Systmes Pathology: Respiratory Failure Flashcards

0
Q

Clinical features of resp failure

A

Signs of resp compensation
Increase sympathetic tone-> tachycardia, hypertension, sweating
End organ hypoxia-> altered mental state, bradycardia, hypertension
Haemoglobin desaturation-> cyanosis
Tachyopnea
Use of accessory muscles
Nasal flaring
Intercostal, suprasternal or supraclavicular recession

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1
Q

Respiratory failure definition

A

Sydrome where one or both gases exchange functions fail
PaO2 < 8kpa type 1
PaCO2 > 6.7kpa type 2
Acute-> happens fast no compensation
Chronic
-type 1-> increased Hb and pulmonary hypertension due to vasoconstriction
-type 2-> metabolic compensation

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2
Q

Resp failure investigations

A
Physical examination
Chest imagine
Atrial blood gas analysis 
Urea and electrolytes
FBC
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3
Q

Resp failure may occur in 3 places

A

1) transfer of O2 across alveolus
2) transport of O2 to tissue
3) removal of CO2 from blood into the alveolus and then into the exhaled breath

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4
Q

Resp failure classification

A

Resp pump failure-> ventilation failure
Lung failure-> oxygenation failure
Hypoxaemic (type 1) hypercapnic (type 2)
Acute or chronic

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5
Q

V/Q mismatch

A

Even in normal lung there isn’t perfect matching of ventilation and perfusion
-> ventilated alveoli not perfused
-> perfused alveoli not ventilated
Low V/Q most common cause of hypoxaemia and hypercapnia -> corrected by 100% O2
As hypoxaemia increases resp rate via resp stimulation-> CO2 not related
High V/Q don’t effect gaseous exchange unless severe

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6
Q

Diffusion problems

A

Physical separation of gas and blood-> scarring in disease

Shortened time of RBCs through capillaries-> emphysema with capillary bed loss

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7
Q

Shunting

A

Persistence of hypoxaemia despite 100% O2
Deoxygenated blood bypasses the ventilated alveoli and mixes with oxygenated blood-> reduce O2
-> pneumonia
-> lung collapse
-> severe pulmonary oedema
Large shunt produces hypercapnia

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8
Q

Type 1 respiratory failure

A

PaO2 < 8 and normal paCO2
Most common
Virtually all acute lung diseases which involve fluid filling or alveolar collapse-> chronic bronchitis, emphysema, pneumonia, pulmonary oedema, pulmonary fibrosis, asthma, pneumothorax, embolism, pneumoconiosis, bronchiastasis, ARDS

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9
Q

Emphysema

A

Permanent dilation of air spaces distal to terminal bronchiole with destruction of their walls in the absence of scarring via protease destruction-> smoking causes elastase release
-> decreased area for gaseous exchange
Breathlessness on slight exertion
Hypoxia
Cyanosis, hypercapnia and cor pulmonale develop late in disease

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10
Q

Chronic bronchitis

A

Hyperplasia of mucous glands in bronchial wall
Smooth muscle hyperplasia
Predispose to secondary bacterial infections-> acute bronchitis and pneumonia

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11
Q

Pneumoconiosis

A

Disease caused by inhalation of non organic mineral dust
-> coal, asbestos, silicosis
Inflammatory reaction and scarring

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12
Q

Extrinsic allergic alveolitis

A

Inhalation of organic ducts with local allergic reaction in lungs
Inflammation leads to fibrosis

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13
Q

Type 2 failure

A

Hypercapnia resp failure
PaCO2 > 6.7
Hypoxaemia common if breathing normal air
Blood pH depends on bicarbonate, which is dependent on duration of hypercapnia
-> chronic bronchitis, emphysema, severe asthma, poisoning, neuropathies, primary muscle disorder, head and spinal chord damage, primary alveolar hypoventilation, obesity hypo ventilation syndrome, pulmonary oedema

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14
Q

Pulmonary hypertension

A

Often present in resp failure
Alveolar hypoxaemia potentiated by hypercapnia-> pulmonary arteriolar constriction
-> chronic also-> Hypertrophy and hyperplasia of pulmonary arterial smooth muscle
-> increased vascular resistance-> increase RV pressure-> RV failure-> enlargement of liver and peripheral oedema -> cor pulmonale

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