Suggested Level of Knowlege: Detailed

NOTE

You should have a detailed knowledge of the techniques that you use in your daily practice. Most modern anaesthetic machines use two or more of Infrared Absorption, Paramagnetism and Fuel Cells.

Mass spectrometry and Raman scattering are less commonly used now, but you should have some knowledge of them.

You should consider why we don't routinely monitor nitrogen, even though it is often the gas in greatest concentration in the anaesthetic circuit.

There are many other methods of gas analysis, although it is very unlikely that you would be asked about them. If you are interested, you can read about them in Sykes Vickers and Hull.

DON'T FORGET that we measure gas partial pressures in blood as well as in respiratory gases.

LOs

BT_SQ 1.6 Describe the methods of measurement applicable to anaesthesia, including clinical utility, complications and sources of error in particular:

· SI units

· Measurement of volumes, flows, and pressures, including transducers.

· Measurement of blood pressure

· Measurement of cardiac output

· Measurement of temperature

· Oximetry

· Gas analysis, including capnography

· Methods used to measure respiratory function, including:

- Forced expiratory volume  

-  Peak expiratory flow rate  

-  Vital capacity  

-  Flow-volume loops  

-  Functional residual capacity and residual volume

Past SAQs

2016.1 Discuss the physical principles and equipment used for measurement of exhaled carbon dioxide by infrared analysis using sidestream sampling. Outline the potential sources of error.

2015.2 Describe the fuel cell and the paramagnetic oxygen analyser. Discuss their use in anaesthetic practice.

2006.1, 2001.1 Briefly describe the measurement of pH in a blood sample using a pH electrode.

2006.2 Briefly explain how oximetry can be used to estimate the partial pressure of oxygen in a blood sample.

1999.2 Describe how the partial pressure of oxygen in a blood sample is measured using a Clark electrode.

References

Recommended Texts

Magee & Tooley Chapter 16

Davis & Kenny 5th Ed Chapter 19

Miller Chapter 7th Ed. 38

Al-Shaikh & Stacey 4th ed Chapter 10

Other Texts

Dorsch and Dorsch 4th ed. Chapter 17

Sykes Vickers and Hull, Principles of measurement and monitoring in anaesthesia and intensive care. This is quite an old reference, but explains gas analysis well. It does cover a lot of older measurement techniques which you could ignore.

Gas Analysis