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Respiratory > Hypoxia > Flashcards

Hypoxia Flashcards

1
Q

Define hypoxia

A

Describes a specific environment (PO2)

Much less oxygen in the ambient air

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2
Q

Define hypoxaemia

A

Describes blood environment (PaO2)

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3
Q

What is ischaemia

A

Describes tissue receiving inadequate oxygen

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4
Q

Which factors put the body under hypoxic stress

A

Altitude
Disease
Exercise

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5
Q

What is the partial pressure of oxygen in the atmosphere compared to the tissues

A

21.3kPa vs 5.3kPa

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6
Q

Describe age related decline in lung function

A

As you age your PaO2 decreases

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7
Q

What is the oxygen cascade

A

Describes decreasing oxygen tension from inspired air to respiring cells
Pressure gradient can be affected by breathing hypoxic gas, affecting flow rate
Largest proportion of oxygen loss is in the mixing phase

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8
Q

Describe oxygen and carbon dioxide dissociation graphically

A

Linear dissociation for CO2

Sigmoid dissociation for O2

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9
Q

Which factors can affect the oxygen cascade

A

Alveolar ventilation
V/Q matching
Diffusion capacity
Cardiac output

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10
Q

What is the effect of the following on the oxygen cascade: oxygen therapy, humid air, hyper/hypoventilation, diffusion defect

A

oxygen therapy - increased ambient air PO2
humid air - decreased ambient air PO2
Hyperventilation - increased alveolar PO2
Hypoventilation - decreased alveolar PO2
Diffusion defect - Decreased post-alveolar capillaries PO2

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11
Q

What may effect ambient air PO2

A

Oxygen therapy

Humid air

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12
Q

What may affect the alveolar air PO2

A

hyper ventilation

Hypoventilation

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13
Q

What may affect post-alveolar capillary PO2

A

Diffusion defect

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14
Q

What is the limit of humans altitude wise

A

Mount Everest summit (just under 10,000)

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15
Q

What altitude pressure are airplanes pressurised to

A

2000m

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16
Q

Why must ascent to high altitude be done slowly

A

Allows body to acclimatise

Immediate exposure = incapacitate in less than a minute, kill in 2

17
Q

What is acclimation

A

Stimulated by an artificial environment e.g. hypobaric chamber or breathing hypoxic gas

18
Q

What are the anatomical and physiological adaptations of native highlanders

A

Barrel chest - larger TLC, more alveoli, greater capillarisation
Increased haematocrit - greater O2 carrying capacity of the blood
Larger heart- pumps through vasoconstricted pulmonary circulation(pulmonary perfusion)
Increase mitochondrial density - greater O2 utilisation at cellular level

19
Q

What is acetazolamide

A

Carbonic anhydrase inhibitor

Accelerates slow renal compensation to hypoxia-induced hyperventilation

20
Q

Describe the causes and pathophysiology of chronic mountain sickness

A

Unknown cause

Secondary polycythaemia increases the blood viscosity
Blood sludges through the capillary and impedes delivery

21
Q

Describe the symptoms, consequences and treatment for chronic mountain sickness

A

Cyanosis and fatigue

Ischaemic tissue damage
Heart failure
Eventual death

Return to lower altitudes

22
Q

Describe the causes and pathophysiology of acute mountain sickness

A

Maladaptation to the high-altitude environment.
Usually associated with recent ascent, onset within 24 hours and can last more than a week

Associated with mid-cerebral oedema

23
Q

Describe the symptoms and consequences for acute mountain sickness

A

Nausea, vomiting, irritability, dizziness, insomnia, fatigue, and dyspnoea

Development into HAPE or HACE

24
Q

What is the treatment for acute mountain sickness

A

Monitor symptoms
Stop ascent
Analgesia
Fluids
Medication (acetazolamide) Hyperbaric O2 therapy
Symptoms tend to subside after 48 hrs of increased renal compensation

25
Q

Describe the causes and pathophysiology of High altitude pulmonary oedema

A

Rapid ascent or inability to acclimatise

Vasoconstriction of pulmonary vessels in response to hypoxia increased pulmonary pressure, permeability and fluid leakage from capillaries fluid accumulates once production exceeds the maximum rate of lymph drainage

26
Q

Describe the symptoms and consequences for high altitude pulmonary oedema

A

Dyspnoea, dry cough, bloody sputum, crackling chest sounds

Impaired gas exchange, impaired ventilatory mechanics

27
Q

What is the treatment for high altitude pulmonary oedema

A

Descent
Hyperbaric O2 therapy
Nifedipine (CCB)Salmeterol (relaxant
Sildenafil (viagra)

28
Q

Describe the causes and pathophysiology of High altitude cerebral oedema

A

Rapid ascent or inability to acclimatise

vasodilation of vessels in response to hypoxaemia (to increase blood flow) more blood going into the capillaries increases fluid leakage cranium is a ‘sealed box’ – no room to expand so intracranial pressure increases

29
Q

Describe the symptoms and consequences for high altitude cerebral oedema

A

Confusion, ataxia, behavioural change, hallucinations, disorientation

Irrational behaviour, irreversible neurological damage, coma, death

30
Q

What is the treatment for high altitude cerebral oedema

A

Immediate descent
O2 therapy
Hyperbaric O2 therapy
Dexamethasone

31
Q

What is respiratory failure

A

Failure of pulmonary gas exchange, generally V/Q inequality

CO2 can diffuse but oxygen cannot

32
Q

Describe type 1 respiratory failure

A

Hypoxic respiratory failure
PaO2 < 8kPa
PaCO2 = low/normal

Hypoventilation
V/Q mismatch
Diffusion abnormality

Pulmonary oedema
Pneumonia
Atelectasis

33
Q

Describe type 2 respiratory failure

A

Hypercapnic respiratory failure
PaO2 < 8 kPa
PaCO2 > 6.7 kPa

Increased CO2 production
Decreased CO2 elimination (unable to clear out of the lungs)

Decreased CNS drive
Increased work of breathing
Pulmonary fibrosis
Neuromuscular disease
Increased physiological dead space
Obesity

Respiratory (16 decks)

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