Monitoring

Question 1

Disadvantages of SpO2 monitoring:

Answer 1

• Poor trace

Shutdown
Light artefact
Movement
Dark skin
Arrhythmia
Non-pulsatile flow (eg. Bypass)
IV contrast

• Lag
• Doesn’t reflect ventilation/CO2- inadequate as sole monitoring in sedation
• Inaccurate in anaemia
  may be well saturated, but net low
• Doesn’t differentiate carboxyHb or methHb
• Becomes less accurate < sPO2 90% and very inaccurate by 80%
  Also, stops at 100%, but paO2 might keep rising
  get gas

Question 2

What is paO2 at spO2 of 90%? What is clinical relevance of this threshold?

Answer 2

60 mmHg

Below here, rapid drop in sats (O2-Hb curve) and hypoxic ischaemia of tissues

Question 3

Why is SpO2 of 90% a significant clinical threshold?

Answer 3

Correlates with paO2 60 mmHg

After this, rapid drop of binding/saturation and at risk of tissue hypoxic ischaemia

Question 4

What is a normal paO2?

Answer 4

75 mmHg +

Correlates with sPO2 95%+

Question 5

Accuracy of spo2 (vs paO2)?

Answer 5

Within 2-3% (between 80-100%)

Question 6

Accuracy of ETCO2 (vs PaCO2)?

Answer 6

Always lower (dead space)

Up to 5mmHg normal

Question 7

Indications for ETCO2 monitoring?

Answer 7

-Confirm tube placement
—> incl calorimetric
-Monitor ventilation in sedation
—> earlier change than sats
—> sedative OD, PSA
-Monitor the intubated patient
—> waveforms help troubleshoot
-Quality of CPR
—> should be >10mmHg

Question 8

What is a ‘normal’ ETCO2?

Answer 8

Should be around 5mmHg lower than paCO2. So:

30-40mmHg

Question 9

Causes of ETCO2:
Increasing
Decreasing
Flatlining

Answer 9

INCREASING
More blood CO2
Hypoventilation
T2RF
Fever
NaBic
More blood to lungs
ROSC
Improving shock
Lysis
More breathed out
Resolution of obstruction, T2RF
Recruitment

DECREASING
Less blood CO2
Hypothermia
Improving resp failure
Deep coma/sedation
Less blood to lungs
PE
Shock
Arrest
Less breathed out
ETT/circuit obstruction
Airway obstruction
Bronchoconstriction
Insufficient I:E
Equipment
Leak
Malfunction
Calibration

FLATLINING
as above
Total airway obstruction (incl ETT)
Apnoea
Cardiac arrest
Disconnected

Question 10

Normal capnography waveform:

Answer 10

Phase 1: BASELINE
- Should be zero

Phase 2: EXPIRATORY UPSTROKE
- Dead space

ALPHA ANGLE

Phase 3: ALVEOLAR PLATEAU
- Alveolar

BETA ANGLE
- Where ETCO2 is measured

Phase 4: INSPIRATORY DOWNSTROKE

Question 11

Answer 11

Sawtooth or Sharkfin

Bronchospasm- COPD, asthma

Question 12

Answer 12

5 or 6, small waves decreasing in amplitude to zero

ARREST
OESOPHAGEAL INTUBATION

Question 13

Answer 13

Curare cleft
Represents patient inspiratory efforts

DYSSYNCHRONY

Question 14

Answer 14

Rapid increase
Indicates restoration of ventilation or perfusion

ROSC
RESOLUTION OF OBSTRUCTION
Lysis of PE

Question 15

Answer 15

Rapid breaths, low CO2
HYPERVENTILATION

Question 16

Answer 16

Long, slow expiration
Will start to see ETCO2 increase

HYPOVENTILATION

Question 17

What SBP is required to feel the following pulses:
Radial
Femoral
Carotid

Answer 17

Radial
80

Femoral
70

Carotid
60

Question 18

Causes of inaccurate art line reading:

Answer 18

Transducer position:
Should be at LA
- Too high- BP looks low
- Too low- BP looks high

Overdamped
*Flat, low, loss of notching’
Kinks
Bubbles
Clots
Spasm
Loose tubing
=SBP reads too low. MAP unaffected.

Underdamped
Sharp, pronounced
Excessive catheter movement in vessel (“whip”)
Stiff tubing
= SBP reads too high. MAP unaffected.

Not calibrated
Malpositioned catheter

Question 19

Utility of CVP:

Answer 19

Normal = 0-8mmHg in spont breathing adult. (12-16 if ventilated)

Limited evidence and utility as marker of hypovolaemia/ fluid responsiveness
- In theory, sustained change of 7 significant.

Useful:
- In conjunction with other haemodynamic markers
- Prove mechanical capture with pacing
- Prove central line placement correct (waveform)
- DDx type of shock state:
—> LOW in sepsis, distributive
—> HIGH in cardiogenic, obstructive

Question 20

Arterial waveform:

Answer 20

Question 21

5 causes of elevated CVP:

Answer 21

Normal = 0-8 (spont), 12-16 (PPV)

• RV failure (MI, pulm HTN etc.)
• Tricupsid regurg
• SVC obstruction
• Fluid overload
• Tamponade
• Restrictive pericarditis
• PPV/ high PEEP
• Lung disease with autoPEEP