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Respiratory > Session 5 > Flashcards

Session 5 Flashcards

1
Q

Give the normal ranges for pCO2, pO2, [bicarbonate] and pH

A

pCO2: 4.2-6.0 kPa
pO2: 9.8-14.2 kPa
[bicarbonate]: 21-29 mmol/L
pH: 7.35-7.45

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2
Q

What is hyperventilation?

A

Ventilation increase without change in metabolism. Hypoventilation is the opposite.

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3
Q

What to central chemoreceptors respond to?

A

CSF pH, which is affected by pCO2 since only CO2 can cross the blood-brain barrier (not H+ or HCO2-).

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4
Q

What controls the CSF [HCO3-]?

A

Choroid plexus cells (that produce CSF)

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5
Q

What determines CSF pH?

A
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6
Q

What sets the control system to a particular pH?

A

CSF [HCO3-] determines which pCO2 is associated with normal CSF pH.
Persisting changes in pH are corrected by choroid plexus cells which change CSF HCO3. It then resets to operate around a different pCO2.

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7
Q

Where are receptors sensitive to O2 located?

A

In the carotid bodies and aortic bodies (peripheral)

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8
Q

What drives normal breathing and when does this change?

A

CO2. In patients with chronic hypoxia and hypercapnia (e.g. COPD) pO2 is most important as they are unresponsive to CO2. Respiration now driven by hypoxia via peripheral chemoreceptors.

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9
Q

What is hypoxia?

A

Oxygen deficiency at tissue level

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10
Q

Outline the different types of hypoxia

A

Hypoxaemic/respiratory - poor oxygenation in the lungs. Low pO2 and O2 saturation.
Anaemic - normal pO2 but insufficient Hb to carry O2. Anaemia or CO poisoning.
Circulatory - reduced perfusion to tissues. Could be global (shock) or local (peripheral vascular disease).
Cytotoxic - tissue unable to utilise O2. E.g. Cyanide

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11
Q

What are the two types of respiratory failure and their causes?

A

Type 1 - characterised by a low pO2 with a normal or low pCO2, caused by poor diffusion across alveolar membrane or mismatching of ventilation and perfusion.
Type 2 - characterised by a low pO2 and a high pCO2, caused by hypoventilation.

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12
Q

What are the causes of hypoventilation?

A

Hard to ventilate lungs - fibrosis, severe asthma or acute exacerbation of COPD (commonest cause)
Respiratory centre depression - head injury, drug OD
Nerve damage anywhere between brainstem and NMJ leading to respiratory muscle weakness
Chest wall problems - kyphosis/scoliosis, flail segment

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13
Q

How are acute and chronic type 2 respiratory failure managed?

A

Acute - usually needs assisted ventilation
Chronic - allows time for compensatory mechanisms to develop, allowing hypoxia and hypercapnia to be tolerated (reset central chemoreceptors)

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14
Q

What changes occur in the body sure to chronic hypoxia?

A

Polycythaemia (increased [Hb]) due to increased erythropoietin, increase in 2-3BPG and hypoxic vasoconstriction of pulmonary arterioles (can lead to cor pulmonale)

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15
Q

What is a potential complication following O2 therapy to a patient with type 2 hypoventilation?

A

Corrects hypoxia and the stimulus remains for respiration (hypoxic drive) leading to respiratory depression. 24% O2 should be given and patients regularly monitored.

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16
Q

What are the causes of poor diffusion across the alveolar membrane?

A

Increased thickness - fibrosis

Decreased surface area - emphysema

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17
Q

Why can CO2 be lower than normal in type 1 respiratory failure?

A

Hypoxia stimulates peripheral chemoreceptors, stimulating hyperventilation which removes more CO2

18
Q

What are the causes of reduced ventilation to a part of the lung?

A

Pneumonia, early acute severe asthma and respiratory distress of the newborn.

19
Q

Why does reduced ventilation to parts of the lung not lead to hypercapnia?

A

There is increased CO2 removal by other parts of the lung.

20
Q

What is the common cause of reduced perfusion to a part of the lung?

A

Pulmonary embolism

21
Q

Describe how reduced perfusion or reduced ventilation to a part of the lung will lead to type 1 respiratory failure

A

Reduced ventilation - blood draining these areas with a low v/q ratio are poorly oxygenated
Reduced perfusion- causes a diversion of blood to unaffected parts, decreasing their v/q ratio. Although parts with reduced flow have an increased v/q ratio, net result is hypoxia because most of the lung is over perfused.

22
Q

Why does a V/Q mismatch lead to type 1 respiratory failure?

A

Poor O2 uptake cannot be compensated by other parts of the lung but poor CO2 removal can.

23
Q

What are the clinical features of respiratory failure?

A

Exercise intolerance, tachypnoea, confusion (central hypoxia) and central cyanosis (late)

24
Q

What causes peripheral cyanosis?

A

Increased O2 extraction from sluggish capillary circulation. Can occur without central cyanosis.

25
Q

What factors can indicate the causative organism for pneumonia/LRTI?

A

Age, community/hospital acquired, presence of chronic lung disease, immunosuppression and travel history

26
Q

What patient samples can be taken in suspected pneumonia?

A

Throat/nose swab, sputum, lung biopsy, urine and blood culture

27
Q

What is pneumonia?

A

The general term for inflammation of the gas exchange region of the lung usually due to infection

28
Q

How many pneumonias be classified?

A

Lobar/broncho (diffuse and patchy), community/hospital, aspiration, pneumonia in the immunocompromised host

29
Q

List the common causative organisms of community acquired pneumonia

A 
Streptococcus pneumoniae (commonest)
Haemophilus influenza
Lebsiella pneumoniae
Staphylococcus aureus 
Streptococcus pyogenes
30
Q

List the important organisms in hospital acquired pneumonia

A

Gram negative bacteria
Staphylococcus aureus inc. MRSA
Anaerobes
Fungi

31
Q

When is aspiration pneumonia likely to occur and what are the common causative organisms?

A

In altered consciousness (e.g. Anaesthesia, stroke, alcoholics). Organisms include oral flora and anaerobes

32
Q

What are the clinical features of pneumonia?

A

Malaise, fever, productive cough

Maybe chest pain, breathlessness

33
Q

How is the severity of pneumonia abscesses?

A 
CURB 65 score. If >1=hospital admission
C: new mental confusion
U: urea >7mmol/L
R: respiratory rate >30/min 
B: BP <90/60
Age >65
34
Q

Under what circumstances does prognosis for pneumococcal pneumonia decrease?

A 
Increasing age
Increasing CURB 65 score
High/low white cell count
Absence of fever
Rise in blood urea
35
Q

What is the general management for pneumonia?

A

Fluids
Anti pyretic drugs to remove fever and malaise
Analgesics for pleural pain
IV fluids and O2 in severe cases

36
Q

What antibiotics are used for pneumonia?

A

Hospital - target gram -ve, IV co amoxicalv

Community - target pneumococcus, penicillin

37
Q

What are some complications of pneumonia?

A

Pleural effusion
Empyema (pus in cavity)
Lung abscess formation

38
Q

What are the natural defences of the respiratory tract against infection?

A

Cough and sneezing
Muco ciliary escalator
Respiratory mucosal immune system - alveolar macrophages, IgA, IgG

39
Q

List some common LRTIs

A

Rhinitis, Pharyngitis, Sinusitis, Otitis media (middle ear)

40
Q

What are some preventative measures for pneumonia?

A

Immunisation - flu and pneumococcal vaccines

Chemoprophylaxis to high risk patients (splenectomy, immunocompromised)

41
Q

What causes atypical pneumonias?

A

Organisms without a cell wall - legionella, chlamydia. Needs antibiotics that work on protein synthesis

Respiratory (9 decks)

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