Anaesthesia Machine and Monitoring

Question 1

The basic machine consists of:

Answer 1

1. Supply of gases under pressure (pipeline, cylinders)
2. Means of controlling and measuring gas flow
3. Means of administering anaesthetic vapours
4. Conduit to deliver gases/vapour to patient (breathing system)
5. Means for providing IPPV (reservoir bag, mechanical ventilator)
6. Additional safety devices

Question 2

Breathing systems mostly used:

Answer 2

Open circuit: Jackson Rees modified Ayre’s T-piece (Mapleson F)
Closed circuit: the circle system

Question 3

Signs of exhausted soda lime?

Answer 3

Colour change (white to purple)
Temperate (warm to cold)
Capnograph - rising baseline ETCO2
Clinical signs of hypercarbia (TOO LATE)

Question 4

Modes of IPPV?

Answer 4

CMV (continuous mandatory ventilation)/ VCV (volume controlled ventilation)
PCV (pressure controlled ventilation)
PEEP (positive end-expiratory pressure)
SIMV (synchronised intermittent mandatory ventilation)
PSV (pressure supported ventilation)

Question 5

Which mode of IPPV is used in adults with cuffed ETT?

Answer 5

CMV/VCV (preset tidal volume is delivered and airway pressures vary, therefore monitoring of airway pressure is NB)

Question 6

Which mode of IPPV is used in paediatrics with uncuffed ETT?

Answer 6

PCV (compensates for leaks in the system)

Question 7

Role of PEEP?

Answer 7

Aids oxygenation

Prevents atelectasis

Question 8

Monitors of machine-patient interface?

Answer 8

Oxygen analyser (at common gas outlet)
Ventilation: TV, RR, flow rate, I:E ratio, MV
Airway pressure
Capnograph
Agent monitor for inspired and expired vapour concentration (i.e. fiISO, etISO)

Question 9

Monitors of patient well-being?

Answer 9

Non-invasive: ECG, BP, Capnograph, Pulse oximeter, Temperature, Nerve stimulater

Invasive: Urinary catheter, CVP, arterial BP, pulmonary artery catheter (Swan-Ganz), trans-oesophageal echocardiograpy (TOE)

Question 10

Maximum airway pressure to prevent barotrauma?

Question 11

Normal tidal volume?

Answer 11

6-10ml/kg

Question 12

Normal minute volume?

Answer 12

80-100ml/kg

Question 13

Oxygen transport to tissues depends on:

Answer 13

Fi02
Airway
Breathing
Circulation

Question 14

Normal SATS?

Answer 14

96-99%

Question 15

Normal ET C02 with IPPV?

Answer 15

4-5,3kPa

Higher values may indicate hypo-ventilateion, and lower values may indicate hyperventilation.

Question 16

Reasons for increased ET CO2?

Answer 16

Decreased alveolar ventilation:
Decreased RR and TV

Increased equipment dead space

Increased CO2 production:
Fever
Hypermetabolic state - malignant hyperthermia, thyrotoxicosis

Increased inspiratory CO2:
Rebreathing
Exhausted soda lime
External CO2 source

Question 17

Reasons for reduced ET CO2?

Answer 17

Increased alveolar ventilation:
Increased RR and TV

Reduced CO2 production:
Hypothermia
Hypometabolic state - myxodoema

Increased alveolar dead space:
Reduced CO
PE
High PEEP

No CO2 delivery:
Cardiac arrest
Massive PE

Sampling error

Question 18

Elements of CVS monitoring?

Answer 18

NIBP/invasive BP
HR
ECG
CVP
Pulmonary artery catheter

Question 19

Monitoring the depth of anaesthesia:

Answer 19

Increased HR and BP (response to stimulation)

Processed EEG monitors - BIS and Entropy:
Slow EEG waves = deeper anaesthesia
Target: 40-60 where 0 is isoelectric EEG and 100 is awake

Auditory evoked potentials (AEP)

Question 20

In which procedures should temperature be monitored?

Answer 20

All procedures > 15minutes

Question 21

Places for temperature probe insertion?

Answer 21

Oral
Nasal
Oesophageal (core)
Rectal
Dermal
In bladder (core)
In outer ear

Question 22

Why is heat loss is common in anesthesia due to:

Answer 22

Cold theatre temperatures
Cold circulating air (heat loss via convection)
Exposed body areas
Vasodilation from anesthetic agents
inability to shiver and generate heat (paralysed)

Question 23

Adverse effects of hypothermia:

Answer 23

Vasoconstriction
Shivering
Poor enzyme function
Respiratory depression
Diminished muscle relaxant effect
Slowed emergence from GA

Question 24

Beneficial effects of hypothermia:

Answer 24

Brain cell protection from hypoxia (used to our advantage in cardiac surgical procedures or cardiac-pulmonary bypass)

Question 25

Most important checks in machine check?

Answer 25

1. Primary O2 supply - is there a constant flow of 02 available?
2. Secondary O2 supply - is there enough O2 in the reserve cyllinder?
3. Is the self-inflating resuscitator (Ambubag) present and functional
4. Is there no leak in the breathing system with pressure testing and open vapouriser?
5. Is all suction equipment working and functional?

Question 26

Where can central venous catheterisations be places?

Answer 26

“Cavafix”

Jugular vein
Subclavian vein
Basilic vein

Question 27

Use of the Pulmonary Artery floatation catheter (Swan-Ganz) catheter?

Answer 27

Measures CO
Pulmonary artery pressure monitoring
Pulmonary capillary wedge pressure monitoring
Temperature monitoring
Injection of fluids

Question 28

Flow of Swan-Ganz Catheter?

Answer 28

SVC - RA - RV - PA

Question 29

Wall outlets in theatre?

Answer 29

Oxygen = white
Nitrous oxide = blue
Air = black
CO2 = green
Suction/vacuum = yellow

Question 30

Pulse oximeter?

Answer 30

Rate of transmission of infrared inversely proportional to Hb saturation of O2

Question 31

Ayre’s T-piece?

Answer 31

Open-ended reservoir bag

Used mainly in paediatrics and children

Question 32

Arterial lines/arterial pressure transducer?

Answer 32

Consists of an
Arterial line connected by heparinised saline filled non-compressible tubing to a pressure transducer

Pressure transducer converted the pressure waveform into an electrical signal to measure BP, which is displayed on the bedside monitor

Pressurised saline ensures forward flow of blood