Anaesthesia

Question 1

At what partial pressure of oxygen considered ‘low’ ? At what partial pressure is CO2 too high ?

Answer 1

Less than 60mmHg of oxygen is low, more than 60mmHg of CO 2 is high

Question 2

Name the 7 inputs that affect the respiratory centre in the medulla oblongata and the pons?

Answer 2

Cortex, stretch receptors in lungs, irritant receptors in lungs, central chemoreceptors, peripheral chemoreceptors, hypothalamus (emotional stimuli), receptors in muscles and joints

Question 3

What does PEEP stand for? Which kind of patient might this be useful for?

Answer 3

Positive end expiratory pressure, prevents alveoli from collapsing completely at the end of expiration, less effort to then re inflate the alveoli at next breath. Useful for obese or larger patients.

Question 4

Describe the differences between Quantitative and Qualitative assessment of ventilation.

Answer 4

Quantitative = mechanical means of ventilation, measured by tidal volume and respiratory rate 
Qualitative = measuring the efficiency of that ventilation, eg oxygen saturation of Hb, end tidal CO2

Question 5

What does ‘triggering’ refer to when discussing IPPV and ventilators?

Answer 5

Initiating the inspiration of a patient, at the end of expiration

Question 6

What does ‘cycling’ refer to when discussing IPPV and ventilation?

Answer 6

Initiating the switch from inspiration to expiration

Question 7

What does ‘limiting’ refer to when discussing IPPV and ventilators?

Answer 7

The maximum time, pressure, flow or volume for the system to cut out, to prevent causing lung trauma

Question 8

Name the 4 types of ventilator

Answer 8

1) bag squeezer
2) mechanical thumb
3) intermittent blower
4) volume divider

Question 9

Give a brief explanation of how a bag squeezer ventilator works

Answer 9

Bellows in a bottle, pressure in the bottle but outside the bellows is altered to draw the bellows up and down. Dials include inspiratory time, expiratory time and volume.

Question 10

Give a brief description of how a Mechanical Thumb ventilator works

Answer 10

As if a thumb were occlude get the expiratory limb of a t-piece, the inspiration time is the length of time the expiratory limb is occluded.

Question 11

Give a brief explanation of how an intermittent blower ventilator works

Answer 11

A valve delivers flow, powered by electricity or FGF.

Question 12

Give a brief description of how a minute volume divider works.

Answer 12

The FGF (MV) is set, as well as number of breaths, the machine will divide the MV over breaths. A reservoir fills with gas, and is devil reed to the patient when the volume is reached. Not volume cycled as breaths a factor.

Question 13

What methods can be used to gain control over a patient whom is fighting ventilation?

Answer 13

NMBA, respiratory depressant drugs (opioids, midazolam, ketamine), a few breaths in quick succession to decrease ET CO2.

Question 14

A lack of which facility would make ventilation a contraindication to the patients welfare?

Answer 14

Capnography !

Question 15

What are the most common procedures encountered for orthopaedic and spinal surgery ?

Answer 15

Surgery to treat CCL disease
Fracture repair
Arthroscopy
Decompression of the spinal cord after herniation of an intervertebral disc

Question 16

Describe the advantages and disadvantages of of side stream and main stream capnography

Answer 16

Side: adv: minimal dead space, machinery away from patient, easy to connect, non-intimated patients via nasal catheter. Dis: moist sample so may not be accurate, must travel up sampling line, water trapped in sampling line

Mainstream: adv: no scavenging needed, no water in sample, rapid response as no sampling line. Dis: more expensive, heavy so can cause drag, more difficult to clean, difficult to use in unusual positions

Question 17

You are monitoring an anaesthetic and you notice the alpha angle of the capnogram has increased, there is a greater phase III slope. What does this mean?

Answer 17

More late emptying alveoli. Greater ventilation perfusion mismatch