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B2 > Pathophysiology of Resp Failure > Flashcards

Pathophysiology of Resp Failure Flashcards

1
Q

What are 3 significant areas that contribute to asthma?

A

Genetic factors
Environmental factors
Acute triggers

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2
Q

Name obstructive airway diseases

A 
COPD
Asthma (extrinsic or intrinsic)
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3
Q

Explain obstructive airway disease

A

Narrowing of the airways leading to shortness of breath as it is hard to exhale;; usually high amount of air left in airways

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4
Q

What is COPD?

A

Umbrella term for chronic obstructive airway changes (usually irreversible)

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5
Q

What is extrinsic asthma?

A

The result of inappropriate adaptive immunity response to inhaled antigen, more common in children

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6
Q

What is intrinsic asthma?

A

No personal history of asthma, usually acquired in middle age from upper respiratory tract infection

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7
Q

What’s the pathophysiology of asthma?

A

Accumulation of mucus in bronchial lumen due to increased goblet cells and submucosal gland hypertrophy
Chronic inflammation -> eosinophils, neutrophils and macrophage recruitment
Thickened basement membrane, hypertrophy and hyperplasia of smooth muscle cells

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8
Q

What’s the sensitisation phase of asthma? And the effector phase?

A

Allergen binds to DC, presents itself to Th2 and B-cells to secrete IgE

Effector phase: IgE binds to mast cell to release bronchoconstrictors (histamine) for acute asthma or in chronic asthma activates eosinophils

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9
Q

Outline the three different phases of asthma pathogenesis

A

Early - allergen causes IgE release -> mast cells secrete histamine -> smooth muscle constriction

Late - inflammatory mediator infiltration to leaky epithelium, neutrophils and eosinophils recruited, mucous production

Chronic (remodelling): smooth muscle hypertrophy and hyperplasia, epithelial damage and basement membrane thickening

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10
Q

Asthma signs during exacerbation? Why is it important to understand?

A

Inability to say complete sentence, tachypnoea, tachycardia, wheeze.
Exacerbation ie acute asthma attack then airways will recover to normal. Diagnosis can be trial of treatment as patient will present well in absence of allergen.

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11
Q

Types of COPD?

A

Emphysema - enlargement of airway spaces, alveolar wall destruction and smaller airways

Chronic bronchitis - larger airways: mucous gland hypertrophy and hyperplasia and hypersecretion of mucous

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12
Q

Define respiratory failure using physiological outcome and gas tensions

A

Type 1: hypoxaemia when PaO2 <8 kPa due to reduced diffusion

Type 2: hypercapnia when PaCO2 >6.7 kPa due to reduced alveolar ventilation

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13
Q

Explain the Oxygen cascade

A

Declining O2 tension from atmosphere to mitochondria.
Shouldn’t be much of a difference in PO2 between alveoli and arterial blood. Any change will be due to diffusion/V/Q mismatch/shunt.

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14
Q

Define ventilation and perfusion and the relationship between the two.

A 
V = amount of gas exchanged through the lungs per minute.
Q = amount of blood flow through the lungs per minute.
V/Q = ideally matched so all O2 is inhaled and all CO2 is exhaled
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15
Q

What sites may cause hypoventilation?

What’s the effect of hypoventilation on V/Q?

A

Brainstem, spinal cord, nerve root, nerve, airway, pleura, lung, chest wall

Alveolus perfused but not ventilated (shunt) so V/Q = 0

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16
Q

What’s the pathophysiology of hypoxaemia?

A

Low FiO2 = hypoventilation = V/Q mismatch = diffusion abnormality.
Shunting = V/Q = 0 and no improvement with 100% O2
Low V/Q <1 = improvement with 100% O2

17
Q

Causes of pulmonary shunting?

Effect of unilateral shunt?

A

Pneumonia, pulmonary oedema, lung collapse, pulmonary haemorrhage

Local vasoconstriction in hypoxia so SaO2 increases as blood is directed to prevent abnormal diffusion and aims to match V/Q

18
Q

Causes of hypoxaemia?

A

Hypoventilation, ventilation without perfusion (dead space), diffusion abnormality, perfusion without shunting, low FiO2

19
Q

Signs/Symptoms of respiratory monitoring in hypoxaemia and how do you measure SaO2?

A 
RR > 30 bpm (<8 in later stages)
Difficulty completing sentences 
Agitated, confused, comatosed
Cyanosed or SpO2 <90%
Deteriorating despite therapy
20
Q

What are 5 clinical signs of respiratory failure?

A 
Tissue hypoxia
Hypercapnia
Haemoglobin desaturation
Sympathetic stimulation
Respiratory compensation
21
Q

What are sources of error on pulse oximetry?

A 
Poor peripheral perfusion
Poorly adherent/positioned probe
Nail varnish/false nails
Lipaemia
Bright ambient light
Excessive motion
Cold
At <85% SaO2, most oximeters are less accurate
22
Q

How can you test haemoglobin desaturation?

A

Pulse oximetry

23
Q

What are signs of hypercapnoea?

A

Flapping tremor
Respiratory acidosis
Confusion/coma
Sympathetic stimulation

24
Q

How can you tell if someone is in respiratory compensation?

A

Tachypnoea
Use of accessory muscles
Nasal flaring
Splinting of accessory muscles

25
Q

What are some triggers of asthma?

A 
Environmental allergens (mould, dust, grass, pollen)
Viral infections (rhinovirus, RSV)
Cold air
Emotion
Irritant vapours and fumes (cigarette smoke, perfume)
Drugs (NSAIDs, beta-blockers)
Atmospheric pollution
Exercise
Occupational sensitisers
26
Q

What’s the triad of pathophysiological features in asthma?

A

Airway obstruction (reversible)
Airway hyper-responsiveness
Airway inflammation

27
Q

How is asthma diagnosed?

A

Clinical presentation: Hx, symptoms: cough, wheeze, chest tightness, worse at night, associated with allergy

Trial treatment
Peak flow diary
Reversibility on spirometry with Salbutamol

28
Q

What are the reversible and irreversible causes of airflow obstruction in COPD?

A

Reversible: accumulation of inflammatory cells, mucous and plasma exudate in bronchi, smooth muscle contraction in peripheral airways, dynamic hyperinflation during exercise

Irreversible: fibrosis and narrowing of the airways, loss of elastic recoil due to alveolar destruction, destruction of alveolar support that maintains patency of small airways

29
Q

What are clinical features of COPD?

A 
Productive cough - sputum
Wheeze
Breathlessness - dyspnoea
Frequent infective exacerbations with purulent sputum
Signs of respiratory failure
30
Q

How is COPD diagnosed?

A

Spirometry: reduced FEV1:FVC ratio
CXR may show hyperinflation
Hb may be raised in chronic hypoxia

B2 (21 decks)

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