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Respiratory and urinary > Anaesthetic respiration > Flashcards

Anaesthetic respiration Flashcards

1
Q

What is the normal tidal volume?

A

10ml/kg

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2
Q

What is the normal RPM?

A

20-30

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3
Q

What is the equation for minute ventilation?

A

Minute ventilation = tidal volume X RPM

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4
Q

What 3 reasons cause respiratory efficiency to decrease during anaesthesia?

A

Drugs
Recumbency
Equipment

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5
Q

Why do anaesthetic drugs decrease respiratory efficiency?

A

Suppressing CNS also depresses CV and respiratory systems

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6
Q

Anaesthetics drugs can have direct effect on respiratory efficiency. Explain how

A

Drugs have direct effect on medulla oblongata - not under conscious control
Cause reduced response to input in respiratory centre
(Chemoreceptors and irritant receptors)

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7
Q

Anaesthetic drugs can also have an indirect effect on respiratory efficiency. Give an example of this

A

Over infusion of IV fluids

Causes pulmonary oedema (fluid in alveoli) due to increased HSP

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8
Q

How does lateral and dorsal recumbency have a negative impact on respiratory efficiency?

A

Lateral recumbency = atelectasis - collapse of dependent lung and surgeon leaning on side too!
Dorsal recumbency = abdominal contents on diaphragm

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9
Q

How does recumbency and anaesthetic drugs have a negative impact on mucus production and clearing?

A

Recumbency causes mucus build up

Anaesthetic drugs reduce ciliary function

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10
Q

How does anaesthetic equipment decrease respiratory efficiency? (3 ways)

A

Increases dead space and resistance to airflow
Potentially inadequate oxygen supply or rebreathing of expired gases
Air is not warmed and humidified

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11
Q

What are the results of reduce respiratory efficiency under anaesthetic?

A

Ventilation: perfusion mismatch
Low PaO2
Respiratory centre unable to do much to compensate for changes

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12
Q

What are the consequences of persistently deranged blood gases?

A

Acidosis
Prolonged hypoxia causes brain damage
Hypercapnia

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13
Q

What effect does hypercapnia have on the body?

A

Causes vasodilation

Raises intracranial pressure - further depression of CNS

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14
Q

Monitoring patients under anaesthetic is best hands on. Additional methods can be used to aid this. What 3 methods can be used to monitor patients

A

Pulse oximeter
Capnography
Blood gas analysis

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15
Q

How do you attach a pulse oximeter to a patient?

A

Clip onto vascular, non-pigmented area

E.g. tongue, ear or genitals

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16
Q

How does a pulse oximeter work? What 3 things does it measure?

A

Shines infrared light through tissue

Measures differential absorption, % oxygen saturation of haemoglobin and pulse rate

17
Q

At what level of PaO2 does haemoglobin saturation significantly decrease?

A

80 mm/Hg

18
Q

Why might a pulse oximeter show adversely affected results?

A

Vasoconstriction of area attached to pulse oximeter
Abnormal haemoglobin
Equipment movement

19
Q

Pulse oximeter measures % of oxygen saturation of haemoglobin. What doesn’t a pulse oximeter show?

A

Adequacy of ventilation

Patient is on pure oxygen

20
Q

What 2 things does capnography measure?

A

End tidal CO2 -concentration/partial pressure of CO2 in expired air (via breathing system)
Respiratory rate

21
Q

What is the PCO2 of expired air? (Also normal peak of capnogram)

A

40

22
Q

Describe each phase of the capnogram

A

A-B early expiration
B-C expiratory upstroke
C-D alveolar plateau
D-E inspiratory upstroke

23
Q

What can lead to a raised ETCO2?

A

Increased metabolism (without increased minute ventilation)
Increased cardiac output (causes ventilation perfusion mismatch)
Inadequate ventilation/rebreathing of expired gas

24
Q

Blood gas analysis is the gold standard of anaesthetic monitoring. What does it measure?

A

PaO2 and PaCO2 directly

Also pH, electrolytes, lactate, HCO3-

25
Q

Is arterial or venous blood used for blood gas analysis?

A

Both
Arterial more representative of respiratory function
Venous used when not looking at respiratory function

26
Q

Where should you take blood gas analysis reading and why?

A

Just after lungs

Tissue metabolism affects reading

27
Q

What would you expect a normal PaO2, PaCO2 and pH of the blood to be in a blood gas analysis reading?

A

PaO2 >100 as on pure oxygen
PaCO2 = 40
pH = 7.4

28
Q

When should you stop monitoring respiratory parameters and why?

A

When ET tube removed

Under conscious control

29
Q

Why should you still monitor patients respiratory function after the anaesthetic has finished and their breathing is under conscious control?

A

Removed oxygen supply

After anaesthesia, body less effective at responding to chemoreceptors

Respiratory and urinary (8 decks)

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