)
67
IE: Rheumatic fever
- Group A Streptococcus - Post-infectious, autoimmune, multi-system disease
68
IE: Epidemiology Risk factors (4) NVIE PVIE P-AE NIE
A. Native valve infective endocarditis B. Prosthetic valve infective endocarditis C. PWID-associated endocarditis D. Nosocomial infective endocarditis
69
A. Native Valve Endocarditis - C - PDH - U - BC
- Cardiac abnormalities - Poor dental hygienes: viridans streptococci - Urinary tract infection: Enterococcus - Bowel cancer: S. gallolyticus
70
B. Prosthetic valve endocarditis: - Cause - Prevalence - Pathogen - Presentation
- Prosthetic valve or cardiac device related - 1-5% of cases, within first 2 months of surgery - Coagulase negative staphylococci - Low virulence pathogens so often sub-acute
71
C. IVDU-associated endocarditis - Age - Features - Pathogen
- Median age 30 (M>F) - Right sided infection more common tricuspid 50%; Aortic 25%; Mitral 20% - Staphylococcus aureus (including MRSA) predominates, can be other organisms
72
D. nosocomial infective endocarditis - Incidence - Age - Causes
- Increasing (>10%) - > 60 years - Often underlying cardiac disease, IV lines, invasive procedures
73
IE pathogenesis: - Immune system
- The immune system is unable to eradicate an organism once located on the endocardium
74
IE pathogenesis: transient bacterium
- Dental related - Procedures in non-sterile sites e.g. urethral catheterisation - Portals of entry for bacterium (wounds, lines) - Source of bacterium often not found
75
IE clinical syndrome: - Common (=/>70%) M P Cm H
- Malaise (95%) - Pyrexia (90%) - Cardiac murmurs (90%) - Haematuria (70%)
76
IE clinical syndrome: - Uncommon (<70%) A CF ON JL SH RS S CE
- Arthraglia (25%) - Cardiac failures (5%) - Oslers node's (15%) - janeway lesions (5%) - Splinter haemorrhages (10%) - Roth spots (5%) - Splenomegaly (40%) - cerebral emboli (20%)

Med Yr2 (12 decks)

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